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Conservation approaches for woody, early successional communities in the eastern United States
Abstract
There is significant concern about the status of some early successional wildlife because of recent declines in populations and amount of habitat in the eastern United States (U.S.). We review types of semi-wooded, early successional habitats in the eastern U.S. and information on their status, and discuss management and planning approaches for their conservation. These habitats are dominated by persistent shrubs, seedling-sapling-sized trees, grasses, and forbs. The area of seedling-sapling forests and many natural shrubland habitats have declined in most of the eastern U.S. Silviculture creates early successional habitats primarily by regenerating stands. The selection of a regeneration method, size and distribution of cuts, and rotation age or reentry period influence availability of these habitats. Multi-scale planning approaches can be used to address regional concerns for these habitats and biological diversity, while facilitating landscape and local planning. We suggest that management for early successional communities is an important issue that should be addressed in conservation and land-management planning. Professional land managers and planners and the public need to address how many of these wildlife species we want and how we want them distributed throughout the region. In many landscapes silviculture will play an important role in providing habitat for these species.
... ESH is critical to maintaining the diversity of flora and fauna in deciduous forests and has a role in forest dynamics in terms of tree regeneration and the maintenance of disturbance generated plant species [5]. The early stage of succession, with an openness caused by the absence of a closed canopy, harbors more pioneer species of grasses and shrubs that better coexist with some endangered, threatened, or sensitive plant and animal species [2,6,7]. The importance of ESH to wildlife is especially well-documented for certain birds [8] and various mammals [9]. ...
... Forest management practices affect both the edge environment and habitat for forest-dependent interior species [21,22]. Timber harvest is one of the most effective ways to create ESHs in managed forest ecosystems [6], serving to enhance connectivity among disturbed sites and altering the abundance of early successional species at the stand level and the relative abundance of open, edge, and closed forest vegetation at the landscape level [23][24][25]. ...
... Studies of state natural resource agencies in the northeastern United States found timber harvesting to be an important tool to promote ESH and suggested increasing its use in developing ESH through alternatives that employ cost-effective management techniques [16,28]. Our research demonstrates a cost-effective technique that created various sized patches or gaps after timber harvest, and patch size has been shown to be crucial for some endangered species [1,6,10,26]. ...
Early successional habitat (ESH) is an important component of natural landscapes and is crucial to maintaining biodiversity. ESH also impacts endangered species. The extent of forest disturbances resulting in ESH has been diminishing, and foresters have developed timber management regimes using standard silvicultural techniques that enhance ESH. We developed a financial framework to evaluate these ESH-enhancing forest management regimes, driven by differences in timber harvest costs and timber revenue. The economic model was applied to on-the-ground prescriptions in the Nantahala National Forest (NNF) designed to increase biodiversity and foster improved public awareness of the importance of ESH. Bats, a current conservation concern, commonly exploit ESH and were the focus of our prescriptions. The prescriptions were based on shelterwood cuts of varying patch size, spacing between the cuts, and the trail area required to move from patch to patch. The results showed that prescriptions with large patch areas were effective in increasing ESH, with minimal impact on the financial performance of timber harvesting operations. This information can be used to minimize financial losses while catering to wildlife species that prefer ESH, in addition to increasing overall biodiversity.
... Both types of habitat are dominated by low, woody vegetation, but they vary in structure. Young forest habitats are typically more transitory than shrublands because tree saplings grow relatively quickly, produce a canopy, and shade out herb and shrub layers to some extent (Thompson and DeGraaf 2001). ...
... Historically, such habitats were always successional in the eastern United States, with the exception of xeric sites, including various types of barrens, and hydric sites, primarily shrub-scrub wetlands. The latter are presently the most prevalent natural shrubland type in DEWA (Thompson and DeGraaf 2001). ...
... As succession proceeds in the eastern United States the number of bird species rapidly levels off at around 30 during years 1-2 following abandonment (Thompson et al. 1996). For continued existence of some of these species, both size and distribution of shrubland patches are equally important (Thompson and DeGraaf 2001). For example, prairie warblers (Dendroica discolor) tend to avoid small, isolated clearcuts (Annand and Thompson 1997). ...
A two-year survey of the early successional habitat avian community was conducted during the
breeding seasons of 2002 and 2003 in the Delaware Water Gap National Recreation Area. Bird
species richness, diversity, density, detection rates, and occurrence were determined and
compared between years, among fields, and with vegetative parameters to elucidate the
distribution and abundance of birds characteristic of open field habitats within the park. This
information was used to develop management suggestions regarding the enhancement of habitat
for these species.
Key Words: bird, guild, grassland, shrubland, point count, structure, composition.
... They are considered to be habitat generalists because they will use open fields with dense herbaceous vegetation as well as open woodlands with a dense shrubby understory. They are common in regenerating fields and clearcuts, or in disturbance caused openings in mature forests but not abundant in mature forests with closed canopies (Thompson et al. 1992;Askins, 1994;Hunter, 2001;Thompson & DeGraaf, 2001). ...
... As noted in the Golden-winged warbler section above, Blue-winged and Golden-winged Warblers interbreed which also may be contributing to their decline. Studies have shown Blue-wing Warbler populations respond positively to clearcuts that maintain the canopy openings and dense undergrowth this species needs (Thompson et al. 1992;Thompson & DeGraaf, 2001). ...
... Habitat fragmentation is a likely threat, because of the increase in predation in fragmented forests. Canada Warblers respond well to forest management practices, especially clearcuts that retain scattered residual trees (Thompson & DeGraaf 2001;Flaspohler et al. 2002;Lambert & Faccio, 2005). ...
The term “early successional habitat” describes the shrubs, trees, and other plants that grow back on the land after older vegetation has been removed or cut back. We can visualize this important habitat type as all the stages of plant growth from open grasslands to young forest. Historically, these habitats were created by natural disturbances, extreme physical conditions such as poor soils or harsh climates, the abandonment of agricultural land, and logging. In recent years, human development has greatly reduced the amount of land available to wildlife, and many of the disturbances that once gave rise to early successional habitat – fire, extensive areas of flooding caused by beavers, and heavy logging – have been suppressed (Trani et al. 2001). As a result, populations of wildlife that need early successional habitat have fallen drastically (Litvaitis, 1993; Thompson & Dessecker, 1997).
In addition to grasslands, important early successional habitats include shrublands and young forest.
Shrublands are dominated by sparse-to-dense shrubs intermixed with young trees, vines, and herbaceous vegetation. Shrublands may develop in abandoned fields. They may persist in areas with poor soils or following repeated disturbances such as flooding or fire, although eventually the young trees will outcompete the shrubs as the vegetation inexorably matures to become forest.
Young forest typically has a dense understory where tree seedlings and saplings, woody vines, shrubs, and herbaceous vegetation grow together. If a mature forest canopy is removed – by logging, fire, or windstorm – and an understory of tree seedlings and saplings is left intact, a young forest composed of late-successional tree species will rapidly spring up, and will persist for 10 to 20 years, until the canopies of the maturing trees knit together and block sunlight from reaching the ground.
Because their canopies intercept most of the light, older forests generally do not support a densely vegetated understory. However, mature forests typically will have scattered patches of thick understory growth where small light-admitting gaps have opened in the canopy after trees have died or fallen down. Beneath the more-open forest canopies of certain tree species, higher light levels can spur the growth of different plants, including shrubs and herbaceous vegetation that attract insect pollinators (Bouget and Duelli, 2004). Such forest stands can support high insect populations (Greenberg, 2001), offering important food to birds, mammals, reptiles, and amphibians.
Young forest and shrublands tend to have a greater variety of fruiting shrubs and herbaceous vegetation than mature forests of any species composition. Seasonally or year-round, many kinds of wildlife, including mammals and young birds that have recently left the nest, feed on these plants and the insects they attract (Askins, 2001; Anders et al. 1998; Vega Rivera et al. 1998). Studies have shown that forest habitats with a dense understory can support abundant wildlife (MacArthur & MacArthur 1961; Conner et al. 1983; Rice et al. 1984; Schulte & Niemi, 1998). In general, habitats with a higher structural diversity of cover will support a greater diversity of wildlife.
... Historically, such habitats were always successional in the eastern United States, with the exception of xeric sites, including various types of barrens, and hydric sites, primarily shrub-scrub wetlands. The latter are presently the most prevalent natural shrubland type in DEWA (Thompson and DeGraaf 2001). ...
... As succession proceeds in the eastern United States the number of bird species rapidly levels off at around 30 during years 1–2 following abandonment (Thompson et al. 1996). For continued existence of some of these species, both size and distribution of shrubland patches are equally important (Thompson and DeGraaf 2001). For example, prairie warblers (Dendroica discolor) tend to avoid small, isolated clearcuts (Annand and Thompson 1997). ...
... However, size is generally of less importance than with grassland species because many shrubland birds are adapted to colonizing relatively small patches of disturbance within a forested landscape (Rudnicky and Hunter 1993; Krementz and Christie 2000; Litvatis 2001). Regeneration habitats are often more ephemeral than the naturally occurring ones (Thompson and DeGraaf 2001). Maintenance of these habitats is dependent on planned anthropogenic disturbance regimes utilizing prescribed burns, chaining, cabling, scalping tillages, or felling with chainsaws (Yoakum et al. 1980). ...
Point count based survey of bird inhabiting early successional habitats throughout the park.
... Patch cuts are small clearcuts where the overstory is completely removed in 1.2 ha (Table 1; Figure 1). These silvicultural treatments also create ephemeral early successional habitat needed by some bird species (Costello et al., 2000;Thompson and DeGraaf, 2001;DeGraaf and Yamasaki, 2003;Yamasaki et al., 2014). ...
... Following treatment, shelterwoods and patch cuts produce greater average species richness of birds than unmanaged forest (Goodale et al., 2009;Duguid et al., 2016). These silvicultural treatments create early successional habitat needed by birds using young forests (Costello et al., 2000;Thompson and DeGraaf, 2001;DeGraaf and Yamasaki, 2003;Yamasaki et al., 2014). Thus, shelterwood and patch cut treatments may both increase biodiversity and improve forest production and regeneration. ...
Managing multiple forest insect pests and diseases is challenging. For example, in eastern white pine ( Pinus strobus ) stands whereas partial shading and high seedling density is encouraged to reduce damage by white pine blister rust ( Cronartium ribicola ) and white pine weevil ( Pissodes strobi ), dense conditions in the understory may increase damage by foliar diseases such as brown spot needle blight ( Lecanosticta acicola ) and Caliciopsis canker ( Caliciopsis pinea ). We evaluated the effect of silvicultural treatments, shelterwoods (residual basal area < 18 m ² ha ⁻¹ ), low density thinnings (residual basal area ≤ 14 m ² ha ⁻¹ ), patch cuts (1.2 ha openings), and untreated controls on damage by these insect pest and diseases in residual overstory trees and regeneration. Shelterwoods and low density thinnings provided a good balance of some shading and reduced stem density, which resulted in less weevil damage and foliar disease severity. Crown condition and quality of regeneration was better in all treatments compared to unmanaged controls. Shelterwoods, low density thinnings and patch cuts have the added benefit on increasing seral habitat, resulting in greater songbird diversity.
... Since the 1950s, shrubland habitat throughout most of New England has been declining due to human suppression of natural disturbances (e.g. beaver flooding and fire), a reduction in large-scale timber harvesting, and development on past agricultural land (Litvaitis, 1993;Askins, 2001;Thompson & DeGraaf, 2001). As a result, wildlife species that require shrubland habitat (including New England cottontails, and birds such as prairie warblers, field sparrows, and eastern towhees) have also been declining (Litvaitis, 1993;Thompson & DeGraaf, 2001;Lorimer & White, 2003). ...
... beaver flooding and fire), a reduction in large-scale timber harvesting, and development on past agricultural land (Litvaitis, 1993;Askins, 2001;Thompson & DeGraaf, 2001). As a result, wildlife species that require shrubland habitat (including New England cottontails, and birds such as prairie warblers, field sparrows, and eastern towhees) have also been declining (Litvaitis, 1993;Thompson & DeGraaf, 2001;Lorimer & White, 2003). In fact, of the approximately forty species of shrubland-dependent songbirds in New England, over twenty species have been declining at a rate of four to seven percent per year (Schlossberg & King, 2007). ...
