Article

Application of the fire–grazing interaction to restore a shifting mosaic on tallgrass prairie

Journal of Applied Ecology

July 2004
41(4):604 - 614

DOI:10.1111/j.0021-8901.2004.00937.x

Authors:

Samuel D. Fuhlendorf

Oklahoma State University - Stillwater

David M. Engle

Oklahoma State University - Stillwater

Management of rangelands has long operated under the paradigm of minimizing spatially discrete disturbances, often under the objective of reducing inherent heterogeneity within managed ecosystems. Management of grazing animals has focused on uniform distribution of disturbance, so that no areas are heavily disturbed or undisturbed (i.e. management to the ‘middle’). A model of the fire–grazing interaction argues that grazing and fire interact through a series of positive and negative feedbacks to cause a shifting mosaic of vegetation pattern across the landscape. This interaction was important in the evolution of species in the North American Great Plains grasslands. This approach has the potential to serve as an ecological‐based model for management of grasslands with a long evolutionary history of grazing. We compared a heterogeneity‐based approach, in which fire is applied to discrete patches, with typical homogeneity‐based land management in the North American Great Plains, to determine if patch burning followed by focal grazing creates a shifting mosaic pattern of vegetation structure and composition. Our data suggest that spatially discrete fires promote focal grazing, where grazing animals devote 75% of grazing time within the one‐third of the area that has been burned within the past year. These focal disturbances cause local changes in the plant community and increase patch‐level heterogeneity across landscapes. As the focal disturbance is shifted to other patches over time, successional processes lead to changes in local plant communities and the patchwork landscape can be described as a shifting mosaic. A patch‐dynamic approach can be accomplished in the tallgrass prairie through applying spatially discrete fires and allowing animals free access to a diversity of landscape elements that vary in time since focal disturbance. This increases heterogeneity across the landscape, a variable that has been shown to be critical to some wildlife species as well as the structure and function of grassland ecosystems. Synthesis and applications. Our study demonstrates that the fire‐grazing model may be useful for generating heterogeneity in grassland management. Discrete fires are applied to patches, and patchy grazing by herbivores promotes a shifting vegetation mosaic across the landscape. Furthermore, application of the model has the potential of increasing the area of rangelands under management for conservation purposes, because livestock production is maintained at a level similar to traditional management. So, by managing transient focal patches that move through the landscape, heterogeneity has the potential to be a central paradigm for managing landscapes for multiple objectives, such as biodiversity and agricultural productivity.

Reconstructing Large Herbivore Abundance and Environmental Interactions in Postglacial North America

Thesis

Full-text available

Dec 2023

John Wendt

Large herbivores drive critical ecological processes, yet their long-term dynamics and effects are poorly understood due to the limitations of existing paleoherbivore proxies. To address these shortcomings, long-term records of paleoherbivores were constructed by (i) applying new analytical techniques to existing bison fossil datasets; and (ii) examining fecal steroid data that characterize temporal changes in ungulate abundance and community composition. These paleoherbivore reconstructions were analyzed in relation to their environmental contexts to better understand herbivore-ecosystem interactions through time in three separate studies: First, spatiotemporal changes in postglacial bison distribution and abundance in North America were examined by summarizing fossil bison observations. Bison observations were compared with simulated climate variables in a distribution modeling framework to project probable bison distributions in 1000-year intervals from the Last Glacial Maximum to present in light of changing climatic drivers over time. Since the Bolling-Allerod Interstadial (14.7-12.9 ka) the geographic distribution of bison is primarily explained by seasonal temperature patterns. Second, Holocene records of bison abundance were compared to paleofire reconstructions spanning the midcontinental moisture gradient to determine the relative dominance of herbivores and fire as biomass consumers. Bison dominated biomass consumption in dry settings whereas fire dominated consumption in wetter environments. Historical distributions of herbivory and burning resemble those of Sub-Saharan Africa, suggesting a degree of generality in the feedbacks and interactions that regulate long-term consumer dynamics. Third, the utility of fecal steroids in lake sediments for reconstructing past herbivore abundance and identity was tested by (i) characterizing the fecal steroid signatures of key North American ungulates, (ii) comparing these signatures with multiproxy data preserved in lake sediments from the Yellowstone Northern Range, and (iii) comparing influxes of fecal steroids over time to historical records of ungulate biomass and use. Bison and/or elk were abundant at Buffalo Ford Lake over the past c. 2300 years. Ungulate densities in the watershed were highest in the early 20 th century and likely contributed to decreases in forage taxa and possibly increased lake production. These results demonstrate long-term ecological impacts of herbivores and highlight opportunities for continued development of paleoherbivore proxies.

Long‐term frequent fire and cattle grazing alter dry forest understory vegetation

Article

Full-text available

May 2024
ECOL APPL

Understanding fire and large herbivore interactions in interior western forests is critical, owing to the extensive and widespread co‐occurrence of these two disturbance types and multiple present and future implications for forest resilience, conservation and restoration. However, manipulative studies focused on interactions and outcomes associated with these two disturbances are rare in forested rangelands. We investigated understory vegetation response to 5‐year spring and fall prescribed fire and domestic cattle grazing exclusion in ponderosa pine stands and reported long‐term responses, almost two decades after the first entry fires. In fall burn areas open to cattle grazing, total understory cover prior to utilization was about 12% lower compared with fall burn areas where cattle were experimentally excluded. This response was not strongly driven by a particular palatable or unpalatable plant functional group. Fire and grazing are likely interacting in a numerically mediated process, as we found little evidence to support a functionally moderated pathway. Post‐fire green‐up may equalize forage to a certain extent and concentrate herbivores in the smaller burned areas within pastures, constraining a positive understory response to burning. Fall fire and grazing also increased annual forbs and resprouting shrubs. The effects of spring burning were relatively minor, and we found no interaction with grazing. The nonnative annual grass Bromus tectorum (cheatgrass) remains a problematic invader linked to fall burning but not grazing in stands that had higher propagule pressure when the experiment was initiated. At these sites, exotic grass was a major component of the vegetation by 2015, and invasion was also increasing in spring burn and unburned areas. Information from our study suggests that frequent fall fires and cattle grazing combined may reduce understory resilience in similar dry ponderosa pine forests. Consideration of longer fire return intervals, resting areas after fire, virtual fencing, or burning entire pastures may help to mitigate the effects noted in this study.

Spatio-temporal patterns of rangeland forage nutritive value and grazer selection with patch-burning in the US northern Great Plains

Article

Mar 2024
J ENVIRON MANAGE

Pyric herbivory in a temperate European wood‐pasture system

Article

Full-text available

Mar 2024
J APPL ECOL

The term pyric herbivory was first introduced in 2009, describing how fire shapes herbivory as burned areas attract herbivores and, simultaneously, herbivory shapes fuel load and fire behaviour. Pyric herbivory results in a mosaic of patches with varying levels of herbivory and grazing intensity fire intensity and frequency. The importance of pyric herbivory for ecosystem heterogeneity and biodiversity has been described for North American, Australian and African systems, but the concept remains largely untested in a European context. We introduced fire and herbivory in a full‐factorial experiment in a temperate European wood‐pasture system to test whether pyric herbivory operates in ways comparable to grassy systems elsewhere in the world. Using camera traps, we observed the behaviour of cattle in burned subplots (49 m²) compared with unburned subplots. We measured grass height and the proportion of the subplot that burned as variables affecting cattle preference and to assess how grazing affects fire behaviour. We also examined the effect on plant species and life‐form composition after six seasons of treatment. Cattle spent more time grazing in burned than in unburned subplots in the most productive paddock, where a larger proportion of the subplot burned. The proportion of a subplot that burned was positively related to pre‐fire grass height. Moreover, both grass height and the proportion of subplot burned declined in the burned subplots during the 6‐year study period and fire and cattle grazing altered the relative cover of graminoids and shrubs (Rubus spp.), with more graminoids in grazed and/or burned subplots and more shrubs in ungrazed subplots at the end of the study. Synthesis and applications. In our temperate European wood pasture, fire and (cattle) grazing interacted in ways comparable to pyric herbivory in grassy ecosystems elsewhere in the world, especially in the most productive paddock. Fire attracted grazing, with cattle grazing longer on subplots that burned more fully. Grazing also affected fire, where over the course of our experiment cattle grazing reduced grass height and the proportion of a subplot that burned. We suggest that pyric herbivory is an interesting management method to further explore in the European context to address the loss of biodiversity in open ecosystems, particularly in more productive sites.

Factors affecting the adoption of patch-burn grazing in the southern Great Plains in the US

Article

Feb 2023
LAND USE POLICY

Patch-burn grazing, a combination of fire and grazing, has been identified as a novel approach to maintaining biodiversity in the Great Plains of the United States. Many ranchers, however, are not aware of the practice and very few of them had adopted it on their land. Utilizing the data obtained from a survey of landowners residing in the southern Great Plains of the United State conducted in 2021, we analyzed the factors affecting the awareness and adoption of patch-burn grazing. Since an adoption behavior study might suffer from selection bias if the level of awareness is not appropriately accounted for, we used a bivariate probit model for data analysis. The study results indicated that repeated wildfires, nature conservancy, and university/county extension positively affected the probability of patch-burn grazing awareness while the effect of age and livestock membership had a negative impact. The research further revealed that larger landholding size, management objectives to control blackberry, repeated wildfires, and university/county extension positively influenced the likelihood of patch-burn grazing adoption. In contrast, the management objective to control red cedar, along with respondent age, and higher-income negatively influenced the patch-burn grazing adoption. Since many landowners are not convinced to adopt patch-burn grazing, study results suggest further extension needs to educate traditional and non-traditional ranchers on the ecological and production benefits of patch-burn grazing.

Pyric Herbivory and the Nexus Between Forage, Fire and Native and Introduced Large Grazing Herbivores in Australian Tropical Savannas

Article

Full-text available

Nov 2022
ECOSYSTEMS

Earth’s tropical savannas typically support high biomass of diverse grazing herbivores that depend on a highly fluctuating resource: high-quality forage. An annual wet–dry cycle, fire and herbivory combine to influence forage quality and availability throughout the year. In the savannas of northern Australia, a depauperate suite of large native (marsupial) herbivores (wallaroos [Osphranter spp.] and the agile wallaby [Notamacropus agilis]) compete for resources with non-native large herbivores introduced in the late nineteenth century, particularly bovines (feral and managed cattle [Bos spp.] and feral water buffalo [Bubalus bubalis]) that now dominate the landscape. Anecdotal reports of recent population declines of large macropods and negative impacts of bovines highlight the need to better understand the complex relationship between forage, fire and abundance of native and introduced large herbivores. The pyric herbivory conceptual model, which posits complex feedbacks between fire and herbivory and was developed outside Australia, predicts that native and introduced large herbivores will both respond positively to post-fire forage production in Australian savannas where they co-occur. We used grazing exclosures, forage biomass and nutrient analyses and motion-sensor camera-trapping to evaluate the overall robustness of the pyric herbivory model in the Australian context, specifically whether forage quantity and quality are impacted by herbivory, season and fire activity, and which forage attributes most influence large grazing herbivore abundance. Forage quantity, as measured by live, dead and total herbaceous biomass and proportion of biomass alive, was higher inside herbivore exclosures, even at relatively low densities of herbivores. Forage quality, as measured by fibre content, was not affected by herbivory, however, crude protein content of live herbaceous biomass was greater outside herbivore exclosures. Recent fire was an important predictor of all measures of forage quantity and quality. Recent fire occurrence decreased overall quantity (biomass) but increased quality (decreased fibre content and increased crude protein content); late dry season fires resulted in forage with the highest crude protein content. The predictions of the pyric herbivory conceptual model are consistent with observations of the feeding behaviour of introduced bovines and some large macropods in northern Australian savannas, lending support to the global generality of pyric herbivory in fire-prone grassy biomes.

Using airborne and DESIS imaging spectroscopy to map plant diversity across the largest contiguous tract of tallgrass prairie on earth

Article

Full-text available

Nov 2022
REMOTE SENS ENVIRON

Grassland ecosystems are under threat globally, primarily due to land-use and land-cover changes that have adversely affected their biodiversity. Given the negative ecological impacts of biodiversity loss in grasslands, there is an urgent need for developing an operational biodiversity monitoring system that functions in these ecosystems. In this paper, we assessed the capability of airborne and spaceborne imaging spectroscopy (also known as hyperspectral imaging) to capture plant α-diversity in a large naturally-assembled grassland while considering the impact of common management practices, specifically prescribed fire. We collected a robust in-situ plant diversity data set, including species composition and percent cover from 2500 sampling points with different burn ages, from recently-burned to transitional and pre-prescribed fire at the Joseph H. Williams Tallgrass Prairie Preserve in Oklahoma, USA. We expressed in-situ plant α-diversity using the first three Hill numbers, including species richness (number of observed species in a plant community), exponential Shannon entropy index (hereafter Shannon diversity; effective number of common species, where species are weighed proportional to their percent cover), and inverse Simpson concentration index (hereafter Simpson diversity; effective number of dominant species, where more weight is given to dominant species) at four different plot sizes, including 60 m × 60 m, 120 m × 120 m, 180 m × 180 m, and 240 m × 240 m. We collected full-range airborne hyperspectral data with fine spatial resolution (1 m) and visible and near-infrared spaceborne hyper-spectral data from DESIS sensor with coarse spatial resolution (30 m), and used the spectral diversity hypothesis -i.e., that the variability in spectral data is largely driven by plant diversity-to estimate α-diversity remotely. In recently-burned plots and those at the transitional stage, both airborne and spaceborne data were capable of capturing Simpson diversity-a metric that calculates the effective number of dominant species by emphasizing abundant species and discounting rare species-but not species richness or Shannon diversity. Further, neither airborne nor spaceborne hyperspectral data sets were capable of capturing plant α-diversity of 60 m × 60 m or 120 m × 120 m plots. Based on these results, three main findings emerged: (1) management practices influence grassland biodiversity patterns that can be remotely detected, (2) both fine-and coarse-resolution remotely-sensed data can detect the effective number of dominant species (e.g., Simpson diversity), and (3) attention should be given to site-specific plant diversity field data collection to appropriately interpret remote sensing results. Findings of this study indicate the feasibility of estimating Simpson diversity in naturally-assembled grasslands using forthcoming spaceborne imagers such as National Aeronautics and Space Administration's Surface Biology and Geology mission.

Avian Nesting Diversity and Nest Success in a Modified Twice-Over Rest-Rotation Grazing System

Technical Report

Full-text available

Jan 2021

We are evaluating the impacts of a modified twice-over rest-rotation grazing system on avian nesting diversity and apparent nesting success. The modified twice-over rest-rotation grazing system creates heterogeneity using four different grazing intensities that rotate each year. Our preliminary results suggest that variation in grazing intensity alters vegetation structure, which influences the avian nesting diversity and apparent nesting success. These results provide additional insight into the importance of heterogeneity in rangelands managed for biodiversity.

