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• 51. [Article] The roles of provenance and phylogeny in recruitment, community assembly, and species coexistence in invaded California grasslands

  Biological invasions pose one of the greatest threats to global biodiversity, but many naturalized invaders coexist with the native community. Community ecology theory provides a framework for understanding ...

  Citation × Citation Citation Abstract Copy Title: The roles of provenance and phylogeny in recruitment, community assembly, and species coexistence in invaded California grasslands Author: Brandt, Angela J. Biological invasions pose one of the greatest threats to global biodiversity, but many naturalized invaders coexist with the native community. Community ecology theory provides a framework for understanding the mechanisms by which invaders might coexist with native species or exclude them from the community, thus informing management practices to maximize their effectiveness at conserving native biodiversity. Differences in functional or phylogenetic similarity of invaders to native residents can affect invasion success and the probability they will coexist with natives. For example, functionally dissimilar species may not compete strongly and distantly related species may share fewer natural enemies. Furthermore, environmental heterogeneity can promote species coexistence by providing the opportunity for a greater number of coexistence mechanisms to operate, thereby mitigating the potential for species invasions to lead to native extinction. My thesis examines how provenance (i.e., native origin) and phylogenetic relatedness of plant species affect community dynamics and species interactions in the invaded California grasslands. To do this I have assembled two unique community data sets, one spanning 48 years across a 1000-ha site and one spanning 7 years along a 500-km latitudinal transect. I show that native and exotic species abundance and diversity is highly variable in both time and space, but these provenance group responses are rarely negatively correlated (Chapter 2). Thus, exotic species do not generally appear to exclude natives from communities. Long-term abundance patterns further suggest that the system remains in a state of transience, and populations of several native species are declining at local scales (Chapter 3). Recruitment limitation due to the build-up of plant litter associated with exotic grasses may be generally responsible for these declines, but habitat suitability, land-use history, and community composition also affect native recruitment. Across the grasslands, disturbance and resource supply can interact to affect both species and phylogenetic diversity (Chapter 4). Disturbance in particular can increase diversity, likely by increasing opportunities for colonization by removing plant litter that previously limited recruitment. Both phylogeny and provenance can also affect biotic interactions, such as with communities of soil organisms (Chapter 5). Thus, I have shown that spatio-temporal heterogeneity, alterations to the biotic environment mediated by exotic invasion, and phylogenetic relationships among species are all important considerations when evaluating impacts of invasion and designing management strategies to conserve native biodiversity, especially in light of anthropogenic influence on disturbance regimes and resource supply. Title: The roles of provenance and phylogeny in recruitment, community assembly, and species coexistence in invaded California grasslands Author: Brandt, Angela J. Biological invasions pose one of the greatest threats to global biodiversity, but many naturalized invaders coexist with the native community. Community ecology theory provides a framework for understanding the mechanisms by which invaders might coexist with native species or exclude them from the community, thus informing management practices to maximize their effectiveness at conserving native biodiversity. Differences in functional or phylogenetic similarity of invaders to native residents can affect invasion success and the probability they will coexist with natives. For example, functionally dissimilar species may not compete strongly and distantly related species may share fewer natural enemies. Furthermore, environmental heterogeneity can promote species coexistence by providing the opportunity for a greater number of coexistence mechanisms to operate, thereby mitigating the potential for species invasions to lead to native extinction. My thesis examines how provenance (i.e., native origin) and phylogenetic relatedness of plant species affect community dynamics and species interactions in the invaded California grasslands. To do this I have assembled two unique community data sets, one spanning 48 years across a 1000-ha site and one spanning 7 years along a 500-km latitudinal transect. I show that native and exotic species abundance and diversity is highly variable in both time and space, but these provenance group responses are rarely negatively correlated (Chapter 2). Thus, exotic species do not generally appear to exclude natives from communities. Long-term abundance patterns further suggest that the system remains in a state of transience, and populations of several native species are declining at local scales (Chapter 3). Recruitment limitation due to the build-up of plant litter associated with exotic grasses may be generally responsible for these declines, but habitat suitability, land-use history, and community composition also affect native recruitment. Across the grasslands, disturbance and resource supply can interact to affect both species and phylogenetic diversity (Chapter 4). Disturbance in particular can increase diversity, likely by increasing opportunities for colonization by removing plant litter that previously limited recruitment. Both phylogeny and provenance can also affect biotic interactions, such as with communities of soil organisms (Chapter 5). Thus, I have shown that spatio-temporal heterogeneity, alterations to the biotic environment mediated by exotic invasion, and phylogenetic relationships among species are all important considerations when evaluating impacts of invasion and designing management strategies to conserve native biodiversity, especially in light of anthropogenic influence on disturbance regimes and resource supply. Close

• 52. [Article] Rapid endangered species assessment : a novel approach to improve extinction risk assessments in poorly known species

  The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine ...