... We expected that Field Sparrow, Common Yellowthroat, and Red-eyed Vireo would have equal densities in fenced and unfenced harvests and our results support this prediction for the latter two species. Common Yellowthroats use a variety of vegetation communities for nesting habitat, such as thickets, old fields, and regenerating forests up to 10 years post-harvest (Thompson and DeGraaf 2001, Schlossberg and King 2009, Guzy and Ritchison 2020. This species has previously shown a positive relationship with low statured shrubs (Yahner 1986, Schlossberg et al. 2010) and a negative relationship with density of overstory trees and basal area (Yahner 1986). ...
... We also predicted Field Sparrow would be a "deer-neutral" species, however, we found its density was considerably greater in unfenced harvests. This species nests in old fields and young regenerating timber harvests (Yahner 1986, Thompson and DeGraaf 2001, Keller et al. 2003 and is understood to have a positive association with grass cover (Pennington and Blair 2011) and negative association with tree density (Reidy et al. 2014). Our unfenced harvests had shorter woody stems, more herbaceous cover, and similar amounts of residual canopy trees relative to fenced harvests (Parker et al. 2020). ...
Forests of eastern North America have been negatively impacted by excessive white-tailed deer browsing for decades. Previous studies have shown how deer-driven changes to forest structure, plant species composition, and microhabitat negatively impact forest birds. However, most experimental studies used relatively small plot sizes with few replications, limiting the transferability of findings to operational-scale timber harvests and landscape-scale management. We studied the influence of white-tailed deer browsing on breeding bird communities in ten pairs of operational-sized fenced and unfenced regeneration timber harvests in northcentral Pennsylvania. Based on a previous study that examined correlations between bird and deer abundance in Pennsylvania, we developed species-specific predictions about how density would vary between fenced and unfenced harvests. We predicted six species would show a negative response to deer and three would show a neutral response. Overall, diversity and composition of breeding bird communities did not differ between fenced and unfenced harvests. However, four species showed a negative response to deer, four showed a neutral response to deer, and one showed a positive response to deer. Thus, six of nine focal species aligned with our predictions: negative (n = 4) and neutral (n = 2). Densities of two remaining focal species were associated with vegetative features that also were consistent with our predictions. Our final focal species showed a strong positive association with unfenced harvests, contrary to our prediction. Our findings demonstrate that deer-induced impacts on vegetation in operational-scale timber harvests can have considerable influence on densities of some avian species. We conclude that the use of deer-exclusion fencing after timber harvests is an effective and sometimes necessary management tool to achieve maximum forestry and wildlife benefits.
... Nonetheless, sensitive forest management has a role in maintaining habitat suitability for some old-forest specialists, perhaps especially through forms of so-called close-to-nature silviculture, ecological forestry or retention forestry (Schütz 1999;Seymour & Hunter 1999;Lindenmayer et al. 2012), which may also have wider benefits for bird diversity. In both Europe and North America, there is concern that many young-growth species have recently declined and that conservation should be taking more account of their needs (Askins 2001;Thompson & DeGraaf 2001;Fuller 2012a). In this chapter, therefore, we emphasise the resource needs and conservation actions for species associated with both the earliest and latest stages of succession. ...
... Calladine et al. (2015) reported that whilst bird assemblages in continuous cover conifer forests in Britain were richer in bird species and held a higher abundance of 'mature forest birds', rotational clearfells were preferred by a small number of young-growth species. Evidence from US forests indicates that clearfelling rotational systems offer more opportunities for early successional species than continuous cover managed by group-felling or tree selection (Costello et al. 2000;Thompson & DeGraaf 2001;Gram et al. 2003). Other studies in the United States have examined responses of birds to management within continuous cover systems and shown that early successional species can respond favourably to selection harvesting (e.g., Holmes & Pitt 2007). ...
... Many young forest birds have experienced population declines in correlation with this loss of habitat . It is widely accepted that successful conservation of young forest birds relies, in part, on restoring or mimicking natural disturbances to create suitable breeding habitat on both public and private land , Thompson and DeGraaf 2001, Roth et al. 2012b). ...
... sessment of the impact of the shearing BMPs. Ultimately, it is important to remember that no two sites are alike. Regenerating vegetation characteristics following shearing will vary due to soils, vegetation species composition, microclimates, and elevation, thus site-specific management prescriptions are important for reaching conservation goals. Thompson, F. R. I., and R. M. DeGraaf. 2001 ...
Early successional forest and shrubland habitats are collectively called young forest. Changes in disturbance regimes and land use conversion resulted in declines of young forest and associated wildlife across eastern North America. Conservation of declining young forest birds relies on the maintenance and creation of young forest habitats used for breeding. American Woodcock (AMWO; Scolopax minor) and Golden-winged Warbler (GWWA; Vermivora chrysoptera) are two declining young forest species. Conservation plans for both species use an adaptive management framework, which is an iterative process of planning, management actions, and monitoring and evaluation, in the context of species conservation goals. Adaptive management programs often fail to meet their conservation goals when monitoring and evaluation is missing or ineffective. To address this short coming, my research focuses on the monitoring and knowledge gathering aspects of the iterative process. First, I investigated the role of landowners in monitoring the response of AMWO to habitat management on private properties. I interviewed Wisconsin landowners to determine their monitoring preferences and then developed a pilot monitoring protocol where landowner citizen scientists documented the response of male AMWO to habitat management on their properties. I conducted sideby- side AMWO monitoring with landowners followed by an interview to gauge landowner understanding, ability, and satisfaction with the monitoring protocol. Although landowners were willing and excited to participate in AMWO monitoring, their hearing often limited their ability to collect quality data. In order to create a successful AMWO monitoring program that suits the needs of landowners and managers, I recommend in-person training, periodic hearing assessments, and flexible data submittal options. Second, I quantified the response of male GWWA to woody vegetation shearing, a best management practice intended to create quality breeding habitat. GWWA point counts and associated patch-level vegetation surveys were conducted in three habitat management types throughout Minnesota and Wisconsin (mature alder shrubland, sheared alder shrubland, and sheared aspen sapling). Using integrated likelihood models in a distance sampling framework, I investigated the impact of 1) habitat management, and 2) patch-level vegetation characteristics, on the relative abundance of male GWWA. Habitat-management type and habitat age were included in my top supported management model, and occurrence of graminoids, no woody regeneration, and 1-2m tall woody regeneration were supported habitat factors affecting male GWWA abundance. I recommend the continuation of the shearing management practice, particularly when habitat elements are missing. Finally, I tracked the migratory connectivity patterns of GWWA and Blue-winged Warbler (BWWA; Vermivora cyanoptera) in four previously unstudied populations. I used light-level geolocators deployed on male Vermivora to determine individual wintering ranges. Previous research has shown weak migratory connectivity structure in BWWA and strong migratory connectivity structure in GWWA, with GWWA breeding in the Great Lakes region wintering in Central America and those breeding in the Appalachians wintering in South America. I discovered previously unknown intricacies of GWWA migratory connectivity structure with birds from one site in the Great Lakes region wintering in Central America (n=2) and South America (n=3). I propose incorporating migratory connectivity as a criterion for population segment and conservation region designation.
... Forest management and ecosystem restoration are advocated to create, restore, or sustain landscapes for early successional species (Thompson and DeGraaf 2001, King et al. 2011, Reidy et al. 2014). These practices affect large areas in North America and include both ecological and economic objectives. ...
... In the absence of additional disturbance, this stage is ephemeral as conditions transition to a dense stand of young trees in the stem exclusion stage and these trees shade-out herbs and shrubs. Succession to a dense tree stage can happen as quickly as 5-20 years in eastern forests, depending on factors such as growing season length, site factors, and tree species (Thompson and DeGraaf 2001). We consider savannas, open woodlands, and closed woodlands as different phases of open forests. ...
Wildlife biologists classify some bird species as early successional because of apparent dependence on early successional vegetation such as forbs, grasses, shrubs, and small trees. We propose that many “early successional” species were more often associated with open forests such as savannas and woodlands, which covered a much greater extent of the eastern United States under historical disturbance regimes than more ephemeral early successional forest. We draw on several lines of evidence, including knowledge of historical ecosystems and disturbance, landscape analyses, and general literature review to evaluate benefits of open forest ecosystems for early successional birds. Early successional forests covered 1–13% of forestlands in the eastern United States prior to Euro-American settlement, whereas open forests covered large extents of the United States. Many early successional songbirds reach great densities in open forests and potentially greater numbers in landscapes with historical amounts of open forest than in present-day landscapes and those under intensive even-aged forest management. Restoration and management of open forests has not been prioritized or well-articulated for management of early successional birds and other species. Although both early successional forests and open forests provide habitat for birds, we suggest the great reduction in the historical extent of open forests needs to be addressed through greater restoration and management of open forests if we want to better meet the needs of some early successional birds and other wildlife. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.
... Nonetheless, sensitive forest management has a role in maintaining habitat suitability for some old-forest specialists, perhaps especially through forms of so-called close-to-nature silviculture, ecological forestry or retention forestry (Schütz 1999;Seymour & Hunter 1999;Lindenmayer et al. 2012), which may also have wider benefits for bird diversity. In both Europe and North America, there is concern that many young-growth species have recently declined and that conservation should be taking more account of their needs (Askins 2001;Thompson & DeGraaf 2001;Fuller 2012a). In this chapter, therefore, we emphasise the resource needs and conservation actions for species associated with both the earliest and latest stages of succession. ...
... Calladine et al. (2015) reported that whilst bird assemblages in continuous cover conifer forests in Britain were richer in bird species and held a higher abundance of 'mature forest birds', rotational clearfells were preferred by a small number of young-growth species. Evidence from US forests indicates that clearfelling rotational systems offer more opportunities for early successional species than continuous cover managed by group-felling or tree selection (Costello et al. 2000;Thompson & DeGraaf 2001;Gram et al. 2003). Other studies in the United States have examined responses of birds to management within continuous cover systems and shown that early successional species can respond favourably to selection harvesting (e.g., Holmes & Pitt 2007). ...
Cambridge Core - Natural Resource Management, Agriculture, Horticulture and forestry - Ecology and Conservation of Forest Birds - edited by Grzegorz Mikusiński
... The abandonment of farmland has led into a long- term decrease of recently disturbed, early-successional sites that are able to develop freely, leading into the endangerment of many species that inhabit early- successional habitats (Askins 2001, Thompson & DeGraaf 2001, Long 2009). In the 2007 assessment of the conservation status of habitat types in 25 EU countries, the status of agricultural habitats, which represent a large number of disturbed and early- successional habitats, was worse than the status of other habitat types ( Halada et al. 2011). ...
... We demonstrated such site selection (IV) by choosing candidate conservation sites based on landowner capability for site maintenance, but the low number of resulting candidate conservation sites (IV) and our organizational analysis (V) suggest that a large fraction of landowners are either not interested in, or not eligible for, support via agri-environment schemes. Since early-successional habitats can be fast to develop in suitable environmental conditions, a potential workaround could be to look for areas where large enough clusters of conservation sites could be created with landowner consent and co-operation (Thompson & DeGraaf 2001, Brooks 2003, DeGraaf & Yamasaki 2003, Rayfield et al. 2008, Ross et al. 2008. A well-designed habitat suitability model (III) could be of help in the planning where new protected sites could be created, as it would help to avoid using conservation resources at sites that have low probabilities of developing high-quality habitats for the species of interest. ...
... Interpreting the significance of projected shifts in the representation of closed-and open-canopy habitat classes is difficult without appropriate ecological con-text. One viewpoint is that the historical balance between closed-and open-canopy habitat classes should be the standard because these are the conditions under which organisms evolved (Askins, 2001;Litvaitis, 2003;Lorimer, 2001;Thompson and DeGraaf, 2001). Estimating the frequency and extent of historical disturbance events and open-canopy habitat is difficult for a variety of reasons, including difficulty differentiating natural from anthropogenic disturbances and spatiotemporal variation in disturbance rates (Lorimer, 2001). ...
... Estimating the frequency and extent of historical disturbance events and open-canopy habitat is difficult for a variety of reasons, including difficulty differentiating natural from anthropogenic disturbances and spatiotemporal variation in disturbance rates (Lorimer, 2001). To cope with temporal variability in disturbance rates, researchers have suggested managing habitat classes to maintain a balance that falls within the range of historical variability (Thompson and DeGraaf, 2001). With respect to wildlife management, it is important to consider the minimal amount of open-canopy (or other habitat class) required to support viable populations (Askins, 2001;Lorimer, 2001). ...