Uncovering the hidden: Leveraging sub-pixel spectral diversity to estimate plant diversity from space

Article

Full-text available

Jul 2023
REMOTE SENS ENVIRON

Remotely sensed spectral diversity has emerged as a promising proxy for plant diversity. However, spectral diversity approaches relate image spectra to plant community diversity by only incorporating variation among adjacent pixels, considering each pixel as a homogeneous entity composed of one class, and disregarding the within-pixel variability. Although such approaches might work for remotely-sensed data with fine spatial resolution , they might not be viable solutions to estimate plant diversity using coarse-resolution data from forthcoming spaceborne imagers. To address the limitations associated with spectral diversity approaches, we proposed a novel approach, known as endmember diversity, for remote estimation of plant diversity through quantifying spectral diversity at the sub-pixel level and taking into account the within-pixel variability. The approach consisted of deriving the number and abundance of distinct spectral entities within each pixel via spectral unmixing. In doing so, we considered the spectral signature of each pixel as a mixture of distinct spectral entities, commonly known as endmembers. We then used the per-pixel endmembers and their abundance to calculate different spectral diversity metrics for every pixel. We assessed the performance of the endmember diversity approach at estimating plant taxonomic and phylogenetic diversity based on two experiments using a simulated spectral dataset and a real-world spaceborne DESIS (DLR Earth Sensing Imaging Spectrometer) dataset. In both experiments, we found significant associations between endmember diversity and in situ plant diversity. Additionally, our method applied to DESIS data outperformed a conventional spectral diversity metric based on the coefficient of variation when applied to 1-m airborne imaging spectroscopy data. Collectively, our results demonstrate the capability of forthcoming spaceborne imagers to monitor local plant diversity.

Review of Conservation Challenges and Possible Solutions for Grassland Birds of the North American Great Plains

Article

Full-text available

Aug 2023
RANGELAND ECOL MANAG

North America's grassland birds remain in crisis despite decades of conservation effort s. This review provides an overview of factors contributing to these declines, as well as strategies and resources available to a diversity of stakeholders to help conserve grassland bird communities with an emphasis on the Great Plains-a grassland region of global ecological significance and a habitat stronghold for grassland birds. Grassland bird declines are driven by historical and continuing threats across the full annual cycle including grassland habitat loss, agriculture intensification, woody encroachment, and disruption of fire and grazing regimes. More recently, energy development activities, the use of neonicotinoid pesticides, and anthropogenic climate change have emerged as additional threats. While threats to grassland birds are numerous and often synergistic, possibilities for conservation are also diverse and multifaceted. Land set-aside programs, incentives and voluntary practices for producers, improved environmental management by energy and utility companies, and policy and regulation can all contribute to the conservation of these unique species. We suggest that future grassland bird research should focus on poorly studied aspects of the annual cycle, such as overwinter survival and habitat use, and the migratory period, which remains completely unexplored for many species. Filling these knowledge gaps may facilitate more sophisticated population modeling that can identify limiting factors and more effectively guide investment in conservation.

Patch‐burn management affects grassland butterfly communities in cattle‐grazed rangelands

Article

Mar 2023

Grassland butterflies are undergoing worldwide population decline due to habitat loss and degradation. Rangelands in the Southern Great Plains can provide a habitat for grassland butterflies depending on management practices. Patch‐burn grazing is a management regime that involves burning portions of grazed pastures at different times. The combination of rotational fire and grazing creates a shifting mosaic of recently burned to older burned areas and lightly grazed to heavily grazed areas. However, the impact of fire and grazing on butterfly communities is complex and the effects of different management regimes on butterfly communities are not clear. We investigated the impact of time since prescribed fire and season of fire on butterfly communities in eight cattle‐grazed pastures, each with three burn units, in northern Oklahoma. Treatments included units burned in spring 2018, summer 2018, summer 2019, and spring 2020, with three replicates of each for a total of 12 burn units. Surveys were conducted three times per year in each burn unit in 2019 and 2020 using two standardised Pollard transects. A total of 909 butterflies and 35 species were observed. Species diversity varied by time since fire and season of fire, with spring‐burned sites having the lowest species diversity and summer‐burned sites having the highest. Dominant vegetation cover and blooming forb presence differed with time since fire and season of fire. Patch‐burn grazing creates a mosaic of successional vegetation stages which can benefit different butterfly species and support the overall community. Some species such as Cercyonis pegala , Danaus plexippus , and Atrytone arogos may benefit from fire every 1–2 years, while other species such as Echinargus isola may need longer times between fire treatments. Patch‐burn grazing regimes can support butterfly communities with species that need different fire return intervals by providing a mosaic of areas with different times since fire and associated grazing intensities.

Wildfire-Grazing Impact on Forage Quality Assessed with Near-Infrared Spectroscopy and Generalized Partial Least Squares Regression

Article

Jan 2023
RANGELAND ECOL MANAG

Fire and grazing are key drivers of plant community structure in the Great Plains ecoregion, with critical impacts on the quantity and quality of forage. While the impact of fire on forage quality is well understood in many ecosystems, few studies have examined this question in the northern mixed-grass prairie. We investigated the postburn nutrient content of forbs and graminoids over a 4-yr timeframe, asking 1) how forage quality changed over the 4 yr post fire and 2) whether the effect of fire on quality was impacted by the resumption of grazing. We used near-infrared spectroscopy and generalized partial least squares regression (plsRglm) methods to assess crude protein. We show that the use of generalized models provides improved estimates of percent nitrogen than the standard partial least squares approach. Both crude protein and fiber varied annually after the wildfires, with no effect of grazing on forage quality. In the first and second years, burned sites displayed higher protein than unburned locations. Fire did not affect crude protein between plant functional groups; however, forbs showed higher nutrient values than grasses throughout the 4 yr. Fire affected fiber content with grasses showing higher fiber than forbs. There was a positive relationship between neutral and acid detergent fiber and litter in burned sites. These results indicate no long-term effect of wildfire on protein content, which stabilizes in the third year post burn. The improvement of forb digestibility and retention of protein under dry conditions could modify the grazing capacity of the prairies at large scales. This may also change the foraging behavior of large ungulate grazers through mechanisms such as increasing patch reselection (i.e., intensified grazing cycles) and broadening feeding preferences to forbs when grasses are limited or have high fiber content.

Effects of Prescribed Burning on Abundance of Common Herbivores in Matekenya Vlei

Article

Full-text available

Nov 2022

Innocent Mahakata

Fire is commonly used to remove long, dry, low-nutritious grass and generate fresh grass for wildlife. The study sought to examine the impact of prescribed burning on common herbivore abundance and habitat selection in Matekenya Vlei, Sengwa Wildlife Research Area (SWRA). Four-line transects, two in each block (burnt and unburnt) were set. The average length of each transect was 2.5 km. Daytime transect surveys were conducted between 07:00 hours and 08:00 hours morning and 16:00 hours and 17:00 hours afternoon. Two observers walked along transect lines on the 6th and 7th September 2020 recording all sightings at first sight. Comparison of individual species group size between burnt and unburnt blocks and between morning and afternoon were done using parametric paired-t-test and nonparametric Mann-Whitney U-test respectively. A total of eleven common herbivore species (n = 11) were recorded in all blocks. There was no significant difference in group size of impala (Aepyceros melampus), zebra (Equus burchelli), and warthog (Phacochoerus aethiopicus) except for waterbuck (Kobus ellipsiprymnus) (p < 0.005) between burnt and non-burnt blocks. Waterbuck (Kobus ellipsiprymnus), zebra (Equus burchelli), reedbuck (Redunca arundinum), impala (Aepyceros me-lampus) and warthog (Phacochoerus aethiopicus) preferred burnt areas. Buffalo (Syncerus caffer) and elephant (Loxodonta africana) were predominantly found in tall unburnt areas. Sightings between morning and afternoon varied with species. Researches to establish how management fires can be used to influence herbivore abundance over a long period after prescribed burning are recommended .

The LTAR Grazing Land Common Experiment at Archbold Biological Station‐University of Florida

Article

Full-text available

Jun 2024
J ENVIRON QUAL

The Archbold Biological Station‐University of Florida (ABS‐UF) Long‐term Agroecosystem Research (LTAR) site lies in the heart of south‐central Florida, representing subtropical humid grazing lands in North America and globally. Beef producers in this region face challenges due to climate variability, limited nutritive value of forages, poor soils, public concerns about water quality and greenhouse gas emissions, management trade‐offs, economic uncertainty, and increasing urban encroachment. The ABS‐UF Common Experiment, co‐designed with stakeholders, will assess innovative management systems in comparison to prevailing management systems on key indicators of sustainability. Innovative management systems being tested are alternative fire (frequency and spatial extent) and grazing practices (stocking rate and system). The common experiment framework was implemented across a management intensity gradient spanning from native rangeland to cultivated pastures, including embedded wetlands. Issues that have arisen to date include difficulties in implementing prescribed fire and reduced productivity in cultivated pastures associated with innovative management, which led to an adjustment of the experimental treatment. A stakeholder advisory council will codesign future alternative treatments and guide experimental changes in this long‐term experiment. Stakeholder engagement efforts revealed research priorities centered on financial strength, carbon (C) and greenhouse gas emissions, and water quality. Stakeholders are also interested in testing emerging technology such as the utility of virtual fencing. Results from ABS‐UF provide a unique perspective from subtropical humid grazing lands for continental‐scale cross‐site synthesis on sustainable agroecosystems across LTAR.

The LTAR‐integrated grazing land common experiment at the Texas Gulf

Article

Full-text available

May 2024
J ENVIRON QUAL

Extreme weather and climate events have become more frequent and directly affect the ecological structure and function of integrated grazing lands. While the Great Plains have experienced a long history of regular disturbances from drought and floods, grazing, and fires, the increased frequency and magnitude of these disturbances can reduce ecological resilience, largely depending on management practices. Alternative strategies designed to adaptively manage grazing land resources based on the ecology of the system should increase the resistance and resilience to disturbances when compared to prevailing practices. Determining the ecologic and economic value of alternative strategies will require long‐term evaluations across large spatial scales. The Long‐Term Agroecosystem Research Network has been established to evaluate the differences between alternative and prevailing practices among 18 strategically located sites and across decadal time scales throughout the continental United States. A key integrated grazing land site within this network is the Texas Gulf located at the Riesel Watersheds in the Blackland Prairie of Central Texas. At this study site, the differences between alternative and prevailing grazing management strategies are now being evaluated. The alternative strategy was designed using a combination of knowledge of the site and species ecology with modern‐day tools and technologies. Alternatively, the prevailing practice implements a conventional year‐round continuous grazing system with heavy reliance on hay and supplemental protein during winter. Results will provide grazing land managers with economically viable adaptive management choices for increasing ecological resilience following extreme and frequent disturbance events.

Impact of plant diversity and management intensity on magnitude and stability of productivity in North American grazing lands

Article

Full-text available

May 2024

Questions Grasslands provide important provisioning services worldwide and their management has consequences for these services. Management intensification is a widespread land‐use change and has accelerated across North America to meet rising demands on productivity, yet its impact on the relationship between plant diversity and productivity is still unclear. Here, we investigated the relationship between plant diversity and grassland productivity across nine ecoclimatic domains of the continental United States. We also tested the effect of management intensification on diversity and productivity in four case studies. Methods We acquired remotely sensed gross primary productivity data (GPP, 1986–2018) and plant diversity data measured at different spatial scales (1, 10, 100, 400 m ² ), as well as climate variables including the Palmer drought index from two ecological networks. We used general linear mixed models to relate GPP to plant diversity across sites. For the case study analysis, we used linear mixed models to relate plant diversity to management intensity, and tested if the management intensity influenced the relationship between GPP (mean and temporal variation) and drought. Results Across all sites, we observed positive relationships among species richness, productivity, and the temporal stability of mean annual biomass production. These relationships were not affected by the scale at which species richness was observed. In three out of the four case studies, we observed that management effects on species richness were only significant at broader scales (i.e., ≥10 m ² ) with no clear effect found at the commonly used 1‐m ² quadrat scale. In one case study, species‐poor, intensively managed pastures presented the highest productivity but were more sensitive to dry conditions than less intensified pastures. However, in other case studies, we did not observe significant effects of management intensity on the magnitude or stability of productivity. Conclusions Generalization across studies may be difficult and require the development of intensification indices general enough to be applied across diverse management strategies in grazilands. Understanding how management intensification affects grassland productivity will inform the development of sustainable intensification strategies.

The long shadow of woody encroachment: An integrated approach to modeling grassland songbird habitat

Article

Full-text available

Feb 2024
ECOL APPL

Animals must track resources over relatively fine spatial and temporal scales, particularly in disturbance‐mediated systems like grasslands. Grassland birds respond to habitat heterogeneity by dispersing among sites within and between years, yet we know little about how they make post‐dispersal settlement decisions. Many methods exist to quantify the resource selection of mobile taxa, but the habitat data used in these models are frequently not collected at the same location or time that individuals were present. This spatiotemporal misalignment may lead to incorrect interpretations and adverse conservation outcomes, particularly in dynamic systems. To investigate the extent to which spatially and temporally dynamic vegetation conditions and topography drive grassland bird settlement decisions, we integrated multiple data sources from our study site to predict slope, vegetation height, and multiple metrics of vegetation cover at any point in space and time within the temporal and spatial scope of our study. We paired these predictions with avian mark‐resight data for 8 years at the Konza Prairie Biological Station in NE Kansas to evaluate territory selection for Grasshopper Sparrows (Ammodramus savannarum), Dickcissels (Spiza americana), and Eastern Meadowlarks (Sturnella magna). Each species selected different types and amounts of herbaceous vegetation cover, but all three species preferred relatively flat areas with less than 6% shrub cover and less than 1% tree cover. We evaluated several scenarios of woody vegetation removal and found that, with a targeted approach, the simulated removal of just one isolated tree in the uplands created up to 14 ha of grassland bird habitat. This study supports growing evidence that small amounts of woody encroachment can fragment landscapes, augmenting conservation threats to grassland systems. Conversely, these results demonstrate that drastic increases in bird habitat area could be achieved through relatively efficient management interventions. The results and approaches reported pave the way for more efficient conservation efforts in grasslands and other systems through spatiotemporal alignment of habitat with animal behaviors and simulated impacts of management interventions.

