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Changes in plant densities in a mesic species-rich grassland after imposing different grazing management
Abstract
Changes in plant density were evaluated monthly in the first three vegetation seasons after imposing different grazing management treatments on abandoned semi-natural grassland in the Czech Republic. There was no agricultural management in the 5 years before the start of the experiment in 1998. A completely randomized block experiment was established with the following five treatments: unmanaged control, intensive continuous grazing, extensive continuous grazing and a harvest in June followed by either intensive or extensive continuous grazing for the rest of the growing season. The sward was maintained at a target height of 5 and 10 cm under the intensive and extensive grazing managements respectively. An almost immediate increase in the densities of all sward components, especially grass tillers, occurred after the introduction of grazing on the previously abandoned grassland in comparison with the unmanaged control treatment. Trifolium repens was able to colonize and increase the number of its stolon growing-points in all managed treatments, particularly in intensively grazed patches during the second and third experimental seasons. Delay to defoliation in both treatments containing a harvest in June resulted in an increase in the number of forb plants, particularly in the number of Taraxacum spp. plants, most probably due to an enabling of its seed production. It is evident that increases in plant density as a function of intensive defoliation are not restricted to the frequently documented effect on grass tillers but also can occur in many legume and forb species in species-rich grasslands.
... In between the extremes of intense management and no management lies a broad spectrum of management regimes in which human interference and natural processes are balanced to different degrees (Falkengren-Grerup & Tyler 1991;Rubio et al. 1999;Smith et al. 2002;Zerbe 2002;Gamborg & Larsen 2003). European studies of forests (Hedl 2004;Gärtner & Reif 2005) and grasslands (Marriott et al. 2004;Pavlu et al. 2006;Jacquemyn et al. 2003;Hansson & Fogelfors 2000) have shown that change from one management regime to another affect vegetation composition. In this context, there has been an increasing attention to so called sustainable management regimes as initiatives to improve diversity of economically important nature types (Gamborg & Larsen 2003;Marriott et al. 2004). ...
... Grazing is an indirect management type and is therefore to some extend harder to regulate than the direct management described above. However, since domestic grazing often occurs within fenced areas with a fixed number of animals, the effect can in fact be well regulated by adjusting the number of animals per unit area (Pavlu et al. 2006). Domestic grazing animals are used in the management of open habitat types including open forests to preserve their special flora and diversity (Marriott et al. 2004;Pavlu et al. 2006;Strandberg et al. 2005), but wild grazers can also influence forest vegetation composition. ...
... However, since domestic grazing often occurs within fenced areas with a fixed number of animals, the effect can in fact be well regulated by adjusting the number of animals per unit area (Pavlu et al. 2006). Domestic grazing animals are used in the management of open habitat types including open forests to preserve their special flora and diversity (Marriott et al. 2004;Pavlu et al. 2006;Strandberg et al. 2005), but wild grazers can also influence forest vegetation composition. Deer, for example, are highly selective in their food choice and can suppress the growth of certain plant functional groups (Rooney 2001;Waller & Alverson 1997;Latham et al. 1999;de Jong et al. 1995). ...
... Generally, herbage growth declines with increasing trampling intensity. According to Pande and Yamamoto (2006) this is caused mainly by a decrease in tiller density, although higher grass tiller density was found under intensive than extensive grazing by Pavlu et al. (2006). Pasture cover and the impact of trampling damage is higher on wet soils and also in the summer, when many tillers are developing flowers (Edmond, 1963). ...
... According to our long term visual observations the vegetation under fences is conspicuously different in plant species richness and structure from other grazed plots, but this has not previously been recorded. Therefore we performed a comparative study inside the long-term Old richov Grazing Experiment (OGE) (Pavlu et al., 2007), in which trampling under electric fence lines had been completely absent throughout the 12-years since the OGE was established. There were additional treatments where defoliation (grazing as well as cutting and aftermath grazing) and trampling were applied to areas with different long term grazing intensities. ...
... The trampling study was established and conducted in 2010 after 12-years of different management under OGE. The experimental site was established in 1998 on formerly abandoned grassland (Pavlu et al., 2007). Since then the experimental pasture has been continuously stocked every year with young heifers from May to October and no additional fertilizers have been applied. ...
There are no long-term experimental studies dealing with plant community responses to trampling. Here we report the results for soil penetration resistance and plant species changes in mesotrophic temperate Central European grassland after 12-years of grazing management with and without trampling by cattle. Five grazing treatments (intensive and extensive grazing; cut for hay in June followed by intensive or extensive grazing; and intensive grazing with no trampling under permanent electric fencing) with two replicate blocks have been applied since 1998. Species richness, species composition, sward height, nutrient availability in soil and soil penetration resistance were recorded and evaluated. For statistical analysis we used one way ANOVA and RDA with the Monte Carlo test. Long term grazing by large herbivores had a significant effect on soil penetration resistance with the lowest values in the ‘not trampled’ treatment. Legumes, particularly Trifolium repens, and short forbs (especially Veronica serpyllifolia) were supported by intensively defoliated and trampled treatments, whereas tall forbs (mainly Aegopodium podagraria, Hypericum maculatum) prevailed under the extensively managed treatments. The cover of tall and short graminoids was not dependent on applied treatments. The ‘not trampled’ treatment had the highest prevalence of bryophytes (domination of Rhytidiadelphus squarrosus) and was also the richest in a number of vascular plant species; however, it also had the lowest evenness index. Long-term defoliation by grazing animals without trampling does not lead to the creation of typical pasture swards. Species forming pasture communities are essentially dependent on regular defoliation by grazing and regular trampling by hooves, which causes a high degree of soil compaction as well as sward disruption.
... Also, the species 8 International Journal of Ecology number increased by 30 per cent in late grazing, but remained constant after six years in continuous stocking. Similar observations are made by, for example, Pavlů et al. [45], who reported an increase of forbs in the vegetation after delayed onset of grazing on old leys. An increase of seed production in late grazed areas was pointed out as one of the possible explanations. ...
... In full-scale grazing experiments, the different treatments will always be located in adjacent areas because of the otherwise biased effects of fences (e.g., [45]). Yet, this may cause problems in separating treatment effects from area effects. ...
Seminatural grasslands are maintained by regular anthropogenic disturbance, usually grazing or mowing. Management action late in the growing season was historically more common than today. Two experimental grazing regimes, continuous stocking from May to September and late-onset grazing from mid-July, were compared in two Swedish grasslands. Effects on flowering and fruit production were studied and related to plant functional traits. Change in vegetation composition over six years was analysed in one grassland. Delayed onset of grazing enhanced fruit production up to four times. Phenology of reproduction was the most important plant trait explaining differences in reproduction among species. Diversity of vascular plant species was higher after six years of late-onset grazing. No differences in vegetation height or proportion of grazed shoots were found by the end of the season. The results suggest that early reproduction may function as an escape from damage and that late onset of grazing may be used as a substitute for labour-intense traditional mowing.
... Next to influences by treading and redistribution of nutrients, large herbivores reduce the height of the vegetation, thus affecting species diversity (Olff and Ritchie, 1998;Rook et al., 2004). In contrast to mowing, the animals create a mosaic of patches differing in sward height (Correll et al., 2003;Pavlů et al., 2006;Sahin Demirbag et al., 2009) due to selective feeding. Such patches have been found to be relatively stable over time (van den Bos and Bakker, 1990;Hofmann and Tallowin, 2003). ...
... So far, effects of grazing intensity on vegetation diversity have usually been investigated in relation to stocking rates or mean sward height, without taking the patchy sward structure into account (Fuhlendorf et al., 2001;Marriott et al., 2002;Pavlů et al., 2006;Marriott et al., 2009). Areas of different sward height have however been found to contain different species (Correll et al., 2003) and may cause different reactions of sward diversity to changes in management (Scimone et al., 2007). ...
The development of phytodiversity was analysed on a paddock (1 ha) as well as on a patch scale (1 m2) over nine years on paddocks managed for compressed sward heights (CSH) of 6 (moderate stocking, MC), 12 (lenient stocking, LC) or 18 cm (very lenient stocking, VLC) on moderately species-rich mesotrophic grassland. Neither grazing treatments nor nutrient availability caused differences in diversity measures in this study. The local quadrat vegetation height had a significant influence on average species number and Shannon diversity, independent of the grazing treatment. Patches with short vegetation allowed seed germination and reduced dominant species, making a diversification of the vegetation measurable at an earlier stage than on the paddock scale.
... Also, the species 8 International Journal of Ecology number increased by 30 per cent in late grazing, but remained constant after six years in continuous stocking. Similar observations are made by, for example, Pavlů et al. [45], who reported an increase of forbs in the vegetation after delayed onset of grazing on old leys. An increase of seed production in late grazed areas was pointed out as one of the possible explanations. ...
... In full-scale grazing experiments, the different treatments will always be located in adjacent areas because of the otherwise biased effects of fences (e.g., [45]). Yet, this may cause problems in separating treatment effects from area effects. ...
Early and intense grazing of semi-natural grasslands replacing traditional mowing and late grazing has been identified as a threat to grassland biodiversity. We compared fruit production, fruit set attributes (e.g. plant size or phenology of reproduction), and differences in potentially negative effects (accumulation of ungrazed vegetation) in continuous grazing from May through September, with an experimental management regime, grazing from mid-July, within two different grasslands in Sweden. Veg et ation and reproductive parts were monitored in plots at five to eight occasions over the season. The delayed onset of grazing enhanced fruit production of grassland plants up to four times. Among species, phenology of reproduction appeared to be the most important plant trait explaining differences in reproduction between management regimes. No differences in vegetation height or proportion of grazed shoots were found by the end of the season. The results suggest that early reproduction may function as an escape from damage under both continuous and late grazing, but that the functionality of this adaptation is limited under intense and early disturbance. Further, an increased use of traditional management methods may have positive effects on biodiversity of semi-natural grasslands.
... Dormaar & Willms, 1998;Stroh et al., 2019). However, this is a complicated relationship which is dependent upon the size and species of livestock, stocking density, the timing of grazing, and the grazing environment (Smith & Ruston, 1994;Bakker et al., 2003;Pakeman, 2004;Pavlů et al., 2006). Grazing management may also produce different effects at different spatial scales (Chaneton & Facelli, 1991;Olff & Ritchie, 1998). ...
The Wicken Fen Vision (Cambridgeshire, UK) is a landscape-scale habitat restoration project that uses process-driven, open-ended approaches to develop habitats on highly degraded and drained peat soils of former intensive arable land. The project land is extensively grazed with herds of free-roaming, minimally managed herds of Highland cattle and Konik horses. In one 119 ha area, seven 25m x 25 m grazing exclosures were erected and vascular plant species were recorded from 2007 to 2017. Plant species data were analysed to (1) compare changes in plant species composition and diversity in grazed and ungrazed areas; (2) use plant species traits and plant-environment associations to explore the nature of changes in plant composition; (3) use remote sensing to explore changes in vegetation structure; (4) examine the influence of land use histories on grazing outcomes in different parts of the site.
There was a clear divergence through time between grazed and ungrazed areas, attributed to significantly greater canopy height, Ellenberg L (Light) and Ellenberg N (fertility) values within the exclosures. Species richness was significantly higher in grazed compared with ungrazed areas and species assemblages separated through the study period. After ten years, extensive free-roaming grazing has had significant impacts on vegetation structure and species richness but effects varied across the study site because of differing historical land use.