  Citation × Citation Citation Abstract Copy Title: Rapid endangered species assessment : a novel approach to improve extinction risk assessments in poorly known species Author: Bianchi, Carlos A. The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine conservation priorities and many species lack information even to be evaluated (i.e., “data deficient”). Here I proposed and tested the Rapid Endangered Species Assessment approach, combining methods including distribution modeling, landscape/habitat availability analysis and an evaluation of population spatial structure to improve information about species of concern and make future extinction risk assessments more attainable. I used the Pfrimer’s Parakeet (Pyrrhura pfrimeri) an endemic Brazilian species, as a case study. I modeled and validated the potential distribution of the species, known to occur in association with the tropical dry forests in central Brazil, using the Maxent method. The model predicted potential occurrence in three regions in central Brazil. Field surveys used to validate model found the species at 17 sites, all located in the dry forests of the Paranã River Basin. Modeling results set boundaries for the analysis of loss and fragmentation of the species’ habitat. Satellite imagery and remote sensing techniques were used to estimate deforestation trends over a large spatiotemporal scale (31 years). Results indicated a 66.3% decrease in forest extent, average annual deforestation rate of 2.1% and significant increase in fragmentation, suggesting that these forests may disappear in less than 20 years if current deforestation rates persist. The habitat availability analysis set boundaries for the investigation of spatial arrangement of local populations of Pfrimer’s Parakeets, which was carried out by collecting information on abundance, densities estimates, species home range, and habitat use. Twenty individuals were monitored with radio transmitters and home range estimates averaged between 195.7 ha (fixed kernel) and 261.8 ha (minimum convex polygons). Habitat use was estimated with behavioral observations of birds flying through a mosaic of forests and pastures. I found no evidence that the species used open areas farther than 300m from the forest edge. Systematic line transects and observations of parakeets per time effort produced estimates of population densities at 11.7 individuals/km2; indicating strong variation in abundance indices among areas, suggesting a population decline. The Rapid Endangered Species Assessment represents a broad and integrative approach carried out over a short term and was successfully used to produce relevant data about a poorly known species. Thus, I propose the use of this approach as a minimally ideal yet scientifically viable method to generate information for extinction risk assessment of species. Title: Rapid endangered species assessment : a novel approach to improve extinction risk assessments in poorly known species Author: Bianchi, Carlos A. The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine conservation priorities and many species lack information even to be evaluated (i.e., “data deficient”). Here I proposed and tested the Rapid Endangered Species Assessment approach, combining methods including distribution modeling, landscape/habitat availability analysis and an evaluation of population spatial structure to improve information about species of concern and make future extinction risk assessments more attainable. I used the Pfrimer’s Parakeet (Pyrrhura pfrimeri) an endemic Brazilian species, as a case study. I modeled and validated the potential distribution of the species, known to occur in association with the tropical dry forests in central Brazil, using the Maxent method. The model predicted potential occurrence in three regions in central Brazil. Field surveys used to validate model found the species at 17 sites, all located in the dry forests of the Paranã River Basin. Modeling results set boundaries for the analysis of loss and fragmentation of the species’ habitat. Satellite imagery and remote sensing techniques were used to estimate deforestation trends over a large spatiotemporal scale (31 years). Results indicated a 66.3% decrease in forest extent, average annual deforestation rate of 2.1% and significant increase in fragmentation, suggesting that these forests may disappear in less than 20 years if current deforestation rates persist. The habitat availability analysis set boundaries for the investigation of spatial arrangement of local populations of Pfrimer’s Parakeets, which was carried out by collecting information on abundance, densities estimates, species home range, and habitat use. Twenty individuals were monitored with radio transmitters and home range estimates averaged between 195.7 ha (fixed kernel) and 261.8 ha (minimum convex polygons). Habitat use was estimated with behavioral observations of birds flying through a mosaic of forests and pastures. I found no evidence that the species used open areas farther than 300m from the forest edge. Systematic line transects and observations of parakeets per time effort produced estimates of population densities at 11.7 individuals/km2; indicating strong variation in abundance indices among areas, suggesting a population decline. The Rapid Endangered Species Assessment represents a broad and integrative approach carried out over a short term and was successfully used to produce relevant data about a poorly known species. Thus, I propose the use of this approach as a minimally ideal yet scientifically viable method to generate information for extinction risk assessment of species. Close

• 53. [Article] Divergent Carbon Dynamics under Climate Change in Forests with Diverse Soils, Tree Species, and Land Use Histories

  Accounting for both climate change and natural disturbances—which typically result in greenhouse gas emissions—is necessary to begin managing forest carbon sequestration. Gaining a complete understanding ...

  Citation × Citation Citation Abstract Copy Title: Divergent Carbon Dynamics under Climate Change in Forests with Diverse Soils, Tree Species, and Land Use Histories Author: Scheller, Robert M., Kretchun, Alec M., Van Tuyl, Steve, Clark, Kenneth L., Lucash, Melissa S., Hom, John Year: 2012 Accounting for both climate change and natural disturbances—which typically result in greenhouse gas emissions—is necessary to begin managing forest carbon sequestration. Gaining a complete understanding of forest carbon dynamics is, however, challenging in systems characterized by historic over-utilization, diverse soils and tree species, and frequent disturbance. In order to elucidate the cascading effects of potential climate change on such systems, we projected forest carbon dynamics, including soil carbon changes, and shifts in tree species composition as a consequence of wildfires and climate change in the New Jersey pine barrens (NJPB) over the next 100 years. To do so, we used the LANDIS-II succession and disturbance model combined with the CENTURY soil model. The model was calibrated and validated using data from three eddy flux towers and the available empirical or literature data. Our results suggest that climate change will not appreciably increase fire sizes and intensity. The recovery of C stocks following substantial disturbances at the turn of the 20th century will play a limited but important role in this system. In areas characterized by high soil water holding capacity, reduced soil moisture may lead to lower total C and these forests may switch from being carbon sinks to becoming carbon neutral towards the latter part of the 21st century. In contrast, other areas characterized by lower soil water holding capacity and drought tolerant species are projected to experience relatively little change over the next 100 years. Across all soil types, however, the regeneration of many key tree species may decline leading to longer-term (beyond 2100) risks to forest C. These divergent responses were largely a function of the dominant tree species, and their respective temperature and soil moisture tolerances, and soil water holding capacity. In summary, the system is initially C conservative but by the end of the 21st century, there is increasing risk of de-stabilization due to declining growth and regeneration. Title: Divergent Carbon Dynamics under Climate Change in Forests with Diverse Soils, Tree Species, and Land Use Histories Author: Scheller, Robert M., Kretchun, Alec M., Van Tuyl, Steve, Clark, Kenneth L., Lucash, Melissa S., Hom, John Year: 2012 Accounting for both climate change and natural disturbances—which typically result in greenhouse gas emissions—is necessary to begin managing forest carbon sequestration. Gaining a complete understanding of forest carbon dynamics is, however, challenging in systems characterized by historic over-utilization, diverse soils and tree species, and frequent disturbance. In order to elucidate the cascading effects of potential climate change on such systems, we projected forest carbon dynamics, including soil carbon changes, and shifts in tree species composition as a consequence of wildfires and climate change in the New Jersey pine barrens (NJPB) over the next 100 years. To do so, we used the LANDIS-II succession and disturbance model combined with the CENTURY soil model. The model was calibrated and validated using data from three eddy flux towers and the available empirical or literature data. Our results suggest that climate change will not appreciably increase fire sizes and intensity. The recovery of C stocks following substantial disturbances at the turn of the 20th century will play a limited but important role in this system. In areas characterized by high soil water holding capacity, reduced soil moisture may lead to lower total C and these forests may switch from being carbon sinks to becoming carbon neutral towards the latter part of the 21st century. In contrast, other areas characterized by lower soil water holding capacity and drought tolerant species are projected to experience relatively little change over the next 100 years. Across all soil types, however, the regeneration of many key tree species may decline leading to longer-term (beyond 2100) risks to forest C. These divergent responses were largely a function of the dominant tree species, and their respective temperature and soil moisture tolerances, and soil water holding capacity. In summary, the system is initially C conservative but by the end of the 21st century, there is increasing risk of de-stabilization due to declining growth and regeneration. Close