Large-scale and long-term habitat management plans are needed to maintain the diversity of habitat classes required by wildlife species. Planning efforts would benefit from assessments of potential climate and land-use change effects on habitats. We assessed climate and land-use driven changes in areas of closed-and open-canopy forest across the Northeast and Midwest by 2060. Our assessments were made using projections based on A1B and A2 future scenarios developed by the Intergovernmental Panel on Climate Change. Presently, forest land covers 70.2 million ha and is evenly divided between closed-and open-canopy habitats. Projections indicated that total forest land would decrease by 3.8 or 4.5 million ha for A2 and A1B, respectively. Within persisting forest land, the balance between closed and open-canopy habitats depended on assumed harvest rates of woody biomass. Standard harvest rates led to closed-canopy habitat attaining a slight majority of total forest land area. Intensive harvest rates resulted in the majority of forest land being in open-canopy habitat for A1B or maintained the even split between closed-and open-canopy habitats for A2. Ultimately, managers need to identify benchmark habitat conditions informed by historical conditions and wildlife population dynamics and plan to meet these benchmarks in dynamic forest landscapes. © 2013 Publisher of the Mathematical and Computational Forestry & Natural-Resource Sciences.
... During spring of 2018 and spring and summer of 2019, the burned region had the largest number of disturbance-dependent species of birds. This result supports findings of other studies comparing successional avian communities in disturbed and undisturbed habitats (Akresh et al. 2015, Allen et al. 2006, King et al. 2011, Roberts and King 2017, Sheehan et al. 2014, Thompson and Degraaf 2001, Yahner 2003. While these studies were similar in methodology, most were focused on thinning, clearcutting, and other disturbance. ...
In eastern deciduous forests, fire-disturbance and its ecological implications haven't been heavily studied. In Tennessee, an intensely burned plot of forest (2016) presented a unique opportunity to analyze successional habitat regrowth 2–3 years after a wildfire occurred. To examine post-fire recovery, we observed the diversity of avian species in 1 burned site (1-km transect) and 1 unburned site (690-m transect) during 2018–2019. We used line-transects to examine avian diversity and performed a vegetation analysis to compare the sites. Our results showed that though the unburned site was higher in avian diversity (mean Shannon diversity: 2.844 in unburned vs. 2.521 in burned), the burned site appeared to be suitable habitat for multiple disturbance-dependent avian species. Bird species associated with low to medium vegetation heights and overstory heights and low residual basal areas in early successional forests, such as Setophaga discolor (Prairie Warbler), Passerina cyanea (Indigo Bunting), and Icteria virens (Yellow-breasted Chat), were found only in the burned site, suggesting the fire created suitable habitat for these species, with its average canopy height of 3.55 m and canopy coverage of 18.75%.This study supports the need for greater fire research in Eastern deciduous forests. The results suggest regular fires could create patches of habitats that benefit struggling species of disturbance-dependent birds in this region.
... For each model, we include the number of parameters (k), Δ Akaike's Information Criterion adjusted for small sample size (ΔAIC c ), model weight (w) and log-likelihood (LL). a result of land parcelization, shifting attitudes regarding forest management, and other factors (Litvaitis, 1993, Thompson and DeGraaf, 2001, Brooks, 2003. To combat the increasing scarcity of young forest, a number of land management initiatives have been developed (e.g., USDA -NRCS 'Working Lands for Wildlife', 'Regional Conservation Partnership Program'; Ciuzio et al., 2013. ...
Despite their role as keystone organisms, insect pollinator populations have declined across many regions. Although pollinator populations face a multitude of threats, among the most important is habitat loss and degradation. In eastern North America, forested landscapes are thought to serve as strongholds for robust pollinator populations, however, even these high-quality landscapes are increasingly unsuitable for pollinators due to suppression of natural disturbances, which results in mature forests with few floral resources. To enhance landscapes for forest-dependent wildlife, land managers increasingly recognize the value of silviculture for promoting forest regeneration to support early-successional species. Although timber harvest has proven to be an invaluable tool for enhancing forest pollinator habitat, the role of microhabitat components like log landings remains unassessed. Log landings (open areas where harvested logs are loaded for transport) may serve as an important microhabitat component of early seral stands because they are expected to support open conditions and high floral abundance. We sampled 20 log landing/timber harvest interior pairs for bees, butterflies, floral resources, and structural vegetation in the Pocono Mountains of Pennsylvania from June-September 2019. Hierarchical distance models revealed that log landings supported twice as many bees (897 vs 351 bees/ha) and five times as many butterflies (433 vs 88 butterflies/ha) as timber harvest interiors. Likewise, log landings supported about 14 times as many floral resources than timber harvest interiors (109,572 vs 8,431/transect). Among log landings, those with the most floral resources also supported the most bees and butterflies. Collectively, our results support the hypothesis that log landings serve as concentrated resource hubs for bees and butterflies. Future work exploring the role of different plant species (e.g., native vs exotic) in habitat quality for early-successional pollinators would prove useful.
... Early successional habitats are components of ecosystems and need to be maintained as such within larger forested landscapes (Swanson et al. 2011). Many plants and animals depend on early successional habitats and the decline of early successional habitats over the latter part of the 20 th century has resulted in the decline of these species (Hunter et al. 2001;Litvaitis 2001;Thompson and DeGraaf 2001;Warburton et al. 2011). Thus, several efforts are currently underway to restore early successional habitat throughout forests of the eastern and Midwestern U.S. (Rankin and Herbert 2014). ...
... Birds that breed in early-successional shrubland habitats are declining more rapidly than most bird species in North America (Hunter et al. 2001, Dettmers 2003, and quantifying and managing suitable habitat for these species is critically important. Shrub land habitats rely on disturbance, both natural and anthropogenic, and alteration of spatial and temporal patterns of disturbance presents ongoing man-agement challenges and opportunities (Askins 2001, 2002, Thompson & DeGraaf 2001, DeGraaf & Yamasaki 2003, Litvaitis 2003, Shake et al. 2012. Shrubland habitats are now among the rarest habitats in the northeastern USA (DeGraaf & Yamasaki 2003). ...
Birds that breed in early-successional shrubland habitats are declining throughout North America. The Florida scrub-jay Aphelocoma coerulescens depends on Florida scrub, a shrubland plant community endemic to peninsular Florida, USA. The Florida scrub-jay is nonmigratory, federally listed as threatened, globally listed as Vulnerable, and experiencing ongoing population declines. The largest remaining population occurs in Ocala National Forest (Ocala NF), where the effects of intensive management of scrub for forest product extraction are unknown. During 2011-2014, we conducted the first quantitative evaluation of Florida scrub-jay density and productivity at Ocala NF in relation to the age, size, and connectivity of early-successional habitat patches. Regenerating clearcut stands 3-10 yr post-harvest provided suitable habitat conditions for Florida scrub-jays, with the maximum number of family groups and juveniles occurring in stands 6.5 and 7.4 yr post-harvest, respectively. Our findings indicate that previous definitions of suitable habitat for the species in Ocala NF (e.g. 0-20, 3-15, 3-12 yr post-harvest) are overly broad. We suggest that managers define suitable habitat conservatively given that few stands >10 yr post-harvest were occupied by scrub-jays, and annual productivity in those stands was relatively low. Our findings that scrub-jays readily occupied small scrub patches and did not avoid forested edges should be interpreted with caution, and more demographic study is needed to understand survival and dispersal among patches. Managers can maximize Florida scrub-jay populations in Ocala NF by increasing the availability of habitat that is within 3-10 yr post-harvest.
... Clearcutting, on the other hand, has been criticized for leading to homogenous forests and loss of biodiversity (Rosenvald andLohmus 2008, Kuuluvainen 2009). However, regenerating clearcuts have been found to be important for the conservation of shrubland species (Hunter et al. 2001, Thompson and DeGraaf 2001, King and Schlossberg 2014 and are used extensively by mature forest bird species during the post-fledging period (Marshall et al. 2003, Vitz and Rodewald 2006, Stoleson 2013. Immediately following harvest, clearcut stands are characterized by increased horizontal heterogeneity (e.g., grassy openings among saplings) which allows for both terrestrial gleaners and low-foliage gleaners to inhabit the regenerating stands (Keller et al. 2003). ...
In recent decades, concern for migratory birds has stimulated research assessing the relationships between forest management and bird populations. The Missouri Ozark Forest Ecosystem Project (MOFEP) is a long‐term, landscape‐scale experiment designed to examine the effects of even‐aged (i.e., clearcutting), uneven‐aged (i.e., selection cutting), and no‐harvest forest management on ecosystem‐level processes. The management systems were randomly assigned to three sites each (mean area = 400 ha) with harvest occurring on a different portion of trees every 15 yr over a 100‐yr rotation. We used non‐metric multidimensional scaling and linear mixed models to investigate the effects of silvicultural treatment and year‐since‐harvest on bird communities over a 24‐yr period, before and after two harvests (1996 and 2011). Bird community compositions diverged among treatments immediately post‐harvest, but the differences in community composition and structure began to diminish by 8 yr post‐harvest. Species richness was higher in treated stands than no‐harvest controls and lowest approximately 10 yr post‐harvest regardless of treatment. Species diversity showed a linear decrease with year‐since‐harvest. Our findings demonstrate that even‐aged and uneven‐aged forest management can affect bird community composition and structure within the early post‐harvest period, but differences may diminish relatively quickly as harvested stands regenerate. We recommend using a variety of silvicultural methods to provide the diversity of habitats needed for the conservation of diverse forest bird communities.
... Eastern North America is an exception to the worldwide focus on mature forests, as the vulnerability of open-canopy habitats and shrubland birds in this region has received more emphasis in the past few decades (Hunter et al., 2001;Thompson and DeGraaf, 2001). Historically, these open habitats were created and maintained by natural disturbances, including beaver activity and associated flooding, as well as Native American burning regimes before European colonization (Askins, 2000). ...
The effects of forest management on native fauna are of key interest to managers and conservationists. Individual studies have expanded our knowledge of management impacts, but meta-analyses of multiple studies are needed to summarize and integrate findings into a more generalizable form. Most meta-analyses on the effects of tree harvesting have focused on mature forest taxa because of concerns for these species; however, early-successional specialists, such as shrubland birds in the eastern United States, are also of key conservation concern. Using data from 34 studies that examined the effects of silvicultural treatments on bird communities, we conducted a meta-analysis to determine the effects of tree retention on a suite of bird species reported to be associated with shrubland habitats within the northeastern United States. Of 21 putative shrubland bird species for which we had sufficient sample sizes for analyses, most (62%) exhibited monotonic declines of density with increasing tree retention, defined as percent basal area or canopy cover retained. Five other species (24%) exhibited quadratic relationships with tree retention. Finally, three additional species (14%) considered to be shrubland birds did not exhibit significant relationships with tree retention. We also calculated density estimates of shrubland birds in three categorical classifications of basal area retention corresponding to common management regimes: regen-eration harvests with little retention (clearcut and seed-tree methods), regeneration harvests with moderate retention (shelterwoods), and high retention management regimes (commercial thinning, selection methods, no management). Many of the shrubland species had high densities in clearcuts as well as in stands with low levels (5-25%) of mature tree retention, and some species had equally high densities in stands with moderate tree retention (30-70%), supporting the use of retention forestry approaches, which can provide other benefits associated with mature trees. Overall, our findings provide managers and conservationists with robust, quantitative relationships of shrubland birds with tree retention. Managers can use these quantitative relationships for more detailed planning and evaluation of silvicultural projects, more so than what was feasible using previous findings of shrubland bird responses to discrete silvicultural treatments from disparate studies.
... Since postharvest changes in bird community composition with time have been attributed to regenerating vegetation but not statistically correlated, there remains a clear need to directly demonstrate relationships between changing forest structure and bird communities (Donner, Ribic, & Probst, 2010;Duguid et al., 2016;Thompson & DeGraaf, 2001). ...
Many studies have demonstrated the importance of early‐successional forest habitat for breeding bird abundance, composition, and diversity. However, very few studies directly link measures of bird diversity, composition and abundance to measures of forest composition, and structure and their dynamic change over early succession. This study examines the relationships between breeding bird community composition and forest structure in regenerating broadleaf forests of southern New England, USA, separating the influences of ecological succession from retained stand structure. We conducted bird point counts and vegetation surveys across a chronosequence of forest stands that originated between 2 and 24 years previously in shelterwood timber harvests, a silvicultural method of regenerating oak‐mixed broadleaf forests. We distinguish between vegetation variables that relate to condition of forest regeneration and those that reflect legacy stand structure. Using principal components analyses, we confirmed the distinction between regeneration and legacy vegetation variables. We ran regression analysis to test for relationships between bird community variables, including nesting and foraging functional guild abundances, and vegetation variables. We confirmed these relationships with hierarchical partitioning. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While measures of regeneration condition explain bird abundance and diversity variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground‐story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Our results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood harvests contributes to greater bird community diversity. Interestingly, this is particularly important during the structurally depauperate phase of stem exclusion of young regenerating forests. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While regeneration explains bird variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground‐story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood timber harvests contributes to greater bird community diversity, particularly during the depauperate phase of stem exclusion.