... In contrast, management (cutting or non-cutting) had no discernible effect on the vertical distribution or on the upper-layer biomass (except for forbs) of any of the functional groups, although it had significant effects on the total harvested biomass. This is mainly because the increased frequency of defoliation rather than the type of defoliation (such as cutting in spring) influences total biomass more, increasing the densities of all sward components like grass tillers (Pavlů et al., 2006b). ...
The nutrient concentration in herbage and biomass productivity analyses are dependent on the vertical distribution of different sward layers where the sampling is done. Notably, a majority of studies indicate clipping biomass to the ground level without any consideration of the vertical distribution. This study examined the effect of cutting and grazing intensities on the vertical distribution of plant functional groups.
Oldřichov Grazing Experiment, northern Czechia.
During a 15‐year experiment: (a) intensive and (b) extensive grazing without cutting; (c) cutting in June followed by intensive and (d) extensive grazing; and (e) undefoliated treatment were applied throughout the vegetation season. Biomass data were collected at two layers in the sward (below and above 3 cm) and separated into five functional groups. Biomass data were analysed to examine the succession and effects of treatments on vertical distribution of functional groups.
Treatment effects were differentiated after 2–3 years from the introduction of management, but the composition of functional groups fluctuated over time. Treatments significantly affected total biomass of all functional groups and the vertical distribution within swards of most groups. Particularly intensive grazing significantly decreased the total biomass of graminoids, forbs, and dead biomass in favour of legumes (which increased). This led to a shift in the relative biomass distribution from the upper sward layer to the lower layer for most functional groups except for legumes and mosses.
The high proportion of dead biomass in the lower sward layer suggests the need for a methodological approach that considers clipping of biomass only above 3 cm when sampling for productivity and forage quality analysis. This approach would avoid including biomass from below 3 cm or the lower layer, which would be ungrazed by cattle. Many previous studies may have reported a distorted or inflated value in herbage productivity or forage quality results.
... Seeds were obtained from Cruydt-Hoeck (Nijberkoop, The Netherlands). On May 1, 2017, 100 three-week old seedlings of each species were planted separately into each mesocosm to create monocultures with densities comparable or lower than those typically seen in European grasslands (Pavlů et al., 2006), with a total of five replicate mesocosms per species (30 mesocosms total). Mesocosms were distributed across the field in a randomized block design. ...
In response to environmental conditions, plants can alter the performance of the next generation through maternal effects. Since plant–soil feedbacks (PSFs) influence soil conditions, PSFs likely create such intergenerational effects. We grew monocultures of three grass and three forb species in outdoor mesocosms. We then grew one of the six species, Hypochaeris radicata, in the conditioned soils and collected their seeds. We measured seed weight, carbon and nitrogen concentration, germination and seedling performance when grown on a common soil. We did not detect functional group intergenerational effects, but soils conditioned by different plant species affected H. radicata seed C to N ratios. There was a relationship between parent biomass in the differently conditioned soils and the germination rates of the offspring. However, these effects did not change offspring performance on a common soil. Our findings show that PSF effects changed seed quality and initial performance in a common grassland forb. We discuss the implications of our findings for multi‐generational plant–soil interactions, and highlight the need to further explore how PSF effects shape plant community dynamics over different generations and across a broad range of species and functional groups. We show that plant‐soil feedback effects experienced by the parent plant resulted in changes in seed quality and initial performance of a common grassland forb.
... Overall, weed pressure was not affected by stocking method, but this was not the case for clover establishment. White clover was more favored by continuous stocking in part because the prostrate growth habit of this species makes it tolerant to close grazing [30,31], which is common under continuous stocking. We also found reasonable white clover abundance in mob-stocking treatments, which was surprising as it should be more intolerant of shading by grasses. ...
Mob stocking is a type of livestock management method where high densities of animals are restricted to a small area of grassland for short periods of time (e.g., 12-24 hr.) before being moved to new forage. Use of mob stocking has generated considerable interest among forage-livestock professionals in recent years, but questions remain about its purported benefits to cattle and forage plants. To address questions about the possible benefits of mob stocking, a 3-yr study (2014-2016) was conducted in Virginia, USA comparing mob, rotational, and continuous stocking methods in a temperate grassland common to that region. The main objective of this study was to evaluate how mob-stocking management affected selected forage variables, cattle performance, and legume/weed abundance. Herbage mass and nutritive value were measured monthly. Cow and calf weights and body condition score (BCS) were used as indicators of animal performance. Legumes (red and white clover) were over-seeded prior to the study, and their abundance along with weeds were evaluated annually thereafter. Mean herbage mass and forage nutritive values were similar across mob, rotational and continuously stocked systems despite extra-long rest periods that allowed grasses to grow tall and over-mature under mob stocking. Cow weights going into winter were lower (P < 0.05) under mob stocking (619 kg) compared with continuous stocking (688 kg) possibly because many tall grasses were trampled and not grazed. Lastly, we found mob stocking can favor establishment of erect-growing red clover (Trifolium pretense L.), but it had no effect on weed abundance. Overall, we found few compelling reasons why mob stocking should be adopted for season-long forage and livestock production over other stocking methods in this environment.
... These plants have also greater adaptive ability, especially under grazing and have high potential for regrowth compared to legumes. Further, animals showed a greater preference for the legumes (Papanikolau et al. 1993, Pavlu et al. 2006. Forbs and other plant species also constituted a good portion of biomass and gradually increased from November (5.50%) to February (21.07%), which were highly palatable to goats and well adapted to Indian semi-arid grazing lands. ...
A grazing trial of 120 days duration was conducted in goats on rangeland vegetation to record herbage mass and its quality, and nutritional status of animals. Yearling female Barbari goats divided into groups G1, G 2 and G3 of 9 animals each, were allowed to graze on 3 ha of vegetation (@ 9 animals/ha) during winter for 6.5 to 8 h daily following 3 different grazing management practices viz. continuous, rotational and deferred rotational, respectively. They were also supplemented with barley grain (@ 1.0% of body weight) as energy source. Availability of herbage mass (kg DM/ha) of grass dominated vegetation was comparatively higher (2910) under deferred rotational than rotational (2677) and continuous (2365) system of grazing management However, quality of herbage mass in terms of CP (4.57 to 4.70%), NDF (77.8 to 79.7%) and ADF (46.6 to 50.3%) was comparable among the different grazing management practices. Similarly average CP of mouth grab forage samples was comparable amongst the treatment groups and ranged from 10.7 to 11.9%. Daily feed (DM) intake was 506, 512 and 546 g in goats under G1, G 2 and G3 groups, respectively, and the differences were nonsignificant among the groups. The digestibility of nutrients was statistically similar among the groups. Goats were also on similar plane of nutrition consuming comparable quantities of CP and TDN. Concentration of glucose, plasma protein and urea-nitrogen was similar in G1, G2 and G3 groups. It was concluded that at similar stocking rates, grazing management practices did not have any influence on herbage mass and its quality as well as nutrient utilization and blood metabolites in goats allowed to graze on rangeland vegetation of Bundelkhand with supplementation of barley.
... The species composition, described by the numbers of growing points of each functional group, was not stable over the whole season. Pavlů et al. (2006) also encountered fluctuating numbers of grass tillers, legume buds and non-leguminous forb plants when comparing vegetation density in mown and continuously grazed pastures. In our experiment, nutrient addition, especially in combination with defoliation, stimulated the formation of grass tillers while reducing the numbers of buds in nonleguminous forbs and legumes. ...
In biodiversity experiments based on seeded experimental communities, species richness and species composition exert a strong influence on canopy structure and can lead to an improved use of above ground resources. In this study we want to explore if these findings are applicable to agriculturally managed permanent grassland. Vertical layered profiles of biomass, leaf area and light intensity were measured in a removal-type biodiversity experiment (GrassMan) to compare the canopy structure in grassland vegetation of different plant species composition (called sward types). Additionally, the altered sward types were subjected to four different management regimes by a combination of the factors fertilization (unfertilized, NPK fertilized) and cutting frequency (one late cut or three cuts). In spite of large compositional differences (ratio grasses : non-leguminous forbs : leguminous forbs ranging from 93:7:0 to 39:52:9), the vegetation of the same management regime hardly differed in its canopy structure, while the management regimes brought about distinct vertical profiles. However, the allocation of biomass in response to cutting and fertilization differed among the sward types. Vegetation dominated by grasses was denser and had more leaf area when fertilized compared to vegetation rich in dicots which merely grew taller. In functionally more diverse vegetation, light interception was not increased compared to vegetation consisting of more than 90% of grasses in terms of biomass. Management had a much stronger influence on structure and light interception than plant species composition in this grassland experiment.
Published by Oxford University Press on behalf of the Annals of Botany Company.
... Removal of vegetation allows light to reach the lowest vegetation layers and the soil surface, triggering competition for resources, such as the light (Rook and Tallowin 2003). Several plant species grow rapidly in canopy openings, especially creeping plants, such as Trifolium repens L. (Pavlu et al. 2007; Pavlu et al. 2006). Trampling induces gaps in the vegetation resulting from the death of established individuals. ...
Research has delivered convincing findings on the effect of biodiversity on ecosystem functioning and humankind. Indeed, ecosystems
provide provisioning, regulating, supporting, and cultural services. The global value of annual ecosystem services of grasslands
and rangelands is about US$ 232 ha−1 year−1. Nevertheless, the precise evaluation of biodiversity benefits remains challenging. This issue is due to valuation methods,
subjective assumptions, and complexity of drivers of plant community dynamics. Here, we review the primary factors that influence
plant diversity of permanent grasslands, and we describe underlying processes. These factors must indeed be identified to
focus policies meant to preserve and restore plant diversity and to advise farmers about efficient decision rules. We show
that plant dynamics of permanent grasslands cannot be explained simply by agricultural management rules, e.g., grazing, fertilization,
and mowing, implemented at the field scale. The configuration of the surrounding landscape, e.g., landscape heterogeneity,
habitat fragmentation, and connectivity, acts as a species filter that defines the regional species pool and controls seed
flow. The regional species pool often contains higher species richness in a heterogeneous landscape, because of a higher diversity
of suitable habitats. This regional pool could be a major species sources for permanent grasslands according to the seed flow.
We discuss the need to consider all of these factors to understand plant species composition of permanent grasslands and the
necessity to study plant communities using both taxonomic and functional approaches. In order to report this integrative approach,
we propose a conceptual model based on three ecological challenges—dispersal, establishment, and persistence—that are considered
to act as filters on plant diversity, and a graphical representation of the complexity of such studies due to the interaction
effects between plant dispersal abilities, forage productivity, disturbances induced by farming practices, and landscape heterogeneity
on plant diversity. Last, we discuss the ability of farmers to manage each factor and the necessity of such study in the improvement
of the current agro-environment schemes efficiency for farmland biodiversity restoration or preservation.
... With the change of landuse from meadows harvested in late July, to seminatural pasture grazed already in early May, many herb species that were abundant in the old meadows have become endangered (Wissman, 2006). Delayed onset of grazing or cutting on part of a botanically diverse grazing area could help preserve some of these endangered species (Pavlu et al., 2006) The effect of grazing every other year or delayed onset of grazing on seed production and germination of seeds was studied by Wissman (2006) who found that these grazing regimes gave significantly higher seed production and number of germinated plants compared with conventional grazing and is therefore beneficial for botanical biodiversity. However, the effects on animal performance of these grazing regimes are not sufficiently studied. ...