• 54. [Article] Marine bird colony and at-sea distributions along the Oregon coast: Implications for marine spatial planning and information gap analysis

  Increasingly diverse interests in commercial and recreational use of marine resources are creating new challenges for coastal ocean management. One concern of increased offshore use and development off ...

  Citation × Citation Citation Abstract Copy Title: Marine bird colony and at-sea distributions along the Oregon coast: Implications for marine spatial planning and information gap analysis Author: Lowe, Roy W., Suryan, Robert M., Phillips, Elizabeth M., Zamon, Jeannette E., So, Khemarith, Stephensen, Shawn W. Increasingly diverse interests in commercial and recreational use of marine resources are creating new challenges for coastal ocean management. One concern of increased offshore use and development off the Oregon coast is the potential impact on marine bird populations. We summarized the primary surveys of seabird breeding colonies and at-sea distribution along the Oregon coast to describe spatial patterns in species distribution and identify gaps where additional data are needed. The abundance of breeding birds during the summer (over 1 million in total, primarily Common Murre Uria aalge and Leach’s Storm-Petrel Oceanodroma leucorhoa) is greatest in northern and southern Oregon due to the availability of breeding habitat on large offshore rocks and islands. While there are fewer breeding colonies along sandy shorelines, the adjacent coastal waters are still frequented by breeding birds and nonbreeding migrants, but generally in lower densities during summer. Seabird density, and likely potential interaction with offshore structures, is greatest nearshore and steadily declines to lowest levels beyond the outer continental shelf. Dynamic soaring species, however, which have a greater potential to interact with taller structures such as wind turbines, tend to be more common on the middle to outer shelf. Species composition also changes dramatically among seasons. Low flying (< 30 m above sea level) diving species dominate in most seasons, however, which has potential conservation implications for interactions with structures above and below the water’s surface. Given the abundance of storm-petrels, increased light pollution is also a concern for these and other nocturnal, phototactic species. Dramatic declines or redistributions have occurred at some breeding colonies, indicating long-term planning should consider changing habitat requirements. The greatest data needs currently include fall/winter/spring at-sea distribution, summer distribution off southern Oregon, and more accurate estimates and monitoring of burrow-nesting seabirds. Oregon’s coastal waters provide habitat for a large portion of breeding and nonbreeding marine birds along the U.S. west coast and a thorough knowledge of their spatial distribution, seasonal abundance, and migration corridors is critical for well-informed marine spatial planning. Title: Marine bird colony and at-sea distributions along the Oregon coast: Implications for marine spatial planning and information gap analysis Author: Lowe, Roy W., Suryan, Robert M., Phillips, Elizabeth M., Zamon, Jeannette E., So, Khemarith, Stephensen, Shawn W. Increasingly diverse interests in commercial and recreational use of marine resources are creating new challenges for coastal ocean management. One concern of increased offshore use and development off the Oregon coast is the potential impact on marine bird populations. We summarized the primary surveys of seabird breeding colonies and at-sea distribution along the Oregon coast to describe spatial patterns in species distribution and identify gaps where additional data are needed. The abundance of breeding birds during the summer (over 1 million in total, primarily Common Murre Uria aalge and Leach’s Storm-Petrel Oceanodroma leucorhoa) is greatest in northern and southern Oregon due to the availability of breeding habitat on large offshore rocks and islands. While there are fewer breeding colonies along sandy shorelines, the adjacent coastal waters are still frequented by breeding birds and nonbreeding migrants, but generally in lower densities during summer. Seabird density, and likely potential interaction with offshore structures, is greatest nearshore and steadily declines to lowest levels beyond the outer continental shelf. Dynamic soaring species, however, which have a greater potential to interact with taller structures such as wind turbines, tend to be more common on the middle to outer shelf. Species composition also changes dramatically among seasons. Low flying (< 30 m above sea level) diving species dominate in most seasons, however, which has potential conservation implications for interactions with structures above and below the water’s surface. Given the abundance of storm-petrels, increased light pollution is also a concern for these and other nocturnal, phototactic species. Dramatic declines or redistributions have occurred at some breeding colonies, indicating long-term planning should consider changing habitat requirements. The greatest data needs currently include fall/winter/spring at-sea distribution, summer distribution off southern Oregon, and more accurate estimates and monitoring of burrow-nesting seabirds. Oregon’s coastal waters provide habitat for a large portion of breeding and nonbreeding marine birds along the U.S. west coast and a thorough knowledge of their spatial distribution, seasonal abundance, and migration corridors is critical for well-informed marine spatial planning. Close

• 55. [Article] Vegetation response following thinning in young Douglas-fir forests of western Oregon : can thinning accelerate development of late-successional structure and composition?

  Across western Oregon, Washington, and British Columbia, forest management practices over the past century reduced the amount of late-successional forest while simultaneously increasing the amount of young ...

