Travis Belote - Academia.edu (original) (raw)
Papers by Travis Belote
available online at www.jpe.oxfordjournals.org CO2 enrichment accelerates successional developmen... more available online at www.jpe.oxfordjournals.org CO2 enrichment accelerates successional development of an understory plant community
Background/Question/Methods Rising concentrations of atmospheric carbon dioxide ([CO2]) are likel... more Background/Question/Methods Rising concentrations of atmospheric carbon dioxide ([CO2]) are likely to have effects on terrestrial ecosystems via both direct and indirect effects on understory plant communities. Elevated [CO2] can directly affect understory plant communities through stimulation of photosynthesic responses and overall performance of plant species. Elevated [CO2] can indirectly affect understory plant communities via direct effects on forest structure. Here, we describe how elevated [CO2] affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility. From 2001 to 2003, we estimated species-specific, woody vs. herbaceous, and total aboveground biomass by harvesting subplots within the established understory plant community using four 1 m 0.5 m quadrats in each FACE plot. In 2008, we estimated herbaceous biomass as previ...
Background/Question/Methods Invasive species, such as Tamarix spp. (tamarisk), often alter ecosys... more Background/Question/Methods Invasive species, such as Tamarix spp. (tamarisk), often alter ecosystem properties and reduce native species diversity. However, native and exotic species diversity are often positively correlated within plots sampled across landscapes. Thus, a goal of restoration that removes dominant invasive species should include changing the relationship between native and exotic species by reducing richness and abundance of exotic species while increasing native species. Tamarisk has invaded thousands of hectares of riparian zones in the southwestern US, including ecosystems in Grand Canyon National Park. The National Park Service and partner organizations began a tamarisk management project in 2000, which included a restoration study investigating the effects of tamarisk removal on native plant diversity and composition. Plant species composition and diversity were sampled along transects in tamarisk-dominated stands prior to tamarisk removal. Transects were then ...
Ecological Restoration, 2010
The removal of non-native species is often an important restoration goal in natural areas, includ... more The removal of non-native species is often an important restoration goal in natural areas, including national parks. There is often a positive correlation between non-native and native plant species richness, so that areas with the greatest number of native species support the greatest number of non-natives. This pattern may create both challenges and opportunities for restoration. Native species may be inadvertently damaged or killed during mechanical or chemical treatments targeted toward non-natives. However, greater numbers of native species may better colonize subsequent openings. We used data from an ongoing active management project in Grand Canyon National Park to test three predictions of plant community response to invasive tamarisk (Tamarix spp.) removal. We investigated patterns of native and nonnative species abundance and richness, compositional shifts, and the relationship between native and non-native species before and after treatments. In general, native species richness and abundance did not increase, but species composition following tamarisk removal tended to become more similar to that in uninvaded stands. Native and non-native species richness and abundance were positively correlated before tamarisk removal. While treatment successfully reduced cover of tamarisk after one to three years, our results suggest that it may not increase richness of native species during the same period. Furthermore, investigating native and non-native species relationships may be a useful tool for exploring hypotheses and consequences of restoration via invasive species removal.
![Research paper thumbnail of Response of an understory plant community to elevated [CO2] depends on differential responses of dominant invasive species and is mediated by soil water availability](https://attachments.academia-assets.com/87412612/thumbnails/1.jpg)
](New Phytologist, 2004
• Rising atmospheric CO 2 concentrations are likely to have direct effects on terrestrial ecosyst... more • Rising atmospheric CO 2 concentrations are likely to have direct effects on terrestrial ecosystems. Here, we describe effects of elevated concentrations of CO 2 on an understory plant community in terms of production and community composition. • In 2001 and 2002 total and species-specific above-ground net primary productivity (ANPP) were estimated by harvesting above-ground biomass within an understory community receiving ambient [CO 2 ] and elevated [CO 2 ] at Oak Ridge National Laboratory's free-air carbon dioxide enrichment (FACE) facility. • During a wet year, community composition differed between plots receiving ambient [CO 2 ] and elevated [CO 2 ], but total ANPP did not differ. By contrast, during a drier year, community composition did not differ, but total ANPP was greater in elevated than ambient [CO 2 ] plots. These patterns were driven by the response of two codominant species, Lonicera japonica and Microstegium vimineum , both considered invasive species in the southeastern United States. The ANPP of L. japonica was consistently greater under elevated [CO 2 ], whereas the response of M. vimineum to CO 2 enrichment differed between years and mediated total community response. • These data suggest that community and species responses to a future, CO 2enriched atmosphere may be mediated by other environmental factors and will depend on individual species responses.