... Pervasive loss of early-successional ecosystems has become a major challenge for wildlife conservation in eastern North America (Thompson and DeGraaf 2001, Greenberg et al. 2011, King and Schlossberg 2014. Changes in land use, disruption of disturbance regimes, and efforts to restore contiguous mature forests have contributed to the ongoing decline of early-successional ecosystems and the organisms that rely on them (Litvaitis 1993, Lorimer 2001, Trani et al. 2001. ...
Conservation of birds that breed in early‐successional forests will require an understanding of their response to patch size and shape during the early seral stages following disturbance. We modeled the effects of patch area, patch shape, and time period following harvest on territory densities of 5 shrubland bird species and bird community composition in 36 clearcuts from 1997 to 2014 in the Missouri Ozarks, USA. Our best‐supported models indicated that densities of indigo bunting (Passerina cyanea), yellow‐breasted chat (Icteria virens), and prairie warbler (Setophaga discolor) declined from the early time period (1–7 years post‐harvest) to the late time period (12–18 years post‐harvest), regardless of clearcut area or shape. Yellow‐breasted chat density and bird species richness were positively related to clearcut shape complexity. Bird species richness increased, and bird species density decreased with clearcut area during both time periods. Non‐metric multidimensional scaling indicated that bird community composition was strongly related to time since harvest. Within the spatial scale of our study, successional stage is more influential than clearcut size and shape, and some bird species may benefit from relatively small or irregularly shaped clearcuts. © 2019 The Wildlife Society. Successional stage had a strong influence on bird communities in regenerating clearcuts that ranged in size from 0.94 ha to 16.79 ha for up to 18 years following harvest. Forest management to benefit shrubland birds should include relatively frequent harvest frequencies, regardless of the size or shape of individual clearcuts.
... Furthermore, the conservation value of these birds that use ghost forests were comparable to that of birds in unaffected forests. Many of the birds we observed that were most likely to occur in ghost forests, including common yellowthroat, northern bobwhite, and yellow-breasted chat, are early seral species that rely on dense shrub and herbaceous cover [51][52][53]. The reduced canopy and midstory cover in ghost forests allows light to reach the understory, facilitating growth of grasses, forbs, and shrubs that are more tolerant than trees to saltwater exposure. ...
Rising sea levels dramatically alter the vegetation composition and structure of coastal ecosystems. However, the implications of these changes for coastal wildlife are poorly understood. We aimed to quantify responses of avian communities to forest change (i.e., ghost forests) in a low-lying coastal region highly vulnerable to rising sea level. We conducted point counts to sample avian communities at 156 forested points in eastern North Carolina, USA in 2013–2015. We modelled avian community composition using a multi-species hierarchical occupancy model and used metrics of vegetation structure derived from Light Detection and Ranging (LiDAR) data as covariates related to variation in bird responses. We used this model to predict occupancy for each bird species in 2001 (using an analogous 2001 LiDAR dataset) and 2014 and used the change in occupancy probability to estimate habitat losses and gains at 3 spatial extents: 1) the entire study area, 2) burned forests only, and 3) unburned, low-lying coastal forests only. Of the 56 bird species we investigated, we observed parameter estimates corresponding to a higher likelihood of occurring in ghost forest for 34 species, but only 9 of those had 95% posterior intervals that did not overlap 0, thus having strong support. Despite the high vulnerability of forests in the region to sea level rise, habitat losses and gains associated with rising sea level were small relative to those resulting from wildfire. Though the extent of habitat changes associated with the development of ghost forest was limited, these changes likely are more permanent and may compound over time as sea level rises at an increasing rate. As such, the proliferation of ghost forests from rising sea level has potential to become an important driver of forest bird habitat change in coastal regions.
... Conservation concern has been raised for decades about early-successional forests due in large part to long-term population declines of organisms that depend on these habitats during critical periods of their life cycle (Thompson and DeGraaf 2001, King et al. 2011, Swanson et al. 2011, Kwit et al. 2014. A number of bird species associated with early-successional forest have undergone strong and consistent population declines over the last several decades (Betts et al. 2010(Betts et al. , 2013King and Schlossberg 2014), including those that require broadleaf vegetation that is targeted by herbicide application (Hagar et al. 2007, Betts et al. 2010, Ellis and Betts 2011. ...
Early-successional forest birds, which depend on disturbance events within forested landscapes, have received increased conservation concern because of long-term population declines. Herbicides are often used to control vegetation within early-successional forests, with unknown effects on avian vital rates. We used a large-scale experiment to test how nest and post-fledging survival were influenced by herbicide intensity within managed conifer plantations across 2 breeding seasons. We created a gradient of 4 stand-scale herbicide treatments (light, moderate, and intensive, and no-spray control) and evaluated the reproductive response of the White-crowned Sparrow (Zonotrichia leucophrys), a declining songbird in managed forest landscapes of the Pacific Northwest. Against initial predictions, we found no evidence that either daily nest survival (n > 760 nests across all treatments) or post-fledging survival (n = 70 individuals reared in control and moderate treatments) were influenced by herbicide application intensity. Increased herbicide intensity resulted in an extensive reduction in vegetation cover at both stand and nest-patch scales; in contrast, vegetative cover at nest sites did not differ across herbicide treatments, nor was nest survival related to vegetation concealment measures. As the largest experimental investigation to assess forest herbicide effects on songbird demography, our study indicates that components of sparrow reproductive success were not influenced by experimental vegetation control measures, although additional work on other early-successional species will be useful to evaluate the generalities of our findings.
... rubrum), beech (Fagus grandifolia), northern red oak (Quercus rubra), American hemlock (Tsuga canadensis), white pine, and shagbark hickory (Carya ovata). We classified clearcuts or shelterwoods created within the last 20 years as early-successional because they typically have dense understory vegetation suitable for shrubland birds (Annand and Thompson 1997, King and DeGraaf 2000, Thompson and DeGraaf 2001. From the original dataset, we created 4 composite land covers: forest (forests and forested wetlands), shrubland (logged areas, old fields, and shrub wetlands), agriculture (hayfields, pastures, and row crops), and developed areas (human-built areas, roads, other infrastructure). ...
In forested landscapes, creation of habitat for early‐successional shrubland birds is controversial because of perceived conflicts with the conservation of mature‐forest birds. Nonetheless, many mature‐forest birds, especially fledglings, readily use early‐successional stands during the post‐breeding period. This suggests that for mature‐forest birds, creating habitat for early‐successional birds could involve a tradeoff: reduced abundance and nest survival due to the loss of nesting habitat versus enhanced fledgling survival in early‐successional stands. Our research addressed the effects of the creation of early‐successional habitat for shrubland birds on wood thrushes (Hylocichla mustelina) in western Massachusetts, USA. We compared wood thrush abundance, nest success, fecundity, and post‐fledging survival in landscapes with high (∼20%) or low (∼1%) cover of early‐successional stands suitable for shrubland birds. We found no differences in nest success, fecundity, and post‐fledging survival between the 2 types of landscapes. Abundance of breeders, however, was significantly greater on the sites with high cover of early‐successional habitat. We conclude that in forested landscapes, creation of early‐successional habitat at levels recommended for the conservation of shrubland birds is compatible with viable wood thrush populations. © 2018 The Wildlife Society.
... Early-successional habitat has declined substantially in the northeastern US because of a reduction in agriculture, expanding urban and suburban developments, and modified timber harvests (Litvaitis 1993, Thompson andDeGraaf 2001). In this region, a variety of insects, birds, reptiles, and mammals are dependent on shrubby thickets and young forests (e.g., King and Byers 2002, Litvaitis 1993, Litvaitis et al. 1999. ...
We examined the abundance and species richness of bees at 10 sites managed for Sylvilagus transitionalis (New England Cottontail Rabbit) in southeastern New Hampshire. In 2015, we sampled bees using a streamlined bee-monitoring protocol (SBMP) developed for rapid assessment of bee communities, and in 2015 and 2016, we employed bee bowls (modified pan traps) painted fluorescent blue, yellow, or white and filled and with soapy water that were intended to mimic flower colors and attract bees. We compared the abundance of all species combined and species richness among management treatments (clearcuts, old fields, and gravel pits), patch area, and time since management action. We also compared the combined captures from bee bowls to relative abundance indices from the SBMP, as well as flower abundance and richness. Neither captured bee abundance nor species richness differed among management treatments; however, by removing a possible outlier, both abundance and richness were greatest in gravel pits compared to other habitats. There was no correlation between bee captures and the SBMP, and no correlation between captures and flower abundance or floral diversity. Our study demonstrates that habitats managed for New England Cottontail support a diverse assemblage of native bees. Gravel pits are potentially valuable targets for native bee conservation, but old fields and clearcuts offer alternatives in landscapes without gravel pits. Native bees are essential to support ecosystem function, and understanding their distribution and natural history is important to develop habitatmanagement efforts that benefit not only bees but multiple species of conservation concern within early-successional habitats.
... Despite negative effects in some cases, both thinning and harvesting of CWD offer opportunities to enhance availability of habitat for some species. Reduced harvesting and other disturbances in some regions of the U.S. and on federal lands have led to decreased availability of early seral habitat conditions, resulting in declines of species associated with structural features such as abundant herbaceous plants and a low woody plant component (Litvaitis, 2001;Hunter et al., 2001;Thompson and DeGraaf, 2001;Brennan and Kuvlesky, 2005;Van Lear et al., 2005;King and Schlossberg, 2014). Management practices that reduce overstory cover and/or disturb sites in other ways therefore provide opportunities to promote early seral habitat conditions and can enhance biodiversity (Trani et al., 2001;Miller et al., 2009). ...
Lower-value biomass (LVB) in forests constitutes non-commercial material traditionally left on site following harvesting. Emerging markets for energy and bioproducts have increased incentives to harvest and utilize this material in some cases. Removal of LVB can reduce forest health risks stemming from wildfire, diseases, and pests but has raised questions about effects on forest productivity and environmental sustainability. The status, trends, and quantities of forest biomass are most often estimated from forest inventories but socioeconomic and physical factors limit the quantity of residual biomass available for use. National forest inventory data suggest quantities of LVB are likely substantial, with annual timberland growth exceeding harvest removals in all states where data are available and unutilized dead biomass roughly half that of current harvest removals. Cost-effective transport distance and logistical factors limit the practical availability of LVB, with in-woods chipping as part of conventional harvesting operations generally providing the greatest economic returns. Harvesting LVB removes higher quantities of nutrients from forested sites with greater potential impact on soil physical properties, soil carbon, and forest productivity than traditional, stem-only harvesting. However, global assessments show inconsistent forest productivity and soil responses and impacts across contrasting sites and soil types. Lower residue retention and changes in forest structure resulting from LVB harvesting can also influence habitat for some wildlife species. Some field studies suggest removals of downed coarse woody debris negatively impact bird diversity and abundance while other assessments suggest minimal or only temporary effects with benefits to other species, particularly those associated with early seral habitat. While LVB harvesting and residue removal have the potential to increase soil disturbance and delivery of sediment and nutrients to streams compared to traditional harvesting, best management practices demonstrated effective in protecting water quality through decades of field research should be largely applicable to practices that include LVB harvesting. Although states and other entities have developed biomass harvesting guidelines and revised certification standards that restrict or modify intensive harvesting practices, the efficacy of such guidelines is uncertain due to highly variable site limitations and responses and a lack of site-specific response data. This paper provides an overview of environmental implications and practical considerations related to harvesting LVB in forests and how they differ from harvesting of traditional, commercial biomass sources.
... Concern has increased in recent years regarding species that require early-successional forest habitat due to long-term population declines (Litvaitis, 1993;Thompson and DeGraaf, 2001;Schlossberg and King, 2009; vegetation for foraging and nesting during the breeding season (Hagar, 2007;Betts et al., 2010;Ellis and Betts, 2011). Indeed, a recent review found that >50% of species of conservation concern in the Pacific Northwest region of North America use or require early-successional forest during their life cycle, including many state conservation-listed species . ...