Upland Sandpipers select for later time since fire and experience high nest survival in grasslands managed with patch-burn grazing

Article

Jan 2024
CONDOR

Upland Sandpipers (Bartramia longicauda) are a grassland obligate shorebird that nests in dense vegetation structure near recently disturbed areas and could benefit from management practices that promote heterogenous vegetation structure. Upland Sandpipers primary breeding range is generally managed for livestock production using traditional practices that lack patchy disturbances to facilitate higher levels of structural heterogeneity. Patch-burn grazing (PBG) could be an alternative management practice for Upland Sandpiper conservation for its use to create areas of dense vegetation structure near recently disturbed areas. However, limited information is available regarding nest production of Upland Sandpipers within a PBG framework. To assess the compatibility of PBG with Upland Sandpiper conservation, we estimated nest site selection and survival of Upland Sandpiper nests on private lands managed with PBG in the unglaciated plains region of North Dakota. We located 59 nests from 2017 to 2020. Upland Sandpipers avoided 1 year since fire (YSF) patches and selected for 2 and 3 YSF patches for nest sites. Additionally, nest site selection decreased with increased bare ground and at intermediate distances to the nearest Upland Sandpiper nest. Upland Sandpipers experienced high overall nest survival during the study with 51 of 59 nests successfully hatching, which limited our ability to make inferences between daily survival rates and variables of interest. Our findings suggest that PBG can provide suitable nesting cover for Upland Sandpipers in later YSF patches despite annual prescribed fire and livestock grazing during the nesting season. PBG seems a suitable grassland management strategy that should be included in conservation planning within Upland Sandpiper’s breeding distribution.

Dynamic Plant–Herbivore Interactions between Bison Space Use and Vegetation Heterogeneity in a Tallgrass Prairie

Article

Full-text available

Nov 2023

Investigations into plant–herbivore interactions are of importance for understanding grassland ecosystem dynamics. Our research quantified the effects of vegetation heterogeneity at a patch scale of 30 m on bison space use in a tallgrass prairie through the analyses of the resource utilization function. In addition, we assessed the vegetation heterogeneity associated with bison locations by comparing the patch-scale vegetation characteristics between areas with high and low bison space use through Mann–Whitney U tests. Furthermore, we simulated the interactions between bison and vegetation patches (2 × 2 m) during the early growing season for the lowland topographic positions using agent-based modeling (ABM) as a preliminary study of linking bison foraging site selection with vegetation responses to bison grazing dynamically. The bison grazing strategy in the ABM of the grassland system was adjusted to ensure consistency in the vegetation pattern variations related to bison space use between the simulation and the empirical on-the-ground observations. The results indicated the following: (1) The effects of the patch-scale vegetation heterogeneity on the bison foraging site selection varied across the seasons, which were most evident in the middle of the growing season. (2) A relatively high level of bison space use generally resulted in diverse grassland canopies with high variability and interspersion. (3) From the ABM of the grassland system, it can be implied that bison select patches with high quality and quantity at the beginning of the growing season; as the vegetation quality and quantity improve overall, the bison graze randomly. This pattern was confirmed by observations of the bison foraging site selection in our study site. The ABM proved to be valuable in exploring and elucidating the underlying mechanisms of the grassland dynamics with a native North American grazer.

Soil-landscape-vegetation relationships in grassland-forest boundaries, and possible applications in ecological restoration

Article

Oct 2023
J S AM EARTH SCI

Edaphic influence on plant distribution is essential to community ecology studies, and for vegetation management and restoration in grasslands-forest ecosystems. Pampa biome is a subtropical grassland with high floristic diversity and with an important role in food production in South America, including tree plantations where recent changes in land use soil has been questioned about the impacts on water consumption, soil degradation and potential biodiversity loss. We assessed the relationship of soil physical, chemical and morphological properties with forest and grassland species occurrence, to improve our understanding of soil and landscapes with grasslands-forest mosaics, and contribute to ecological restoration in the biome. Soil physical and chemical properties were determined in different toposequences localized in two forest farms in southern Brazil, both covered with grassland and native forest use. Natural fertility of the studied soils was highest in the lowlands, along with highest moisture and lowest toxic aluminum content. Soil saturated hydraulic conductivity was highest in the summit and backslope soils, influenced by coarser fractions in the granulometry. Soil bulk density, total porosity, microporosity, macroporosity, saturated hydraulic conductivity field capacity, permanent wilting point and available water content, influenced by sand, silt and clay contents, varied among soils and landscape and contributed to vegetation diversity. Some of the plant species occupied specific soils and landscapes. The greatest vegetation frequency was of grassland species (Poaceae and Asteraceae) in both study sites. Grasslandforest area has forest individuals in the middle of the grassland and riparian, while in grassland area the riparian vegetation is composed naturally by grassland. Forest fragments expanded in grassland-forest area during the 15 years prior to our study, but in the grassland area there were no changes in the phyto-physiognomy, demonstrating that the vegetation of grassland occurs naturally in the riparian environment. This study highlights that many of sites covered naturally by grassland, in the Pampa biome, should be protected from disruptive activities and/or recovered with species endemic to the ecosystem, without necessarily by forest enrichment as usually recommended for restoration activities.

Grazing intensity effects on herbaceous community composition in burned sagebrush steppe

Article

Full-text available

Oct 2023

There is limited knowledge of grazing impacts on longer term plant community dynamics following fire in sagebrush steppe. This study evaluated vegetation response to different intensities of deferred rotation cattle grazing over 16 years (2007–2022) on burned Wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis (Beetle & Young) Welsh) steppe in eastern Oregon. Treatments were applied in a randomized complete block, which included no grazing on burned (nonuse, n = 5) and unburned (control, n = 5) steppe; and cattle grazing at low (low, n = 4), moderate (moderate, n = 4), and high (high, n = 4) intensities on burned steppe. Vegetation dynamics were evaluated by repeated measures analysis of canopy cover and density of shrub and herbaceous species and functional groups. Herbaceous functional groups were an early‐season bunchgrass (one species, Sandberg bluegrass [ Poa secunda J. Presl]), tall perennial bunchgrasses, perennial forbs, annual grass (one species, cheatgrass [ Bromus tectorum L.]), and annual forbs. Tall perennial bunchgrass, Sandberg bluegrass, and perennial forb cover and density did not differ among the treatments but did decrease over time in all treatments. The cover of several tall bunchgrass species was generally less in the high treatment, mainly, Idaho fescue ( Festuca idahoensis Elmer) and Thurber's needlegrass ( Achnatherum thurberianum (Piper) Barkworth). The cover of cheatgrass and annual forbs varied among years but was greater in the burned‐grazed and nonuse treatments than in the control. Native plant cover in the burned treatments (grazed and nonuse) represented 77%–85% of total herbaceous cover versus the control where native plants comprised 91% of the total. Annual weather variability appears to account for most of the compositional dynamics measured in the various grazed and ungrazed treatments.

Exotic herbivores and fire energy drive standing herbaceous biomass but do not alter compositional patterns in a semiarid savanna ecosystem

Article

Full-text available

Oct 2023

Questions Fire regime alterations are pushing open ecosystems worldwide past tipping points where alternative steady states characterized by woody dominance prevail. This reduces the frequency and intensity of surface fires, further limiting their effectiveness for controlling cover of woody plants. In addition, grazing pressure (exotic or native grazers) can reinforce woody encroachment by potentially reducing fine‐fuel loads. We investigated the effects of different fire energies on the herbaceous plant community, together with mammalian wildlife herbivory (exotic and native combined) exclusion, to inform best management practices. Location Texas semi‐arid savanna, southern Great Plains, USA. Methods We conducted an experiment in which we manipulated fire intensity and herbivore access to herbaceous biomass in a split‐plot design. We altered fire energy via fuel addition rather than applying fire under different environmental conditions to control for differences in standing biomass and composition attributable to differential plant physiological status and fire season. Results High‐energy fire did not reduce herbaceous biomass or alter plant community composition, although it did increase among‐plot variability in composition and forb biomass relative to low‐energy fire and non‐burned controls. Grazing pressure from native and non‐native mammalian herbivores reduced above‐ground herbaceous biomass regardless of fire treatments, but did not alter community composition. Conclusions Managers seeking to apply high‐intensity prescribed fire to reduce woody encroachment will not negatively impact herbaceous plant productivity or alter community composition. However, they should be cognizant that repeated fires necessary for greatly reducing woody plants in heavily invaded areas might be difficult to accomplish due to fine‐fuel reduction from wild herbivores. High fencing to restrict access by wildlife herbivores or culling might be necessary to build fuels sufficient to conduct high‐intensity burns for woody‐plant reduction.

Freese et al. - 2018 - Bison Management Plan, American Prairie Reserve

Technical Report

Full-text available

Jul 2023

APR aims to achieve the following objectives for bison conservation that reinforce and build on the objectives of the original reintroduction plan and incorporate criteria of the Sanderson et al. (2008) scorecard for making an “exceptional contribution” (the highest category) to fulfilling the goals of the “Vermejo Statement” on ecological recovery of bison.

Countering ecological misconceptions with strategic translocation and assessment of microhabitat use

Article

Full-text available

Jun 2023
BIOL CONSERV

Wildlife translocations to human-modified and inferred formerly occupied habitats can be controversial when they involve a high degree of perceived risk of failure, often stemming from a large number of unknowns or misconceptions regarding the focal species' ecology. However, it is increasingly recognised that such trans-locations are necessary to guide effective conservation strategies, particularly for species that persist in a subset of the habitats they formerly occupied. As a step towards alleviating some of the perceived risks around these translocations, we suggest the focal species' microhabitat use in the recipient locality of a trial translocation be compared with that where they still persist. Using a case study of a threatened Australian rodent, the pookila (Pseudomys novaehollandiae, New Holland mouse), we demonstrate how such an assessment can shed light on ecological misconceptions that may need to be addressed, and bring about the revision of species-specific recommendations for restoration works and release tactics. Feeding this knowledge back into the decision-making process, practitioners may more confidently direct future conservation activities (including further trial trans-locations) across a broader diversity of habitats within the species' indigenous range. Widespread and systematic implementation of this approach may help to reverse the impacts of shifting baseline syndrome, and should ultimately aid the resilience of species to future environmental change.

Asian Journal of Research in Crop Science, Evaluation of Tillage and Mulch Practices on the Growth of Selected Cereal and Legume Crops in the Foothills Agro-ecological Zone of Lesotho

Article

Full-text available

May 2023

Its about evaluation of tillage practices and mulch on fodder production

Evaluation of Tillage and Mulch Practices on the Growth of Selected Cereal and Legume Crops in the Foothills Agro-ecological Zone of Lesotho

Article

Full-text available

May 2023

The trial was conducted to evaluate the influence of tillage and mulch practices on growth response of maize and selected forage legumes. With three replications, the experiment was carried out using a split-plot design. Mulch and no mulch were used as the major plot treatments Mulch was maize straw left from the previous cropping season. The subplot treatments were different tillage practices namely Minimum (0.2 m) and Deep tillage (0.35 m).The research was carried out in the Foothills of Lesotho in Ha-Matela in Nazareth, east of Maseru District, during summer season for four months (December, January, February, and March). A mouldboard plough was used to prepare the experimental field, and it was harrowed to get fine tilth. The broadcasting method was used to Original Research Article Molata et al.; Asian J. 40 plant the legume species namely soybean (Glycine max L), lablab (Lablab purpureus L) and grazing vetch (Vicia villosa), whereas a planter was used to sow maize seeds at a rate of two per hole, 0.25 m apart, and 0.05 m deep. For maize and the forage legumes, 12.5 kg of NPK inorganic fertilizer was applied per plot. Low moisture content and poor soil conditions under minimum tillage and no-mulch resulted in low plant growth. Maize and forage legumes plant height was significantly (P<0.05) higher under deep tillage and mulch. Vegetative characteristics in respect of leaf, stem, and root lengths were also significantly (P<0.05) higher under deep tillage and mulch. Cereal maize had a low and positive correlation relationship between its growth indices whereas; legume crops had a high correlation relationship and were significant. Therefore, maize and forage legumes may be produced under deep tillage and mulch to support improved plant growth.

Detecting ecological traps in human-altered landscapes: A case study of the thick-billed longspur nesting in croplands

Article

Full-text available

Apr 2023

Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in spring cereal and pulse crop fields during the breeding season in northeastern Montana, USA, suggest such fields also provide cues for habitat selection. Maladaptive selection for poor-quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection, but frequent human disturbance would result in reduced reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native grassland sites during 2020-2021. Across both years, settlement patterns were similar between site types and occupancy ranged from 0.52 ± 0.17 SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year, and changes in abundance during the breeding season appeared to be associated with precipitation-driven vegetation conditions rather than habitat type. While an index of nest density was lower in crop than native sites, the number of young fledged per successful nest (2.9 ± 0.18 SE) and nest survival (0.24 ± 0.03 SE; n = 222 nests) were similar for crop and native sites. Collectively, the data did not support our ecological trap hypothesis: longspurs did not exhibit a clear preference for crop sites and reproductive output was not significantly reduced. Our results indicate that croplands may provide alternative breeding habitat within a human-dominated landscape.

Influence of Livestock Grazing History on Plant Community Composition on Native Prairies of the Southern Prairie Pothole Region

Article

Full-text available

Apr 2023
RANGELAND ECOL MANAG

The southern Prairie Pothole Region (PPR) of central North America is a highly modified landscape where remnant unplowed prairies could serve as repositories of native plant biodiversity. A previous study paired two historically idle US Fish and Wildlife Service (USFWS) National Wildlife Refuges with nearby privately owned grazing lands in North Dakota and found differences in invasive grass frequency, notably that smooth brome (Bromus inermis Leyss.) was less prevalent on annually grazed lands. A broader assessment, conducted over a wider geographic area, was warranted to investigate whether this relationship held across the southern extent of PPR in North Dakota and South Dakota. To this end, we selected 26 USFWS native prairie sites paired with adjacent/nearby native prairie sites with a history of livestock grazing in the PPR of North Dakota and South Dakota. We estimated plant species’ cover in five 10 × 10 m plots at each paired site in June or July of 2021. Plant community composition on USFWS sites was distinct from paired sites under private or state ownership (permutational analysis of variance (P = 0.021, F = 1.935). Additionally, paired t-tests revealed that sites under private or state ownership (with a long-term history of grazing) had higher total species richness (P = 0.006) and floristic quality index (a measure of species richness and disturbance tolerance) values (P = 0.042) than USFWS sites (without a long-term history of grazing). Smooth brome relative cover was lower (P = 0.019) at sites with a long-term history of grazing (13.4% mean relative cover) than paired USFWS sites (23.3% mean relative cover). Given these differences, remnant native prairies with long-term histories of annual grazing may provide unique opportunities for conserving native plant diversity and impeding smooth brome spread in the southern PPR.