Journal of Plant Ecology, 2010
Aims Rising concentrations of atmospheric carbon dioxide ([CO 2 ]) may influence forest successio... more Aims Rising concentrations of atmospheric carbon dioxide ([CO 2 ]) may influence forest successional development and species composition of understory plant communities by altering biomass production of plant species of functional groups. Here, we describe how elevated [CO 2 ] (eCO 2) affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility in eastern Tennessee, USA. We asked if (i) CO 2 enrichment affected total understory biomass and (ii) whether total biomass responses could be explained by changes in understory species composition or changes in relative abundance of functional groups through time. Materials and methods The FACE experiment started in 1998 with three rings receiving ambient [CO 2 ] (aCO 2) and two rings receiving eCO 2. From 2001 to 2003, we estimated species-specific, woody versus herbaceous and total aboveground biomass by harvesting four 1 3 0.5-m subplots within the established understory plant community in each FACE plot. In 2008, we estimated herbaceous biomass as previously but used allometric relationships to estimate woody biomass across two 5 3 5-m quadrats in each FACE plot. Important findings Across years, aboveground biomass of the understory community was on average 25% greater in eCO 2 than in aCO 2 plots. We could not detect differences in plant species composition between aCO 2 and eCO 2 treatments. However, we did observe shifts in the relative abundance of plant functional groups, which reflect important structural changes in the understory community. In 2001-03, little of the understory biomass was in woody species; herbaceous species made up 94% of the total understory biomass across [CO 2 ] treatments. Through time, woody species increased in importance, mostly in eCO 2 , and in 2008, the contribution of herbaceous species to total understory biomass was 61% in aCO 2 and only 33% in eCO 2 treatments. Our results suggest that rising atmospheric [CO 2 ] could accelerate successional development and have longer term impact on forest dynamics. Keywords: community composition d FACE d aboveground biomass d woody d herbaceous d sweetgum d Microstegium vimineum d Lonicera japonica
Frontiers in Ecology and the Environment, 2006
Quality and quantity of publications are among the most important measures determining the succes... more Quality and quantity of publications are among the most important measures determining the success of ecologists. The past 50 years have seen a steady rise in the number of researchers and collaborative manuscripts, and a corresponding increase in multi-authored articles. Despite these increases, there remains a shortage of useful and definitive guidelines to aid ecologists in addressing authorship issues, leading to a lack of consistency in what the term "author" really means. Deciding where to draw the line between those who have earned authorship and those who are more appropriately credited in the acknowledgments may be one of the more challenging aspects of authorship. Here, we borrow ideas from other scientific disciplines and propose a simple solution to help ecologists who are making such decisions. We recommend improving communication between co-authors throughout the research process, and propose that authors publish their contributions to a manuscript in a separate byline.