In a five year experiment the weight gain of a total of 106 steers on three grazing treatments was studied: Partial–Delay (delayed onset of grazing in part of the grazing area), Intermittent (grazing every second year) and Continuous (continuous yearly grazing). Daily weight gain of steers was similar between treatments during the first three years but lower (P<0.05) on the Partial–Delay (0.6 kg) compared with the Intermittent and Continuous treatments (0.8–0.9 kg) during the last 2 experimental years. The mean proportions of grass, forbs and senescent plant material were similar between treatments: 59–61, 23–24, 15–17% of dry matter (DM), respectively.
... Gaps facilitate the germination of seeds and their size influences the numbers of seedlings that become established (Hanley et al., 1996b). The failures in management practices that enable dandelions to disperse and survive in grassland have been well studied (Pavlu et al., 2006aPavlu et al., , 2006b) and they also indicate the importance of seed availability and gap size. Numbers of newly established plants decreased when seed input was diminished by mowing the immature inflorescences (Pavlu et al., 2008b) or when the gaps were an inappropriate size (Hanley et al., 1996a). ...
Dandelion (Taraxacum officinale agg.) seedlings colonize gaps in agricultural grassland and give rise to weedy pastures. It was investigated how this colonization is affected by seed availability and gap size. Flowering, seed production and spontaneous seedling emergence in artificial gaps were recorded at seven grassland sites. Fifteen to 126 flowers m−2 (2·2–18·6 thousands of seeds m−2) were produced at particular sites in May 2005. Seed availability explained 0·91 of the between-site variation in seedling abundance. Seedling populations represented c. 0·03 of the seed produced at these sites. Shading, pH, soil nutrients and soil texture did not affect seedling emergence. In 2006, seed was sown at one site in small (33 cm2) and large (400 cm2) gaps on eight occassions during the growing season. Time to germination was on average 10 d shorter and 0·20 more of the seed germinated in small than large gaps, and both varied significantly with date of sowing. Germination was not limited by low temperature. Predation of seeds may have decreased the density of established seedlings. Patches of dandelions in sparse or weakly disturbed grassland are unlikely to disappear spontaneously and repeated cutting during spring flowering is recommended as an effective means of management.
... Common management practices in grasslands include prescribed fire at varying times and frequencies, mowing, grazing, and selective herbicide application (Howe 1995(Howe , 1999Fynn et al. 2005;Tjelmeland et al. 2008). These practices have been widely investigated in terms of altering the dominance of the native grasses in native or semi-natural grasslands worldwide (Archer et al. 1988;Hayes & Holl 2003;Pykälä 2003;Cipriotti & Aguiar 2005;Fynn et al. 2005;Altesor et al. 2006;Pavlů et al. 2006); however, less is known about the applicability of these management practices for modulating dominance of the native grasses in the context of restoration. Although the specific removal methods used in our study are not practical and were not designed for large-scale restorations, our results do provide insight on how subordinate species may respond to management practices that reduce dominant species abundance. ...
Warm-season (C4) grasses commonly dominate tallgrass prairie restorations, often at the expense of subordinate grasses and forbs that contribute most to diversity in this ecosystem. To assess whether the cover and abundance of dominant grass species constrain plant diversity, we removed 0, 50, or 100% of tillers of two dominant species (Andropogon gerardii or Panicum virgatum) in a 7-year-old prairie restoration. Removing 100% of the most abundant species, A. gerardii, significantly increased light availability, forb productivity, forb cover, species richness, species evenness, and species diversity. Removal of a less abundant but very common species, P. virgatum, did not significantly affect resource availability or the local plant community. We observed no effect of removal treatments on critical belowground resources, including inorganic soil N or soil moisture. Species richness was inversely correlated with total grass productivity and percent grass cover and positively correlated with light availability at the soil surface. These relationships suggest that differential species richness among removal treatments resulted from treatment induced differences in aboveground resources rather than the belowground resources. Selective removal of the dominant species A. gerardii provided an opportunity for seeded forb species to become established leading to an increase in species richness and diversity. Therefore, management practices that target reductions in cover or biomass of the dominant species may enhance diversity in established and grass-dominated mesic grassland restorations.
... been shown to occur as in Hellströms study (Hellström et al. 2003) after only three years of grazing. However, changes in both cover of presented plant species and in plant densities of all grassland components, especially grass tillers, were revealed after the introduction of grazing management (Pavlů et al. 2006c). The positive effect of grazing on species richness compared to unmanaged grassland is well documented in many other studies (e.g. ...
Question: How are plant species and functional group composition, and potential sward height affected by implementation of different grazing regimes on previously abandoned semi-natural grassland?
Location: The Jizerské mountains, northern Czech Republic.
Methods: We established a randomized block experiment with the following treatments: unmanaged control (U), intensive (IG) and extensive (EG) continuous grazing, first cut followed by intensive (ICG) and first cut followed by extensive (ECG) continuous grazing for the rest of the growing season. The percentage cover of all vascular plant species was recorded in 40 permanent plots.
Results: Total plant species richness increased in all managed treatments, whereas species number was reduced in U at the end of the experiment. Tall forbs (Aegopodium podagraria, Galium album, Anthriscus sylvestris, Cirsium arvense) as well as tall grasses (Elytrigia repens and Alopecurus pratensis) were more abundant in U. Species associated with both grazing treatments (IG, EG) were Dactylis glomerata, Festuca rubra agg. and Phleum pratense. Agrostis capillaris, Taraxacum spp., Trifolium repens, Ranunculus repens and Cirsium vulgare were promoted by ECG and ICG. Abundance of tall grasses and tall forbs reflected the intensity of management in the order U>EG, ECG>IG, ICG. Prostrate forbs, on the other hand, increased their cover with increasing intensity: ICG>IG>ECG>EG.
Conclusions: Plant species composition of semi-natural grasslands is affected by the defoliation regime. Continuous grazing on abandoned grassland alters the sward structure towards a permanent pasture with short, light-sensitive grasses and prostrate forbs. To maintain or enhance plant species richness in semi-natural grasslands, understanding the effects of different grazing regimes on plant species composition is necessary.
... This was not consistent with the tiller size/ density compensation principle. According to this principle, a decrease in tiller size under intensive defoliation is compensated by a substantial increase in tiller density in grass species which tolerate defoliation (see Matthew et al., 1995; Pavlů et al., 2006; Roscher et al., 2007). The tiller size/density principle did not apply to C. villosa as the decrease in tiller density together with tiller size was recorded using Cut and Cut–Fer treatments. ...
Calamagrostis villosa has recently expanded in Nardus stricta-dominated sub-alpine grassland of the Giant Mountains (Krkonoše/Karkonosze, the Czech Republic). To investigate whether this expansion has been promoted by high nitrogen deposition or by the cessation of agricultural management, grassland plots dominated by C. villosa were manipulated with four treatments: control (Con), fertilised (Fer), cut (Cut) and cut–fertilised (Cut–Fer). NH4NO3 was used at the rate of 30 kg N ha−1 and fertilisation and cutting were performed once a year after data collection in late July between 2000 and 2006.Plant species composition (analysed by RDA) was significantly influenced by cutting but not by fertilisation. Cutting reduced the cover, biomass, sward height and tiller density of C. villosa. Seedlings of N. stricta and panicles of C. villosa were recorded only in plots with cutting management.To investigate the effect of treatments on the spread of C. villosa, grassland sods dominated by N. stricta were transplanted into the experimental plots. Six years later, the density and cover of C. villosa spreading into the N. stricta sods were highest in Fer treatment.C. villosa was recognised as a defoliation-sensitive species and this sensitivity cannot be overcome by an increase in N supply. Recent expansion of C. villosa in the sub-alpine grassland can by explained by a long-term succession after the cessation of agricultural management and an increase in the N availability in recent decades.
... Empirical studies have suggested that the recruitment of grassland plants is limited rather by seed production than by germination sites (Eriksson & Ehrlén, 1992;Turnbull et al., 2000;Wissman, 2006). Empirical studies have also demonstrated increasing densities of plant individuals in the sward when late disturbance was introduced (Wissman, 2006), and an increased content of forbs in the vegetation (Pavlů et al., 2006). Early-flowering plant species, which have historically been favoured by late management, can be expected to be particularly negatively affected by the loss of late disturbance. ...
In conclusion, in the pre-industrial agricultural landscape, suboptimal management in some grasslands and during some time periods was probably not a problem because the vast grassland areas created a variety of management regimes and could support viable metapopulations of grassland species. In the current landscape, few species exhibit functioning metapopulations, hence restoration and management measures need to ensure sufficient habitat quality more or less in each single grassland. We therefore urge for knowledge-based management for conservation and regulation of environmental subsidies. This study indicates the need to focus on restoration of grassland quality. It also shows that more multi-disciplinary research is needed that combines historical, ecological and agricultural knowledge. Although restoration of habitat quality should thus be based on ecological-historical analyses of the grassland habitats and their species, the restoration methods may well be based on novel tools as long as the new methods provide all necessary ecological variables. Seeing as grasslands owe their species richness to past land-use practices, studying the components of historical land use in greater detail and in an ecological context may reveal not only new details of grassland ecology as such. It may also contribute to significant knowledge also of the ecology of the agricultural landscape in general, thereby providing keys as to the development of new conservation tools and strategies.
... Several studies have questioned the use of intense continuous grazing in species-rich grasslands that in many cases have a historical use as hay-meadows (Ehrlén et al., 2005;Garcia, 1992;Hansson & Fogelfors, 2000;Kruess & Tscharntke, 2002;Lennartsson, 2000;Lennartsson & Oostermeijer, 2001;Simán & Lennartsson, 1998). At ceased management, semi-natural grasslands inevitably turn into forest or shrubland and therefore, continuous grazing is better for grassland biodiversity than no grazing at all (Ekstam & Forshed, 1997;Pavlů et al., 2006;Pykälä et al., 2005). The consequences of the intense management regime that is prevailing today, is however much less known. ...
The dominating grazing regime in semi-natural grasslands today is continuous grazing
throughout the season, and a high grazing pressure is often advised in order to avoid litter
accumulation. Traditional management, on the other hand, included late mowing and
grazing, which favoured plant flowering and seed production. This thesis studies the effects
of alternative grazing regimes that may ecologically mimic traditional management. The
ingoing papers examines: 1) Plant reproduction under late onset of grazing compared to
continuous grazing; 2) The tradeoff between disturbance and competition for plant seed
production and establishment; 3) Effects of increased flower density in late grazed
grasslands on pollinator abundance, visitation rate, and pollen limitation; 4) The impact of
landscape, habitat, population, and management on pollination, reproduction, and
population structure of Primula veris. The studies were performed by using grazing and
pollination experiments combined with estimates of habitat and landscape properties. Late
grazing enhanced the fruit set without increasing the litter depth. The management effect for
individual plant species depended mainly on the species’ phenology of reproduction. Late
grazing and 1-yr grazing interruption increased seed production linearly, but reduced
seedling establishment as a threshold function. The net effect was an increased seedling
density and, after six years, species density. Increased flower density in late grazing
attracted more pollinators, but resulted in competition for pollinators among flowers. No
pollen limitation was, however, found in two experimental species. Direct grazing of
reproductive organs outweighed indirect effects on plant reproduction through effects on
pollination. Reproduction and population structure of P. veris was mainly controlled by
seedling establishment, pollen limitation, and direct grazing of fruits. No constant landscape
effects were found. Grazed populations had high proportions of seedlings and juveniles due
to high recruitment and mortality of adult plants, whereas ungrazed populations had higher
proportions of adult plants due to low recruitment. The net effect was similar densities of
young plants in grazed and ungrazed populations. Management regimes such as less intense
grazing, late summer grazing, or late summer mowing would increase both seed production
and establishment, thereby favouring populations of P. veris.