A plea for scale, and why it matters for invasive species management, biodiversity and conservation

Article

Full-text available

Apr 2023
J APPL ECOL

Invasive species are suspected to be major contributors to biodiversity declines worldwide. Counterintuitively, however, invasive species effects are likely scale dependent and are hypothesized to be positively related to biodiversity at large spatial scales. Past studies investigating the effect of invasion on biodiversity have been mostly conducted at small scales (<100 m²) that cannot represent large dynamic landscapes by design. Therefore, replicated experimental evidence supporting a negative effect of invasive plants on biodiversity is lacking across many landscape types, including large grasslands. We collected data across eight large (333–809 ha) grassland landscapes managed with pyric herbivory—that is the recoupling of fire and grazing—to test how an invasive legume Lespedeza cuneata affected plant and bird communities at spatial grains ranging from 0.1 m² to >3,000,000 m². Lespedeza cuneata invasion effects on grassland plant diversity and composition changed with scale, being negative at small spatial grains (0.1 m²) and neutral or positive at large spatial grains (>3,000,000 m²). Lespedeza cuneata abundance did not significantly affect bird diversity at any spatial grain measured. Lespedeza cuneata may negatively affect biodiversity if abundances are greater than those observed in this study. However, previous research suggests that Lespedeza cuneata may not be capable of exceeding 20% canopy cover across large landscapes (>400 ha). Control and eradication strategies can be costly and are fraught with risk. If data do not clearly support a negative Lespedeza cuneata abundance–biodiversity relationship, and if invasion is spatially limited across large landscapes, ongoing control and eradication efforts may be unwarranted and ineffective. Synthesis and applications: Invasive species effects gleaned from small‐scale studies may not reliably predict their effects at larger scales. Although we recognize the importance of small‐scale studies in potentially isolating individual mechanisms, management strategies based solely on results from small‐scale studies of invasion are unlikely to increase or conserve biodiversity across large landscapes. Rather, processes that generate landscape heterogeneity—like pyric herbivory—are probably more important for promoting biodiversity across all scales. Scale is a central problem in ecology, and defining scale in management objectives is essential for effective biodiversity conservation.

Grassland and managed grazing policy review

Article

Full-text available

Mar 2023

Perennial grasslands, including prairie and pasture, have declined with tremendous environmental and social costs. This decline reflects unequal policy support for grasslands and managed grazing compared to row crops. To create a resource for community partners and decision-makers, we reviewed and analyzed the policy tools and implementation capacity that supports and constrains grasslands and managed grazing in the U.S. Upper Midwest. Risk reduction subsidies for corn and soybeans far outpace the support for pasture. Some states lost their statewide grazing specialist when the federal Grazing Lands Conservation Initiative lapsed. The United States Department of Agriculture, Natural Resources Conservation Service support for lands with prescribed grazing practices declined after 2005 but remained relatively steady 2010–2020. These results reveal the policy disadvantage for grasslands and managed grazing in comparison with row crop agriculture for milk and meat production. Grassland and grazing policies have an important nexus with water quality, biodiversity, carbon and outdoor recreation policy. Socially just transitions to well-managed, grazed grasslands require equity-oriented interventions that support community needs. We synthesized recommendations for national and state policy that farmers and other grazing professionals assert would support perennial grasslands and grazing, including changes in insurance, conservation programs, supply chains, land access, and fair labor. These policies would provide critical support for grass-based agriculture and prairies that we hope will help build soil, retain nutrients, reduce flooding and enhance biodiversity while providing healthy food, jobs, and communities.

Restoration age and re-introduced bison may shape soil bacterial communities in restored tallgrass prairies

Article

Jan 2023

Knowledge of how habitat restoration shapes soil microbial communities often is limited despite their critical roles in ecosystem function. Soil community diversity and composition change after restoration, but the trajectory of these successional changes may be influenced by disturbances imposed for habitat management. We studied soil bacterial communities in a restored tallgrass prairie chronosequence over six years to document how diversity and composition changed with age, management through fire and grazing by re-introduced bison, and in comparison to pre-restoration agricultural fields and remnant prairies. Soil C:N increased with restoration age and bison, and soil pH first increased and then declined with age, although bison weakened this pattern. Bacterial richness and diversity followed a similar hump-shaped pattern as soil pH, such that the oldest restorations approached the low diversity of remnant prairies. β-diversity patterns indicated that composition in older restorations with bison resembled bison-free sites, but over time they became more distinct. In contrast, younger restorations with bison maintained unique compositions throughout the study, suggesting bison disturbances may cause a different successional trajectory. We used a novel random forest approach to identify taxa that indicate these differences, finding that they were frequently associated with bacteria that respond to grazing in other grasslands.

Aboriginal fire use: from responsible for Australia’s environmental change to a successful tool for the management of natural fires.

Article

Full-text available

Dec 2022

Detecting Ecological Traps in Human-Altered Landscapes: A Case Study of the Thick-billed Longspur Nesting in Croplands

Preprint

Full-text available

Nov 2022

Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. The thick-billed longspur (Rhynchophanes mccownii) is an obligate grassland bird whose populations have declined 4% annually during the past 50 years. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in crop fields during the breeding season suggest such fields also provide cues for habitat selection. Maladaptive selection for poor quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection but frequent human disturbance and increased exposure to weather and predators would have negative consequences for reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native sites in northeastern Montana, USA. Settlement patterns were similar across site types and occupancy ranged from 0.52 ± 0.17SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year and changes in abundance during the breeding season were associated with precipitation-driven vegetation conditions, rather than habitat type. Standardized nest density (0.19 ± 0.27SD nests/plot/hour), the number of young fledged per successful nest (2.9 ± 0.18SE), and nest survival (0.24 ± 0.03 SE; n=222 nests) were similar for crop and native sites. Collectively, the data did not support our hypothesis that crop fields are ecological traps: longspurs did not exhibit a clear preference for cropland and reproductive output was not significantly reduced. Our results indicate that crop fields provide alternative breeding habitat within a human-dominated landscape.

Potential Management Alternatives for Invaded Rangelands in the Northern Great Plains

Article

Full-text available

Jan 2010

Full Issue

Article

Jan 2022

Frank R. Thompson

Livestock production land and conservation areas play a complementary role in the conservation of a critically endangered grassland bird

Article

Full-text available

Oct 2022

In many parts of the world, livestock production and biodiversity conservation are important land uses of native grasslands in agricultural landscapes. Approaches to managing grasslands typically differ between production farms and conservation areas as they have different goals. Such differences may have consequent effects on the spatial and temporal habitat suitability for grassland fauna. In semi‐arid grasslands of south‐eastern Australia, the critically endangered Plains‐wanderer (Pedionomus torquatus) is a grassland habitat‐specialist bird that can occur on land managed for livestock production and conservation, but it is unclear if, and when, habitat suitability is affected in each land‐use type. Here, we investigate how land‐use type (livestock production, conservation) and rainfall (preceding accumulated rainfall) affect habitat suitability for the Plains‐wanderer using 11 years of bird occurrence and remotely sensed habitat structure data. We found habitat suitability for the Plains‐wanderer was driven by an interaction between land use and rainfall, with conservation areas supporting larger areas of preferred habitat structure during dry periods but less during wet periods. By contrast, Plains‐wanderers were more likely to occur on livestock production farms during wet periods. We speculate this is because higher grazing pressure on livestock production farms was able to limit biomass accumulation and, hence, maintain more areas of preferred habitat structure. Our findings show that land used for livestock production can complement conservation areas by providing preferred habitat for the Plains‐wanderer during climatic periods that promote grass growth. Furthermore, we highlight that land use and climate are important temporal drivers of grassland dynamics, and approaches to biodiversity conservation should consider how patterns of habitat suitability may shift across landscapes over time. Strategic, landscape‐scale planning and effective agri‐environmental initiatives will be critical to the future of grassland birds such as the Plains‐wanderer.

Northern Bobwhite and Fire: A Review and Synthesis

Conference Paper

Full-text available

Sep 2022

Our understanding of the relationship between northern bobwhite (Colinus virginianus; hereafter, bobwhite) and fire began with Herbert Stoddard’s work in the early 20th century. Research on the topic has continued, but our application of fire is deeply rooted in Stoddard’s work, even as it has become evident that fire regimes must be adapted to variable environmental conditions that are evolving with a changing landscape and climate. A comprehensive review and synthesis of the literature on this topic would help formalize research advancements since Stoddard and identify knowledge gaps for future research. Results from experiments suggest fire creates favorable local habitat conditions for bobwhite such as plant composition, bare ground, and plant structure. Frequent prescribed fire is closely tied to where bobwhite populations are at their greatest (e.g., Red Hills region of Georgia and Florida, USA). However, an empirical gap exists between patch-level conditions and the bobwhite-landscape ecology interface. For example, it is well established that a 2-year fire return interval in pine savanna ecosystems with fertile soil is best for bobwhite. But causal evidence is limited for areas of different soil types, precipitation, and past land use across the bobwhite range. We review the extant literature describing prescribed fire use for bobwhite management, focusing on documented effects of fire on life-history characteristics of bobwhite under different environmental conditions. Habitat outcomes of fire management depend on fire frequency, seasonality, scale, and interaction with other management, and different strategies should be employed depending on the environment and desired effects. Adaptive management strategies will be necessary to address the challenges of rising temperatures associated with a changing climate, which are likely to alter the conditions under which burns occur and increase the difficulty of meeting basic burn criteria. Positive public attitudes toward prescribed fire will be key to developing a policy and management framework that supports efficient prescribed fire application. Our review elucidates range-wide processes and patterns to better inform the site-specific application of fire.

Mapping edaphic soils' conditions to identify conservation targets for pine barren and sandplain ecosystems in New York State

Article

Full-text available

Sep 2022

Small habitat patches can be important reservoirs for biodiversity, capable of hosting unique species that are largely absent from the surrounding landscape. In cases where such patches owe their existence to the presence of particular soil types or hydrologic conditions, local-scale edaphic variables may be more effective components for models that identify patch location than regional-scale macroclimatic variables often used in habitat and species distribution models. We modeled the edaphic soil conditions that support pine barren, sandplain, and related ecosystems in New York State with the purpose of identifying potential locations for biodiversity conservation. We quantified soil percent sand and soil depth of 156 known high-quality remnant pine barren and sandplain ecosystems to calculate threshold soil characteristics. We then mapped all soils in the state that were at least as sandy and deep as the threshold values we calculated. The total area of our map of suitable soil conditions was over 9500 km2, made up of forested (57%), urban (26%), agricultural (13%), and open (4%) land covers. Our analysis nearly doubled the recognized area of barren, shrubland, and grassland habitat on deep, sandy soils in New York State. Extensive forested and even agricultural cover on these soils could also be the subject of restoration to further support the biodiversity of these unique ecosystems. The presence of extensive soils in coastal and interior New York that, with the appropriate disturbance regime, have the potential to host pine barren and sandplain ecosystems offers a new perspective on these ecosystems' distribution in the past-and about how to better align conservation and restoration to preserve the future.

Effects of Hemiparasites in Grassland Restorations Are Not Universal

Article

Full-text available

Feb 2024
Diversity

Root hemiparasites infiltrate the vascular tissue of host roots to acquire water and nutrients, which often reduces host growth. Hemiparasites are postulated to be keystone species in grassland communities if they suppress dominant species and increase plant community biodiversity, and ecosystem engineers if they increase nutrient accessibility for surrounding species. We examined keystone effects by evaluating species richness and evenness in 1 m2 plots in a recent prairie restoration where Castilleja sessiliflora was naturally present or absent, and in a longer-established prairie restoration with or without Pedicularis canadensis. We examined ecosystem engineer effects by determining nitrate and phosphate concentrations under, 25 cm from, and 50 cm from hemiparasites, and in the center of hemiparasite-free plots. On the C. sessiliflora site, plots with the hemiparasites had higher species richness due to more forbs and higher floristic quality, consistent with the keystone species hypothesis. Soil phosphate levels were also greater in plots with C. sessiliflora present, consistent with the hypothesis of ecosystem engineering by this hemiparasite. In contrast, plots with/without P. canadensis showed no associations of any community metrics with the hemiparasite, and no correspondence between the presence of hemiparasites and soil nutrients. Although hemiparasites can increase grassland community heterogeneity, the effect is not universal, and the direction and strength of effects likely depends on local conditions.

Analysis of the Cost and Cost Components of Conducting Prescribed Fires in the Great Plains

Article

Jan 2024
RANGELAND ECOL MANAG

Amorpha canescens and Andropogon gerardii Recruit Comparable Foliar Fungal Communities Across the Steep Precipitation Gradient in Kansas

Article

Nov 2023

Past and present biomass consumption by herbivores and fire across productivity gradients in North America

Article

Full-text available

Nov 2023
ENVIRON RES LETT

Herbivores and fire are important consumers of plant biomass that influence vegetation structure, nutrient cycling, and biodiversity globally. Departures from historic biomass consumption patterns due to wild herbivore losses, livestock proliferation, and altered fire regimes can have critical ecological consequences. We set out to (i) understand how consumer dominance and prevalence responded to spatial and temporal moisture gradients in Holocene North America and (ii) examine how past and present consumer dominance patterns in North America compare to less altered consumer regimes of modern Sub-Saharan Africa. We developed long-term records of bison abundance and biomass burning in Holocene midcontinent North America and compared these records to reconstructions of moisture availability and vegetation structure. We used these reconstructions to characterize bison and fire prevalence across associated moisture and vegetation gradients. We found that bison herbivory dominated biomass consumption in dry settings whereas fire dominated in wetter environments. Historical distributions of herbivory and burning in midcontinent North America resemble those of contemporary Sub-Saharan Africa, suggesting disturbance feedbacks and interactions regulate long-term consumer dynamics. Comparisons of consumer dynamics in contemporary North America with Holocene North America and Sub-Saharan Africa also reveal that fire is functionally absent from regions where it was once common, with profound ecological implications.

Growing Season Fires and Herbicide May not Be the Silver Bullet to Lespedeza cuneata Management

Article

Aug 2023
RANGELAND ECOL MANAG

Invasive species are generally managed across rangelands to achieve livestock productivity and biodiversity maintenance objectives. The invasive legume Lespedeza cuneata (Dum. Cours.) G. Don. is managed across much of the Great Plains with aerially applied herbicides that target broadleaf forbs and dormant season (late March- early April) fire. It is hypothesized that altering fire timing to the growing season or integrating late-season herbicide into fire-management may lead to more successful reduction of L. cuneata without negatively affecting rangeland plant communities. However, most of the literature outlining the effects of L. cuneata and its management is limited to small scale (< 100 m2), highly controlled studies that are not transferrable to large working rangelands. We manipulated eight large (333-766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to assess whether growing and dormant season fires, herbicide application, or the interactive effect of fire timing and herbicide reduced L. cuneata without negatively affecting broad rangeland plant composition (i.e., functional group cover) from 2019-2021. Our study was performed at two scales relevant to rangeland management: the pasture and burn patch scales. None of our treatments (i.e., fire timing, herbicide application, or the interaction of fire timing and herbicide) had a significant effect on L. cuneata canopy cover at either the pasture or patch scale. Our treatments also did not affect forb or shrub cover at the pasture or patch scales. Grass and sedge cover was significantly increased post- herbicide at the patch scale, but not at the pasture scale. Grass and sedge cover was unaffected by any other treatment at both scales considered in this study. Our results add to nearly two decades of research conducted elsewhere that pyric herbivory alone may be sufficient to manage L. cuneata and promote rangeland biodiversity in the tallgrass prairie.