  Citation × Citation Citation Abstract Copy Title: Vegetation response following thinning in young Douglas-fir forests of western Oregon : can thinning accelerate development of late-successional structure and composition? Author: Beggs, Liane R. Across western Oregon, Washington, and British Columbia, forest management practices over the past century reduced the amount of late-successional forest while simultaneously increasing the amount of young (less than 80 years old), managed Douglas-fir (Pseudotsuga menziesii) dominated forests. Recently, concerns over loss of late-successional habitat pushed management objectives on public lands away from timber production and toward maintenance and restoration of late-successional habitat. In accordance with these new objectives, The Young Stand Thinning and Diversity Study (YSTDS) was developed to test if thinning could accelerate development of latesuccessional habitat in young managed Douglas-fir forests. Though the YSTDS examines several components of forest ecosystems, the goal of this study was to investigate short-term (5-7 years post-treatment) responses of vegetation to thinning treatments and to evaluate this response in relation to long-term objectives of late-successional development. The study is located on the western slope of the central Oregon Cascades. It consists of four replications of four thinning treatments (treatment areas average 30 ha each) in 30-50 year old second-growth Douglas-fir forest stands. Treatments include a control, heavy thin, light thin, and light thin with gaps. Unlike traditional thinning, the thinning treatments in this study sought to maintain and enhance overstory structural diversity by: (1) retaining species other than Douglas-fir, (2) simulating low densities that characterized development of some old-growth stands, and (3) adding canopy gaps to enhance spatial diversity. Following treatment completion, first, third, and fifth-year vegetation responses were measured Results for overstory vegetation indicate that heavy thinning may accelerate development of large trees, one important component of old-growth structure. This was evident by faster growth of the largest trees in the heavy thin than in the control. A heavy thin may also permit more time for understory development than a lighter thin because canopies of heavy thinned stands remained open longer than canopies of light thinned stands. Variation in overstory cover, which may promote heterogeneous understory development, was higher in the treatment that included canopy gaps than in other treatments including the control. Although accelerated development of a multi-layered canopy was not evident in any treatment, retention of non-dominant tree species prevented simplification of vertical canopy structure by retaining layers that are typically removed by a low thinning prescription. In addition, mortality of non-dominant species was not greater in thinned treatments than in the control. In the understory, results suggest that thinning can increase abundance of some vegetative layers without encouraging homogenization of the understory by clonal shrubs or exotic species. The thinnings resulted in initial declines of bryophytes, tall shrubs, and low shrubs followed by subsequent recovery and growth. While herbs displayed little initial response, a release of early-seral species was evident by 5-7 years post-treatment. Initial changes following thinning were likely due to harvesting damage and/or alteration of microclimate while subsequent changes were probably also related to increased resource availability. It is expected that eventually similarities and differences in overstory structure among thinned treatments will be reflected in the understory. For example, variation in canopy cover created by the addition of canopy gaps was already reflected in the understory, as plant assemblages differed across the gradient from gaps to the thinned forest matrix. Hence, although understory vegetation was similar among heavy and light thins in the short-term, early closure of the canopy following a light thin could preclude continuation of late-seral understory development. Finally, the effect of canopy gaps on the understory was more apparent at a within-stand scale than at a stand scale. Had the within-stand scale been ignored, relevant information regarding understory response would have been overlooked. This indicates that spatial scale should be considered when assessing ecological patterns. In conclusion, it is acknowledged that there are drawbacks to thinning (e.g., certain species decline following thinning) It is also acknowledged that the short-term nature of the data permits only speculation regarding long-term succession. While these limitations are recognized, current trends indicate that a moderate to heavy thinning in combination with gap formation can hasten development of late-successional features in thinned stands relative to unthinned stands. Thus, thinning similar to that used in this study can be one useful tool in the management of young Douglas-fir forests. Title: Vegetation response following thinning in young Douglas-fir forests of western Oregon : can thinning accelerate development of late-successional structure and composition? Author: Beggs, Liane R. Across western Oregon, Washington, and British Columbia, forest management practices over the past century reduced the amount of late-successional forest while simultaneously increasing the amount of young (less than 80 years old), managed Douglas-fir (Pseudotsuga menziesii) dominated forests. Recently, concerns over loss of late-successional habitat pushed management objectives on public lands away from timber production and toward maintenance and restoration of late-successional habitat. In accordance with these new objectives, The Young Stand Thinning and Diversity Study (YSTDS) was developed to test if thinning could accelerate development of latesuccessional habitat in young managed Douglas-fir forests. Though the YSTDS examines several components of forest ecosystems, the goal of this study was to investigate short-term (5-7 years post-treatment) responses of vegetation to thinning treatments and to evaluate this response in relation to long-term objectives of late-successional development. The study is located on the western slope of the central Oregon Cascades. It consists of four replications of four thinning treatments (treatment areas average 30 ha each) in 30-50 year old second-growth Douglas-fir forest stands. Treatments include a control, heavy thin, light thin, and light thin with gaps. Unlike traditional thinning, the thinning treatments in this study sought to maintain and enhance overstory structural diversity by: (1) retaining species other than Douglas-fir, (2) simulating low densities that characterized development of some old-growth stands, and (3) adding canopy gaps to enhance spatial diversity. Following treatment completion, first, third, and fifth-year vegetation responses were measured Results for overstory vegetation indicate that heavy thinning may accelerate development of large trees, one important component of old-growth structure. This was evident by faster growth of the largest trees in the heavy thin than in the control. A heavy thin may also permit more time for understory development than a lighter thin because canopies of heavy thinned stands remained open longer than canopies of light thinned stands. Variation in overstory cover, which may promote heterogeneous understory development, was higher in the treatment that included canopy gaps than in other treatments including the control. Although accelerated development of a multi-layered canopy was not evident in any treatment, retention of non-dominant tree species prevented simplification of vertical canopy structure by retaining layers that are typically removed by a low thinning prescription. In addition, mortality of non-dominant species was not greater in thinned treatments than in the control. In the understory, results suggest that thinning can increase abundance of some vegetative layers without encouraging homogenization of the understory by clonal shrubs or exotic species. The thinnings resulted in initial declines of bryophytes, tall shrubs, and low shrubs followed by subsequent recovery and growth. While herbs displayed little initial response, a release of early-seral species was evident by 5-7 years post-treatment. Initial changes following thinning were likely due to harvesting damage and/or alteration of microclimate while subsequent changes were probably also related to increased resource availability. It is expected that eventually similarities and differences in overstory structure among thinned treatments will be reflected in the understory. For example, variation in canopy cover created by the addition of canopy gaps was already reflected in the understory, as plant assemblages differed across the gradient from gaps to the thinned forest matrix. Hence, although understory vegetation was similar among heavy and light thins in the short-term, early closure of the canopy following a light thin could preclude continuation of late-seral understory development. Finally, the effect of canopy gaps on the understory was more apparent at a within-stand scale than at a stand scale. Had the within-stand scale been ignored, relevant information regarding understory response would have been overlooked. This indicates that spatial scale should be considered when assessing ecological patterns. In conclusion, it is acknowledged that there are drawbacks to thinning (e.g., certain species decline following thinning) It is also acknowledged that the short-term nature of the data permits only speculation regarding long-term succession. While these limitations are recognized, current trends indicate that a moderate to heavy thinning in combination with gap formation can hasten development of late-successional features in thinned stands relative to unthinned stands. Thus, thinning similar to that used in this study can be one useful tool in the management of young Douglas-fir forests. Close

• 56. [Article] The influence of prescribed fire on the rare endemic plant Delphinium pavonaceum (Peacock larkspur)

  In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered ...