Management of grassland is one of the important factors in traditional livestock farming systems. A survey was conducted in Madi of Chitwan Nepal to understand the perceptions of the farmers/graziers about grassland and feed management. For that, a well-prepared pretested set of questionnaires was used to collect information related to feeds and grassland ecological knowledge of the farmers. The questionnaire consisted of a set of questions about the household, factors affecting grassland productivity and alternative feeding resources. The survey revealed variations in household livestock ownerships, mostly for cattle (1–3) and buffalo (1–5), whilst goat ownership was similar across the survey sites. Grazing duration in months was similar in the study sites (about 7 months per year). Likewise, there was no conflict for grazing livestock, whereas it is believed that goat and buffalo have the same level of detrimental effect on grassland. A significantly higher number of respondents reported that flooding had a negative impact (p = 0.032) on grassland productivity. The Imperata cylindrica (L.) P. Beauv. locally known as Siru was a dominant forage species followed by the mosaics of Saccharum spontaneum L. locally known as Kaans in Nepali and Jhaksi in Tharu language, Saccharum bengalense Retz. locally known as Baruwa in Nepali and Narkat in the Tharu language. The respondents also pointed out that at least 2 to 3 years were needed for the recovery of grasslands when hampered by flooding and riverbank cut-off. Similar species dominated in the recovered grasslands over time of flooding. The seasonal fodder plantation was a major area of grassland improvement issue across the survey sites. There were high dependencies of the graziers on natural herbages and crop residues for feeding livestock in summer and winter, though the herbage species and preferences remained different. This study provides the primary background of the biophysical factors of grassland management for sustainable uses that require institutional support. The study further provides an insight into the need for implementation of the demand-based grassland technology interventions, possibly at a higher rate of adoption than the current local scale. However, the social-ecological consequences of grassland systems, i.e. the impact of climate change, herd dynamics and nutrient flow in vegetation and soil, have to be monitored in a long run.
Native perennial grasslands have been proposed as a source of feedstocks for the production of second-generation lignocellulosic biofuels in the Midwestern USA. Although the consequences of some management decisions for biomass production and plant community composition are well understood (e.g. fertilization), less is known about the effects of harvesting frequency. We compared a once- and twice-annual harvesting regime at two restored prairies in southwestern Michigan established with identical seed mixtures as part of a large-scale bioenergy experiment. We determined biomass production and species composition in experimental plots and also measured the availability of light, inorganic nitrogen and soil moisture. The plant communities that established at the two sites differed markedly in composition and there was little evidence of convergence after five years. At the site dominated by warm-season C4 grasses, single harvests generally produced more biomass than double harvests. By contrast, biomass production was unaffected by harvesting at the more diverse site. Contrary to our prediction that a summer harvest would increase diversity, we found small and subtle effects on plant community composition. This may be due in part to the timing of our harvest treatment. Our results suggest that a single, end-of-season harvest is the best practice for maximizing biomass production in prairies, especially at sites where warm-season grasses dominate. However, at more diverse sites, two harvests can produce the same total biomass and may support other beneficial ecosystem services. This study indicates that in the short term, double harvests are unlikely to affect plant species diversity or community composition in prairie plantings.
Patchiness is one of the important features of grazed temperate grasslands, but little is known about the structure of sward height patches under different grazing intensities. The present study examined the effect of continuous intensive and extensive stocking of heifers on the proportions of sward-height patch categories (short ≤ 5cm, moderate 5.5–10 cm, tall ≥ 10.5 cm) and their plant species composition in an Agrostis capillaris grassland. A four-year study was performed on an upland grassland maintained under a long-term grazing experiment in the Jizerské hory Mts (Jizera Mountains), Czech Republic. The contrasting stocking densities form the differences in the proportion of sward-patch categories and generated a similar level of patch heterogeneity, which was mainly affected by the proportion of tall- and short-sward patches. The floristic composition of patches within the same sward height category depended upon stocking density. Moderate and tall patches under a given stocking density had similar botanical composition. Vegetation within short patches differed considerably from that of other patches under extensive grazing whereas under intensive grazing the differences between short, moderate and tall sward-height patches were small. The findings show that grazing intensity is a key driver of the proportion as well as the floristic composition of sward-height patches in grasslands dominated by A. capillaris. These findings have implications for nature conservation, as they support the recommendation for extensive management of upland grasslands. © 2015, Institute of Botany, Academy of Sciences of the Czech Republic.
Dynamics of vegetation is more and more affected by human activities. The more human society changes or the more and more systems are being built, the more important it is to understand how human activities affect succession. Human dominance of the systems covers a great variety of the management or control. The evolution and succession of the vegetation is developing permanently as a result of the development law and human impact, the development of the vegetation cover being analysed by the scientists from different countries. Through this work we are trying to do an appreciation on the effect of restriction of mowing and grazing on a permanent grassland of Poa pratensis L. The study was developed in the Surducului Hills that are placed at the base of the Poiana Rusca Mountains, at the east of the Bega river terraces. The observations were done on permanent grassland during five years (2006-2009). The vegetation was determined using the linear point-quadrate method, the results being calculated on the base of the botanical surveys. The geographical coordinates were determined with the help of a GPS receptor Magellan. The statistical method used was the correlation analysis. In conclusion we can say that the dynamics of the vegetation is in an intermediate evolution state created by the disturbances connected with the mowing and grazing; the underexploitation and the microclimate created by the presence of the Surduc Lake has determined the trend of the species from the point of view of the FS%; there is a negative correlation between VP and FS% of the legumes and between VP and FS% of the species belonging to other botanical families isn't any correlation. Thus, our purpose is to continue this study for the applying and implementing of some restoration measures for the increase of the quantity and quality of the yield obtained on the surface of these permanent grasslands.
Because of the expansion of agricultural crops that cover mainly fertile land areas, pastures were constraint to draw back on less fertile lands. Man's intervention in the structure of pasture ecosystems consists in the way he harvests biomass and in the land maintenance works. Man's impact on the biocoenoses changes their composition and structure. The reason that land surfaces are improperly managed is due to the fact that the land has become private property and the new owners aren't concerned about the applying of any management. All these aspects correlated with the decrease of the number of cattle resulting in a lower grazing pressure have influenced the dynamics vegetation and pastoral value. In this paper we make appreciations on the floristic composition and on the pastoral value of some permanent pastures around the Hăuzeşti area, trying to identify measures to improve . The study took place in Western Romania in the hills of Surduc which are situated at the bottom of the Poiana Rusca Mountains, east from the Bega – Luncani River and north from the terraces of the Bega River. The study was carried out on two permanent pastures, assessment of the vegetal cover was done through the double meter method and the results were processed on the ground of the botanical sampling. The statistical method used was the analysis of the correlations. Following the study, we drew the conclusion that irrational exploitation of these ecosystems resulted in the simplification of the floristic composition and in the decrease the pastoral value, which asks for new measures to be adopted in their management. Therefore our intention to continue this study is to notify the specialists regarding the implementation of rehabilitation measurements needed for the improvement of the quality and the quantity of forage produced on these surfaces.
The aim of this study was to determine the effects of different long-term management options on re-establishment of traditional species-rich grassland in a Lolio-Cynosuretum grassland. The experiment was set up in 1987 in a low-fertilized mown pasture in the Eifel Mountains (Germany). Two and four cuts per year each with three levels of nitrogen fertilizer application were compared to no application of P and K fertilizer. Biomass production increased as a result of N application, whereas crude protein content and digestibility of organic matter improved in the four-cut treatments. During a 20-year period, we found a significant shift in dominant grass species without any significant effect on species richness. Lolium perenne and Elytrigia repens were replaced by Holcus lanatus and Alopecurus pratensis, especially in the two-cut treatments with N application. In the unfertilized plots, several individuals of Platanthera bifolia appeared when swards were cut only twice per year, probably as a result of nutrient depletion together with low cutting frequency. An increase in number of cuts mainly supported plant species well adapted to intensive management, even under low N application and relatively low plant-available P content in the soil. Therefore, we conclude that cutting frequency was a key driver on plant species composition in this experiment. The re-establishment of traditional species-rich grassland from intensively managed Lolio-Cynosuretum was not achieved within 20 years of cutting management combined with absence of P and K application.
Little is known about the immediate effect of high nitrogen (N), phosphorus (P) and potassium (K) application rates on sown grasslands cut twice per year. We asked how quickly plant species composition, biomass yield, biomass chemical properties and nutrient balance respond to N, P and K application. An experiment using unfertilized control, P, N, NP and NPK treatments was established on seven‐year‐old cut grassland in the Czech Republic in 2007 and monitored over four years. Annual application rates were 300 kg N ha−1, 80 kg P ha−1 and 200 kg K ha−1. The immediate response of plant species composition to N application was recorded and was found to be different to the response over the four years of the study period. Highly productive grasses (Dactylis glomerata, Festuca arundinacea and Phleum pratense) were promoted by N application in 2008 and then retreated together with legumes (Medicago sativa, Trifolium pratense and Trifolium repens) in all N treatments where the expansion of perennial forbs (Urtica dioica and Rumex obtusifolius) and annual weeds (Galinsoga quadriradiata, Impatiens parviflora, Lamium purpureum and Stellaria media) was recorded. At the end of the experiment, Festuca rubra was the dominant grass in the control and P treatment, and species richness was lowest in all treatments with N application. Mean annual dry‐matter yield over all years was 3.5, 3.9, 5.8, 5.6 and 6.8 t ha−1 in the control, P, N, NP and NPK treatments, respectively. Concentrations of N in the biomass ranged from 20.0 to 28.7 g kg−1 in the P and N treatments; concentrations of P ranged from 3.2 to 3.7 g kg−1 in the N and P treatments; and concentrations of K ranged from 24.1 to 34.0 g kg−1 in the NP and NPK treatments. The N:P, N:K and K:P ratios did not correctly indicate the nutrient limitation of biomass production, which was primarily N‐limited, and K‐limitation was only recorded for high production levels in treatments with N applications. On the basis of the nutrient‐balance approach, the balanced annual application rates were estimated as 140 kg N ha−1, 30 kg P ha−1 and 100 kg K ha−1. We concluded that high N, P and K application rates can very quickly and dramatically change species composition, biomass production and its chemical properties in sown cut grasslands. High N application rates can be detrimental for tall forage grasses and can support the spread of weedy species.