The Long-Term Dynamics of Stocks of the Live Aboveground Phytomass in a Steppe Phytocoenosis after a Fire (Based on the Example of the Burtinskaya Steppe Site of the Orenburgsky Reserve)

Article

May 2023

Effect of burn season and grazing deferment on mountain big sagebrush plant communities

Article

Full-text available

May 2023
PLANT ECOL

Fire and grazing play an important role in managed rangeland ecosystems. These disturbances interact to shape plant communities and outcomes for rangeland biodiversity and livestock production. However, managers have a limited toolbox to reach vegetation management goals in shrub-steppe ecosystems. It is commonly assumed that deferring grazing for up to two growing seasons after a fire is necessary to ensure plant community recovery. We report on a 4-year long replicated experiment comparing the effects of season of fire (spring or fall) and sheep grazing deferment on sagebrush-steppe rangelands in east Idaho, USA. Deferment treatments included either no grazing for one or two growing seasons after fire, or no deferment, in which domestic sheep returned in the season after fire. We found no evidence that grazing deferment affected plant community composition in any plots compared to no grazing deferment, but deferred areas did have more litter relative to grazed areas 4 years after the fire. Burn treatment had a consistent effect on plant communities. One year after fire, spring and fall burned plots had 24 and 30% reductions in native shrub cover, respectively. After 4 years, fall and spring burned areas had moderate, statistically significant (14 and 9%, respectively) reductions in litter. Burned areas had less than 6% increases in perennial native grass cover, but no significant increases in invasive plants. The effects of fire and grazing management tools is context-dependent across climatic gradients in the sagebrush biome. At our study site, prescribed fire seasonality and grazing deferment have important economic but relatively moderate ecological implications.

The Effects of Management Practices on Grassland Birds—Dickcissel (Spiza americana)

Chapter

Full-text available

Apr 2023

Keys to Dickcissel (Spiza americana) management include providing dense, moderate-to-tall vegetation, particularly with a well-developed forb component, and moderately deep litter. Dickcissels have been reported to use grassland habitats with 4–166 centimeters (cm) average vegetation height, 6–85 cm visual obstruction reading (VOR), 11–68 percent grass cover, 1–86 percent forb cover, less than or equal to (≤) 10 percent shrub cover, less than (<) 27 percent bare ground cover, <30 percent litter cover, and ≤6 cm litter depth.

Cattle Graze Central US Milkweeds at Least as Much as Grasses, Even Under Patch-Burn-Grazing Management

Article

Mar 2023
RANGELAND ECOL MANAG

Legacy earthen berms influence vegetation and hydrologic complexity in the Altar Valley, Arizona

Article

Dec 2023

Northern Bobwhite Demographics and Resource Selection Are Explained by Prescribed Fire with Grazing and Woody Cover in Southwest Missouri

Article

Full-text available

Jan 2022

Distributed under Creative Commons CC-BY 4.0 Effects of grazing strategy on facultative grassland bird nesting on native grassland pastures of the Mid-South USA

Article

Full-text available

Sep 2022

Understanding how livestock grazing strategies of native warm season grasses (NWSG) can impact facultative grassland bird nesting can provide insight for conservation efforts. We compared pre and post treatment effects of rotational grazing (ROT) and patch-burn grazing (PBG) for facultative grassland bird species nest success and nest-site selection on NWSG pastures at three Mid-South research sites. We established 14, 9.7 ha NWSG pastures and randomly assigned each to either ROT or PBG and monitored avian nest-site selection and nest success, 2014-2016. We collected nesting and vegetation data in 2014, before treatment implementation, as an experimental pre-treatment. We implemented treatments across all research sites in spring 2015. We used a step-wise model selection framework to estimate treatment effect for ROT or PBG on avian nest daily survival rate (DSR) and resource selection function (RSF) at the temporal scale and within-field variables. Daily survival rates were 0.93% (SE = 0.006) for field sparrow (Spizella pusilla), 0.96% (SE = 0.008) for red-winged blackbird (Agelaius phoeniceus), and 0.92% (SE = 0.01) for indigo bunting (Passerina cyanea). Model support for PBG treatment and vegetation height were indicated as negative and positive influences for field sparrow DSR, respectively. Red-winged blackbirds' DSR were negatively influenced by ROT while vegetation height positively affected DSR, and DSR for indigo bunting did not differ among treatments. Combined RSF models indicated nest-site selection for all species was positively related to vegetation height and only weakly associated with other within-field variables. We provide evidence that ROT and/or PBG effects vary by species for DSR for these three facultative grassland birds, and vegetation characteristics affected their nest-site selection in the Mid-South USA. A lack of disturbance in Mid-South grasslands can lead to higher successional stages (i.e., mix shrub-grassland), but some combination of ROT, PBG, and unburned/ungrazed areas can provide adequate nesting habitat on small pasture lands (∼1.8-7.8 ha) for various facultative grassland birds and potentially offer How to cite this article Buckley BR, Lituma CM, Keyser PD, Holcomb ED, Smith R, Morgan JJ, Applegate RD. 2022. Effects of grazing strategy on facultative grassland bird nesting on native grassland pastures of the Mid-South USA. PeerJ 10:e13968 http://doi.org/10.7717/peerj.13968 the opportunity to simultaneously maintain livestock production and grassland bird nesting habitat.

The keystone role of bison in North American tallgrass prairie

Article

Full-text available

Jan 1999

The New Paradigm in Ecology: Implications for Conservation Biology Above the Species Level

Chapter

Full-text available

Jan 1992

Conservation biology has traditionally focused on the fine scale and the species level of biological organization (Soulé and Wilcox 1980), and biotic conservation is only one of the various goals that has directed the preservation and management of natural areas and resources. Resource management goals have largely been utilitarian or commercial, such as the maintenance of large areas for watersheds; preservation of marshes, bogs, and seasonal wetlands for flood water storage, nursery areas, and flow continuity in river systems, and the sustained yield of forests, fisheries, and wildlife (Temple et al. 1988; Aplet, Laven, and Fiedler in press). There have, however, been both practically and theoretically motivated calls for widening the focus to include scales beyond that of the individual site and levels of organization above that of the species (Soulé 1989; Western 1989) to approach new goals. This essay will explore the relationship of this new frontier for conservation biology to advances in ecology. Much of the new ecological focus of conservation biology is driven by the shift in the overarching paradigm of ecology itself. We begin by defining the concept of paradigm and characterizing the classical paradigm of ecology. The classical paradigm had definite implications for conservation, and these are shown to be problematical. Therefore, we outline the contemporary paradigm in ecology and show how the science of ecology has been affected by the shift in paradigm.

Habitat Structure, Patchiness, and Avian Communities in North American Steppe Vegetation: A Multivariate Analysis

Article

Full-text available

Oct 1980

We investigate the relationships between vegetational structure, spatial heterogeneity, avian community structure, and the ecological responses of the breeding bird populations in the structurally simple steppe vegetation of North America. We examined the effect of variation in several measures of both horizontal and vertical patchiness in vegetation distribution on bird distribution and abundance, then integrated these measures into a smaller subset of variables using Principal Component Analysis (PCA). We interpreted the new PCA variables as reflective of proximate niche parameters to which bird species responded. Out of 550 structure/bird abundance bivariate correlations, 18.5% achieved a significant level of at least P

Fire and Grazing in the Tallgrass Prairie: Contingent Effects on Nitrogen Budgets

Article

Full-text available

Aug 1991

Fire and grazing occur together in many of the world's grasslands, but their effects on nutrient cycling have usually been studied as if they acted separately. We hypothesized that grazing by large herbivores results in conservation of nitrogen that would otherwise be lost from burned grasslands. We tested this hypothesis in a series of experiments on burned and unburned tallgrass prairie grazed by cattle. We manipulated grazing using exclosures and mowing. Combustion losses of N from ungrazed plots (1.8 g@?m^-^2@?yr^-^1) burned in the spring were double those from similarly burned, grazed plots (0.9 g@?m^-^2@?yr^-^1). These losses represented about half of the preburn, aboveground stocks of N. The magnitude of N loss was proportional to the standing crop biomass available for combustion. Fire temperatures and energy release were reduced by grazing. We used mowing to simulate locally heavy grazing in patches. In the absence of burning, mowing patches increased the likelihood that a patch would be regrazed and caused persistent reductions in the residual biomass remaining in a patch at the end of the growing season. Mowing did not influence patch utilization or residual biomass when pastures were burned. Thus, the effects of fire on grassland N budgets were modified by grazing, and the effects of grazing on the patch structure of grasslands were modified by fire. We conclude that accurately predicting volatile losses of nutrients from grassland ecosystems resulting from biomass burning may depend on understanding effects of grazing.

Interactive Effects of Fire, Bison (Bison bison) Grazing and Plant Community Composition in Tallgrass Prairie

Article

Full-text available

Jan 1993

Fire and native large herbivore grazing were two important influences on the structure and function of North American grasslands. In 1988 and 1989 the influence of fire regime on grazing patterns of North American bison (Bison bison) was studied on the Konza Prairie in northeastern Kansas. Bison grazing was spatially and temporally nonrandom and was influenced by fire regime and local plant community composition. During the growing season, bison were observed up to 3 x more frequently than expected on watersheds burned in the spring. Summer grazing was concentrated in large watershed areas (79-119 ha) dominated by warm-season, perennial, C4 grasses. During the autumn and winter, bison grazed both burned and unburned watersheds more uniformly but grazed most intensively in areas with large stands of cool-season, C3 grasses. On a smaller spatial scale (5-10 m2), bison selected patches during the growing season with low forb cover dominated by the perennial C4 grass, Andropogon gerardii. Grazed patches were larger on frequently burned than on infrequently burned watersheds. The importance of fire history in determining patterns of bison grazing over the landscape indicates that interactions between bison grazing and fire regime may be important to the composition and spatial heterogeneity of tallgrass prairie vegetation.

The Keystone Role of Bison in North American Tallgrass Prairie

Article

Full-text available

Jan 1999

Disturbance Frequency and Community Stability in Native Tallgrass Prairie

Article

Full-text available

Mar 2000

Scott Collins

frequency. A modified time series analysis indicated that plant communities were undergoing directional change (unstable) on all watersheds, regardless of fire frequency. Contrary to expectations, directional change was greatest on the annually burned sites and lowest on the infrequently burned sites. Unlike the plant communities, breeding bird, grasshopper, and small mammal communities were temporally stable, despite high-compositional variability from 1 yr to the next. Stability among the consumer communities within these dynamic plant communities occurs because three-dimensional vegetation structure does not change over time, despite changes in plant species composition. Evidence suggests that instability in the plant community results from strong biotic interactions among temporally persistent core species and stochastic dynamics among infrequent satellite species. Overall, community stability cannot be assessed if the pattern of temporal dynamics is unknown. Long-term empirical studies of different taxa under different disturbance regimes are needed to determine over what time frames and spatial scales communities may be stable. Such studies are essential for the development of generalities regarding the relationship between disturbance frequency and community stability in terrestrial and aquatic systems.

Botanical Composition of Bison Diets on Tallgrass Prairie in Oklahoma

Article

Full-text available

Jul 1998

Diets of bison (Bison bison L.) were examined using microbii-tological fecal analysis in a 2-yr study on a tallgrass prairie site in northcentral Oklahoma. Graminoids comprised at least 98% of the diet across all seasons. Bin showed strong feeding selectivi-ty; grasses and sedges formed a significantly higher proportion of diets than was generally available in herbage on the landscape. Bin avoided forbs, which were 5 2 40 of the diet. Sedges were a large (17-4440) diet component in winter and spring but decreased substaintially during summer and fall (11-162). These changes in sedge use corresponded to seasonal variation in sedge availability. Our results confii that bison are primarily grazers in prairie habitats, potentially having a sign&ant role in shaping structure and function of tallgrass prairie.

Effects of Prescribed Fire on Sand Shinnery Oak Communities

Article

Full-text available

Nov 2001

Sand shinnery oak (Quercus havardii Rydb.) communities are shrublands extending from northern Texas and western Oklahoma southward into the Chihuahuan Desert. They are dominated by sand shinnery oak, a member of the white oak group. Structure and composition of sand shinnery oak communities in relation to natural disturbances, such as fire, have not been adequately investigated. The objectives of this study were to determine the influence of fire on shrub composition and vegetation structure of sand shinnery oak communities, and to determine the persistence of structural and compositional changes. Data were collected on Black Kettle National Grassland (BKNG) in western Oklahoma during the growing seasons of 1998 and 1999. Vegetation measurements included line transects, visual obstructions, heights, cone of vulnerabilities, shrub patch sizes, and shrub patch densities were used to estimate functional group canopy cover, shrub composition, and structure of sand shinnery oak communities. One growing season after fire, burned sand shinnery oak communities had significantly less shrub cover (P

Evaluation of Habitat Structural Measures in a Shrubland Community

Article

Full-text available

Sep 2002

Accurate and efficient monitoring of habitat structure on rangelands is important for understanding wildlife responses to land management practices. Unfortunately, studies of wildlife responses to changes in habitat structure often use monitoring techniques that fail to measure variation in multiple structural dimensions. Our objectives were to evaluate relationships between measures of habitat structure in a shrubland community and to discuss the usefulness of several techniques in integrating multiple structural dimensions into a single index of habitat structure. We evaluated relationships between shrub cover, herbaceous cover, shrub patch number, average shrub patch size, average vegetation height, visual obstruction across multiple strata of a profile board, cone of vulnerability, and angle of obstruction using a principle component analysis. Many of these variables were redundant with each other. Average visual obstruction estimates, using a profile board, were associated with variability in vertical structure as indicated by its association with height. Coefficients of variation for cone of vulnerability and visual obstruction were dependent upon their means and of limited use in describing horizontal patchiness. In contrast, shrub patch number was not linearly correlated with any other single measure in our analysis, and may be useful in describing horizontal patchiness. Cone of vulnerability and angle of obstruction are recently developed techniques that provided useful, single indices of multidimensional habitat structure. Efficient monitoring of wildlife habitat structure should employ multiple, independent techniques that measure distinct dimensions of habitat structure or a single measure that integrates multiple dimensions.