Many species that use or require early-successional forest are of conservation concern, including a number of songbirds that have experienced long-term population declines. In this study, our initial goal was to test whether herbicide application intensity was linked to offspring sex ratio in the White-crowned Sparrow (Zonotrichia leucophrys), a species that requires early-successional forest within forested landscapes. However, a rapid and accurate method using direct PCR to sex a large sample of birds (n > 1000 individuals) was unavailable, so our secondary goal was to develop a new approach for rapidly determine offspring sex. We obtained blood samples from sparrow young during the 2013–2014 breeding seasons in regenerating conifer plantations that were treated with one of four treatments (i.e. light, moderate, and intensive herbicide application, or no-spray control). We then optimized a protocol that used a commercially available, direct PCR kit to amplify sex-specific fragments of the CHD (chromo-helicase-DNA-binding) genes directly from whole blood stored in lysis buffer. Using this approach, we found no evidence that offspring sex ratio was linked to herbicide application intensity or to food availability across herbicide treatments. Our molecular sexing technique was 100% accurate when validated on known-sex adults, and 99.9% of our blood samples amplified successfully after being stored in lysis buffer stored for up to 3 years. The application of direct PCR for sexing birds eliminated the need for DNA extraction and substantially reduced sample processing time, cost, and the opportunity for errors during the extraction step. We conclude that forest herbicide application intensity does not influence sparrow offspring sex ratio in our study system, and that our approach provides a rapid, accurate, and tractable method for sexing birds that can facilitate studies that require processing of a large number of samples.
... In particular, habitat patch networks can be dynamic for species that occupy early successional habitats, in which case individual habitats may emerge and disappear depending on local disturbance patterns and the process of succession (Johst et al. 2011). As the intensification of human land use has caused changes to disturbance regimes across ecosystems (Lytle and LeRoy Poff 2004, Enck and Odato 2008, Lourival et al. 2011, the availability of early successional habitats has decreased in many ecosystems (Thompson andDeGraaf 2001, Halada et al. 2011), and this has caused the endangerment of early successional species (Askins 2001, Dettmers 2003, Long 2009). These developments have resulted in spatially explicit conservation planning needs for species that live in spatiotemporally changing habitat networks (Van Teeffelen et al. 2012). ...
Species living in metapopulations depend on connected habitat networks for their survival. If habitat networks experience fast temporal dynamics, species conservation requires preventing habitat discontinuities that could lead to metapopulation extinctions. However, few institutional solutions exist for the maintenance of spatiotemporally dynamic habitat networks outside of protected areas. To explore this often neglected problem, we studied the institutional fit of false heath fritillary (Melitaea diamina) conservation in Finland from the perspective of conservation institutions’ ability to manage early successional habitat availability for this endangered species. We identified four institutional arrangements that enable effective conservation management of dynamic habitat networks: (1) acknowledgment of habitat dynamics, (2) monitoring of and responding to changes in the habitat network, (3) management of resources for fluctuating resource needs, and (4) scaling of activities through flexible collaborations. These arrangements provide the institutional flexibility needed for responding to temporal changes in habitat availability.
... Studies of birds in semi-natural forests of North America, that are either selectively felled to maintain uneven age stands with near continuous cover or are managed through clearfelling, have identified conflicts between management that favours mature forest birds and the maintenance of habitats of sufficient extent for shrubby, early successional bird communities (Costello et al., 2000;Thompson and DeGraaf, 2001;King and Schlossberg, 2014). Despite expectations, evidence for enhanced biodiversity under CCF management is scarce and mixed, particularly in Europe. ...
Continuous cover forestry (CCF) systems are increasingly advocated for stand management, with biodiversity among the ecosystem services perceived to benefit. However, long term (>100 years) influences of such silvicultural systems on biodiversity in managed forests are poorly understood. Timed point counts in Scots pine forests in Scotland were used to quantify associations between species richness, diversity and abundance of breeding birds and different forest structures provided by CCF. Managed forests with old growth features (some including particularly old pines and snags) were considered surrogates for long term CCF stands. A stand category with an understorey of young trees (understorey reinitiation) was the most species rich (other categories in descending order were old growth, commercially maturing stands with no regenerating understorey and exclusively pre canopy-closure young growth stage) but differences were small and marginally non-significant. Heterogeneity in canopy layer structure at a scale typical of many song bird territories (ca 1 ha) and the occurrence of old growth features were associated with greater abundance in a number of individual bird species but many associations were species-specific. Knowledge of species-specific responses to forest structure can inform management for the benefit of species of conservation concern and other priority species but requires better understanding of optimal structural mosaics including frequencies of old trees and snags for those species and groups. Bird distributions can change in response to extrinsic factors within the expected long-term plans for CCF managed forests; the contribution of structural mosaics to the resilience of forests in supporting a changing avifauna deserves further attention.
... Additionally, oak savanna is considered high quality habitat for many important game species including northern bobwhite, wild turkey (Meleagris gallapavo), fox squirrels (Sciurus niger), cottontail rabbits (Sylvilagus spp), and white-tailed deer which adds significant economic implications to the restoration of these communities (Henderson, 1995). The transitional nature of oak savanna and woodland communities provides a mosaic of 11 vegetative structures beneficial to many wildlife species (Askins, 1993;Thompson and DeGraaf, 2001). ...
The decline and degradation of oak savanna and woodland communities throughout the Mid-South underscores the need to develop management techniques capable of their efficient and successful restoration. Therefore, my objectives for this work were to document plant community response to variations in canopy disturbance level, fire seasonality, and herbicide control of hardwood midstories. In Chapter One, I provide a thorough review of the current body of knowledge concerning open-oak communities and their restoration, with specific focus on herbaceous and woody plant response to canopy disturbance, fire, and herbicide midstory management. Chapter Two details the response of herbaceous and woody vegetation to variations in canopy disturbance level and fire-season during a replicated experiment in Tennessee. I conclude that higher canopy disturbance levels and fire application positively impacted restoration goals with increases in herbaceous groundcover, richness, and diversity. Limited differences among the fire-season treatments were observed, with similar, prolific resprouting of mesophytic oak competitor species following both fire-season treatments. I suggest exploration into burn timings that will limit this resprouting such as earlier fall or spring fires, to accelerate the restoration timeframe. Chapter Three addresses herbaceous and woody vegetation response to woody midstory herbicide treatments. Herbicide treatments reduced the cover and density of woody plants more than fire alone, and included reductions of larger size classes that were unaffected by fire. Herbicide applications were most effective following late growing-season fire. These reductions occurred without harming desirable understory herbaceous vegetation, and increased graminoid cover within heavy canopy disturbance and growing-season fire treatments. Herbicide treatments cost $193.61ha-1. Incorporating the valuable lessons learned through this research will improve the efficiency of future restoration attempts and result in the return of healthy and sustainable oak savannas and woodlands in the Mid-South.
... The positive effect of habitat heterogeneity on the species diversity of breeding birds is well known (Greenberg et al. 2011, Hunter andSchmiegelow 2011). Silvicultural openings are used by a wide range of birds because they create habitat for earlysuccessional species (Annand and Thompson 1997, King et al. 2001, Thompson and DeGraaf 2001, Gram et al. 2003 and enhance foraging conditions for species that breed in mature forest and forage in early-successional habitat (Anders et al. 1998, Pagen et al. 2000, Vitz and Rodewald 2006, McDermott and Wood 2010. Previous research has shown that uneven-aged silviculture has stronger positive effects on breeding bird species richness compared to even-aged silviculture and preservation management (Gram et al. 2003, Morris et al. 2013, although even-aged silviculture is also recommended for maintaining diversity of Neotropical migrants (Keller et al. 2003). ...
Contemporary forest management offers a trade-off between the potential positive effects of habitat heterogeneity on biodiversity, and the potential harm to mature-forest communities caused by habitat loss and perforation of the forest canopy. While the response of taxonomic diversity to forest management has received a great deal of scrutiny, the response of functional diversity is largely unexplored. However, functional diversity may represent a more direct link between biodiversity and ecosystem function. To examine how forest management affects diversity at multiple spatial scales, we analyzed a long-term dataset that captured changes in taxonomic and functional diversity of moths (Lepidoptera), longhorned beetles (Coleoptera: Cerambycidae), and breeding birds in response to contemporary silvicultural systems in oak-hickory hardwood forests. We used these datasets to address the following questions: how do even- and uneven-aged silvicultural systems affect taxonomic and functional diversity at the scale of managed landscapes compared to the individual harvested and unharvested forest patches that comprise the landscapes, and how do these silvicultural systems affect the functional similarity of assemblages at the scale of managed landscapes and patches? Due to increased heterogeneity within landscapes, we expected even-aged silviculture to increase and uneven-aged silviculture to decrease functional diversity at the landscape level regardless of impacts at the patch level. Functional diversity responses were taxon-specific with respect to the direction of change and time since harvest. Responses were also consistent across patch and landscape levels within each taxon. Moth assemblage species richness, functional richness, and functional divergence were negatively affected by harvesting, with stronger effects resulting from uneven-aged than even-aged management. Longhorned beetle assemblages exhibited a peak in species richness two years after harvesting, while functional diversity metrics did not differ between harvested and unharvested patches and managed landscapes. The species and functional richness of breeding bird assemblages increased in response to harvesting with more persistent effects in uneven- than in even-aged managed landscapes. For moth and bird assemblages, species turnover was driven by species with more extreme trait combinations. Our study highlights the variability of multi-taxon functional diversity in response to forest management across multiple spatial scales. This article is protected by copyright. All rights reserved.
... However, clearcutting can also serve as an effective management tool for promoting early successional habitat or increasing habitat heterogeneity (Thompson and DeGraaf, 2001;Franklin et al., 2002;DeGraaf and Yamasaki, 2003). Clearcutting may be particularly important for migratory songbird species that have experienced recent population declines because of earlysuccessional habitat loss (Litvaitis, 1993;Brawn et al., 2001;Hunter et al., 2001). ...
Anthropogenic habitat degradation is a primary threat to global biodiversity. The overarching
theme of my dissertation is one of conservation-based research for reducing the impacts of
anthropogenic disturbances, specifically timber harvesting, on forest wildlife. Although the
primary objective of my dissertation is to assess the effectiveness of structural retention (i.e.,
canopy green trees and coarse woody debris) for conserving wildlife in harvested forests, it also
provides valuable insight to other areas of ecology and wildlife management. Throughout my
dissertation I highlight the need to use design- and model-based approaches for minimizing bias
associated with the limited detectability of wildlife. Doing so allowed me to achieve stronger
inference when determining how wildlife interacts with their environment. For my first two
chapters I use species occupancy models and multiple sampling techniques to estimate detection
probabilities of forest-floor wildlife. These chapters demonstrate the need to incorporate species
detectability when comparing the effectiveness of different trapping methodologies.
Furthermore, these studies highlight the utility of power analyses for exploring study design
tradeoffs for research and monitoring programs. I used results from these chapters to develop a
strong sampling design for Chapter 5. In Chapter 3 I lead a detailed investigation into the
performance of wildlife occupancy models when model assumptions were openly violated.
Analyses from Chapter 3 revealed general sensitivity of estimates from single-season occupancy
models to violations of closure. This chapter highlights the importance of addressing the
population “closure” assumption and the impact of non-random organism movements in wildlife
occupancy studies. I provide multiple solutions for minimizing bias associated with non-random
changes in occupancy within a field season. For my final two chapters I assess the effectiveness
of structural retention for conserving wildlife in harvested forests. Both studies represent an
empirical evaluation of the Michigan Department of Natural Resources (MDNR) structural
retention guidelines in harvested aspen stands. Results from Chapters 4 and 5 suggest that
broad-scale conservation goals for forest songbirds and terrestrial salamanders will not be
accomplished by simply retaining structure within individual harvest units. Rather, successful
conservation efforts for these species may also require conservation of late-successional forests
as part of managed landscapes. Future management objectives in aspen forests should reflect the
value of clearcutting to early-successional and generalist bird species while recognizing that
green-tree and coarse woody debris (CWD) retention, as observed here, did little to promote site
occupancy of interior forest bird and terrestrial salamanders. However, if the management goal
is to reduce mortality of local salamander populations following timber harvest, then my research
suggests that implementing structural retention prescriptions is a viable management option.
Results from Chapter 5 demonstrate that organismal pattern (occupancy) and process (survival)
can function independently in response to habitat change, and thus emphasizes the importance
joint-evaluation of these state variables when evaluating mitigation techniques presumed
beneficial to wildlife.