Frontiers in Ecology and the Environment, 2003
Forest Ecology and Management, 2011
Factors influencing the relationship between ecosystem productivity and biological diversity form... more Factors influencing the relationship between ecosystem productivity and biological diversity form the basis of much ecological theory. An understanding of how productivity-diversity relationships are influenced by scale of observation and unique attributes of ecoregions may provide important insights to aid conservation planning for carbon retention and biodiversity. Here we use publically available datasets to investigate patterns of productivity-diversity and explore potential factors influencing these patterns in forests located in five mid-Atlantic and Appalachian states. We used a geographic information system (GIS) to overlay multiple publically available datasets including remotely sensed estimates of productivity from MODIS and tree diversity estimated from the forest inventory analysis (FIA) database. We evaluated productivity-diversity relationships using two scales of observation (among and within ecoregions). We also determined if productivity-diversity relationships might be related to region-wide patterns in land use, and if the relationships varied by forest type, land management zones, and along gradients of mean productivity and diversity. Productivity-diversity relationships depended on scale and varied among ecoregions, and land use was correlated with both productivity and diversity. Mountainous ecoregions were characterized by positive productivity-diversity relationships, whereas coastal ecoregions were characterized by negative productivity-diversity relationships. Forest types and management zones that were on average less productive and more diverse exhibited positive productivity-diversity relationships across stands (the most productive stands were more diverse). In contrast, ecoregions and forest types that were on average more productive and less diverse exhibited negative productivity-diversity relationships (the most productive stands were less diverse). In conclusion, regional and local ecological and anthropogenic factors likely influence productivity-diversity relationships and these relationships appear to change along gradients of productivity and diversity.
Forest Ecology and Management, 2013
We describe and label four types of monitoring-surveillance, implementation, effectiveness, and e... more We describe and label four types of monitoring-surveillance, implementation, effectiveness, and ecological effects-that are designed to answer very different questions and achieve very different goals. Surveillance monitoring is designed to uncover change in target variables over space and time; implementation monitoring is designed to record whether management actions were applied as prescribed; effectiveness monitoring is designed to evaluate whether a given management action was effective in meeting a stated management objective; and ecological effects monitoring is designed to uncover unintended ecological consequences of management actions. Public land management agencies have focused heavily on implementation and effectiveness monitoring and very little on the more ecologically oriented surveillance and ecological effects monitoring. Tradeoffs, in the form of unintended ecological consequences, are important to consider in the management of natural resources, yet lack of ecological effects monitoring data has hindered our ability to fully understand these tradeoffs. Our proposed monitoring classification scheme offers practitioners and stakeholders a framework that explicitly identifies the type of monitoring they are conducting. We also suggest that, as a start, the effectiveness and ecological effects of a particular type of management activity can be approached rapidly and relatively inexpensively through use of a chronosequence approach to learning.
Environmental Entomology, 2004
Rising levels of atmospheric [CO 2 ] will directly affect the responses and community composition... more Rising levels of atmospheric [CO 2 ] will directly affect the responses and community composition of plants. However, few studies have examined how these changes to plant communities will alter insect communities that rely on them. Here, we report on a study that examined the community-level responses of plants, herbivores, detritivores, predators, parasitoids, and omnivores to increased [CO 2 ] at a Free Air Carbon Enrichment (FACE) facility at Oak Ridge National Laboratory. We found that aboveground net primary productivity for the Þve dominant plant species in the understory community, C:N ratios of leaf tissue for four of the Þve dominant understory taxa, amounts of herbivory, and arthropod abundance and richness across all trophic groups did not differ between ambient and elevated CO 2 plots. Abundance and richness of particular trophic groups were higher in ambient than in elevated CO 2 plots. There were also strong temporal effects on community composition, but no distinct treatment effects. These results, although preliminary, suggest that community-level responses to future atmospheric [CO 2 ] are likely to be species-and trophic-group speciÞc. KEY WORDS insect communities, plant communities, global change, invasive species, CO 2 enrichment
Ecology, 2008
Research examining the relationship between community diversity and invasions by nonnative specie... more Research examining the relationship between community diversity and invasions by nonnative species has raised new questions about the theory and management of biological invasions. Ecological theory predicts, and small-scale experiments confirm, lower levels of nonnative species invasion into species-rich compared to species-poor communities, but observational studies across a wider range of scales often report positive relationships between native and nonnative species richness. This paradox has been attributed to the scale dependency of diversity-invasibility relationships and to differences between experimental and observational studies. Disturbance is widely recognized as an important factor determining invasibility of communities, but few studies have investigated the relative and interactive roles of diversity and disturbance on nonnative species invasion. Here, we report how the relationship between native and nonnative plant species richness responded to an experimentally applied disturbance gradient (from no disturbance up to clearcut) in oakdominated forests. We consider whether results are consistent with various explanations of diversity-invasibility relationships including biotic resistance, resource availability, and the potential effects of scale (1 m 2 to 2 ha). We found no correlation between native and nonnative species richness before disturbance except at the largest spatial scale, but a positive relationship after disturbance across scales and levels of disturbance. Post-disturbance richness of both native and nonnative species was positively correlated with disturbance intensity and with variability of residual basal area of trees. These results suggest that more nonnative plants may invade species-rich communities compared to species-poor communities following disturbance.