Bison Grazing Patterns on Seasonally Burned Tallgrass Prairie

Article

Full-text available

May 1998

Patterns of bison (Bison bison L.) grazing were examined in a 2-year study on a tallgrass prairie site in Oklahoma subjected to a seasonally and spatially variable burning regime. Mixed groups of bison, composed of cows, yearlings, calves, and young (< 5 years of age) bulls, comprised 90% of the study population and showed selectivity by using burned areas significantly more than expected 23 % of the time. Mixed groups avoided unburned areas 63% of the time. In contrast, bull groups of mature bulls > 5 years of age selected unburned areas for grazing 29% of the time and burned areas only 4% of the time. Temporal patterns in bison grazing were evident; selective use of burns persisted for only a short period during the first post-fire growing season, after which burns were grazed in proportion to availability and then selectively avoided as bison shifted grazing efforts to newer burns. Regression analysis verified that bison grazing was negatively related to burn age. Regression also showed that grazing patterns were positively related to burn patch size. Although burn types varied significantly in biomass and overall vegetative composition, bison exhibited only limited preference for any burn type, choosing those with higher relative cover of annual Bromus spp. and sedges. It appears that bison select recently burned areas with relatively low graminoid biomass for grazing, presumably choosing these areas based on forage quality rather than quantity.

The dynamics of a Mitchell grass (Astrebla spp.) rangeland on the Barkly Tableland, Northern Territory

Article

Full-text available

Jan 1984

The response of an area of Astrebla grassland at Helen Springs Station on the Barkly Tableland to the treatments of exclosure and distance from water were studied from 1974 to 1979. The seasonal effect produced by a number of above average rainfall years was greater than the effects of exclosure and distance from water. The total standing biomass varied from 940 kg hdl in 1974 to 2258 kg ha-' in 1979. Both Aristida latifolia and Astrebla pectinata increased in standing biomass and basal cover while the annual Iseilema vaginiflorunz decreased. Apparent responses of some species to the distance from water treatment were explained by local vegetation patterning within a seemingly uniform grassland. Regression relationships were developed that related basal cover to both species and total plant standing biomass.

Fire Frequency and Community Heterogeneity in Tallgrass Prairie Vegetation

Article

Full-text available

Dec 1992

Scott Collins

Few studies have directly addressed the effects of disturbance on spatial and temporal heterogeneity. Spatial heterogeneity is the degree of dissimilarity in species composition from one point to another in a community, whereas temporal heterogeneity is compositional change within a site over time. The purposes of this study were to determine (1) if a quadratic relationship exists between within-site heterogeneity and disturbance frequency as predicted by the intermediate disturbance hypothesis (IDH), (2) if disturbed and undisturbed sites have similar heterogeneity as implied by the disturbance heterogeneity hypothesis (DHM), and whether or not these results differed with scale, and (3) if there is a relationship between spatial and temporal heterogeneity as implied by the DHM. Analyses were based on plant species composition data collected over 9 yr in quadrats permanently located in experimental management units subjected to different burning frequencies at Konza Prairie Research Natural Area, Kansas, USA. The relationship between disturbance frequency and within-site heterogeneity was opposite that predicted by the IDH. Heterogeneity was lowest at intermediate disturbance frequencies. Heterogeneity in annually burned prairie was lower than in unburned prairie and prairies burned once every 4 yr in contrast to predictions of the DHM. However, this relationship did not hold at larger spatial scales. There was a positive relationship between within-site spatial and temporal heterogeneity on annually burned sites, sites burned once every 4 yr, and nearly so on sites burned every other year. Within-site heterogeneity was negatively correlated with cover of Andropogon gerardii, and positively correlated with total richness and species diversity. Studies of variation, in addition to averages, will increase our ability to predict patterns of species distribution and abundance within and between communities in response to disturbance.

Viewpoint: The Response of Central North American Prairies to Seasonal Fire

Article

Full-text available

Jan 2001

Natural fires on the native grasslands of Oklahoma and Kansas were important for maintaining ecosystem structure and function. Today, land managers largely conduct prescribed fires in the late dormant season or they do not burn at all. When wild- fires occur in other seasons, conventional wisdom assumes that desirable forage species for cattle are compromised. This assumption is based on a few fire studies limited in breadth and scope. To address this, we revisited numerous data sets to quanti- fy the influence of season of fire on plant production and species composition. Research demonstrates that tallgrass prairie burned in the late spring starts growth earlier, grows more rapidly early in the growing season, and produces more tall grasses than unburned prairie. We contrast this response with the literature reporting the results of fire occurring in other sea- sons. Fire effects vary with fire frequency, fire-return interval, grazing history, herbicide use, successional stage, weather pat- tern, edaphic features, and topography. Our review of research suggests that a variety of responses to fire season are possible and rules-of-thumb that generalize responses are misleading. Most of the research on fire also does not report the interaction of fire and herbivory. Thus it is difficult to judge the influence of fire within the context of herbivory. Results from ongoing research suggest that the prairie is far more resilient under the interaction of fire and herbivory than earlier believed.

Plant Community Responses to Short Duration Grazing in Tallgrass Prairie

Article

Full-text available

Mar 1991
RANGELAND ECOL MANAG

A key to management of short duration grazing systems is maintaining proper rest periods for individual pastures, but information on the necessary length of rest periods for tallgrass prairie is limited. Research hypotheses for this study were that tallgrass prairie plant communities would respond differently to grazing schedules incorporating rest periods of varying lengths and that this response would be dependent on stocking rate. Treatments consisted of 3 grazing schedules (2, 3, or 4 rotation cycles per 152 day grazing season) and 2 stocking rates (1.6 and 2.2 times the moderate continuous rate). Plant frequency, standing crop, species composition, and forage utilization were sampled from 1985 to 1989. Precipitation was above average in 4 of the 5 study years. Grazing schedule did not affect any vegetation parameter overtime. Stocking rate did not affect plant frequency or species composition. Standing crop was reduced and forage utilization increased at the higher stocking rate but these effects were consistent over time. Frequency of western ragweed [Ambrosia psilostachya DC.] and the relative species composition of the forb component increased in all grazed pastures compared to ungrazed pastures. The overall lack of major treatment effects was attributed to favorable precipitation, spring burning, and the initial high-seral successional stage of the experimental pastures.

Interannual Variability in Primary Production in Tallgrass Prairie: Climate, Soil Moisture, Topographic Position, and Fire as Determinants of Aboveground Biomass

Article

Full-text available

Aug 1995

From 1975 to 1993, aboveground net primary production (NPP) at the Konza Prairie Research Natural Area in NE Kansas varied from 179 g/m(2) to 756 g/m(2). Across a variety of sites, NPP was significantly related to precipitation (r(2) = 0.37), but much variability was unexplained. Thus, we evaluated the relationship between NPP with meteorological variables and soil moisture measurements in tallgrass prairie sites that varied in fire frequency and topographic position. Annually burned lowland sites had significantly higher NPP than either annually burned upland or unburned sites. NPP in burned sites was more strongly related to meteorological variables and soil moisture when compared to unburned sites. The lack of significant correlation between soil moisture with NPP on unburned sites suggests that factors other than water availability limit production in these sites. When NPP data were analyzed separately by life forms, interannual variability in forb NPP was not correlated with any meteorological variables, but was negatively correlated with grass NPP (r = -0.49). The inability of a single factor, such as precipitation to explain a large portion of the interannual variability in NPP is consistent with the concept that patterns of NPP in tallgrass prairie are a product of spatial and temporal variability in light, water, and nutrients, driven by a combination of topography, fire history, and climate.

Integrating Landscape Ecology Into Natural Resource Management

Book

Full-text available

Aug 2002

To achieve sustainable resource management, it is essential to obtain insightful guidance from emerging disciplines such as landscape ecology. This text addresses the links between landscape ecology and natural resource management, discussing these links in the context of various landscape types, diverse sets of resources, and broad ranges of management issues. A large number of landscape ecology concepts, principles, and methods are introduced. Critical reviews of past management practices and a number of case studies are presented. The text provides many guidelines for managing natural resources from a landscape perspective and offers useful suggestions for landscape ecologists to carry out research relevant to natural resource management.

Avifaunal and habitat changes resulting from conversion of native prairie to crested wheat grass: Patterns at songbird community and species levels

Article

Full-text available

May 1998
CAN J ZOOL

Many North American grassland songbirds are experiencing significant population declines, partly because of land-use practices associated with agricultural activity. The aim of this study was to compare the habitat correlates of songbirds breeding in native mixed-grass prairie with patterns found in introduced vegetation dominated by crested wheat grass (Agropyron pectiniforme). We assessed plant species composition, habitat structure, and bird species diversity over 2 years to document species- and community-level trends in southwestern Saskatchewan, Canada. In addition to having higher plant species richness and diversity, native vegetation consisted of significantly more grass and sedge cover, less bare ground, deeper litter, and higher density within 10 cm of the ground than introduced vegetation. Bird species richness and diversity and the abundance of Baird's Sparrows (Ammodramus bairdii) and Savannah Sparrows (Passerculus sandwichensis) increased significantly along a multivariate gradient from open to more sheltered habitat, regardless of vegetation type. Sprague's Pipits (Anthus spragueii) showed a curvilinear increase along the same gradient, occurring in high numbers where habitats offered an intermediate level of cover. Our findings suggest that species richness and diversity within songbird communities and the abundance of some species may be reduced where conversion to crested wheat grass results in more open habitat.

Restoring Heterogeneity on Rangelands: Ecosystem Management Based on Evolutionary Grazing Patterns

Article

Full-text available

Sep 2009

Samuel D. Fuhlendorf

The relative importance of cattle grazing in sub-tropical grasslands—does it reduce or enhance plant biodiversity? J Appl Ecol

Article

Full-text available

Jun 2003
J APPL ECOL

Livestock grazing enterprises have potentially threatening effects on the conservation of plants in grassy subtropical eucalypt woodlands. Commercial levels of grazing could cause local extinctions of sensitive native species and/or reductions in abundance and species richness in native pastures. We studied the nature of grazing impacts on the diversity and composition of herbaceous plants and used a natural experiment to analyse the effects of disturbances (cattle grazing, soil disturbance, water enrichment) and environment (lithology, slope position, presence of trees) on plant community composition in eastern Australia. We sampled pastures and reserves at 191 sites over an area of 3000 ha. Canonical correspondence analysis (CCA) was used to explore the relative importance of disturbance and environment in accounting for floristic variation and to examine individual species responses. From individual responses, we identified seven response groups relating to grazing. The factors analysed explained small but significant amounts of floristic variation, and there were interactions between soil disturbance, water enrichment and grazing. We explored the hypothesis that grazing increased species density at small scales but decreased it at landscape scales, due to the elimination of grazing‐sensitive species. Our data did not support the hypothesis, as there were similar numbers of species that increase with grazing (increasers) and species that decline with increasing grazing (decreasers) in the assemblage. However, there were more native decreasers and more exotic increasers in the assemblage. Synthesis and applications. For land managers to retain plant diversity on grazed landscapes, it would be desirable to provide all levels of grazing pressure across the landscape, including areas protected from livestock grazing. This would apply to all plant communities where both grazing increasers and decreasers are present. Extensive areas supporting grassland with a tall tussock structure that is selectively grazed are most important, as all plant response groups have some representation and ecosystem function is retained under moderate grazing. In terms of regional conservation planning, the protection and enlargement of areas protected from livestock grazing is important in the study area, as these occur on only about 4% of the landscape and are threatened by on‐going disturbances and land‐use intensification.

Vegetation dynamics on rangelands: A critique of the current paradigms

Article

Full-text available

Aug 2003

Rangeland ecologists have been debating the validity of two current paradigms for the evaluation of vegetation dynamics on rangelands. This debate frequently contrasts the conventional model of continuous and reversible vegetation dynamics (range model) with a more contemporary model that can accommodate discontinuous and non‐reversible vegetation change (state‐and‐transition model). The range and the state‐and‐transition models are conceptually related to the equilibrium and non‐equilibrium paradigms within ecology, respectively. The methodological dichotomy that has developed between the range and the state‐and‐transition models has fostered the perception that these two ecological paradigms are mutually exclusive. We challenge this perception and contend that both methodologies and their corresponding paradigms are non‐exclusive. Equilibrium and non‐equilibrium ecosystems are not distinguished on the basis of unique processes or functions, but rather by the evaluation of system dynamics at various temporal and spatial scales. Consequently, ecosystems may express both equilibrium and non‐equilibrium dynamics. This confirms early interpretations that ecosystems are distributed along a continuum from equilibrium to non‐equilibrium states. Although both equilibrium and non‐equilibrium dynamics occur in numerous ecosystems, the empirical evidence is frequently confounded by (i) uncertainty regarding the appropriate evidence necessary to distinguish between paradigms; (ii) disproportionate responses among vegetation attributes to climate and grazing; (iii) comparisons among systems with varying degrees of managerial involvement; and (iv) the evaluation of vegetation dynamics at various spatial and temporal scales. Synthesis and applications . This critique supports the conclusion that a paradigm shift has not taken place in rangeland ecology, but rather, the debate has forced a more comprehensive interpretation of vegetation dynamics along the entirety of the equilibrium–non‐equilibrium continuum. Therefore, the rangeland debate should be redirected from the dichotomy between paradigms to one of paradigm integration.

The impact of cattle ranching on large-scale vegetation patterns in a coastal savanna in Tanzania

Article

Full-text available

Jun 2003
J APPL ECOL

The success of large‐scale cattle ranching in African savanna vegetation has often been limited by problems of bush encroachment and disease (in particular trypanosomiasis spread by tsetse flies). Mkwaja Ranch, occupying an area of 462 km ² on the coast of Tanzania, is a recent example of a large ranching enterprise that failed within the savanna environment. It was closed in 2000 after 48 years of operation. In this paper we describe the main vegetation types of the area (excluding closed forest vegetation) and relate their patterns of distribution to the former use of the ranch for cattle. The study area comprised the former ranch and parts of the adjacent Saadani Game Reserve, which had not been grazed by cattle for many years and had never been used for large‐scale ranching. Following field surveys, 15 distinct types of grassland and bush vegetation were defined and a vegetation map was created using a Landsat TM satellite image. A multispectral classification using the maximum likelihood algorithm gave good results and enabled all 15 vegetation types to be distinguished on the map. Two main spatial trends were detected in the vegetation. One was a large‐scale decrease in the cover of bushland from the most intensively used parts of the ranch through more extensively used areas to the game reserve; this trend was attributed to differences in management history as well as to climatic and topographic factors. A second trend was a radial vegetation pattern associated with the enclosures where cattle were herded at night. High amounts of three bushland types [dominated by (i) Acacia zanzibarica , (ii) Dichrostachys cinerea , Acacia nilotica or Acacia mellifera and (iii) Terminalia spinosa ] occurred in a zone between 300 and 2500 m from the paddocks, with a peak in bush density at about 900 m (mean value for 18 paddocks). In contrast, bushland dominated by Hyphaene compressa was scarce close to the paddocks and became more abundant with distance. There was also a radial trend in the grassland communities: close to the paddocks there was short grass vegetation containing many ruderals and invasive weedy species, while the tall grassland types with species such as Hyperthelia dissoluta and Cymbopogon caesius occurred further away in the areas less affected by cattle. Synthesis and applications. The intensive modern livestock ranching as practised on Mkwaja Ranch proved to be unsustainable both economically and ecologically. In the end, the biggest problem faced by the ranch managers was not controlling disease, as had originally been feared, but preventing the spread of bush on pasture land. The results of our study demonstrate just how severe the problem of bush encroachment was, especially in areas close to paddocks. An important lesson for management is that grazing patterns need to be taken into consideration when determining the sustainable stocking rate for an area. To reduce the risk of bush encroachment in grazing systems with focal points such as paddocks or watering points, stocking rates need to be lower than in systems with a more uniform grazing distribution.