... The importance of ecosystems dominated by shrub vegetation is often neglected because they are considered as successional transient communities (Thompson and DeGraaf 2001), dominated by nuisance species (Van Auken 2000), which are difficult to manage (Schlossberg et al. 2010). Shrubland ecosystems have the potential to store a large amount of carbon in the soil and in plant tissues; the latter can be enhanced with proper management of shrublands (Wenhiu et al. 2014;Adhikari and White 2016). ...
Rapid assessment of plant size and population densities is important for estimating biomass over large areas, but it has often been limited by methods requiring intensive labor and resources. In this study, we demonstrate how shrub biomass can be estimated from fine-grained aerial photographs for a large area (23,000 ha) located in the Lower Rio Grande Valley, Texas, USA. Over the past 30 years, refuge land management has included the replanting of native shrubs to promote the restoration of wildlife habitat and carbon sequestration. To assess shrub regrowth, we developed a method to estimate individual shrub canopy areas from digital aerial imagery that was used to calculate biomass from allometric equations. The accuracy of the automated delineation of individual canopies was 79 % when compared to that of hand-digitized shrub canopies. When applied to photographs across the refuge, we found higher shrub densities for older naturally regenerated sites (174 individuals ha−1) compared to those of younger replanted sites (156 individuals ha−1). In contrast, naturally regenerated sites had less biomass (3.43 Mg ha−1) than replanted sites (4.78 Mg ha−1) indicating that shrubland restored for habitat conservation has the potential to sequester more carbon in a shorter period. There was an inverse relationship between aridity and aboveground shrub biomass for replanted sites in the drier west (p < 0.05). We found a difference in predicted biomass among shrub species in replanted sites that was also associated with climate (p < 0.05). We conclude that the canopy of individual shrubs detected from remote sensing can be used to estimate and monitor vegetation biomass over large areas across environmental gradients.
... Thirteen of the 20 most species rich and diverse wetlands were shrub and open/shrub wetlands, including the top three wetlands for each parameter (Tables 5 and 6) DeGraaf 2001, DeGraaf andYamasaki 2003); thus, no active management is required to maintain this wetland habitat. ...
A two-year survey of wetland birds in the Delaware Water Gap National Recreation Area was
conducted during 2004 and 2005. Bird species richness, diversity, frequency of occurrence by
habitat, species, and guild wetland habitat preferences, and edge vs. interior habitat preferences
were analyzed and compared in order to characterize the distribution and abundance of birds
across wetland habitat types found within the recreation area. This information will be used to
characterize wetland bird communities and comment on management strategies for continued
protection of these habitats and their characteristic avian inhabitants.
Key Words: bird, guild, wetland, point count, detection rate, frequency, richness, diversity, edge,
interior
... Non-crop plant species are usually not eliminated from herbicide-treated sites , but a change in the abundance or a retardation of growth rate of non-crop plant species occurs and is evident in the increased pres-ence and success of conifers. This retardation of growth, compared to increase in plant mortality, has been found to be true in most studies that look at the effects of herbicides on forest vegetation Freedman 1995;Lautenschlager 1990;May et al. 1982;Morrison and Meslow 1983;Newton et al. 1992;Santillo et al. 1989b;Thompson and DeGraff 2001;. Several studies have addressed the question of the richness and diversity of non-crop plant species following herbicide application. ...
This publication reviews and synthesizes the results of many research studies designed to elucidate the ecological effects of the herbicide glyphosate used in forested landscapes. We have not intended our review to be an exhaustive review of all published studies (both laboratory and field investigations) concerned with faunal and floral glyphosate interactions and the environmental fate of glyphosate. We particularly focused on studies that had relevance to north temperate forest ecosystems and selected published investigations to incorporate into our review that cover a wide range of faunal and floral taxa that might be exposed to herbicides during applications.
... As stated previously here and by , the time frame with which early-successional birds can inhabit an area depends on the type of harvest conducted and the individual species of bird. Thompson and DeGraaf (2001) found Indigo Buntings, Prairie Warblers, and Yellowbreasted Chats all first appeared 1-2 after a clearcut and began to decline in abundance 7-10 years after clearcutting in an eastern deciduous forest. found that species such as: Eastern Towhee, Eastern Wood-pewee, Hooded Warbler, Indigo Bunting, Kentucky Warbler, Red-eyed Vireo, and the Yellow-breasted Chat all exhibited a quadratic response to silvicultural treatments (variable retention cuts, clustered thinning with embedded patch-cuts, and variable retention cuts without embedded patch-cuts) in a bottomland hardwood forest in Louisiana. ...
... Thus, edge effects due to bird movements among stands and the surrounding landscape were likely. Even so, marked increases in the abundance of birds associated with early successional forest habitats (Thompson and DeGraaf 2001) were noted within stands subjected to variable patch clearcuts and diagonal corridor thinning. Lack of an increase of bird species that are typically associated with shrub-scrub habitats within stands subjected to row thinning suggests that openings within this treatment were insufficient in area to create habitat conditions that attract colonization by these bird species. ...
During the past 30 years, thousands of hectares of oak-dominated bottomland hardwood
plantations have been planted on agricultural fields in the Mississippi Alluvial Valley. Many of these
plantations now have closed canopies and sparse understories. Silvicultural treatments could create a more
heterogeneous forest structure, with canopy gaps and increased understory vegetation for wildlife. Lack of
volume sufficient for commercial harvest in hardwood plantations has impeded treatments, but demand for
woody biomass for energy production may provide a viable means to introduce disturbance beneficial for
wildlife. We assessed forest structure in response to prescribed pre-commercial perturbations in hardwood
plantations resulting from silvicultural treatments: 1) row thinning by felling every fourth planted row; 2) multiple
patch cuts with canopy gaps of <1 ha; and 3) tree removal on intersecting corridors diagonal to planted rows.
These 3 treatments, and an untreated control, were applied to oak plantations (20 - 30 years post-planting)
on three National Wildlife Refuges (Cache River, AR; Grand Cote, LA; and Yazoo, MS) during summer 2010.
We sampled habitat using fixed-radius plots in 2009 (pre-treatment) and in 2012 (post-treatment) at random
locations. Retained basal area was least in diagonal corridor treatments but had greater variance in patch-cut
treatments. All treatments increased canopy openness and the volume of coarse woody debris. Occurrence of
birds using early successional habitats was greater on sites treated with patch cuts and diagonal intersection.
Canopy openings on row-thinned stands are being filled by lateral crown growth of retained trees whereas
patch cut and diagonal intersection gaps appear likely to be filled by regenerating saplings.
... Recent studies in the past decade have found that eastern whip-poor-wills prefer large areas of early successional forest such as regenerating clearcuts (Wilson and Watts 2008, Hunt 2013, Tozer et al. 2014, which may provide suitable habitat for foraging (Tyler 1940, Cink 2002, Garlapow 2007. Active forest management plays an important role in creating and maintaining early successional forests for eastern whip-poor-wills and other declining early successional bird species (Thompson and DeGraaf 2001). Nevertheless, little is known about key aspects of whip-poor-will breeding ecology, including abundance, nest site characteristics, and nesting success, particularly in relation to these forest management practices (Cink 2002). ...
Numerous wildlife species are dependent on the creation and maintenance of early successional forests, yet little is known about the effects of habitat management on some threatened species. One such species is the eastern whip-poor-will (Antrostomus vociferous), a nocturnal bird of conservation concern. We examined the effects of heavy thinning, mowing, burning, and herbicide treatments on this species by conducting point counts and nest searches on a pitch pine–scrub oak (Pinus rigida–Quercus ilicifolia) barren in western Massachusetts, USA, between 2006 and 2013. Our point-count data showed that the abundance of calling birds was greater in managed shrublands such as scrub oak barrens and heavily thinned pitch pine stands, compared to closed-canopy pitch pine and deciduous forest. We found a high number of whip-poor-will nests (n = 26) and roosts (n = 59), which we located primarily within managed shrublands. We did not search for nests in closed-canopy forests, and we were unable to determine the extent of their use of the forest edge for nesting. Nevertheless, birds selected nest sites under residual deciduous trees within the early successional forests; therefore, canopy cover appears to be important for nest placement at the nest-patch spatial scale, but not necessarily at a broader scale. Nests were found in both dense and sparse understory vegetation; none were found in vegetation patches that were <2 years since treatment. Estimated nest survival was 63% through incubation (daily survival rate = 0.977, n = 21), consistent with other published studies of nightjars in the United States and Canada. Creating and maintaining open-canopy early successional forests in pitch pine–scrub oak barrens, with the retention of some residual deciduous trees, should increase the amount of habitat suitable for courtship, roosting, and nesting by eastern whip-poor-wills.
... We argue that these forests are relevant in studies of avian habitat relationships because many resident bird species, especially neotropical migrants, are habitat specialists (Sherry and Holmes 1995) with narrow habitat preferences (successional forests, mature forests, etc.). Furthermore, successional habitats, whether naturally occurring or caused by human activity, often comprise the majority of forest cover in midwestern landscapes (such as northeast Iowa) and are preferentially used by many bird species in the eastern United States (Brawn et al. 2001, Thompson and DeGraaf 2001) Recent attention has focused on the effects of specific silvicultural practices (e.g., clearcutting, selective cutting) on bird community structure in eastern deciduous and mixed-deciduous forests (Thompson et al. 1995(Thompson et al. , 1996Annand and Thompson 1997;Robinson and Robinson 1999;Gram et al. 2001); however, we know of almost no published research documenting the effects of pasturing on bird communities in eastern deciduous forests. Logging and pasturing usually modify forest structural characteristics and alter patterns of plant species dominance in one or more forest strata (Webb et al. 1977, Thompson et al. 1995. ...
Most previous studies of bird-habitat relationships in midwestern U.S. forests have excluded recently disturbed habitats from consideration. We investigated whether the composition of a forest avifauna varies along a disturbance gradient ranging from mature, infrequently disturbed forests to successional, frequently disturbed forests impacted by logging and pasturing practices. We evaluated the degree of disturbance of 44 forests in northeast Iowa, USA (including mature and recently disturbed forests), using an additive, multicriteria index ranging in value from 20 (mature; infrequently disturbed) to 0 (successional; highly disturbed). We conducted forest bird censuses at these study sites using point counts in 1995 and 1996. Then, we used stepwise regression analyses to test for relationships between the abundance (mean number of birds detected per census point at each site) and species richness (mean number of bird species detected per census point at each site) of birds and the index. For these analyses, birds were divided into subsets by migratory status, nest substrate, and conservation categories. The disturbance index predicted the abundance of 2 out of 10 bird groups; permanent residents were more abundant in frequently disturbed forests, and area-sensitive bird species were more abundant in infrequently disturbed forests. The index predicted the species richness of 7 out of 10 bird groups. Short-distance migrants, permanent residents, and ground nesters were more diverse in frequently disturbed, successional forests, while neotropical migrants, tree nesters, species of high management concern, and area-sensitive birds had higher species richness in mature, infrequently disturbed forests. These results suggest that mature forest vegetation is important habitat for uncommon and rare bird species in northeast Iowa.
... Among the three habitat types, the shrub/scrub areas occupied the largest areas (245 and 402 ha), so it is unlikely that grassland birds were missing because the sites were too small to support them. However, because bird species associated with shrub/scrub habitats are of management concern nationally (Thompson and DeGraaf 2001), these habitats may be serving an important role in the short term. A long-term management strategy of floodplain forest regeneration is compatible with the short-term existence of shrub/scrub habitat as an intermediate stage. ...
Floodplain forests rival all other habitat types in bird density and diversity. However, major successional changes are predicted for floodplain forests along the Mississippi River in the coming decades; young forests may replace the existing mature silver maple (Acer saccharinum L.) forests in some areas. We wanted to assess how the breeding bird community might respond to these changes. We studied stands of young forests along the middle Mississippi River, comparing the breeding bird assemblages among three stages of forest succession: shrub/scrub, young cottonwood (Populus deltoides Marshall) and willow (Salix nigra Marshall) forests, and mature silver maple dominated forests. We recorded a total of 54 bird species; the most frequently observed species were the indigo bunting (Passerina cyanea), red-winged blackbird (Agelaius phoeniceus), and yellow-billed cuckoo (Coccyzus americanus). Bird species richness differed among the habitat types, with mature forests supporting the largest number of species and the most species of management concern. The +shrub/scrub and mature forest bird assemblages were distinct and shared few species, but the young forests had no identifiable bird species assemblage, sharing species found in both of the other habitat types. The bird assemblages we observed in young forests may become more prevalent as aging floodplain forests are replaced with younger stages of forest succession. Under this scenario, we would expect a temporary local decrease in bird species richness and habitat for species of management concern.