  Citation × Citation Citation Abstract Copy Title: The influence of prescribed fire on the rare endemic plant Delphinium pavonaceum (Peacock larkspur) Author: McKernan, Brie-Anne In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered perennial forb, to four unreplicated dormant season fire regimes of 0, 2, 4, or 10 fires that were applied over a 12-year period. Additionally, an unexpected removal of woody plants by refuge staff within some portions of our control area offered an unplanned opportunity for study. In 2002 we measured the density and vigor of reproductive plants, and performed seed germination trials. In 2003 we repeated previous field measurements, sampled immature plant density, and recorded observations of the insects visiting D. pavonaceum in burned and unburned habitats. We hypothesized that this rare endemic species and its insect visitors would respond positively to prescribed burning or the removal of woody species. Low seedling density was found in the unburned and hand-removal areas, likely due to interference from litter and/or taller, shading plants. We also found low seedling density in sites burned the previous year, implying that fire consumes or damages unprotected seeds in the litter layer or exposed on the soil surface. Seedling density was greater in a site burned three seasons previously, suggesting that fire ultimately leads to the enhancement of seedling density following the replenishment of the seed bank. The largest density of recruits was detected in a subunit recently returned to fire management in 1999, and also burned in 2002 following our first field season. However, the other, more-frequently burned sites did not exhibit an increased density of recruits, possibly due to a reduction of the seed bank following repeated bums, and increased intraspecific competition with mature plants. The elevated density of seedlings and recruits we observed in some burned areas may lead to population growth, as we observed a greater density of reproductive plants in the two most-frequently burned subunits during both years of study. Our results also suggest that fewer plants enter summer dormancy in burned areas, and that increases in flowering plant density may decline after 3 years. Plants in the burned and hand-removal sites were shorter, likely resulting from water stress following the removal of shading plants and litter. Additionally, plants in unburned areas might have experienced greater stem elongation due to competition with tall and dense vegetation. Plants in the burned and hand-removal areas were generally similar to the unburned control site for flower and fruit production, fruit set, seed production and seed mass. However, plants in the burned and hand-removal areas produced more flowers per centimeter of height, indicating that they allocated more energy to reproduction than plants in the unburned area. We suggest that the decreased productivity we observed in some vigor traits is not problematic to D. pavonaceum conservation goals and may be ameliorated after 3 years. Bombus ca1ifornicus, B. appositus, and several large moths were the only insects we observed visiting D. pavonaceum during the two years of this study. We did not detect a difference in bumblebee abundance between a frequently burned and unburned study plot during the peak flowering time of D. pavonaceum. However, our small sample size requires that this result be cautiously interpreted and further studied, as it is possible that our visitation data would change appreciably with a broader range of observations. Our results indicate that the current FNWR fire management plan is not in conflict with D. pavonaceum conservation. The choice of fire-return interval seems to influence D. pavonaceum populations and plant vigor, but because the fire-schedule at FNWR was altered in 1997, our ability to recommend an appropriate fire-regime for this species is limited. Although not directly investigated, we suggest that annual fires, when applied for more than five consecutive years, might lead to population declines for this species because fire appears to consume the seed bank and reduce seedling density. If annual fires are returned to FNWR, the potential for this undesirable result should be investigated for at least 10 years by population monitoring. Title: The influence of prescribed fire on the rare endemic plant Delphinium pavonaceum (Peacock larkspur) Author: McKernan, Brie-Anne In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered perennial forb, to four unreplicated dormant season fire regimes of 0, 2, 4, or 10 fires that were applied over a 12-year period. Additionally, an unexpected removal of woody plants by refuge staff within some portions of our control area offered an unplanned opportunity for study. In 2002 we measured the density and vigor of reproductive plants, and performed seed germination trials. In 2003 we repeated previous field measurements, sampled immature plant density, and recorded observations of the insects visiting D. pavonaceum in burned and unburned habitats. We hypothesized that this rare endemic species and its insect visitors would respond positively to prescribed burning or the removal of woody species. Low seedling density was found in the unburned and hand-removal areas, likely due to interference from litter and/or taller, shading plants. We also found low seedling density in sites burned the previous year, implying that fire consumes or damages unprotected seeds in the litter layer or exposed on the soil surface. Seedling density was greater in a site burned three seasons previously, suggesting that fire ultimately leads to the enhancement of seedling density following the replenishment of the seed bank. The largest density of recruits was detected in a subunit recently returned to fire management in 1999, and also burned in 2002 following our first field season. However, the other, more-frequently burned sites did not exhibit an increased density of recruits, possibly due to a reduction of the seed bank following repeated bums, and increased intraspecific competition with mature plants. The elevated density of seedlings and recruits we observed in some burned areas may lead to population growth, as we observed a greater density of reproductive plants in the two most-frequently burned subunits during both years of study. Our results also suggest that fewer plants enter summer dormancy in burned areas, and that increases in flowering plant density may decline after 3 years. Plants in the burned and hand-removal sites were shorter, likely resulting from water stress following the removal of shading plants and litter. Additionally, plants in unburned areas might have experienced greater stem elongation due to competition with tall and dense vegetation. Plants in the burned and hand-removal areas were generally similar to the unburned control site for flower and fruit production, fruit set, seed production and seed mass. However, plants in the burned and hand-removal areas produced more flowers per centimeter of height, indicating that they allocated more energy to reproduction than plants in the unburned area. We suggest that the decreased productivity we observed in some vigor traits is not problematic to D. pavonaceum conservation goals and may be ameliorated after 3 years. Bombus ca1ifornicus, B. appositus, and several large moths were the only insects we observed visiting D. pavonaceum during the two years of this study. We did not detect a difference in bumblebee abundance between a frequently burned and unburned study plot during the peak flowering time of D. pavonaceum. However, our small sample size requires that this result be cautiously interpreted and further studied, as it is possible that our visitation data would change appreciably with a broader range of observations. Our results indicate that the current FNWR fire management plan is not in conflict with D. pavonaceum conservation. The choice of fire-return interval seems to influence D. pavonaceum populations and plant vigor, but because the fire-schedule at FNWR was altered in 1997, our ability to recommend an appropriate fire-regime for this species is limited. Although not directly investigated, we suggest that annual fires, when applied for more than five consecutive years, might lead to population declines for this species because fire appears to consume the seed bank and reduce seedling density. If annual fires are returned to FNWR, the potential for this undesirable result should be investigated for at least 10 years by population monitoring. Close