Ecology, 2009
Whether biological diversity within communities is limited by local interactions or regional spec... more Whether biological diversity within communities is limited by local interactions or regional species pools remains an important question in ecology. In this paper, we investigate how an experimentally applied tree-harvesting disturbance gradient influenced local-regional richness relationships. Plant species richness was measured at three spatial scales (2 ha ¼ regional; 576 m 2 and 1 m 2 ¼ local) on three occasions (one year pre-disturbance, one year post-disturbance, and 10 years post-disturbance) across five disturbance treatments (uncut control through clearcut) replicated throughout the southern Appalachian Mountains, USA. We investigated whether species richness in 576-m 2 plots and 1-m 2 subplots depended on species richness in 2-ha experimental units and whether this relationship changed through time before and after canopy disturbance. We found that, before disturbance, the relationship between local and regional richness was weak or nonexistent. One year after disturbance local richness was a positive function of regional richness, because local sites were colonized from the regional species pool. Ten years after disturbance, the positive relationship persisted, but the slope had decreased by half. These results suggest that disturbance can set the stage for strong influences of regional species pools on local community assembly in temperate forests. However, as time since disturbance increases, local controls on community assembly decouple the relationships between regional and local diversity.
Ecological Applications, 2012
Human-caused changes in disturbance regimes and introductions of nonnative species have the poten... more Human-caused changes in disturbance regimes and introductions of nonnative species have the potential to result in widespread, directional changes in forest community structure. The degree that plant community composition persists or changes following disturbances depends on the balance between local extirpation and colonization by new species, including nonnatives. In this study, we examined species losses and gains, and entry of native vs. exotic species to determine how oak forests in the Appalachian Mountains might shift in species composition following a gradient of pulse disturbances (timber harvesting). We asked (1) how compositional stability of the plant community (resistance and resilience) was influenced by disturbance intensity, (2) whether community responses were driven by extirpation or colonization of species, and (3) how disturbance intensity influenced total and functional group diversity, including the nonnative proportion of the flora through time. We collected data at three spatial scales and three times, including just before, one year postdisturbance, and 10 years post-disturbance. Resistance was estimated using community distance measures between pre-and one year post-disturbance, and resilience using community distance between pre-and 10-year post-disturbance conditions. The number of colonizing and extirpated species between sampling times was analyzed for all species combined and for six functional groups. Resistance and resilience decreased with increasing timber-harvesting disturbance; compositional stability was lower in the most disturbed plots, which was driven by colonization, but not extirpation, of species. Colonization of species also led to increases in diversity after disturbance that was typically maintained after 10 years following disturbance. Most of the community-level responses were driven by postdisturbance colonization of native forbs and graminoids. The nonnative proportion of plant species tended to increase following disturbance, especially at large spatial scales in the most disturbed treatments, but tended to decrease through time following disturbance due to canopy development. The results of this study are consistent with the theory that resources released by disturbance have strong influences on species colonization and community composition. The effects of management activities tested in this study, which span a gradient of timber-harvesting disturbance, shift species composition largely via an increase in species colonization and diversity.