Grasslands, grazing and biodiversity: Editors' introduction

Article

Full-text available

Dec 2001
J APPL ECOL

Natural, semi‐natural and artificial grasslands occur extensively around the globe, but successful management for production and biodiversity poses several dilemmas for conservationists and farmland managers. Deriving from three continents (Africa, Australia and Europe), papers in this Special Profile interface three specific issues: plant responses to grazing, plant invasions and the responses to management of valued grassland biota. Although pivotal in grassland management, plant responses to grazing are sometimes difficult to predict. Two alternative approaches are presented here. The first uses natural variations in sheep grazing around a water hole to model the dynamic population response of a chenopod shrub. The second analyses a long‐term grazing experiment to investigate the links between plant traits and grazing response. Linked often crucially with grazing, but also driven sometimes by extrinsic factors, invasions are often cause for concern in grassland management. The invasions of grasslands by woody plants threatens grassland habitats while the invasions of pastures by alien weeds reduces pasture productivity. The papers in this section highlight how a complementary range of management activities can reduce the abundance of invaders. A final paper highlights how global environmental change is presenting new circumstances in which grassland invasion can occur. The impact of grassland management on biodiversity is explored in this Special Profile with specific reference to invertebrates, increasingly recognized both for the intrinsic conservation value of many groups and for their role in ecosystem processes. The potential for manipulating flooding in wet grasslands to increase the soil invertebrate prey of wading birds is illustrated, together with the roles of management and landscape structure in enhancing insect diversity. In the face of climate change and growing demands for agricultural productivity, future pressures on grassland ecosystems will intensify. In this system in which productivity and conservation are so closely bound, there is a need both to raise the profile of the issues involved, and to improve our understanding of the applied ecology required for successful management.

Scaling effects of grazing in a semi-arid savanna

Article

Full-text available

Oct 1999
J VEG SCI

Previous studies have demonstrated relationships between spatial scale and spatial pattern and developed general hypotheses of scaling effects. Few studies, however, have examined the interactive relationship between scale and pattern-driving processes such as grazing. The goal of this study is to evaluate scale-dependent patterns across three spatial scales for three grazing intensities over 45 yr and to identify some mechanisms that may be associated with scale related differences. Correlation analysis and analysis of the coefficients of variation indicate that the relationships between units are dependent upon spatial scale and treatment. Across all grazing treatments, the relationship between units of the same scale becomes stronger as the spatial scale is increased. However, the rate of increase in the correlation coefficient is different for each treatment. The coefficient of variation responded inversely across scales with the greatest variation between small-scale units and little difference between the intermediate- and large scales. In addition to different relationships between units at each scale, differences in heterogeneity within treatments over time is illustrated by the relationship between small-scale units within each treatment and their associated larger scale units. The strongest relationship occurred in the heavily grazed treatments where correlation coefficients of small-scale units with intermediate- and large-scale units were ca. 0.60, indicating similar dynamics across scales. For the moderately grazed and ungrazed treatments this relationship varied from 0.40 to 0.47.

Effects of seasonal fire, bison grazing and climatic variation on tallgrass prairie vegetation

Article

Full-text available

Dec 1998

We used univariate and multivariate techniques to evaluate vegetation-environment relationships for plant functional groups on a tallgrass prairie site in northern Oklahoma, USA burned seasonally and grazed by bison (Bison bison L.). The objective of the study was to identify important environmental variables associated with variation in residual aboveground standing crop (phytomass) and abundance of plant functional groups. Phytomass was predictably linked to season, with highest levels found in the latter portion of the growing season when the warm-season tallgrasses that dominated the site were most actively growing. When the effects of seasonal phenology were removed, stepwise regression revealed that phytomass variation was best explained by year-to-year climatic variation, seasonal burn type, and bison grazing. Phytomass was negatively related to bison grazing under all conditions. A number of plant functional groups responded to individual environmental variables: relative abundance levels of tallgrasses, little bluestem, annual grasses, forbs and legumes all varied with burn season; little bluestem, annual grasses, and sedges varied by topoedaphic position, while forbs exhibited a positive relationship with bison grazing intensity. Canonical Correspondence Analysis (CCA) was used to directly relate composition patterns of functional groups to environmental variables. CCA bi-plot of the ordination revealed that annual grasses were most closely associated with summer fires; sedges were associated with fall burns and the 1995 sampling year; legumes associated with a gradient representing the length of time since fire; while tallgrasses and little bluestem ordinated nearest a gradient representing bison grazing. Forbs and perennial grasses did not clearly associate with any particular environmental gradient, suggesting they were either simultaneously affected by several parameters or that environmental attributes important to these groups were not measured. Total phytomass and sedges were strongly influenced by yearly climatic variation. Relative abundance of some plant functional groups was principally determined by a single factor, while others were equally influenced by a suite of environmental interactions.

Spatial organisation of landscapes and its function in semi-arid woodlands, Australia

Article

Full-text available

Feb 1995

The spatial organisation of three major landscape types within the semi-arid woodlands of eastern Australia was studied by a detailed analysis of gradient-oriented transects (gradsects). The aim was to characterise the spatial organisation of each landscape, and to account for that organisation in functional terms related to the differential concentration of scarce resources by identifiable processes. Terrain, vegetation and soils data were collected along each gradsect. Boundary analysis was used to identify the types of landscape units at a range of scales. Soil analyses were used to determine the degree of differential concentration of nutrients within these units, and to infer the role of fluvial and aeolian processes in maintaining them. All three major landscape systems were found to be highly organised systems with distinctive resource-rich units or patches separated by more open, resource-poor zones. At the largest scale, distinct groves of trees were separated by open intergroves. At smaller-scales, individual trees, large shrubs, clumps of shrubs, fallen logs and clumps of grasses constituted discrete patches dispersed across the landscape. Our soil analyses confirmed that these patches act as sinks by filtering and concentrating nutrients lost from source areas (e.g., intergroves). We suggest that fluvial runoff-runon and aeolian saltation-deposition are the physical processes involved in these concentration effects, and in building and maintaining patches; biological activities also maintain patches. This organisation of patches as dispersed resource filters (at different scales) has the overall function of conserving limited resources within semi-arid landscape systems. Understanding the role of landscape patchiness in conserving scarce resources has important implications for managing these landscapes for sustainable land use, and for the rehabilitation of landscapes already degraded.

From Balance of Nature to Hierarchical Patch Dynamics: A Paradigm Shift in Ecology

Article

Full-text available

Dec 1995

A common assumption historically in ecology is evident in the term Balance of nature. '' The phrase usually implies that undisturbed nature is ordered and harmonious, and that ecological systems return to a previous equilibrium after disturbances. The more recent concepts of point equilibrium and static stability, which characterize the classical equilibrium paradigm in ecology, are traceable to the assumptions implicit in ''balance of nature. '' The classical equilibrium view, however, has failed not only because equilibrium conditions are ran in nature, but also because of our part inability to incorporate heterogeneity and scale multiplicity into our quantitative expressions for stability. The theories and models built around these equilibrium and stability principles have misrepresented the foundations of resource management, nature conservation, and environmental protection. In this paper, we synthesize recent developments that advance our understandings of equilibrium vs. nonequilibrium, homogen

Integrating landscape structure and scale into natural resource management

Chapter

Aug 2002

The rapidly increasing global population has dramatically increased the demands for natural resources and has caused significant changes in quantity and quality of natural resources. To achieve sustainable resource management, it is essential to obtain insightful guidance from emerging disciplines such as landscape ecology. This text addresses the links between landscape ecology and natural resource management. These links are discussed in the context of various landscape types, a diverse set of resources and a wide range of management issues. A large number of landscape ecology concepts, principles and methods are introduced. Critical reviews of past management practices and a number of case studies are presented. This text provides many guidelines for managing natural resources from a landscape perspective and offers useful suggestions for landscape ecologists to carry out research relevant to natural resource management. In addition, it will be an ideal supplemental text for graduate and advanced undergraduate ecology courses.

25. On Understanding a Non-Equilibrium World: Myth and Reality in Community Patterns and Processes

Chapter

Dec 1984

John A. Wiens

I nterannual variability in primary production in tallgrass prairie: climate, soil moisture, topographic position, and fire as determinants of aboveground biomass

Article

Aug 1995

From 1975 to 1993, aboveground net primary production (NPP) at the Konza Prairie Research Natural Area in NE Kansas varied from 179 g/m to 756 g/m. Across a variety of sites, NPP was significantly related to precipitation (r = 0.37), but much variability was unexplained. Thus, we evaluated the relationship between NPP with meteorological variables and soil moisture measurements in tallgrass prairie sites that varied in fire frequency and topographic position. Annually burned lowland sites had significantly higher NPP than either annually burned upland or unbumed sites. NPP in burned sites was more strongly related to meteorological variables and soil moisture when compared to unbumed sites. The lack of significant correlation between soil moisture with NPP on unbumed sites suggests that factors other than water availability limit production in these sites. When NPP data were analyzed separately by life forms, interannual variability in forb NPP was not correlated with any meteorological variables, but was negatively correlated with grass NPP (r = -0.49). The inability of a single factor, such as precipitation to explain a large portion of the interannual variability in NPP is consistent with the concept that patterns of NPP in tallgrass prairie are a product of spatial and temporal variability in light, water, and nutrients, driven by a combination of topography, fire history, and climate.

Integrating landscape structure and scale into natural resource management

Article

Jan 2002

The Emerging Role of Patchiness in Conservation Biology

Chapter

Jan 1997

John Wiens

Ecology provides the scientific foundations of conservation biology. Two ecological views of patchiness are particularly relevant to placing conservation issues in a spatial context. Metapopulation models consider the dynamics of populations in patchy environments, especially metapopulation persistence in the face of local extinctions. Several conditions underlie such persistence, and conservation biologists should determine whether these conditions are likely to hold before applying metapopulation theory to particular situations. Landscape ecology emphasizes the structure of spatial mosaics, drawing attention to the effects of variations in patch quality, boundary influences, patch surroundings, and connectivity among patches. The interaction of the spatial structure of the mosaic with the responses of organisms to that structure determines the scale and spatial patterns of ecological patterns and processes. Whether these complex features of patchiness must always be considered depends on the questions asked, the level of resolution desired, and the spatial patterns and dynamics themselves. Changes in spatial patterns, such as those accompanying habitat fragmentation, may have threshold effects on populations. Knowing when the spatial arrangement of a mosaic is more important than the amount of habitat present requires an understanding of such thresholds, which may be strongly influenced by the movement of organisms. To overcome the traditional focus in conservation biology on simple patch-matrix or island-mainland conceptualizations of patchiness, greater attention must be given to complex landscape mosaics and their effects. Progress in this area requires better landscape theory and better empirical information on how organisms move and scale environmental patchiness.

Defining the Scientific Issues

Chapter

Jan 1997

This chapter introduces the problems with which the book deals and lays out the structure of the analysis. We introduce the needs, both scientific and practical, for developing a new theory of conservation. Such a theory will have both empirical and conceptual aspects. The structure and content of this new theory must recognize both the internal needs of the science—objectivity, completeness, integration, and as a guide for future research—and the political reality and variety of motivations for the practice of conservation.

Managing for Heterogeneity and Complexity on Dynamic Landscapes

Chapter

Jan 1997

Norman L. Christensen

If spatial and temporal heterogeneity and complexity are critical elements in the function of ecosystems, then it is important that the processes that maintain such heterogeneity and complexity be maintained, even managed. Such processes are often highly variable and unpredictable in their frequency, intensity, and spatial behavior. This variability presents challenges in setting management objectives, developing and executing management protocols and techniques, and evaluating their success. I have three general messages to convey in this chapter. First, heterogeneity, complexity, and diversity are critical elements to sustained ecosystem function. Natural and, for that matter, human disturbances and the successional processes that derive from them are a critical component of that heterogeneity and complexity. Second, we have created a world in which human influences on and the manipulation and management of natural disturbance and ecological change are ubiquitous and inevitable. Finally, management requires explicit operational goals (Rogers, this volume), the means to know whether management interventions (or lack thereof) are achieving those goals, and the institutional structures that can and will adjust and adapt management techniques and protocols if they are not, or move the goalposts if new data or information suggest that we should. To set a framework for discussion I first review a few basic elements of ecosystem management. Second, I consider, as a case study, the challenges posed by the management of natural disturbance in wilderness or wildlands. Finally, I consider how, or if, we can know we are managing it right.

Spatial organisation of landscapes and its function in semi-arid woodlands, Australia

Article

Jan 1995

Effects of Bison Grazing, Fire, and Topography on Floristic Diversity in Tallgrass Prairie

Article

Sep 1996

Grazed and ungrazed sites subjected to different fire frequencies were sampled on the Konza Prairie Research Natural Area in northeast Kansas after 4 years of bison grazing (1987-1991). The objective was to study effects of bison grazing on plant species composition and diversity components (plant species richness, equitability, and spatial heterogeneity) in sites of contrasting fire frequency. Cover and frequency of cool-season graminoids (e.g. Poa pratensis L., Agropyron smithii Rydb., Carex spp.) and some forbs (e.g. Aster ericoides [A. Gray] Howell, and Oxalis stricta L.) were consistently higher in sites grazed by bison than in ungrazed exclosures, whereas the dominant warm-season grasses (Andropogon gerardii Vitman, Sorghastrum nutans [L.] Nash, Panicurn virgatum L., Schizachyrium scoparium [Michx.] Nash) and other forbs (e.g. Solidago missouriensis Nutt.) decreased in response to bison. Plant species diversity (H') and spatial heterogeneity in all areas sampled were significantly increased by bison. Increased heterogeneity and mean species richness in grazed prairie (40 species per sample site) compared to unglazed prairie (29 species per site) were likely a result of greater microsite diversity generated by bison, whereas preferential grazing of the dominant grasses and concomitant increases in subordinate species resulted in an increase in equitability of species abundances. Species/area relationships indicated greater effects of bison on plant species richness with increasing sample area. Increases in plant diversity components associated with bison grazing were generally greater in annually burned than in 4-year burned sites. Effects of ungulate grazers on floristic diversity have important implications given recent evidence that plant species diversity and the compositional and production stability of grassland plant communities are positively related.