The aim of this study was to identify changes in the plant species richness, diversity and composition of a mountain hay meadow (alliance Polygono bistortae-Trisetion flavescentis) after abandonment in comparison with a control cut once per year. The experiment was carried out from 1999 to 2008 in a mountain hay meadow in the Bukovec nature reserve in the north-eastern part of the Jizera Mountains (Jizerské hory, Góry Izerskie, Isergebirge), Czech Republic.The number of vascular plants species with cover greater than or equal to 1% remained almost the same throughout the study period; however, the total number of vascular plants was higher in the cut treatment after the first four years of the study. The cover of Festuca rubra, Agrostis capillaris, Anthoxanthum odoratum, Briza media and Trifolium repens was positively affected by cutting. On the other hand, the cover of Cirsium heterophyllum, Geranium sylvaticum, Hypericum maculatum, Trisetum flavescens and Luzula luzuloides was higher on the abandoned treatment plots.The main effect of the abandonment on plant species composition was the shift in cover of the dominant species. Despite ten years of contrasting management, changes in the vegetation were relatively small with no shift to a different plant community. Therefore the cutting regime combined with several years of no management may be a suitable management strategy for the maintenance of Polygono-Trisetion grasslands and will not be detrimental to the preservation of the target vegetation.
Abstract: The importance of permanent grasslands in Romania has been minimized these last years by
both turning them into arable lands or by abandoning them. The goal of this paper is to characterize
from an ecological point of view and from the point of view of fodder yield some permanent
grasslands in different states of management with a view to establish some corrective measures. The
vegetation of the permanent grasslands was analyzed in 2011, with measurements made in the last
decade of April, in the middle of the second decade of June, and in the second decade of September.
Permanent grasslands are located in the southern part of the Timis County, following the line of the
localities Dudestii Noi – Cenad. Data processing was done based on botanical sampling. Vegetation
determination was done with the linear method (quadrant) calculating pastoral value (PV). Alpha biodiversity
was estimated with the Shannon (H') and Simpson (D) indices, while beta-diversity was
estimated with the Jaccard index (Pj) and with the Hamming (H) distance. Irrational use of permanent
grasslands and the lack of proper improvement measures have lead to the present state of the vegetal
cover. The presence of ruderal plants is obvious and the frequency of invaluable species defines the
grasslands from an agro-ecological point of view.
Many annual cropping lands are being converted to perennial pasture in humid and subhumid areas of the USA as the economic, social, and environmental benefits of managed grazing become evident. Recent evidence about the positive effects of plant diversity on productivity is driving farmers towards management for more complex species mixes than were promoted historically for grazed pastures, but this emphasis has highlighted a lack of understanding about plant community management in pastures. To better understand this system we examined sources of variability in the plant community of a subhumid grassland that was subjected to combinations of disturbance (graze or burn), and amendment (nitrogen, carbon, or ambient), and native grass seeding treatments over 3 years (2004 to 2006). We estimated species cover five times during the study period and ordinated these data with nonmetric multidimensional scaling (NMS). The ordination explained 80% of the variation in the plant community data set. Variance in ordination site scores was ascribed to management (disturbance, soil amendment, and native grass seeding time), the environment (year, season within year, and block), or unexplained (residual) realms with a linear mixed-effects model. The overwhelming source of variability in the plant community (62–99%) was attributed to management. Ordination results illustrated that plant groups sorted out along management gradients: burned plots were shifted towards grasses while forbs and clovers were associated with grazed plots. We demonstrate how a community-level approach can be used to evaluate management regimes in agroecosystems. Our results indicate that disturbance and soil amendments can be used to shape plant communities in subhumid grasslands for specific agronomic and conservation goals.
Terminologický slovník Vydáno ve spolupráci se ZO ČSOP Bílé Karpaty ve Veselí nad Moravou
Two methods for monitoring of grassland vegetation were compared: visual estimation of plant cover (C) and plant densities counting (D). C and D were performed in monthly intervals for three vegetation growing seasons after imposing different grazing regimes on abandoned grassland in 1998. Species scores obtained from paired redundancy analyses (RDA) of C and D data were compared and Spearman's rank correlations were used to show if the two methods give comparable results. Results of C and D were highly correlated in the first two growing seasons only. In the third season, correlation was substantially lower as the sward structure was more heterogeneous due to creation of differently defoliated patches especially under extensive grazing. Presence of the same plant species with different habit in frequently and in infrequently grazed patches, reduced significance of Spearman's rank correlations. Cover estimation can fully substitute plant density counting in grassland with lower proportion of frequently and infrequently grazed patches only, but caution should be used when comparing different management regimes in long term analyses.
The importance of species richness for repelling exotic plant invasions varies from ecosystem to ecosystem. Thus, in order to prioritize conservation objectives, it is critical to identify those ecosystems where decreasing richness will most greatly magnify invasion risks. Our goal was to determine if invasion risks greatly increase in response to common reductions in grassland species richness. We imposed treatments that mimic management-induced reductions in grassland species richness (i.e., removal of shallow- and/or deep-rooted forbs and/or grasses and/or cryptogam layers). Then we introduced and monitored the performance of a notorious invasive species (i.e., Centaurea maculosa). We found that, on a per-gram-of-biomass basis, each resident plant group similarly suppressed invader growth. Hence, with respect to preventing C. maculosa invasions, maintaining overall productivity is probably more important than maintaining the productivity of particular plant groups or species. But at the sites we studied, all plant groups may be needed to maintain overall productivity because removing forbs decreased overall productivity in two of three years. Alternatively, removing forbs increased productivity in another year, and this led us to posit that removing forbs may inflate the temporal productivity variance as opposed to greatly affecting time-averaged productivity. In either case, overall productivity responses to single plant group removals were inconsistent and fairly modest, and only when all plant groups were removed did C. maculosa growth increase substantially over a no-removal treatment. As such, it seems that intense disturbances (e.g., prolonged drought, overgrazing) that deplete multiple plant groups may often be a prerequisite for C. maculosa invasion.
This paper describes the effects of re-establishing seasonal cattle grazing by 0.7 animal.ha(-1) on vegetation in a long-term abandoned, and partly degraded, semi-natural mountain pasture in the Sumava National Park, Czech Republic. There was very uneven grazing intensity inside the locality, and grazing preference changed during the season: cattle grazed most of the time in productive but species-poor Deschampsia cespitosa swards, but changed to a species-rich Violion caninae stand in the middle of the summer. A species-rich Carex rostrata community was only grazed at the end of the season. Species-poor swards dominated by Nardus stricta and Carex brizoides were mainly used as resting areas. Both grazing and excluding from grazing had a negative effect on species diversity of the Deschampsia cespitosa swards. The soil seed bank contained only few species that are characteristic of mountain grassland communities, and seed dispersal of the target species by cattle dung was also found to be very limited. Thus both grazing and exclusion from grazing are probably of limited value for the restoration of species-rich grasslands from species-poor Deschampsia cespitosa swards in this case.
1. Data from permanent grassland plots, collected yearly over a 10 year period were analysed for correlation between weather variables and plant performance. Number of modules and mean biomass of the module were recorded separately. Because the two variables are inter-related, both with each other and with the values in preceding years, regression residuals were used to quantify the response in the particular year. The performance variables were correlated with the monthly averages of temperature and bimonthly averages of precipitation. 2. There was a large year-to-year component of variation in species performance. For biomass, the year-to-year variation is largely explained by correlations with weather; in number of modules, some species show variation which is not explained by the weather variables studied. Weather variables of both current and preceding years showed significant correlations with species performance. 3. Species responded characteristically to weather variables and in any one species, the number of modules and the biomass do not necessarily respond in the same way. This may be an important mechanism creating time lags in the community response to weather variables and, more generally, may be responsible for non-linearity of the community response to the weather.
This book consists of edited and revised versions of the 20 invited papers presented at an International Symposium on Grassland Ecophysiology and Grazing Ecology held at Curitiba, Parana, Brazil on 24-26 August 1999. The papers are on the sustainability of grazing systems (1); environmental constraints and plant responses to defoliation (4); morphogenesis of pasture species and adaptation to defoliation (4); plant-animal interactions (4); sustainable grazing management of natural pastures (4); and problems of animal production related to pastures in subtropical and temperate regions of South America (3). All papers are abstracted separately.
. This paper describes the effects of re-establishing seasonal cattle grazing by 0.7 animal.ha-1 on vegetation in a long-term abandoned, and partly degraded, semi-natural mountain pasture in the Šumava National Park, Czech Republic. There was very uneven grazing intensity inside the locality, and grazing preference changed during the season: cattle grazed most of the time in productive but species-poor Deschampsia cespitosa swards, but changed to a species-rich Violion caninae stand in the middle of the summer. A species-rich Carex rostrata community was only grazed at the end of the season. Species-poor swards dominated by Nardus stricta and Carex brizoides were mainly used as resting areas. Both grazing and excluding from grazing had a negative effect on species diversity of the Deschampsia cespitosa swards. The soil seed bank contained only few species that are characteristic of mountain grassland communities, and seed dispersal of the target species by cattle dung was also found to be very limited. Thus both grazing and exclusion from grazing are probably of limited value for the restoration of species-rich grasslands from species-poor Deschampsia cespitosa swards in this case.
The effect of different cuing and mulching regimes on the structure of the sward and plant species diversity of se - mi-natural meadow (Arrhenatherion alliance) was investigated in manipulative experiment over five years. Mulching once a year in September (MS) and plots without management (U) developed in the same way and resulted in increa- se of Veronica chamaedrys and Galium album and disappearance of light sensitive Trifolium repens. T. repens increased in two cut, two cut without removal of the biomass and in three times mulched treatments. The lowest species diversity was recorded under MS and U treatments on the end of the experiment. Mulching once a year in July altered the vegetation in a different way than the MS treatment. Our results indicate high importance of term of mulching and frequency of defoliation management on the development of grassland vegetation.
This revised and updated edition focuses on constrained ordination (RDA, CCA), variation partitioning and the use of permutation tests of statistical hypotheses about multivariate data. Both classification and modern regression methods (GLM, GAM, loess) are reviewed and species functional traits and spatial structures analysed. Nine case studies of varying difficulty help to illustrate the suggested analytical methods, using the latest version of Canoco 5. All studies utilise descriptive and manipulative approaches, and are supported by data sets and project files available from the book website: Http://regent.prf.jcu.cz/maed2/. Written primarily for community ecologists needing to analyse data resulting from field observations and experiments, this book is a valuable resource to students and researchers dealing with both simple and complex ecological problems, such as the variation of biotic communities with environmental conditions or their response to experimental manipulation.
Sheep grazing was investigated as an alternative to traditional management of meadows in the Krkonoše Mts. Until the second World War these meadows were mown in mid-summer and grazed by cattle for the rest of the season. Subsequent abandonment of the meadows has resulted in decreasing species richness. Degradation phases of the former communities have been replacing the original species-rich vegetation. Significant changes were apparent six years after the introduction of sheep grazing. In grazed plots the proportion of dominant herbs (Polygonum bistorta and Hypericum maculatum) decreased and grasses (Deschampsia cespitosa, Festuca rubra, Agrostis capillaris, Anthoxanthum alpinum) increased. The increase in grasses was positively correlated with an increase in several herbs. The proportion of some herbs increased despite being selectively grazed (Adenostyles alliariae, Melandrium rubrum, Veratrum lobelianum). Any losses caused by grazing of mature plants were probably compensated by successful seedling establishment. Cessation of grazing resulted in significant changes in vegetation within three years. The cover of nitrophilous tall herbs and grasses (e.g. Rumex alpestris, Holcus mollis, Deschampsia cespitosa, Geranium sylvaticum) increased in the abandoned plots. In the plots grazed for nine years cover of species-rich mountain meadow species increased (e.g. fine-leaved grasses, Campanula bohemica, Potentilla aurea, Viola lutea, Silene vulgaris). The main conservation risk is the expansion of a competitive species with low palatability, Deschampsia cespitosa. This species can be suppressed by a combination of grazing and mowing. In order for grazing to be effective, the number of sheep should be proportional to meadow production. This may be difficult to maintain as production is variable and is impossible to predict at the beginning of a growing season. A large part of the biomass may thus remain intact in some years. Negative effects of grazing may be, at least partly, eliminated by a combination of cutting and grazing.
