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Author: Matthew Toenies Publisher: ISBN: Category : Languages : en Pages :
Book Description
Forest biomes face increasing rates of disturbance from many causes, including climate change, introduced pests, and shifting fire regimes, as well interactions between multiple factors. In particular, the introduction of exotic forest pests is increasing globally, frequently resulting in decline and die-off of affected forest types. The loss of foundational forest species can drastically change the structure and composition of vegetation communities in forests, a phenomenon that holds strong implications for avian communities. However, little research has focused on the long-term effects of forest die-off at a community-wide scale. To examine the response of bird communities to forest die-off, we studied the community associated with declining eastern hemlock (Tsuga canadensis) forests affected by the introduced hemlock woolly adelgid (Adelges tsugae). We conducted variable-radius point counts to survey bird communities in both hemlock and hardwood stands in 2000, during early stages of adelgid infestation, and again in 2015 and 2016, following significant hemlock decline. We also measured the severity of hemlock decline and associated vegetation variables in the same hemlock stands where avian surveys occurred. We used multi-species occupancy models to examine species-specific and species group responses to hemlock decline. Results showed that hemlock basal area declined to varying degrees across the hemlock stands, and that hemlock decline was correlated with current vegetation structure, including an increased deciduous understory. Hemlock-associated bird species declined between the two time periods, while all other species groups responded positively, with the strongest responses in species associated with the shrub-layer, forest edge, and mature deciduous habitat. Species composition in hemlock and hardwood stands became more correlated over time, highlighting a trend toward homogenization of the avian community as the unique species assemblages in hemlock stands give way to the avian community of the surrounding hardwood landscape. Where hemlock-associated species persisted, their presence was correlated with the combined effect of greater hemlock basal area and better hemlock condition. Our results demonstrate that the decline and die-off of foundational forest species can restructure vegetation communities and their associated avian communities over time, with strong implications for forest type specialists. Due to regional variation in patterns of forest die-off and community composition, understanding impacts on forest-dependent communities requires examining response at broad spatial and temporal scales. To determine how the responses to forest die-off that we observed in the avian community may vary across a large regional scale, we examined bird communities in hemlock stands at four sites across the range of hemlock woolly adelgid in the northeastern/mid-Appalachian regions of the United States. We surveyed the avian community in earlier stages of infestation and again following hemlock decline, and analyzed this data using a multi-species occupancy modeling approach. Despite variability among sites in characteristics of the avian community and of the die-off itself, changes in species richness over time were similar across all sites. Hemlock-associated bird species declined at all sites, with concurrent increases in other species groups, especially those associated with forest edge and shrub-layer habitats. Finer-scale variation in the magnitude of avian response coincided with the varying stages of hemlock decline across sites. Species-specific trends showed that Acadian Flycatcher declined most consistently across this large regional scale. Understanding these patterns is critical to predicting and preparing for changes to not only forested landscapes affected by the loss of hemlock, but also for those that will experience similar die-offs as forest pest introductions increase globally.
Author: Matthew Toenies Publisher: ISBN: Category : Languages : en Pages :
Book Description
Forest biomes face increasing rates of disturbance from many causes, including climate change, introduced pests, and shifting fire regimes, as well interactions between multiple factors. In particular, the introduction of exotic forest pests is increasing globally, frequently resulting in decline and die-off of affected forest types. The loss of foundational forest species can drastically change the structure and composition of vegetation communities in forests, a phenomenon that holds strong implications for avian communities. However, little research has focused on the long-term effects of forest die-off at a community-wide scale. To examine the response of bird communities to forest die-off, we studied the community associated with declining eastern hemlock (Tsuga canadensis) forests affected by the introduced hemlock woolly adelgid (Adelges tsugae). We conducted variable-radius point counts to survey bird communities in both hemlock and hardwood stands in 2000, during early stages of adelgid infestation, and again in 2015 and 2016, following significant hemlock decline. We also measured the severity of hemlock decline and associated vegetation variables in the same hemlock stands where avian surveys occurred. We used multi-species occupancy models to examine species-specific and species group responses to hemlock decline. Results showed that hemlock basal area declined to varying degrees across the hemlock stands, and that hemlock decline was correlated with current vegetation structure, including an increased deciduous understory. Hemlock-associated bird species declined between the two time periods, while all other species groups responded positively, with the strongest responses in species associated with the shrub-layer, forest edge, and mature deciduous habitat. Species composition in hemlock and hardwood stands became more correlated over time, highlighting a trend toward homogenization of the avian community as the unique species assemblages in hemlock stands give way to the avian community of the surrounding hardwood landscape. Where hemlock-associated species persisted, their presence was correlated with the combined effect of greater hemlock basal area and better hemlock condition. Our results demonstrate that the decline and die-off of foundational forest species can restructure vegetation communities and their associated avian communities over time, with strong implications for forest type specialists. Due to regional variation in patterns of forest die-off and community composition, understanding impacts on forest-dependent communities requires examining response at broad spatial and temporal scales. To determine how the responses to forest die-off that we observed in the avian community may vary across a large regional scale, we examined bird communities in hemlock stands at four sites across the range of hemlock woolly adelgid in the northeastern/mid-Appalachian regions of the United States. We surveyed the avian community in earlier stages of infestation and again following hemlock decline, and analyzed this data using a multi-species occupancy modeling approach. Despite variability among sites in characteristics of the avian community and of the die-off itself, changes in species richness over time were similar across all sites. Hemlock-associated bird species declined at all sites, with concurrent increases in other species groups, especially those associated with forest edge and shrub-layer habitats. Finer-scale variation in the magnitude of avian response coincided with the varying stages of hemlock decline across sites. Species-specific trends showed that Acadian Flycatcher declined most consistently across this large regional scale. Understanding these patterns is critical to predicting and preparing for changes to not only forested landscapes affected by the loss of hemlock, but also for those that will experience similar die-offs as forest pest introductions increase globally.