... For example, mechanically removing woody plants in old fields costs $80 to $486 ha −1 (Oehler, 2003). Because disturbance-dependent habitats are ephemeral, they require frequent treatment to maintain their distinctive ecological characteristics (Thompson and DeGraaf, 2001;DeGraaf and Yamasaki, 2003). Using disturbance as a management tool can be controversial because of concerns about aesthetics, forest fragmentation, and fires (Askins, 2001). ...
Disturbance-dependent habitats such as grasslands and shrublands are declining in many regions. To mitigate these declines, government agencies are using anthropogenic disturbances like logging and mowing to mimic natural ones. Because these programs can be costly or controversial, measuring their effectiveness is important. Here, we evaluate the conservation effectiveness of shrubland management for 15 bird species in Massachusetts, USA. Because shrublands are constantly changing in extent and location, we suggest that the key measure of conservation effectiveness should be how managed areas contribute to habitat availability. We used remotely-sensed data to assess the total area of shrublands in Massachusetts and consulted managers and a timber-harvest database to determine contributions of management by government agencies and non-governmental conservation organizations. We calculated species-specific habitat availability based on the habitat relationships of individual bird species. The area of potential habitat for shrubland birds in Massachusetts averaged 35,000 ± SD of 11,300 ha. Of this total, an average of 20% ± 15% exists because of management by government and NGOs. Management was most important for birds that nest primarily in uplands and avoid wetlands. We conclude that active management by government agencies and NGOs provides a substantial proportion of shrubland habitat in Massachusetts. With habitat on private property being lost to development or succession, active management will be even more important in the future.
... For example, prescribed fires are used to improve old field habitat quality for the Eastern Massasauga Rattlesnake, Sistrurus catenatus catenatus (USFWS 2012). Because prescribed fire is a widely used habitat management tool throughout the United States (Thompson and DeGraaf 2001) that influences snake assemblages (Wilgers and Horne 2006;Steen et al. 2013b), it is important to consider how this management strategy influences individual species, as they are unlikely to respond uniformly due to varying requirements related to thermal conditions, prey base, or microhabitat. In this study, we used a Before-After-Control-Impact (BACI) design to explore how experimental application of prescribed fire to improve habitat quality for an endangered target species (i.e., Eastern Massasauga Rattlesnake) in an old field environment affected habitat quality for more common but non-target snake species. ...
Early successional habitats in the northeastern United States, once generated in part by now rare fire events, are essential for a wide range of specialist species. Many snake species use open early successional habitats for basking (thermoregulation) and foraging, but individual species within an assemblage vary in their requirements. Consequently, management to maintain early successional habitats using prescribed fire may have varied effects on different species. We used a Before-After-Control-Impact (BACI) experimental design to explore how a snake assemblage responded to a prescribed burn intended to improve habitat quality for the endangered Eastern Massasauga Rattlesnake, Sistrurus catenatus catenatus, in an old field habitat in New York. Although we do not employ full statistical analysis given that the fire treatment was operationally applied only to one site, our results suggest that prescribed fire is an important influence of habitat quality for snakes. Further study is required to facilitate generalizations of our findings across multiple prescribed fires and to identify the mechanisms behind these apparent effects of prescribed fire on snake habitat.
Populations of the eastern whip‐poor‐will ( Antrostomus vociferus ; whip‐poor‐will) have declined throughout most of its range, making it a species of high conservation concern in nearly every state and province where it occurs. Researchers have reported whip‐poor‐wills are associated with forest stands with open canopies, and thus silviculture may be a promising means for promoting their populations, yet the ecological literature does not quantify fine‐scale habitat relationships capable of assisting with silviculture prescriptions. Our objective was to quantify the associations between whip‐poor‐wills, canopy openness, and other vegetation characteristics to provide managers with guidance for whip‐poor‐will management. Based on prior research, we hypothesized that whip‐poor‐wills may be associated with intermediate levels of canopy retention and that their numbers would also be affected by understory characteristics. We surveyed whip‐poor‐wills with point counts in managed forest at the Fort Drum Army installation in New York, USA, during 2015 and 2016 and collected vegetation measurements at each point count location to relate whip‐poor‐will occupancy with vegetation structure and composition. Whip‐poor‐will occupancy was strongly related to intermediate levels of basal area, with peak occupancy at 13.8 m ² /ha, a value that corresponds to forest denser than most shrublands but more open than closed‐canopy forest. Whip‐poor‐will presence was negatively related to understory height, which is consistent with prior studies. These findings provide managers with quantitative targets that can be used to increase or maintain whip‐poor‐will numbers and abundance of other disturbance‐associated species similarly unable to persist in unmanaged forests stands. © 2021 The Wildlife Society.
Silvicultural treatments, fire, and insect outbreaks are the primary disturbance events currently affecting forests in the Sierra Nevada Mountains of California, a region where plants and wildlife are highly adapted to a frequent-fire disturbance regime that has been suppressed for decades. Although the effects of both fire and silviculture on wildlife have been studied by many, there are few studies that directly compare their long-term effects on wildlife communities. We conducted avian point counts from 2010 to 2019 at 1987 in situ field survey locations across eight national forests and collected fire and silvicultural treatment data from 1987 to 2016, resulting in a 20-year post-disturbance chronosequence. We evaluated two categories of fire severity in comparison to silvicultural management (largely pre-commercial and commercial thinning treatments) as well as undisturbed locations to model their influences on abundances of 71 breeding bird species. More species (48% of the community) reached peak abundance at moderate-high-severity-fire locations than at low-severity fire (8%), silvicultural management (16%), or undisturbed (13%) locations. Total community abundance was highest in undisturbed dense forests as well as in the first few years after silvicultural management and lowest in the first few years after moderate-high-severity fire, then abundance in all types of disturbed habitats was similar by 10 years after disturbance. Even though the total community abundance was relatively low in moderate-high-severity-fire habitats, species diversity was the highest. Moderate-high-severity fire supported a unique portion of the avian community, while low-severity fire and silvicultural management were relatively similar. We conclude that a significant portion of the bird community in the Sierra Nevada region is dependent on moderate-high-severity fire and thus recommend that a prescribed and managed wildfire program that incorporates a variety of fire effects will best maintain biodiversity in this region.
Changing landscapes in the Northeastern United States over the past century have had a profound effect on the abundance and distribution of native wildlife species that prefer early successional habitat, including New England cottontail (Sylvilagus transitionalis). Populations of New England cottontail have been in decline for several decades, whereas during this same time period the nonnative eastern cottontail (S. floridanus) range has expanded. We conducted intensive vegetation analyses at 17 known locations of New England cottontail and 19 known locations of eastern cottontail in Connecticut to better describe their chosen habitat and identify any difference in habitat used by the two species. Sites that were occupied by New England cottontail had greater canopy closure (73.7%) and basal area (12.3 m2/ha) than sites occupied by eastern cottontail (45.3% and 6.8 m2/ha). Our findings suggest management plans to create habitat for New England cottontails should include retaining more basal area and canopy closure than what is currently prescribed in southern New England; however, further fine-scale research is required to determine if this recommendation applies throughout the range of New England cottontail.
Declines in populations of birds that breed in disturbance-dependent early-successional forest have largely been ascribed to habitat loss. Clearcutting is an efficient and effective means for creating early-successional vegetation; however, negative public perceptions of clearcutting and the small parcel size typical of private forested land in much of the eastern United States make this practice impractical in many situations. Group selection harvests, where groups of adjacent trees are removed from a mature forest matrix, may be more acceptable to the public and could provide habitat for shrubland birds. Although some shrubland bird species that occupy clearcuts are scarce or absent from smaller patches created by group selection, some of these smaller patches support shrubland species of conservation concern. The specific factors affecting shrubland bird occupancy of these smaller patches, such as habitat structure, patch area, and landscape context, are poorly understood. We sampled birds in forest openings ranging 0.02–1.29 ha to identify species-specific minimum-area habitat requirements and other factors affecting shrubland birds. We modeled bird occurrence in relation to microhabitat-, patch-, and landscape-level variables using occupancy models. The minimum-area requirements for black-and-white warblers (Mniotilta varia), common yellowthroats (Geothlypis trichas), chestnut-sided warblers (Setophaga pensylvanica), eastern towhees (Pipilo erythrophthalmus), and gray catbirds (Dumetella carolinensis) were ≤0.23 ha, whereas indigo buntings (Passerina cyanea) and prairie warblers (S. discolor) required openings of 0.56 ha and 1.11 ha, respectively. Notably, prairie warblers were more likely to occur in openings closer to large patches of habitat such as powerline corridors, even if those openings were small in size. We concluded that, despite their inability to support the entire suite of shrubland species, small forest openings can provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics.
Polylepis forests are one of the habitats most at risk in Latin America (Fjeldsa andKessler 1996, Stotz,
et al. 1996, Kessler 2002). Their fragmented distribution and current deterioration of habitat quality are putting the survival of species dependent on these habitats at risk (Lloyd, 2008a). We evaluated the influence of habitat quality on patterns of density, species richness and diversity of bird populations associated with
Polylepis forests in the Huascaran Biosphere Reserve (Ancash, Peru). Using point counts, we evaluated the avifauna and their environment. Additionally, we identified key bird species for conservation (Lloyd & Marsden 2008). Patch size and connectivity have the greatest positive influence on the bird community. However, the patches also show a patterns similar to that predicted by the Intermediate Disturbance Hypothesis (Connell, 1978),where factors such as intra-specific competition and the potential for new ecological niches also appear to play an important role. The influence of other habitat quality variables is more complex and not as clear at the bird community level, for which more detailed future studies at the species level could help clarify their importance (Lloyd, a-d.2008). We propose employing several measures that favor increasing connectivity within
Polylepis patches through reforestation with Polylepis and other native plants, thereby promoting a low contrast matrix which could buffer the possible edge effect which is being generated.
Characterization of scale dependence of fire intervals could inform interpretations of fire history and improve fire prescriptions that aim to mimic historical fire regime conditions. We quantified the temporal variability in fire regimes and described the spatial dependence of fire intervals through the analysis of multi-century fire scar records (8 study sites, 332 trees, 843 fire scars) derived from two historically post oak (Quercus stellata Wangenh.) woodland landscapes. Despite large differences in fire environment conditions, study sites (~1 km2) burned frequently (mean fire interval (MFI) < 10 yr) before Euro-American settlement (pre-EAS), with sites in Tennessee showing higher overall fire frequency than sites in Oklahoma. Pre-EAS MFIs decreased exponentially with increasing spatial extent from individual trees (~1 m2) to landscapes (~100 km2). The relationship between MFI and spatial extent may help to explain how historical observations of annual burning could be recorded in woodlands, when experimental studies suggest this is too frequent for tree recruitment. Further investigations of spatial dependence of fire intervals would improve the ability to relate historical and experimental fire data to present day fire prescriptions and vice versa.
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
We investigated how management for habitat conditions to support the endangered red-cockaded woodpecker effects the biodiversity of the breeding bird community associated with those habitats. Habitat is created by thinning, burning and mid-story control of hardwoods in mature longleaf stands. In addition, similar habitat structurally can be found in recently harvested areas. We tested the hypothesis that diversity and abundance, as well as survival and reproduction would be greater in mature stands. However, mature stands used for recruitment always had fewer species (36/31) than recently harvested areas (54/55). All species that occurred in recruitment stands also occurred in mature stands. No differences in survival rates were found between mature and recent cuts for Bachman's sparrow and indigo bunting.
We examined physical condition, niche dimensions, and survival of New England cottontails (Sylvilagus transitionalis) that occupied 21 habitat patches of different sizes during winter. Rabbits on small patches (2.5 ha) were predominantly males, and both sexes had lower body mass than individuals on large patches (5.0 ha). Niche indices (, where ranges from 0 to 1. and values approaching 1 indicate generalized resource use) of habitat use revealed that rabbits on small patches used a greater variety of microhabitats (based on understory stem density: s, and proximity to cover: c) than rabbits occupying large patches (s=0.65, c=0.66). Rabbits on small patches also consumed low quality forage more often and fed at sites farther from escape cover than rabbits on large patches. There were no significant correlations between rabbit densities and niche dimensions. Niche expansion was not a result of compertitive release or relaxation of predator pressure. Rabbits on small patches apparently modified their niche dimensions in response to resource limitations. This response included occupying sites with limited understory cover that apparently resulted in rabbits on small patches having a lower survival rate (0.35) than rabbits on large patches (0.69) during a 10-week monitoring period. Skewed sex ratios and low survival rates among rabbits on small patches suggest that these habitats act as sinks to dispersing, juveniles from large (source) patches. As a result, local populations of New England cottontails may become vulnerable to extinction if larte patches of habitat are not maintained.