There are few long‐term experimental studies of plant community responses to changes in grazing intensity. Here we report species’ changes in a mesotrophic grassland after 12 years of a grazing experiment and relate these changes to species’ life‐history traits.
The experiment was set up in 1986 on an extensified species‐poor grassland in lowland UK. Treatments comprised sheep grazing vs. no grazing in winter, grazing vs. no grazing in spring, and two grazing intensities in summer, in a 2 × 2 × 2 factorial design with two replicate blocks.
Point quadrat surveys in 1998 showed responses to grazing treatments by 17 of the 22 most common species. Species showed different responses, many of which were specific to a grazing season. Community changes were similar under spring and winter grazing, but the heavier summer grazing had different consequences. Species richness was increased by spring grazing, decreased by heavier summer grazing and unaffected by winter grazing.
More species responded to treatments in the 1998 survey compared with a survey in 1990. Furthermore, the whole experimental grassland had changed between the surveys, probably as a result of falling soil fertility. The two dominant grasses had declined drastically and most other species had increased in abundance. Five new species were found in 1998.
Intensive surveys of dicotyledonous species in 1998 showed five of the 12 most common species had responded to grazing treatments. In most cases dicotyledonous species had increased in abundance under heavier grazing in one or more season, and species richness was increased by spring and winter grazing. Compared with a 1991 survey, the number of species responding to treatments had increased by 1998 and seven new species were found.
We tested whether species’ responses to grazing were linked to life‐history traits according to three hypotheses: that heavier grazing would disadvantage (i) species grazed preferentially, (ii) species less able to colonize gaps or (iii) more competitive species. Mechanisms differed among seasonal treatments. Responses to heavier summer grazing were linked strongly to gap colonization ability. Responses to spring and winter grazing were positively related to grazer selectivity, a surprising result that might be explained if selectivity was positively related to plant regrowth ability.
This study shows the need for long‐term experimental analyses of community responses to grazing as vegetation responses may develop over a long time. The traits analysis suggests it may be possible to predict changes in species composition under grazing through an understanding of the mechanisms of plant responses. Grassland managers require such information in order to manipulate grazing regimes to achieve, for example, diversification or weed control.
Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and biodiversity. Our objective was to identify why grazing causes increases in the spatial heterogeneity of vegetation in some cases, but decreases in others. The immediate effect of grazing on heterogeneity depends on the interaction between the spatial pattern of grazing and the pre-existing spatial pattern of vegetation. Depending on the scale of observation and on the factors that determine animal distribution, grazing patterns may be stronger or weaker than vegetation patterns, or may mirror the spatial structure of vegetation. For each possible interaction between these patterns, we make a prediction about resulting changes in the spatial heterogeneity of vegetation. Case studies from the literature support our predictions, although ecosystems characterized by strong plant-soil interactions present important exceptions. While the processes by which grazing causes increases in heterogeneity are clear, how grazing leads to decreases in heterogeneity is less so. To explore how grazing can consistently dampen the fine-scale spatial patterns of competing plant species, we built a cell-based simulation model that features two competing plant species, different grazing patterns, and different sources of vegetation pattern. Only the simulations that included neighborhood interactions as a source of vegetation pattern produced results consistent with the predictions we derived from the literature review.
The effect of different grazing regimes on pasture vegetation was studied during the intensive grazing of heifers in the Jizerské
hory mountains during 1993–1997. The vegetation was monitored in 3 pairs of permanent 1×1 m plots using a continuous grid
of nine 0.33 × 0.33 m subplots. We applied continuous stocking and rotational grazing. Vegetation varied as a result of time
and differences between treatments. Several prostrate dicotyledonous species (Trifolium repens, Taraxacum sp.,Bellis perennis andLeontodon autumnalis) increased under continuous stocking. This treatment also promoted the growth of the perennial grassLolium perenne, which was able to cope with frequent defoliation. Tall grasses sensitive to frequent defoliation (Poa trivialis, Holcus mollis, Alopecurus pratensis, Dactylis glomerata andElytrigia repens) were more abundant in rotationally grazed paddocks. Species diversity was not significantly influenced by the different
grazing systems. The decrease in the potential sward height under continuous stocking revealed the replacing of tall dominants
by lower species. Our results indicate that different grazing systems alter the composition and structure of grassland vegetation.
Defining the intensity of grazing under continuous stocking or rotational grazing is complex due to the different stocking
rates and the heights of sward during a grazing season. Information about pasture management should therefore involve not
only grazing intensity but also the grazing system used.
Modern rural policies that incorporate agricultural and environmental aims within the broader framework of sustainable rural development are being formulated to address the problem of declines in grassland biodiversity and the destruction of sensitive landscapes and habitats in Europe. Extensification is the process of reducing fertiliser inputs, management intensity and stocking rates, and is central to these sustainable rural policies. However, research in the Less Favoured Areas of Europe has been fragmented and highly variable reflecting the different uses and requirements of our upland areas. Information is needed to determine the nature and timescale of changes in such systems, and whether extensive management is sustainable in the long-term. This paper presents results from a range of grassland extensification experiments across Europe, mainly within the European Union, over the past 30 years that quantify the impacts on soil, plant and animal components of the system. All have the common theme of changing the focus of land management from solely the agricultural product to include a broader range of ecological and environmental objectives. Beneficial changes in biodiversity resulted from more extensive management treatments, but at the cost of reductions in total animal output, and in some cases a reduction in individual animal performance. However, it is clear that it is a long-term process to achieve many of these changes in biodiversity, and this must be recognised by policy makers. We recommend that future extensification studies adopt an approach that will allow their results to be applied throughout Europe.
We investigated the effect of year-round Highland cattle grazing as an alternative management form of species-rich mountain grassland in the Krkonoše National Park (Giant Mts). Traditional management of the Polygono-Trisetion grasslands consisted of mowing once or twice a year and cattle grazing for the rest of the vegetation season. Continuation of the traditional management is not possible for its low profitability. In spring 2000, we established a complete randomized block experiment with four replication and three treatments in 5x5 m plots. Treatments were: no management, mowing once a year and extensive grazing by Highland cattle without any management of non-grazed vegetation. Alopecurus pratensis, Dactylis glomerata, Geranium sylvaticum, Hypericum maculatum, Lathyrus pratensis, Senecio ovatus, Veratrum album subsp. lobelianum, and Veronica chamaedrys were species which increased in cover under no management after three seasons of various management. Differences between grazed and mown plots were not significant in RDA analyses. Trifolium repens was present only in grazed plots, where we did not record any spread of nitrophilous species or excessive trampling. The results of our study indicate that continuous cattle grazing at low intensity is able to prevent tall plant species characteristic of abandoned swards to become predominant. Overwintering of herds with several heads of cattle on the pasture (up to 1 LU*ha-1) and continuous grazing in the vegetation season seem to be an acceptable management alternative in the protected mountain area.
The effect of rotational (RG) and continuous (CG) grazing of heifers on swards was studied in an experimental pasture in upland of the Jizerské hory mountains (lat. 51°20' N, long. 15°02' E) from 1993 to 1997. The number of grass tillers, white clover stolon growing points (sgp), and forbs were measured 3-4 times during the grazing season in each treatment. Clover stolon growing density averaged over time was significantly increased (P < 0.001) by continuous grazing. There was a general trend for sgp to gradually increase during the grazing season. The grazing system did not influence the number of grass tillers. Contrary to the white clover sgp, the number of grass tillers was highest at the beginning of the grazing season and after that it decreased. The average number of forbs tended to be greatest with CG with high variation at both treatment sites during the grazing seasons without significant differences. The number of forbs peaked in the first and last grazing cycle. The seasonal fluctuation of the present species was the main effect on the number of clover sgp, grass tillers and forbs.
This book is primarily written for ecologists needing to analyse data resulting from field observations and experiments. It will be particularly useful for students and researchers dealing with complex ecological problems, such as the variation of biotic communities with environmental conditions or the response of biotic communities to experimental manipulation. Following a simple introduction to ordination methods, the text focuses on constrained ordination methods (RDA, CCA) and the use of permutation tests on statistical hypotheses of multivariate data. An overview of classification methods, or modern regression methods (GLM, GAM, loess), is provided and guidance on the correct interpretation of ordination diagrams is given. Seven case studies of varying difficulty help to illustrate the suggested analytical methods, using the Canoco for Windows software. The case studies utilise both the descriptive and manipulative approaches, and they are supported by data sets and project files available from the book website.
Use of the self-thinning rule to describe size/density compensation (SDC) in defoliated swards is examined. It is shown that defoliation related variation in leaf area and associated morphogenetic changes in plant structure necessitate slope corrections, designated Ca and Cr , respectively. The theory predicts that reduced leaf area in more heavily defoliated swards will result in SDC at slopes more negative than -3/2 (variable leaf area SDC), and that there will be a transition to -3/2 (constant leaf area) SDC at higher herbage mass.
Empirical data from previous experiments with Lolium perenne L. and Medicago sativa L. are examined, and appear to confirm the theoretical predictions, including the slope change at the point of transition from variable to constant leaf area SDC. This transition point, designated di , is subject to interspecific variation and is related to the mature shoot size of a particular species. Some applications of this theory are discussed, and in particular a sward productivity index is proposed.Copyright 1995, 1999 Academic Press
Plant species revegetation of hoof prints in a calcareous fen pasture and of artificially created hoof-print like gaps in an abandoned fen was investigated over two years and compared with the surrounding vegetation. The investigation of abiotic conditions showed that two hoof-print zones had to be distinguished: the steep, drained edge with good light conditions and the flat, dark, but wet bottom. Vegetative spreading and seedling recruitment were examined separately. After two years, hoof prints were not recolonized reasonably, indicating that both hoof-print zones did not offer good conditions for recolonization. Occurrence of frequent species and species numbers were similar in hoof prints, in the surrounding vegetation and in the seed bank. For many fen species germination from the seed bank was better in water-logged pots than in regularly-watered pots. Most species recolonized hoof prints both generatively and vegetatively. In the bottom zone more species germinated than spread vegetatively, but many seedlings died. At the edge, vegetative spreaders finally dominated in spite of high germination rates, because seedling mortality was also high. Overall, recolonization on the edges was more successful than on the bottom, probably because of better light conditions. Only few new species occurred inside hoof prints and only few species were frequent in hoof prints, but not in the surrounding vegetation. Those species were exclusively prostrate species germinating on the edges. The number of recolonizing species did not differ between pasture and abandoned site. Germination, however, was more severely limited in the abandoned fen due to low light availability, litter accumulation and competition by mosses. Altogether, our results show that the presumed importance of hoof prints for species recruitment has to be reconsidered for fen vegetation. On wet peat soil negative effects of soil compaction and changed water and light availability probably prevail over positive effects such as the promotion of subordinate species.