• 57. [Article] Age and growth of young-of-the-year Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris of Upper Klamath Lake, Oregon

  Upper Klamath Lake in southern Oregon has two species of lacustrine suckers, Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris that were historically abundant. Results of ...

  Citation × Citation Citation Abstract Copy Title: Age and growth of young-of-the-year Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris of Upper Klamath Lake, Oregon Author: Logan, Daniel Joseph Upper Klamath Lake in southern Oregon has two species of lacustrine suckers, Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris that were historically abundant. Results of surveys performed in the mid-1980's indicated that populations of both species were declining and ageing with apparent recruitment failure in most years since 1970. In 1988 both species were listed as endangered species and high priority has been placed on investigating recruitment of Upper Klamath Lake suckers. Lapilli are the preferred otolith for ageing suckers. Lapilli form predictably on the day of hatch, have the most conservative morphology of the three otoliths, and deposit easily discernable increments that begin on the day of hatch and proceed daily, and grow in a predictable relationship with somatic growth. Ages estimated by otolith analysis and resulting hatch dates of young-of-the-year Lost River sucker and shortnose sucker were consistent annually and consistent with reported spawning period for suckers from Upper Klamath Lake. Otolith increment analysis is necessarily lethal, whereas scale circuli analysis is not lethal. My findings suggest that scale circuli count is an inefficient estimator of daily Daily age estimates for age in young-of-the-year Lost River sucker and shortnose sucker. any given circuli count varied by approximately 51 days in Lost River sucker and 30 days Additionally, my results do not accurately predict the size or age at in shortnose sucker. which scales are formed, thereby invalidating an assumption of age and growth models. Consequently, scale circuli analysis cannot be used to produce accurate estimates of age or growth for young-of-the-year Lost River sucker and shortnose sucker. Lost River sucker and shortnose sucker achieve a relatively large size by the autumn of their first year, consistent with other members of Catostomidae. Interspecific difference in growth rates was evident in each year with Lost River sucker exhibiting faster growth than shortnose sucker in each year. Abundance of young-of-the-year suckers does not appear to be strongly correlated to somatic growth rate, though hatch date and environmental parameters are highly correlated with abundance. In both Lost River sucker and shortnose sucker, in years with the highest abundance (1991 and 1993), the mean hatch dates of surviving fish were later than in years with the lowest abundance. Also, young-of-the-year Lost River sucker and shortnose sucker experienced wide environmental fluctuations in Upper Klamath Lake as seasonal limnological and climatic variation create a dynamic habitat for young suckers. Water temperature, precipitation, air temperature, and minimum lake elevation are all strongly correlated to abundance of young-of-the-year suckers. Title: Age and growth of young-of-the-year Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris of Upper Klamath Lake, Oregon Author: Logan, Daniel Joseph Upper Klamath Lake in southern Oregon has two species of lacustrine suckers, Lost River sucker Deltistes luxatus and shortnose sucker Chasmistes brevirostris that were historically abundant. Results of surveys performed in the mid-1980's indicated that populations of both species were declining and ageing with apparent recruitment failure in most years since 1970. In 1988 both species were listed as endangered species and high priority has been placed on investigating recruitment of Upper Klamath Lake suckers. Lapilli are the preferred otolith for ageing suckers. Lapilli form predictably on the day of hatch, have the most conservative morphology of the three otoliths, and deposit easily discernable increments that begin on the day of hatch and proceed daily, and grow in a predictable relationship with somatic growth. Ages estimated by otolith analysis and resulting hatch dates of young-of-the-year Lost River sucker and shortnose sucker were consistent annually and consistent with reported spawning period for suckers from Upper Klamath Lake. Otolith increment analysis is necessarily lethal, whereas scale circuli analysis is not lethal. My findings suggest that scale circuli count is an inefficient estimator of daily Daily age estimates for age in young-of-the-year Lost River sucker and shortnose sucker. any given circuli count varied by approximately 51 days in Lost River sucker and 30 days Additionally, my results do not accurately predict the size or age at in shortnose sucker. which scales are formed, thereby invalidating an assumption of age and growth models. Consequently, scale circuli analysis cannot be used to produce accurate estimates of age or growth for young-of-the-year Lost River sucker and shortnose sucker. Lost River sucker and shortnose sucker achieve a relatively large size by the autumn of their first year, consistent with other members of Catostomidae. Interspecific difference in growth rates was evident in each year with Lost River sucker exhibiting faster growth than shortnose sucker in each year. Abundance of young-of-the-year suckers does not appear to be strongly correlated to somatic growth rate, though hatch date and environmental parameters are highly correlated with abundance. In both Lost River sucker and shortnose sucker, in years with the highest abundance (1991 and 1993), the mean hatch dates of surviving fish were later than in years with the lowest abundance. Also, young-of-the-year Lost River sucker and shortnose sucker experienced wide environmental fluctuations in Upper Klamath Lake as seasonal limnological and climatic variation create a dynamic habitat for young suckers. Water temperature, precipitation, air temperature, and minimum lake elevation are all strongly correlated to abundance of young-of-the-year suckers. Close

• 58. [Article] Evaluation of length distributions and growth variance to improve assessment of the loggerhead sea turtle, (Caretta caretta)