The Ecological Basis of Conservation: Heterogeneity, Ecosystems, and Biodiversity

Article

Apr 1999

Landscape Ecology

Book

Jan 1986

Opportunistic Management for Rangelands Not At Equilibrium

Article

Jul 1989

We discuss what concepts or models should be used to organize research and management on rangelands. The traditional range succession model is associated with the management objective of achieving an equilibrium condition under an equilibrium grazing policy. In contrast, the state-and-transition model would describe rangelands by means of catalogues of alternative states and catalogues of possible transitions between states. Transitions often require a combination of climatic circumstances and management action (e.g., fire, grazing, or removal of grazing) to bring them about. The catalogue of transitions would describe these combinations as fully as possible. Circumstances which allow favorable transitions represent opportunities. Circumstances which threaten unfavorable transitions represent hazards. Under the state-and-transition model, range management would not see itself as establishing a permanent equilibrium. Rather, it would see itself as engaged in a continuing game, the object of which is to seize opportunities and to evade hazards, so far as possible. The emphasis would be on timing and flexibility rather than on establishing a fixed policy. Research under the state-and-transition model would aim to improve the catalogues. Frequencies of relevant climatic circumstances would be estimated. Hypotheses about transitions would be tested experimentally. Often such experiments would need to be planned so that they could be implemented at short notice, at an unknown future time when the relevant circumstances arise.

Range Management Principles and Practices

Article

Jan 1991

Stocker Cattle Response to Grazing Management in Tallgrass Prairie

Article

Mar 1999

The effects of stocking rate and grazing method on performance of yearling beef cattle grazing tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1994. Pastures dominated by big bluestem [Andropogon gerardii Vitman], little bluestem [Schizachyrium scoparium (Michx.) Nash], and indiangrass [Sorghastrum nutans (L.) Nash], were allocated to either short duration rotational or continuous stocking methods and stocking rates ranging from 52 animal-unit-days (AUD) ha-1 to 90 AUD ha-1. Steers grazed the units from late April to late September. Precipitation was above average during the study period. Live weight gain per head was higher under continuous stocking than rotational stocking at all stocking rates. At 52 AUD ha-1, individual gains under rotational stocking were 11% less than under continuous stocking. At 90 AUD ha-1, individual gains under rotational stocking were decreased by 20%. Measurements of steer diets and forage standing crop suggest the reduction in weight gain was due to reduced forage intake under rotational stocking. Live weight gain per hectare increased with stocking rate and was higher with continuous stocking at all stocking rates. Net returns per hectare increased as stocking rate increased for both stocking methods but were lower for rotational stocking at all stocking rates. Variable costs per head would have to decrease by 24 to 34% under rotational stocking to equalize net returns between the 2 grazing methods. Unless the decline in gain per head can be reduced or eliminated, there is no economic incentive to implement rotational stocking under the conditions of this study.

Bison Selectivity and Grazing Response of Little Bluestem in Tallgrass Prairie

Article

Jan 1995

The perennial bunchgrass little bluestem (Schizachyrium sco-patium [hlichx.] Nash) was examined in a 5yr study on tallgrass prairie to determine how fire influences its use by bison and its responses to grazing. On unburned prairie, bison grazed only 5% of the available little bluestem, selecting it only 30% as fre-quently as big bluestem, the dominant co-occurring species. On burned prairie, grazing frequency of little bluestem was over 3-fold greater and equal to that of its dominant neighbor. Grazing frequency of little bluestem was affected by plant size (basal area). On burned sites, plants of intermediate size classes were least abundant (40% of total) but were grazed most frequently (>SO%). Small plants were most abundant but were grazed least frequently. Density, tiller numbers, and basal area of little bluestem were significantly greater in annually burned com-pared to infrequently burned sites but were decreased by > 50% in grazed compared to ungrazed sites. Grazing shifted the popu-lation size distribution toward higher frequencies of smaller indi-viduals (< 50 cm* basal area), whereas burning increased the fre-quency of large (> 200 cm* basal area) individuals. In unburned prairie, little bluestem accumulates a persistent clump of stand-ing dead tillers that appear to serve as a physical deterrent to grazing. Although burning enhances its growth, it also removes its canopy of dead tillers exposing the plant to grazers. The shit in population structure toward a high frequency of smaller (and perhaps less drought-or grazing-tolerant) individuals may con-tribute to the decline of little bluestem populations under persis-tent grazing. Thus, plant growth form, population size structure, and fue interact to influence bison grazing patterns and respons-es of little bluestem to grazing on tallgrass prairie.

Rotating Access to Water to Improve Semidesert Cattle Range Near Water

Article

Highlight Seasonal opening and closing of watering places in a 3,200-acre pasture on the Santa Rita Experimental Range in Arizona resulted in lighter use of perennial grasses near water if utilization for the pasture was moderate to light, and if the closed period included the summer growing season. Rotating use of watering places should work best in large range units with waters far apart. Most semidesert grass-shrub cattle ranges are grazed yearlong. Even ranges that are properly stocked may be overgrazed every year near water, while remote areas are grazed lightly or not at all. Deferred-rotation grazing systems rest entire range units periodically, thereby giving all areas of con-centrated use an opportunity to recover. How-ever, the cost of fencing necessary for a deferred-rotation system may be hard to justify on many southwestern semidesert ranges. The objectives of this study were: (1) to determine whether cattle in a pasture with several watering places could be made to rotate their use of forage near water by opening one water at a time, and (2) to determine changes in cover, production, and utilization of perennial grasses near water under such a system.

Abundance and composition of plant species along grazing gradients in Australian rangelands

Article

Dec 2003
J APPL ECOL

The widespread provision of livestock drinking water in previously dry Australian rangelands has supported concomitant increases in cumulative grazing pressure. While the associated impacts on plants of pastoral importance have been well documented, far less is known about the rest of the flora. To address this deficiency, we measured the frequency of occurrence of all plant species at sites along water‐centred grazing gradients in commercial paddocks located in the rangelands of central and southern Australia. Four gradients were in chenopod shrubland vegetation, and four in acacia woodlands. Each gradient extended to a reference site remote from all waters, where grazing by stock was minimal. Five further sites were sampled along each gradient, at locations progressively closer to the gradient's watering point. Ground‐layer species far outnumbered those in upper layers (466 and 134, respectively). Most were geographically localized (72% found at one gradient only) and locally uncommon (46% per gradient occurred with a frequency < 5% per site). Species showing trends of decreasing frequency with proximity to water significantly outnumbered those showing increasing trends. Significantly more species that were recorded only once occurred at the sites furthest from water, where long‐term grazing pressure was least. Some gradients also showed an overall decline in species richness with increasing proximity to water. Most species were native, and among these there were no clearly identifiable ‘global winners’ (i.e. no widespread species advantaged by grazing and associated disturbances). In contrast, the majority of the few exotic species, including two of the three most widespread species found, showed increasing abundance with proximity to watering points. Synthesis and applications. The results from this study indicate consistent and substantial changes in plant composition that are probably related to the accumulated long‐term impacts of water‐centred grazing. The consequences are potentially severe, because artificial watering points are now extremely widespread in the Australian rangelands. Identification and protection of representative, water‐remote refugia for the most grazing‐sensitive species should therefore be a high priority for regional conservation.

Long‐term vegetation dynamics mediated by herbivores, weather and fire in a Juniperus‐Quercus savanna

Article

Dec 1997
J VEG SCI

Long‐term (45‐yr) basal area dynamics of dominant graminoid species were analyzed across three grazing intensity treatments (heavily grazed, moderately grazed and ungrazed) at the Texas A&M University Agricultural Research Station on the Edwards Plateau, Texas. Grazing intensity was identified as the primary influence on long‐term variations in species composition. Periodic weather events, including a severe drought (1951–1956), had little direct influence on composition dynamics. However, the drought interacted with grazing intensity in the heavily grazed treatment to exacerbate directional changes caused by grazing intensity. Species response to grazing was individualistic and noisy. Three response groups were identified. Taller, more productive mid‐grasses were most abundant under moderate or no grazing. Short grasses were most abundant under heavy grazing. Intermediate species were most abundant under moderate grazing and opportunistic to weather patterns. Graminoid diversity increased with the removal or reduction of grazing intensity. The moderately and ungrazed treatments appeared most resistant to short‐term weather fluctuations, while the heavily grazed treatment demonstrated significant resilience when grazing intensity was reduced after over 110 yr of overgrazing. Identification of a ‘climax’ state is difficult. Significant directional change, which took nearly 20 yr, appears to continue in the ungrazed treatment after 45 yr of succession. The observed, relatively linear patterns of perennial grass composition within the herbaceous patches of this savanna were generally explained by traditional Clementsian succession. However, when dynamics of the herbaceous community are combined with the woody component of this savanna, the frequency and intensity of fire becomes more important. Across the landscape, successional changes follow several pathways. When vegetation change is influenced by several factors, a multi‐scale model is necessary to demonstrate interactions and feedbacks and accurately describe successional patterns. Absence of fires, with or without grazing, leads ultimately to a Juniperus/Quercus woodland with grazing intensity primarily influencing the fuel load and hence fire intensity.

The Influence of Geomorphological Heterogeneity on Biodiversity I. A Patch‐Scale Perspective

Article

Apr 1998
CONSERV BIOL

Landscapes composed of spatially heterogeneous abiotic conditions should provide a greater diversity of potential niches for plants and animals than do homogeneous landscapes. We tested this hypothesis in a deciduous forest ecosystem in the northeastern United States. We created an index that summarizes the collective variation in terrain and soil properties in 2‐ha study plots. We measured woody plant species richness and diversity in 20 study plots that had high geomorphological heterogeneity and 20 plots that had low geomorphological heterogeneity. The richness and diversity of trees and shrubs were significantly higher in sites with high geomorphological heterogeneity than in sites that exhibited little change in terrain or soil conditions. Variation in aspect and soil drainage were especially important predictors of biotic diversity. Our results demonstrate an intimate association between abiotic and biotic diversity and have significant implications for long‐term conservation strategies. Influencia de la Heterogeneidad Geomorfológica en la Biodiversidad I. Una Perspectiva a Escala de Parcela Los paisajes compuestos de condiciones abioticas espacialmente heterogeneas deberían proveer una gran diversidad de nichos potenciales para plantas y animales comparados con los paisajes homogéneos. Probamos esta hipótesis en un ecosistema de bosque deciduo del noroeste de los Estados Unidos de Norteamérica. Creamos un índice que sumariza la variación colectiva de las condiciones del terreno y las propiedades del suelo en áreas de estudio de 2 ha. Medimos la riqueza de especies de madera y la divresidad de 20 áreas de estudio con una alta heterogeneidad geomorfológica y 20 con baja heterogeneidad geomorfológica. La riqueza y diversidad de especies de árboles y arbustos fue significativamente mayor en sitios con alta heterogeneidad geomorfológica en comparación con sitios que exhibieron pocos cambios en las condiciones del terreno o del suelo. Variaciones en el aspecto y drenaje del suelo fueron indicadores especialmente importantes de la diversidad biótica. Nuestros resultados demuestran que existe una asociación intima entre diversidad biótica y abiótica, teniendo implicaciones significativas en las estrategias de conservación a largo plazo.

Patterns of species and community distributions related to environmental gradients in an arid tropical ecosystem

Article

Mar 1995

The heterogeneous vegetation mosaic of the South Turkana region of north Kenya is associated with diversity in the region's physical environment. The abundance and distribution of the dominant species are related to gradients in those abiotic factors that influence water availability, including precipitation, soil texture, and topographic relief. Research focused on three Acacia species that are a major component of the Turkana vegetation; A. tortilis, A. senegal, and A. reficiens. These species each exhibit a different response to variations in abiotic factors. Consequently, species abundance varies independently across the landscape, creating a continuum of intergrading populations. Community types can be identified within the mosaic of intergrading populations. Although community borders are not discrete due to continual change in species abundance, types are identifiable and are repeated in areas with similar environmental conditions. The landscape patterns are representative of Whittaker's (1953) climaxas-pattern, with communities created by individual patterns of populations responding to environmental gradients, creating a continuum of community change across the landscape.

Farmland Biodiversity: Is Habitat Heterogeneity the Key?

Article

Apr 2003
TRENDS ECOL EVOL

Agricultural intensification has led to a widespread decline in farmland biodiversity measured across many different taxa. The changes in agricultural practices affect many different aspects of the farmland habitat, but agricultural industry, policy and much previous research has tended to be concerned with specific sectors or practices (e.g. pesticide use or cereal husbandry). Here, we review the empirical literature to synthesize the research effort that has been directed to investigate specific practices or goals to make general statements regarding the causes and consequences of farmland biodiversity decline. We argue that the loss of ecological heterogeneity at multiple spatial and temporal scales is a universal consequence of multivariate agricultural intensification and, therefore, that future research should develop cross-cutting policy frameworks and management solutions that recreate that heterogeneity as the key to restoring and sustaining biodiversity in temperate agricultural systems.

Population Responses to Patchy Environments

Article

Nov 2003
Annu Rev Ecol Systemat

John Wiens

discon tinuities on many scales in time and space. The patterns of these discontinuities produce an environmental patchwork which exerts powerful influences on the distri butions of organisms, their interactions, and their adaptations. Consideration of this environmental patch structure is critical to both the theory and management of populations. Despite the obvious heterogeneity of natural sys te.ms, most of the models that form the theoretical fabric of population biology and ecology (and that are increasingly conditioning our perception of reality) tell mathe matical stories of populations

Pattern and Process in the Plant Community

Article

Jan 1947

A. S. Watt

Application of the fire–grazing interaction to restore a shifting mosaic on tallgrass prairie

Abstract

No full-text available

Recommended publications

Should heterogeneity be the basis for conservation? Grassland bird response to fire and grazing

Soil Nitrogen Availability in Tallgrass Prairie Under the Fire–Grazing Interaction

Seasonal Fires, Bison Grazing, and the Tallgrass Prairie Forb Arnoglossum plantagineum Raf.

The Origins Kakamega Forest Grasslands: A Critical Review