Author: Anthony D'Amato Publisher: Yale University Press ISBN: 0300186770 Category : Nature Languages : en Pages : 336
Book Description
The Eastern Hemlock, massive and majestic, has played a unique role in structuring northeastern forest environments, from Nova Scotia to Wisconsin and through the Appalachian Mountains to North Carolina, Tennessee, and Alabama. A “foundation species” influencing all the species in the ecosystem surrounding it, this iconic North American tree has long inspired poets and artists as well as naturalists and scientists. Five thousand years ago, the hemlock collapsed as a result of abrupt global climate change. Now this iconic tree faces extinction once again because of an invasive insect, the hemlock woolly adelgid. Drawing from a century of studies at Harvard University’s Harvard Forest, one of the most well-regarded long-term ecological research programs in North America, the authors explore what hemlock’s modern decline can tell us about the challenges facing nature and society in an era of habitat changes and fragmentation, as well as global change.
Author: Aric J. Payne Publisher: ISBN: Category : Aquatic biodiversity Languages : en Pages : 100
Book Description
Much research has been conducted on terrestrial communities associated with eastern hemlock forests, however, little emphasis has been placed on investigating aquatic communities. To determine the potential long-term impacts of hemlock forest decline on aquatic biodiversity, I conducted a comparison study of streams in the Daniel Boone National Forest on macroinvertebrate and fish communities, along with stream habitats during May and September 2008. Streams draining hardwood forests contained fish populations that were more dense and diverse than streams draining hemlock forests during both spring and fall samples. In addition, there were distinct differences in fish trophic structure. On average, insectivores composed a significantly larger proportion of the fish community in hardwood streams for both spring and fall samples (t = 3.31, p = 0.016; t = 3.02, p = 0.023, respectively) (mean proportion = 0.73 and 0.70, respectively) than in hemlock streams (mean = 0.37 and 0.21, respectively). Conversely, omnivores composed a significantly larger proportion of the fish community in hemlock streams for both spring and fall samples (t = 3.37, p = 0.009; t = 3.09, p = 0.021, respectively) (mean = 0.61and 0.78, respectively) than in hardwood streams (mean=0.26 and 0.28, respectively). I found no significant differences in macroinvertebrate community structure, although the macroinvertebrate community structure of hardwood streams appeared to be more dense than those of hemlock streams. On average, macroinvertebrate communities in hardwood streams were two times as dense (mean difference = 140 individuals - m −2) than those of hemlock streams during spring samples and 1.3 times more dense (mean difference = 85 individuals - m −2) during fall samples. Streams draining hemlock forests were an average 4 C cooler during summer months than hardwood streams. It is hypothesized the hemlock woolly adelgid-induced decline of the eastern hemlock may result in negative long-term ecological impacts on aquatic biodiversity in eastern Kentucky.
Author: Misty Dawn Huddleston Publisher: ISBN: Category : Eastern hemlock Languages : en Pages : 134
Book Description
An invasive insect, hemlock woolly adelgid (HWA), has initiated widespread hemlock decline and mortality in the Great Smoky Mountains National Park (GSMNP). Riparian hemlock mortality impacts on vegetative and aquatic systems of first-order, headwater streams were evaluated. Reference sites for this study were representative of the best available conditions within the GSMNP, with initial stages of HWA presence. Impacted sites were defined as areas with over 90 percent hemlock mortality. Impacted streams had decreased canopy coverage and increased light availability. Residual red maple, yellow birch, and sweet birch capitalized on the loss of hemlock, with increases in relative basal area and species importance values. Rosebay rhododendron responded with increased density and height at impacted sites, thereby preventing woody regeneration. Since long-term regeneration and post-mortality canopy recruitment are limited, alterations of vegetative composition and structure in the stream riparian zone are expected. A seasonal assessment (Sept. 2009 -- March 2010) of aquatic impacts revealed increased diurnal variation in stream temperature and exhibited cooler temperatures during the colder months than reference streams. Impacted streams exhibited greater amounts and larger size classes of large woody debris (LWD). Higher concentrations for several nutrients, including silicon, sodium, potassium, magnesium, chlorine, and copper were detected in impacted streams than detected in reference streams. Impacted streams were characterized by higher pH and increased acid neutralization capacity, while reference streams exhibited nitrate concentrations three times higher than impacted stream concentrations. Reference streams were experiencing the initial stage of HWA-induced defoliations, increasing stream nitrate concentrations, while impacted sites had levels suggesting nitrate concentrations have returned to pre-infestation levels. A seasonal assessment of macroinvertebrates found species diversity, abundance, and taxa richness were not affected by hemlock mortality. Impacted streams had a lower density of Chironomidae and Ephemeroptera when compared to reference streams, while Pleuroceridae snails were virtually eliminated at impacted stream sites. Reference streams were dominated by the collector/filter functional feeding group (FFG), while impacted streams were dominated by the scraper FFG. Hemlock mortality induced by the presence of HWA has resulted in short-term impacts to vegetative and aquatic dynamics in stream riparian areas of the Great Smoky Mountain National Park.