  Nest counts from the largest subpopulation of the loggerhead sea turtle (Caretta caretta) in the Atlantic, peninsular Florida, have been declining since 1998. Analyzing trends of nests and adult females ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of length distributions and growth variance to improve assessment of the loggerhead sea turtle, (Caretta caretta) Author: Vaughan, Jason R. Nest counts from the largest subpopulation of the loggerhead sea turtle (Caretta caretta) in the Atlantic, peninsular Florida, have been declining since 1998. Analyzing trends of nests and adult females is insufficient to determine the overall status of a sea turtle population, due to variation in nesting frequency and a 25 – 35 year time lag between hatching and maturation. While nest numbers of this threatened species have declined by 50% since 1998, catches of juvenile turtles in many areas have increased. Better assessment of population status and diagnosis of the causes of population trends are possible if we examine existing data on changes in abundance and size distribution from in–water surveys of juvenile and subadult turtles as well as adults. I have plotted the length frequency data and catch rates of neritic turtles (juvenile, subadult and adult turtles that inhabit nearshore waters) collected from 1980 – 2007 at 4 in–water sites ranging from North Carolina to Florida (N=10,486). I also examined the length distributions recorded from strandings of dead turtles found on beaches in the Gulf of Mexico (N=4,308) and along the U.S. east coast (N=10,918) from 1990 – 2005. I found a similar pattern in length distribution shifts over time, which provides compelling evidence that the data are revealing true population change. The data suggest an increase in the overall abundance of juvenile turtles in the southeast U.S. since the late 1990s and an increase in the median size of neritic juveniles (40 – 90 cm) since 1990. There has also been a reduction in the number and proportion of small (<55 cm) juveniles since 2000 in some areas; these are considered “recruits” to the neritic feeding areas on the continental shelf. The shift in median size of juveniles coupled with the increased abundance in North Carolina and Florida indicate that there may be a large cohort or group of similar sized turtles that should reach maturity in the next decade. Changes in length frequency through time could indicate changes in recruitment, survival rates, or behavior, and translating length to age requires a good estimate of variance in growth rates. I developed an individual–based growth model using variance estimated through a new technique that measures growth using increments measured in cross sections of the humerus bone of stranded turtles. The technique permits a reconstruction of the growth history of individual turtles. While the growth patterns are clearly not a smooth, asymptotic function over length and time, there is some consistency among individuals. My re–sampling analysis of growth from 92 turtles provided an estimate of 30.74 years (95% CI = 23.82 – 37.66) required for a U.S. loggerhead turtle to grow from 20 cm (age 1 or 2) to 90 cm. This analysis will improve our estimates of the mean and variance in the length of time loggerheads are spending in various habitats and life stages, and improve future demographic models to determine population status. My analyses incorporate multiple data sets and techniques to improve our understanding of how the whole loggerhead population is changing through time, leading to more accurate diagnosis and predictions about population trends. Title: Evaluation of length distributions and growth variance to improve assessment of the loggerhead sea turtle, (Caretta caretta) Author: Vaughan, Jason R. Nest counts from the largest subpopulation of the loggerhead sea turtle (Caretta caretta) in the Atlantic, peninsular Florida, have been declining since 1998. Analyzing trends of nests and adult females is insufficient to determine the overall status of a sea turtle population, due to variation in nesting frequency and a 25 – 35 year time lag between hatching and maturation. While nest numbers of this threatened species have declined by 50% since 1998, catches of juvenile turtles in many areas have increased. Better assessment of population status and diagnosis of the causes of population trends are possible if we examine existing data on changes in abundance and size distribution from in–water surveys of juvenile and subadult turtles as well as adults. I have plotted the length frequency data and catch rates of neritic turtles (juvenile, subadult and adult turtles that inhabit nearshore waters) collected from 1980 – 2007 at 4 in–water sites ranging from North Carolina to Florida (N=10,486). I also examined the length distributions recorded from strandings of dead turtles found on beaches in the Gulf of Mexico (N=4,308) and along the U.S. east coast (N=10,918) from 1990 – 2005. I found a similar pattern in length distribution shifts over time, which provides compelling evidence that the data are revealing true population change. The data suggest an increase in the overall abundance of juvenile turtles in the southeast U.S. since the late 1990s and an increase in the median size of neritic juveniles (40 – 90 cm) since 1990. There has also been a reduction in the number and proportion of small (<55 cm) juveniles since 2000 in some areas; these are considered “recruits” to the neritic feeding areas on the continental shelf. The shift in median size of juveniles coupled with the increased abundance in North Carolina and Florida indicate that there may be a large cohort or group of similar sized turtles that should reach maturity in the next decade. Changes in length frequency through time could indicate changes in recruitment, survival rates, or behavior, and translating length to age requires a good estimate of variance in growth rates. I developed an individual–based growth model using variance estimated through a new technique that measures growth using increments measured in cross sections of the humerus bone of stranded turtles. The technique permits a reconstruction of the growth history of individual turtles. While the growth patterns are clearly not a smooth, asymptotic function over length and time, there is some consistency among individuals. My re–sampling analysis of growth from 92 turtles provided an estimate of 30.74 years (95% CI = 23.82 – 37.66) required for a U.S. loggerhead turtle to grow from 20 cm (age 1 or 2) to 90 cm. This analysis will improve our estimates of the mean and variance in the length of time loggerheads are spending in various habitats and life stages, and improve future demographic models to determine population status. My analyses incorporate multiple data sets and techniques to improve our understanding of how the whole loggerhead population is changing through time, leading to more accurate diagnosis and predictions about population trends. Close

• 59. [Article] Non-regulatory efforts to combat nonpoint source pollution in Oregon

  This report and accompanying program inventory have been prepared in support of the Oregon Department of Environmental Quality's statewide nonpoint source pollution control efforts and for use in the development ...