Due to economic pressures and policy changes Lolium perenne‐ Trifolium repens sown swards in upland UK sheep systems are likely to become less intensively managed. We present results from the first 5 yr of a long‐term experiment studying vegetation change under more extensive grazing management at three sites. One treatment was representative of current, intensive management and 5 were unfertilized with different intensities of seasonal grazing. The species composition of unfertilized, ungrazed swards changed dramatically within 2 yr and the sown species had virtually disappeared by year 5. Ranunculus repens, Poa trivialis, Agrostis gigantea, Juncus spp. and Carex spp. became dominant at the wettest site. Grasses were dominant at the other sites. In contrast, the sown species were retained in the unfertilized, grazed treatments; there were small shifts in abundance of the species present initially and few additions or losses of species. Some colonizing species were present in the seed bank whereas others with a transient seed bank appeared to have invaded from neighbouring vegetation. Implications of these results for compensation schemes to reduce animal output and increase biodiversity are discussed. Nomenclature: Stace (1991)
Question: How do functional types respond to contrasting levels of herbage use in temperate and fertile grasslands? Location: Central France (3°1' E, 45°43' N), 870 m a.s.l. Methods: Community structure and the traits of dominant plant species were evaluated after 12 years of contrasted grazing and mowing regimes in a grazing trial, comparing three levels of herbage use (high, medium and low). Results and Conclusions: Of 22 measured traits (including leaf traits, shoot morphology and composition, phenology), seven were significantly affected by the herbage use treatment. A decline in herbage use reduced individual leaf mass, specific leaf area and shoot digestibility, but increased leaf C and dry matter contents. Plants were taller, produced larger seeds and flowered later under low than high herbage use. Nine plant functional response types were identified by multivariate optimization analysis; they were based on four optimal traits: leaf dry matter content, individual leaf area, mature plant height and time of flowering. In the high-use plots, two short and early flowering types were co-dominant, one competitive, grazing-tolerant and moderately grazing-avoiding, and one grazing-avoiding but not -tolerant. Low-use plots were dominated by one type, neither hardly grazing-avoiding nor grazing-tolerant, but strongly competitive for light.
The morphology of independent plants of ‘Grasslands Ruanui’ perennial ryegrass ( Lolium perenne L.) and three cultivars of cocksfoot ( Dactylis glomerata L.) (‘Grasslands Apanui’, ‘Grasslands Kara’ and ‘Grasslands Wana’) in mixed pastures under intensive sheep grazing was studied at Palmerston North, New Zealand during 1991/92.
Both perennial ryegrass and cocksfoot exhibited a similar pattern of clonal growth and population structure. Distribution of plants among various orders of branching showed a relatively stable pattern through most of the year except in spring, when stem decay and plant fragmentation exceeded apical growth and regeneration, causing an increase in the proportion of small plants and a corresponding decrease of larger plants. This pattern was similar to that previously reported for white clover ( Trifolium repens L.). Nevertheless, seasonal variation in plant structure (number of leaves, tillers and stems per plant) was small, but variation in organ size (DW or length) was greater. Stolon formation through elongation of internodes occurred throughout the year, but was associated primarily with flowering.
Grazing management caused no differences in plant structure between species or among the cocksfoot cultivars, but did affect the size of organs, and hence plants. Cocksfoot plants were 50–60% heavier than perennial ryegrass under rotational grazing. Under set stocking, only perennial ryegrass and Wana cocksfoot exhibited sufficient phenotypic plasticity to survive, both Kara and Apanui cocksfoot failed to persist. The only consistent difference between the species was greater flowering in perennial ryegrass than in cocksfoot, in both the proportion of plants flowering, and the number of flowering tillers per plant. Both species produced stolons throughout the year, although perennial ryegrass and Wana cocksfoot had a higher proportion of plants with stolons than Apanui and Kara cocksfoot. Length and DW of stolons per plant were similar in both species.
As there was little variation in plant structure and plant density, length of stolons per unit area tended to parallel seasonal changes in pasture tiller density. The role of grazing management in the survival of tillers and plants, and subsequent performance of grass species in pastures is discussed.
The change in structure of continuously grazed versus infrequently cut swards of perennial ryegrass (Lolium perenne L), cv. S23, was investigated during their first full harvest year. Measurements were made from early May until late September. The intensity of stocking by sheep in the grazed sward was adjusted in an attempt to maintain a high level of radiation interception and the cut sward was harvested at approximately monthly intervals.
The herbage mass, lamina area index and radiation interception of the cut sward varied in a cyclic pattern between harvests but in the grazed sward these parameters showed considerably less variation, although they all increased early in the season and then declined later. The proportion of dead material above ground increased throughout the season in both sward types but was more marked in the grazed sward.
There were major differences between the grazed and cut swards in the number of tillers per unit ground area; the difference became more marked throughout the season and by September the tiller densities in the grazed and cut swards were 3·204 m-2 and 6·203 m-2 respectively. Divergence in tiller density was associated with differences in specific stem weight and leaf area per tiller.
Rates of appearance and death of leaves on tillers in the grazed sward were determined. During May, leaf appearance exceeded leaf death but this was reversed in June. During the rest of the season as a new leaf appeared on a tiller so the oldest leaf died.
The long-term influence of sward height from April to July (Phase 1) and from July to early October (Phase 2) on total herbage and white clover production was measured over four years (1988–1991) as herbage accumulation. A subsidiary experiment to determine the influence of leaf area index (LAI) on gross canopy photosynthesis was conducted to aid interpretation of growth from herbage accumulation data. Target sward heights in 0·5 ha plots in two blocks were 5,7 or 9 cm in Phase 1 and 7 or 9 cm in Phase 2, although mean actual heights per phase were slightly higher. Net herbage accumulation (NHA) was measured within mobile exclosure areas over successive two-week intervals. Gross photosynthesis was measured in circular turves removed from the trial area representing a range of LAIs with an at least reasonable clover content. Despite wide differences in mean sward height and herbage mass, NHA and net clover accumulation for a given phase were not generally affected by treatments. Positive effects of grazing at 5 cm in Phase 1 on NHA and clover accumulation later in the year, and of grazing at 7 cm in Phase 2 on NHA in the following spring were sometimes apparent. Gross canopy photosynthesis (g CO2 m−2 h−1) at 1500 μE m−2 s−1 and 18–21°C was linearly related to LAI described by 1·003 + 1·165 LAI over the LAI range 0·7 to 4·5. Total herbage and clover growth, interpreted from NHA by a previously described model, was predicted to be marginally lower in shorter swards. Similarity in NHA and clover accumulation between treatments was considered to be because of lower senescene and decomposition, and a higher proportion of new tissue being assigned to lamina growth, despite lower LAI and gross photosynthesis in the shorter swards. It was concluded that stocking intensity in swards continuously stocked with cattle did not have a strong influence on net total herbage and clover growth.
An extended rising-plate-meter method was used to study the spatial and temporal variability of the sward structure of extensively managed pastures over a grazing season. Two treatments of a long-term grazing experiment with heifers were investigated: extensive continuous grazing (EG) with a target sward height of 10 cm and intensive continuous grazing (IG) with a target sward height of 5 cm. Compressed sward height and related herbage mass (HM), dominant plant species and stage of development of phenology were determined at weekly or twice weekly intervals at fixed measuring points. The results demonstrated a strong variability in sward height and HM, especially on the EG treatment. The botanical composition of the standing herbage differed between treatments and between patches of different heights within the same treatment. In areas with a short sward, the herbage was predominantly composed of Agrostis capillaris, Festuca rubra and Trifolium repens. It was more evenly composed and also included taller growing species, such as Alopecurus pratensis and Galium mollugo, in areas with a tall sward. The area potentially available for reproductive development was high in the EG treatment and low in the IG treatment. The method employed proved suitable to provide a detailed description of the dynamics of the sward structure.
An outbreak of rabies in a pack of endangered wild dogs (Lycaon pictus) in the Madikwe Game Reserve, South Africa, is described. The outbreak, which occurred in early 2000, was the second outbreak of rabies in wild dogs followed their re-introduction to the Reserve in 1995. The outbreak resulted in the death or disappearance of 10 out of 12 eight-month-old pups. Gene sequence analysis indicates that the virus is distinct from that of the previous, 1997, outbreak, although it falls within the same group as other canid isolates from northern South Africa. Since jackals (Canis mesomelas) are the principal host species of rabies in the area and domestic dogs do not occur in the Reserve, it is assumed that the jackal cycle was the source of the infection. Whereas the pups had not been vaccinated, the five adults, all of which survived, had each been vaccinated by the parenteral route at least twice and each had significant rabies serum neutralising antibodies. This indicates that multiple vaccination against rabies is effective in protecting wild dogs against challenge. Our findings extend previous observations that indicated failure of protection against rabies with single parenteral vaccinations in African wild dogs.
The potential productivity of perennial ryegrass/ white clover swards (GC) under continuous stocking management was assessed by comparing their performance, when grazed by sheep at sward surface heights of 3, 6 and 9 cm, with that of an all–grass sward (G) maintained at 6 cm and fertilized with 420 kg N ha–1 The grass/clover swards received no nitrogen fertilizer. The different grazing treatments had a marked effect on animal performance. In the first year for example, for treatments GC3, GC6, GC9 and G6–420 respectively, mean stocking rates to weaning were 19–7, 14–3, 8–9 and 18–4 ewes ha–1 (plus twin lambs); lamb growth rates were 223, 268, 295 and 260 g d–1and so total lamb live weight gain was 1054, 920, 630 and 1148 kg h a–1. The relative performance of the treatments was similar in all three years. All three grazing treatments had a similar effect on the composition of the grass/clover swards. Clover content increased in 1985, and was sustained in 1986 and 1987 during the main grazing season, although a marked decline in clover content during the winter led to a progressive long–term decline in both the proportion and the amount of clover.
It is suggested that a management based on maintaining a sward surface height close to 6 cm (as in all–grass swards) leads to optimum performance in grass/white clover swards grazed using continuous stocking with sheep. Despite the presence of a small and declining clover content, the output of the mixed grass/clover sward managed in this way was 80%, 80% and 82% of that of a grass sward supplied with 420 kg N ha–1 in 1985, 1986, and 1987 respectively and, similarly, 83% of the output in 1987 of a grass sward receiving 210 kg N ha–1.
The effects of management on the seasonal patterns of production of grass swards under continuous grazing are examined using a previously described mathematical model. For continuous set-stocking it is observed that, if the leaf area index of the sward at turn-out is too low, there may be a sustained reduction in animal intake throughout the season. Under continuous variable stocking, where the sward is maintained at a constant leaf area index, animal intake is observed to follow broadly a pattern determined by the environmental conditions. It is concluded that grass production, in terms of both gross tissue production and animal intake, is not independent of management. Furthermore, no evidence is found to suggest that the seasonal patterns of production undercutting and grazing are the same.
Turnover rates of grass laminae and clover leaf tissue were estimated over a range of intervals within three periods each year in the second to fourth years (1983‐85) of a trial involving swards continuously grazed by steers and receiving either 60 kg N ha‐1 in spring (60N) or 360 kg N ha ⁻¹ throughout the year (360N). Within the 60N swards initial stocking rates at turnout were low (60N LS) at 7‐2 steers ha ⁻¹ and high (60N HS) at 90 steers ha ⁻¹ in 1983, and in 1984 and 1985 corresponding rates were 10‐8 and 13‐5 ha ⁻¹ . The 360N swards were initially stocked at turnout at 96 (360N LS) and 120 (360N HS) steers ha ⁻¹ . Stocking rates were reduced by 33% in midsummer except for 60N in 1984 and 1985 when they were reduced by 50%.