Author: Tim Palmer Publisher: Penn State Press ISBN: 0271082496 Category : Nature Languages : en Pages : 197
Book Description
In this magnificently illustrated book, conservationist and celebrated outdoors photographer Tim Palmer launches us on a revealing journey among the hemlock and beech trees that have for millennia towered over America’s eastern woodlands. The eastern hemlock and North American beech once thrived from Maine to Georgia, casting shade on trout streams, nourishing wildlife large and small, and gracing uncounted valleys, mountainsides, parks, and backyards. These trees now face tragic decimation by exotic insects and pathogens. Palmer’s photos record the splendor of the cherished hemlock and beech in the same way that pictures of iconic, historic buildings commemorate classic landmarks gone the way of the wrecking ball. And yet, as Palmer underscores in his final chapter, the lessons learned as we address the fate of these trees can help us chart a better course for all wooded landscapes in the years ahead. This story of loss, scientific inquiry, and prospective recovery is vital to understanding nature in our time. As an act of artistic preservation, a report on the science vital to the survival of these trees, and a call to action, Twilight of the Hemlocks and Beeches assures a lasting legacy for this irreplaceable forest community. With more than one hundred exquisite full-color photographs, this book is a must-have for outdoor enthusiasts, natural historians, ecologists, and all lovers of nature.
Author: C. John Ralph Publisher: DIANE Publishing ISBN: 9780788143441 Category : Languages : en Pages : 192
Book Description
Point counts of birds are the most widely used quantitative method and involve an observer recording birds from a single point for a standardized time period. In response to the need for standardization of methods to monitor bird populations by census, researchers met to present data from various investigations working under a wide variety of conditions, and to examine various aspects of point count methodology. Statistical aspects of sampling and analysis were discussed and applied to the objectives of point counts. The final chapter presents these standards and their applications to point count methodology.
Author: Kurt J. Krapfl Publisher: ISBN: Category : Languages : en Pages : 83
Book Description
Tsuga canadensis (L.) Carr. (eastern hemlock), a long lived and shade tolerant coniferous tree species native to eastern North America, is currently threatened by the hemlock woolly adelgid ( Adelges tsugae Annand, HWA). This exotic, invasive insect poses a serious threat to T. canadensis stands throughout their native range. The loss of this unique tree species is often coupled with numerous ecological consequences. HWA-induced mortality has exceeded 95% in some forest types, and will likely continue to decimate T. canadensis populations in the coming years. Shortly after HWA was found in Great Smoky Mountains National Park (GSMNP), long-term monitoring plots were established across a gradient of T. canadensis associated forest communities to monitor HWA impacts and stand decline. Our objectives were to (1) determine how T. canadensis populations have changed in conjunction with HWA infestation, and (2) document how HWA has affected vegetative community dynamics following five to six years of infestation in GSMNP.
Author: Therese M. Poland Publisher: Springer Nature ISBN: 3030453677 Category : Science Languages : en Pages : 455
Book Description
This open access book describes the serious threat of invasive species to native ecosystems. Invasive species have caused and will continue to cause enormous ecological and economic damage with ever increasing world trade. This multi-disciplinary book, written by over 100 national experts, presents the latest research on a wide range of natural science and social science fields that explore the ecology, impacts, and practical tools for management of invasive species. It covers species of all taxonomic groups from insects and pathogens, to plants, vertebrates, and aquatic organisms that impact a diversity of habitats in forests, rangelands and grasslands of the United States. It is well-illustrated, provides summaries of the most important invasive species and issues impacting all regions of the country, and includes a comprehensive primary reference list for each topic. This scientific synthesis provides the cultural, economic, scientific and social context for addressing environmental challenges posed by invasive species and will be a valuable resource for scholars, policy makers, natural resource managers and practitioners.
Author: Matthew Toenies
Author: Matthew Toenies
Author: Anthony D'Amato
Author: Aric J. Payne
Author: Misty Dawn Huddleston
Author: Tim Palmer
Author: M. W. Tingley (et al)
Author: C. John Ralph
Author: 
Author: Kurt J. Krapfl
Author: Therese M. Poland