  Citation × Citation Citation Abstract Copy Title: Non-regulatory efforts to combat nonpoint source pollution in Oregon Author: Lindberg, Roberta J. This report and accompanying program inventory have been prepared in support of the Oregon Department of Environmental Quality's statewide nonpoint source pollution control efforts and for use in the development of Oregon's new federally mandated Coastal Nonpoint Pollution Control Program (CNPCP). When Congress reauthorized the Coastal Zone Management Act in 1990, it added significant new responsibilities for coastal states regarding water pollution from diffuse, widespread sources that in the past have not been regulated. Section 6217 of the Coastal Zone Act Reauthorization Amendments (CZARA) requires states to adopt enforceable programs to address nonpoint source pollution arising from agriculture, forestry, urban runoff, recreational boating and marinas, channelization, dams and eroding stream banks. "Nonpoint source pollution" in this context includes any discharge to the state's waters which is not regulated by the Clean Water Act's permit system, the National Pollutant Discharge Elimination System (NPDES). When Congress mandated the coastal nonpoint source program, it directed that states' coastal programs and water quality agencies work together in developing and implementing the program. In Oregon, the Department of Land Conservation and Development (DLCD) and the Department of Environmental Quality (DEQ) are jointly responsible for the development of the coastal nonpoint control program. DLCD's Coastal Management Program implements provisions of the federal Coastal Zone Management Act. DEQ's Water Quality Division manages the statewide nonpoint source control program pursuant to Section 319 of the Clean Water Act (CWA). Staff at DLCD's Coastal Management Program prepared an extensive report and analysis of Oregon's current array of enforceable programs and the extent to which those programs satisfy the federal requirements for the new coastal program. Gaps in program coverage were identified, and efforts to fill those gaps are currently in progress. This report is a companion to the DLCD gap analysis. However, instead of focusing on enforceable programs, this report highlights nonpoint source control and watershed management programs that rely on voluntary efforts to achieve their goals. Staff at DEQ have identified nine types of activities which, together with enforcement, make constitute an effective watershed management program. This report presents an inventory of the state and federal government efforts currently underway within the state of Oregon which contribute to the control of nonpoint source pollution but do not rely on a regulatory program to do so. This is a time of extensive reevaluation and reordering of natural resource priorities and strategies at both the state and federal levels. The Clinton Forest Summit and the Forest Ecosystem Management Assessment Team (FEMAT) process have been examining federal forest policy from top to bottom. The two major federal land management agencies, the Forest Service and the Bureau of Land Management, began reviewing their policies and practices well before the Forest Summit, and have made significant changes as a result. At the state level, the Watershed Health Initiative directed $10 million to two regions of the state during the 1993-95 biennium, in an unprecedented effort to restore salmon habitat and improve water quality. The impetus for change comes from the visible results of past natural resource management practices: the collapse of many native salmon runs and the decline in many other species leading to a great expansion of activity under the federal Endangered Species Act. The federal court logging injunction to protect the Northern Spotted Owl triggered much activity at the state and local levels in an effort to avoid further listings and the potential economic dislocations associated with them. Title: Non-regulatory efforts to combat nonpoint source pollution in Oregon Author: Lindberg, Roberta J. This report and accompanying program inventory have been prepared in support of the Oregon Department of Environmental Quality's statewide nonpoint source pollution control efforts and for use in the development of Oregon's new federally mandated Coastal Nonpoint Pollution Control Program (CNPCP). When Congress reauthorized the Coastal Zone Management Act in 1990, it added significant new responsibilities for coastal states regarding water pollution from diffuse, widespread sources that in the past have not been regulated. Section 6217 of the Coastal Zone Act Reauthorization Amendments (CZARA) requires states to adopt enforceable programs to address nonpoint source pollution arising from agriculture, forestry, urban runoff, recreational boating and marinas, channelization, dams and eroding stream banks. "Nonpoint source pollution" in this context includes any discharge to the state's waters which is not regulated by the Clean Water Act's permit system, the National Pollutant Discharge Elimination System (NPDES). When Congress mandated the coastal nonpoint source program, it directed that states' coastal programs and water quality agencies work together in developing and implementing the program. In Oregon, the Department of Land Conservation and Development (DLCD) and the Department of Environmental Quality (DEQ) are jointly responsible for the development of the coastal nonpoint control program. DLCD's Coastal Management Program implements provisions of the federal Coastal Zone Management Act. DEQ's Water Quality Division manages the statewide nonpoint source control program pursuant to Section 319 of the Clean Water Act (CWA). Staff at DLCD's Coastal Management Program prepared an extensive report and analysis of Oregon's current array of enforceable programs and the extent to which those programs satisfy the federal requirements for the new coastal program. Gaps in program coverage were identified, and efforts to fill those gaps are currently in progress. This report is a companion to the DLCD gap analysis. However, instead of focusing on enforceable programs, this report highlights nonpoint source control and watershed management programs that rely on voluntary efforts to achieve their goals. Staff at DEQ have identified nine types of activities which, together with enforcement, make constitute an effective watershed management program. This report presents an inventory of the state and federal government efforts currently underway within the state of Oregon which contribute to the control of nonpoint source pollution but do not rely on a regulatory program to do so. This is a time of extensive reevaluation and reordering of natural resource priorities and strategies at both the state and federal levels. The Clinton Forest Summit and the Forest Ecosystem Management Assessment Team (FEMAT) process have been examining federal forest policy from top to bottom. The two major federal land management agencies, the Forest Service and the Bureau of Land Management, began reviewing their policies and practices well before the Forest Summit, and have made significant changes as a result. At the state level, the Watershed Health Initiative directed $10 million to two regions of the state during the 1993-95 biennium, in an unprecedented effort to restore salmon habitat and improve water quality. The impetus for change comes from the visible results of past natural resource management practices: the collapse of many native salmon runs and the decline in many other species leading to a great expansion of activity under the federal Endangered Species Act. The federal court logging injunction to protect the Northern Spotted Owl triggered much activity at the state and local levels in an effort to avoid further listings and the potential economic dislocations associated with them. Close

• 60. [Article] Community ecology of invasions: direct and indirect effects of multiple invasive species on aquatic communities

  This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/.

  Citation × Citation Citation Abstract Copy Title: Community ecology of invasions: direct and indirect effects of multiple invasive species on aquatic communities Author: Preston, Daniel L., Henderson, Jeremy S. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/. Title: Community ecology of invasions: direct and indirect effects of multiple invasive species on aquatic communities Author: Preston, Daniel L., Henderson, Jeremy S. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/. Close