Meaned over 3 years, 360N HS had lower herbage mass than 60N LS. Tiller density in 360N was almost 50% higher than in 60N and clover growing point density was only one quarter that of 60N with the 60N LS having lower clover densities than 60N HS in 1985.
Generally, leaf extension rate per tiller was higher in 360N than 60N and, when significant, 60N LS had higher senescence rates per tiller than 360N HS.
Rate of increase in new clover lamina tissue per stolon was not affected by treatments, whereas in 1983 LS had higher senescence rates of clover laminae than HS. Petiole growth per stolon was higher in LS than HS in 1983 and 1984, the mean over these years for 360N HS being 77% that of 60N LS. Petiole senescence per stolon was lower in 360N HS than 60N LS only in 1983.
When comparing 60N HS and 360N LS (representing similar levels of grazing intensity, having similar herbage mass) the gross growth of leaf material in the former was 75% of the latter, in contrast to 57% for net growth. Clover contributed 18% to the estimated growth of leaves compared to a mean of 7% in herbage mass. Taking inflorescence and pseudostem into account in 1984 and 1985,60N HS had 7% clover in standing herbage and 14% in net growth. Therefore, the contribution of clover to growth is considerably higher than its presence in herbage mass would suggest in continuously grazed swards. It is concluded that low‐N swards, owing to their lower tiller density and slower grass leaf extension rate, will be less efficiently grazed than swards at higher N levels at a given herbage mass, but the presence of clover will partly offset that disadvantage.
Question: A set of easily‐measured (‘soft’) plant traits has been identified as potentially useful predictors of ecosystem functioning in previous studies. Here we aimed to discover whether the screening techniques remain operational in widely contrasted circumstances, to test for the existence of axes of variation in the particular sets of traits, and to test for their links with ‘harder’ traits of proven importance to ecosystem functioning.
Location: central‐western Argentina, central England, northern upland Iran, and north‐eastern Spain.
Recurrent patterns of ecological specialization: Through ordination of a matrix of 640 vascular plant taxa by 12 standardized traits, we detected similar patterns of specialization in the four floras. The first PCA axis was identified as an axis of resource capture, usage and release. PCA axis 2 appeared to be a size‐related axis. Individual PCA for each country showed that the same traits remained valuable as predictors of resource capture and utilization in all of them, despite their major differences in climate, biogeography and land‐use. The results were not significantly driven by particular taxa: the main traits determining PCA axis 1 were very similar in eudicotyledons and monocotyledons and Asteraceae, Fabaceae and Poaceae.
Links between recurrent suites of ‘soft’ traits and ‘hard’ traits: The validity of PCA axis 1 as a key predictor of resource capture and utilization was tested by comparisons between this axis and values of more rigorously established predictors (‘hard’ traits) for the floras of Argentina and England. PCA axis 1 was correlated with variation in relative growth rate, leaf nitrogen content, and litter decomposition rate. It also coincided with palatability to model generalist herbivores. Therefore, location on PCA axis 1 can be linked to major ecosystem processes in those habitats where the plants are dominant.
Conclusion: We confirm the existence at the global scale of a major axis of evolutionary specialization, previously recognised in several local floras. This axis reflects a fundamental trade‐off between rapid acquisition of resources and conservation of resources within well‐protected tissues. These major trends of specialization were maintained across different environmental situations (including differences in the proximate causes of low productivity, i.e. drought or mineral nutrient deficiency). The trends were also consistent across floras and major phylogenetic groups, and were linked with traits directly relevant to ecosystem processes.
Question: How do functional types respond to contrasting levels of herbage use in temperate and fertile grasslands?
Location: Central France (3°1’E, 45°43’N), 870 m a.s.l.
Methods: Community structure and the traits of dominant plant species were evaluated after 12 years of contrasted grazing and mowing regimes in a grazing trial, comparing three levels of herbage use (high, medium and low).
Results and Conclusions: Of 22 measured traits (including leaf traits, shoot morphology and composition, phenology), seven were significantly affected by the herbage use treatment. A decline in herbage use reduced individual leaf mass, specific leaf area and shoot digestibility, but increased leaf C and dry matter contents. Plants were taller, produced larger seeds and flowered later under low than high herbage use. Nine plant functional response types were identified by multivariate optimization analysis; they were based on four optimal traits: leaf dry matter content, individual leaf area, mature plant height and time of flowering. In the high-use plots, two short and early flowering types were co-dominant, one competitive, grazing-tolerant and moderately grazing-avoiding, and one grazing-avoiding but not -tolerant. Low-use plots were dominated by one type, neither hardly grazing-avoiding nor grazing-tolerant, but strongly competitive for light.
A study was conducted to determine the influence of herbage mass under continuous stocking management with sheep on rates of herbage growth (G), senescence (S) and net production of green herbage (NP) in a mixed‐species sward of Lolium perenne. Poa annua and Trifolium repens. Plots were maintained in as nearly constant herbage mass as possible at 500, 700, 1000 and 1700 kg organic matter (OM) ha ⁻¹ by continuous but variable stocking with sheep for the period May to July inclusive. Estimates of G, S and NP were obtained for each species from repeated measurements over two 2‐week periods on individually identified grass tillers or clover stolons. Estimates of species population densities enabled estimates of G. S and NP per unit area to be made.
Rates of G were higher and of S were lower for Lolium tillers and Trifolium stolons than for Poa tillers. The laminae of Poa tillers occupied inferior positions in the canopy of the swards maintained at higher herbage masses and were less accessible to the grazing animals, so that Poa tissue was less well utilized.
The total population densities of tillers and stolons declined at herbage masses both above and below 700 kg OM ha ⁻¹ . The rate of G for the three species combined increased with herbage
Temporal variability of the biomass of individual populations and total community biomass were studied in a species rich meadow (35–40 species 0.25 m−2 plot). Communities were experimentally subjected to fertilization and removal of the dominant Molinia caerulea in a factorial design. The typical dominance structure, with few dominants and many subordinate species, developed in all the treatments. Variability was measured by the coefficient of variation between years, from the fifth to the eighth year of the experiment (to avoid the initial response to the manipulations). Dominant removal increased the diversity measured by the reciprocal of the Simpson index, while fertilization decreased both species number and diversity and also caused a shift in community composition. The variability of both the total community and of individual species was higher in the fertilized plots. The coefficient of variation decreased with species mean biomass in all the plots. In non-fertilized plots, the dominant species had lower variability than total biomass. The biomass values of individual species fluctuated in a concordant manner over the years (i.e. were positively correlated). All of these factors will decrease the strength of the expected portfolio effect. It is argued that the effect of environmental productivity on variability is more pronounced than the effect of diversity.
Question: Are the recruitment patterns of deliberately introduced wildflower species influenced by cutting frequencies and disturbance treatments? To what extent do these different treatments affect productivity and sward structure of an agriculturally improved grassland?
Location: A mesic lowland grassland near Göttingen, Lower Saxony, Germany.
Methods: Recruitment success of eight sown wildflower species was studied in a permanent grassland treated by a factorial combination of different pre-sowing cutting intervals (1, 3 or 9 wk), post-sowing cutting intervals (1,3 or 9 wk) and disturbance (control, harrowing, removal of sward). Seedling emergence and survival, biomass production and sward structure were followed over two years.
Results: For most species seedling emergence was highest in the harrowing treatment. The complete sward removal did not further increase seedling emergence. Seedling survival was strongly influenced by the post-sowing cutting frequency with highest mortality in the 9 wk cutting interval compared to one and 3 wk cutting intervals. Annual dry matter yield varied between 4.4, 5.9 and 9.4 t.ha-1 in the 1,3 and 9 wk pre-sowing cutting treatment, respectively. In June, when the seeds were sown, the tiller number of the 1 wk cut plots was twice as high as for the 9 wk cut plots and five times higher than in the harrowing treatment.
Conclusions: Disturbance by harrowing provided the optimal environmental cues to trigger germination, whereas seedling survival was facilitated by increased light penetration due to frequent cutting. The investigation revealed the overriding importance of frequent standing crop removal in the early phase of seedling establishment on agriculturally improved grassland.
In a four-year removal experiment we investigated the effect of removing a dominant species (Nardus stricta), the litter layer and moss layer on species composition of established vegetation and on numbers and species composition
of seedlings. The experiment was conducted in an oligotrophic wet meadow (Molinion with some features ofViolion caninae according to phytosociological classification). After four years of the experiment, the redundancy analysis (RDA) did not
reveal any changes in the composition of the established plant community. Seedling numbers and their species composition,
however, varied significantly both among treatments and over years. Whereas the differences between treatments were mainly
in total seedling numbers, the years differed in both seedling numbers and relative representation of individual species.
In particular,Myosotis nemorosa seedlings highly increased their abundance in a favourable year 1995 constituting one third of all the seedlings found, whereas
in other years their abundance was between 4% and 10%. The effects of year and treatment were not additive (significant year
× treatment interaction). This means that plots under different treatments are differently affected by climatic conditions
of individual years. The greatest increase of seedling recruitment was observed in the plots with the moss layer removed.
Microsites with high seedling recruitment persisted in the plots for no more than two years.
Why the established vegetation composition does not differ among treatments even after four years, despite the relatively
pronounced and immediate response of seedlings? The number of species with regular seedling recruitment is limited. They are
mostly perennials, and consequently, it might take even longer than four years before recruitment limitation affects the population
size of established plants.
The purpose of this chapter is to examine the factors most likely to influence the dynamic grass-legume relationships in established pastures. Attention has necessarily been focused on the economically important ryegrass (Lolium perenne)-white clover (Trifolium repens) mixtures and on work conducted in the British Isles and New Zealand (with their different seasonal growth patterns and management practices). Reference has also been made to supporting Australian observations on subterranean clover (Trifolium subterraneum, a winter-growing annual) where this is appropriate. The intention is to use these studies to show how the results obtained may provide answers not only to the essentially agronomic questions originally raised but also to more fundamental questions about the factors that control grass-legume relationships and, in particular, about the role of N in this relationship.
Cattle influence grassland dynamics in three ways: herbage removal, dung deposition and trampling. The objective of this study was to assess the effects of these factors, separately or in combination, and to compare them with cattle grazing over a one year period in a field experiment conducted in the Jura Mountains of northwestern Switzerland.
A set of controlled treatments simulating the three factors was applied in a fenced area: (1) repeated mowing — three levels; (2) intensive trampling — two levels; (3) manuring with a liquid mixture of dung and urine — three levels. All treatments were applied homogeneously to the entire surface of each of the 40 plots inside the exclosure. Additionally, ten plots outside the fenced area represented reference plots with regular cattle pasturing. The multivariate response of species composition was assessed three times with the point‐intercept method: in spring before the treatments, in autumn after one season of treatments and at the beginning of the following year after winter rest.
Multivariate analyses of vegetation data in the first year showed an overwhelming seasonal shift and significant differences induced by treatments. Abandoned and manured plots showed the largest deviation from the cattle grazed reference. Herbage removal, simulated by repeated mowing, appeared to be the most important factor for maintaining vegetation texture. Seasonal treatment effects were only partially carried over to the next spring, showing an unexpected resilience of the plant community, probably due to life‐history traits and competition release following climatic disturbance in winter.
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