Forest fragmentation, the disruption in the continuity of forest habitat, is hypothesized to be a major cause of population
decline for some species of forest birds because fragmentation reduces nesting (reproductive) success. Nest predation and
parasitism by cowbirds increased with forest fragmentation in nine midwestern (United States) landscapes that varied from
6 to 95 percent forest cover within a 10-kilometer radius of the study areas. Observed reproductive rates were low enough
for some species in the most fragmented landscapes to suggest that their populations are sinks that depend for perpetuation
on immigration from reproductive source populations in landscapes with more extensive forest cover. Conservation strategies
should consider preservation and restoration of large, unfragmented "core" areas in each region.
Ecological processes near habitat edges often differ from processes away from edges. Yet, the generality of ''edge effects'' has been hotly debated because results vary tremendously. To understand the factors responsible for this variation, we described nest predation and cowbird distribution patterns in forest edge and forest core habitats on 36 randomly selected plots in three states in the midwestern United States. We tested four hypotheses that may explain the variation and mechanisms responsible for edge effects among the 36 plots: (1) the landscape context, (2) the local predator community, (3) the local bird (host-prey) community, and (4) the nest site microhabitat structure. We used artificial nests baited with quail and clay eggs to determine nest predation patterns and predators and used point count surveys to determine cowbird and host abundance in forest edge and forest core habitats. Raccoons, opossums, canids, and birds accounted for most predation of artificial nests. Neither local host abundance nor mean nest concealment of artificial nests significantly influenced nest predation rates in habitat edge or in habitat core. Nest predation was significantly greater in highly fragmented landscapes than in unfragmented landscapes and was significantly higher in edge habitats than in core habitats. However, detection of edge effects varied, depending upon landscape type. Higher predation rates in edge habitats were detected in highly and moderately fragmented landscapes, but not in unfragmented landscapes. Both mammalian and avian predator groups contributed to higher predation rates along edges in highly and moderately fragmented landscapes. Cowbird abundance was significantly related to host abundance, but the effect of hosts varied depending upon habitat type. In edge habitats, cowbird abundance was negatively associated with host abundance in all three landscapes studied. By contrast, cowbird abundance was positively associated with host abundance in core habitats. Once the effects of host abundance were removed, cowbird abundance in core habitat was greater in highly fragmented landscapes than in moderately and unfragmented landscapes, but did not differ between the latter two. In edge habitat, cowbird abundance did not differ between landscapes, but abundance in edges tended to be highest in the highly fragmented landscape and lowest in the unfragmented landscape. Cowbird abundance did not vary between edge and core habitat in any of the landscapes studied. We suggest that the first approximation to predicting the impact of agricultural or permanently managed edges on forest songbird reproductive success is to assess habitat characteristics at the landscape scale. Given geographic location, local factors such as host abundance and predator composition should be assessed.
Postsettlement invasion of trees and shrubs on the bluestem prairie of Geary County in the Kansas Flint Hills was assessed using aerial photos, General Land Office survey data, and field observations. Tree cover increased 8% from 1856 to 1969 throughout the county, although on regularly burned sites combined tree and shrub cover was effectively maintained at presettlement amounts. On unburned sites, aerial photographs showed that combined tree and shrub cover increased 34% from 1937 to 1969; section-line data showed that tree cover alone increased 24% from 1856 to 1969. Data from two sites suggested that herbicide spraying only slowed the invasion rate. Woody plants increased only slightly on shallow, droughty clay loam soils located on level uplands, ridgetops, and upper slopes. On deeper and more permeable middle- and lower-slope soils, woody plants increased more than 40% from 1937 to 1969. In 1937 trees covered 64% of the unburned, deep, permeable, lowland soils; by 1950 they had increased to 89%; change was slight thereafter. The increase in coverage of the lowland soils from 1856 to 1937 suggests that these soils are rapidly invaded. We conclude that on the Flint Hills bluestem prairie rangeland, (1) burning has been effective in restricting woody plants to natural, presettlement amounts and (2) soil type and topography affect the rate of woody-plant invasion.
There are many uses for prescribed burning in the management of forests, chaparral, grasslands, watersheds, and wildlife. Some of these uses have been pointed out in this paper. There are also many dangers in using fire, both in its application and in its results. To minimize harmful effects, fire should never be used during extended dry periods; burns should always take place when the soil is damp or wet. Moreover, the user should be an experienced professional with a thorough knowledge of eco-systems, weather, and fire behavior.
Uneven-aged forest management has been advocated as a silvicultural practice because of concerns about the negative effects of even-aged management on birds that dwell in mature forests. Recent evidence, however, indicates that in the northeastern United States, bird species that inhabit early successional habitats may be experiencing more widespread declines than their mature-forest counterparts. We compared the effect of group selection, a widely used form of uneven-aged forest management, and clearcutting on nest survival rates of early successional shrubland birds in the White Mountains of New Hampshire. There was no difference in daily nest survival rate between clearcuts (0.990) and groupcuts (0.987) for 16 bird species combined (n = 290), and no difference in daily nest survival rate between clearcuts (0.993) and groupcuts (0.987) for chestnut-sided warblers (Dendroica pensylvanica), the only species for which enough nests were found for separate analysis (n = 217). There was no difference in daily nest survival rates of all species combined between edge (0.983) and interior areas (0.992) of clearcuts (n = 204), and no difference in daily nest survival rates of chestnut-sided warblers between edge (0.984) and interior (0.993) areas of groupcuts (n = 156). Thus, our results suggest that clearcuts and groupcuts provide similar habitat for species of early successional shrubland birds that inhabit both clearcuts and groupcuts. Recent studies, however, indicate that some bird species that use larger openings such as clearcuts do not occupy smaller openings created by group selection, which may limit the utility of group selection in managing habitat for early successional shrubland birds.
Raccoons (Procyon lotor), opossums (Didelphis virginiana), and striped skunks (Mephitis mephitis) are predators of forest songbird eggs and nestlings. We examined the relative abundance of these predators at landscape and local scales to better understand predation risks. At the landscape scale, we examined the relationship between detection rates of raccoons, opossums, and striped skunks on 25 scent-station routes distributed across Missouri and surrounding landscape characteristics. Raccoon abundance was related to latitude, stream density, and mean patch size of agricultural lands. Opossum abundance was related to stream density, contagion, mean nearest-neighbor distance between forest patches, and latitude. Striped skunk abundance was not related to landscape characteristics we examined. At a local scale, we used sooted-plate scent stations to compare the relative abundance of raccoons and opossums in forest interiors to forests adjacent to agricultural fields, roads, clearcuts, and streams. Raccoons were more-abundant in forest edges adjacent to agricultural fields and streams. Opossum abundance varied greatly among years and there was no consistent edge effect on abundance. Local features such as proximity to some types of edge as well as large-scale factors such as landscape patterns in land. use may affect predator abundance and potentially songbird-nest predation rates.
The effects of four cleaning practices (including a control) on species composition and structural characteristics were studied over a 31-year period following treatment of an even-aged 25-year-old northern-hardwood stand that originated after complete clearcutting in 1933–1935. The treatments consisted of: a heavy and a light crop tree cleaning; a drastic species-cleaning treatment that removed nearly all pin cherry (Prunus pensylvanica L.f.), aspen (Populus tremuloides Michx. and grandidentata Michx.), striped maple (Acer pensylvanicum L.), and red maple (Acer rubrum L.) sprout clumps followed by a crop-tree cleaning; and an uncut control. There were no significant differences among treatments in species and structural characteristics in the 56-year-old stand at the end of the study period, except for the presence of a moderate aspen component in the light cleaning and the control. Although previous research shows that cleaning treatments in young northern hardwoods may have silvicultural and economic benefits, the impact of such treatments on long-term stand development is relatively minor.
We studied breeding songbird populations in a managed, predominantly forested landscape, in southeastern Missouri. We determined differences in the relative abundance of breeding birds in forest stands that had been harvested by the clearcut (n = 12), shelterwood (n = 12), group selection (n = 12), and single-tree selection (n = 10) forest regeneration methods, and mature even-aged stands (n = 12). Five migrant songbirds, the blue-winged warbler (Vermivora pinus), prairie warbler (Dendroica discolor), rufous-sided towhee (Pipilo erythrophthalmus), white-eyed vireo (Vireo griseus), and yellow-breasted chat (Icteria virens), were more abundant in clearcut treatments than other treatments (P 0.30). Nest success of species nesting in clearcut and shelterwood treatments was 18-50%. The percent of the site in gaps, shrub stem density, and tree-diameter distribution differed among forest regeneration methods (P
Used estimates of carrying capacity, survival, fecundity, and edge effects to simulate the responses of a forest-interior bird population to selection cutting, clearcutting, and no timber harvest. The author also modeled population sensitivity to changes in fecundity, survival K, and edge relationships. Simulated population size was greater with no timber harvest than with clearcutting, and greater with clearcuting than with group selection when edge effects were included in the model. Without edge effects, population levels were only slightly lower under group selection than under no timber harvest, and greater than clearcutting. Edge effects had only a small impact on population levels under clearcutting. Clearcut size did not have much effect on population levels, but longer and shorter rotation ages resulted in higher and lower population levels, respectively. The model was very sensitive to declines in mean fecundity and survival, suggesting that factors affecting mean demographic rates could be more important than local edge effects. Some methods of timber harvest may be compatible with conservation of forest-interior birds, but better demographic data and information on habitat suitability of selectively cut forests and young even-aged stands is needed to adequately evaluate management options. -from Author
The sequence of farm abandonment, forest colonization, and forest maturation that occurred in New Hampshire were examined in relation to changes in the abundance and distribution of a group of forest mammals and birds that have undergone substantial declines. A modeled pattern of secondary succession resulted in the availability of about 195,000 ha of early seral habitats from 1905 to 1940. By 1960, these habitats then matured into closed-canopy forests. A decline in the populations of 18 of 26 species of migratory passerines that nest in the forests was also observed. Ownership patterns of forest lands revealed 88% private ownership, indicating that large tracts of early successional habitats will be restricted to industrial and state/national forests.
We used a spatially explicit landscape model, landis, to simulate the effects of five management alternatives on a 3216 ha forest landscape in southeast Missouri, USA. We compared management alternatives among two intensities of even-aged management with clearcutting, uneven-aged management with group selection harvest, a mixture of even- and uneven-aged management, and no harvesting. Anticipated disturbances by windthrow and wildfire were included in the 100-year simulations across the landscape. The uneven-aged, even-aged long rotation, and mixed harvest regimes were similar to one another in total area in each forest size class, timber volume produced and volume of wood on the forest floor. However, they varied greatly in quantity of edge habitat and in the extent of the mature forest habitat free from edge effects. The intensive even-aged harvest regime and the no-harvest regime produced the greatest volume of timber and the greatest volume of down wood, respectively. This model provides a quantitative flamework to simultaneously explore multiple factors that affect landscape-scale management decisions.
Because organisms have adapted to the natural disturbance regimes of forest ecosystems such as fires and windfalls, conservationists often suggest that timber harvesting systems be designed to imitate natural disturbance regimes. Using the crown fires that shape true boreal forest ecosystems as spatial models for harvesting would require very large clearcuts; in two studies, mean fire size was 12 710 ha (in Labrador) and 7 764 ha (in Quebec). Most conservationists would be reluctant to advocate such large clearcuts and it is not easy to justify them from the perspectives of various ethical systems. A solution is proposed in which moderate-sized clearcuts would be clustered into portions of land areas bounded by water-bodies. These water-bounded areas have an average size of 770 ha in Labrador and 322 ha in Quebec.
Vegetation change during the past 25 000 years in and near the present Mixed Mesophytic Forest Region is inferred from pollen and plant macrofossil analyses of sediment cores from two sites on the eastern Highland Rim of Middle Tennesse, USA. Beginning about 16 500 yr BP, boreal-like coniferous forest was replaced in midlatitudes (34o to 37oN) by cool--temperate coniferous-deciduous forest. In the early Holocene, between 12 500 and 8000 yr BP, cool-temperate mixed mesophytic forest prevailed between 34o and 37oN. The Mixed Mesophytic Forest Region assumed its present distribution in the mid-Holocene. -from Author