Biological Invasions, 2008
Dominant tree species influence community and ecosystem components through the quantity and quali... more Dominant tree species influence community and ecosystem components through the quantity and quality of their litter. Effects of litter may be modified by activity of ecosystem engineers such as earthworms. We examined the interacting effects of forest litter type and earthworm presence on invasibility of plants into forest floor environments using a greenhouse mesocosm experiment. We crossed five litter treatments mimicking historic and predicted changes in dominant tree composition with a treatment of either the absence or presence of nonnative earthworms. We measured mass loss of each litter type and growth of a model nonnative plant species (Festuca arundinacea, fescue) sown into each mesocosm. Mass loss was greater for litter of tree species characterized by lower C:N ratios. Earthworms enhanced litter mass loss, but only for species with lower C:N, leading to a significant litter 9 earthworm interaction. Fescue biomass was significantly greater in treatments with litter of low C:N and greater mass loss, suggesting that rapid decomposition of forest litter may be more favorable to understory plant invasions. Earthworms were expected to enhance invasion by increasing mass loss and removing the physical barrier of litter. However, earthworms typically reduced invasion success but not under invasive tree litter where the presence of earthworms facilitated invasion success compared to other litter treatments where earthworms were present. We conclude that past and predicted future shifts in dominant tree species may influence forest understory invasibility. The presence of nonnative earthworms may either suppress of facilitate invasibility depending on the species of dominant overstory tree species and the litter layers they produce.
ABSTRACT Background/Question/Methods Understanding the role fire historically played in maintaini... more ABSTRACT Background/Question/Methods Understanding the role fire historically played in maintaining local and landscape composition and biodiversity remains an active research front. In many forest types, fire suppression and land use have altered the structure and composition of forests. In response to altered conditions, various management strategies have been used to restore forest structure, biological diversity, and the ecological role of fire. Fire regimes of forests that historically burned with frequent, low-severity fires are widely studied and provide a useful guide for ecological restoration. In contrast, setting goals for ecosystem management and restoration targets in mixed-severity fire regimes, where the frequency, severity, and effects of fires historically varied in time and space has proven more difficult. Variability in forest conditions and fire severity in space and time make active treatments in forests of mixed severity fire regimes controversial. There, target conditions for forest restoration may be based on limited historical evidence, and relationships between spatially-complicated patterns and processes are not fully understood. We surveyed the literature, burn severity data at local and landscape scales, and our own experiences in collaborative forest restoration to provide conceptual and empirical overview of mixed severity fire regimes. Results/Conclusions Drivers of fire severity vary by scale of observation, with fuel loading, weather, and topography predicting fire severity at small scales, and vegetation, climate and landform influencing fire severity at larger scales. Variability in spatial composition of fire severity among forest fires in the western U.S. appears to be continuous without clear classification thresholds. Thus, classifying fire regimes using a categorical approach, while convenient, may be less helpful than understanding the mechanisms driving fire severity across forest types. Variability in temporal patterns of fire severity (variation in fire return intervals) may also reflect interactions between topographic and climatic drivers and create challenges to understanding and applying historical range of variability. This variability in space and time leads to controversy in prioritizing restoration using mechanical or prescribed fire treatments. Predictions of future impacts of climate change and increasing residential development in fire-prone forests have led collaborations of diverse stakeholders to begin supporting treatments in complex forest types where landscape restoration objectives are not clearly defined. We suggest restoration be conducted with mechanistic understanding of fire’s role in maintaining species diversity and landscape resilience. Where socially and economically feasible, treatments should be implemented using experimental approaches with collaborative input to facilitate collective learning within an adaptive management framework.
Understanding relationships between ecosystem productivity and species diversity may lead to impr... more Understanding relationships between ecosystem productivity and species diversity may lead to improved management for carbon sequestration and biodiversity. Few ecologists have yet investigated whether land management alters the relationship between productivity and diversity ...
available online at www.jpe.oxfordjournals.org CO2 enrichment accelerates successional developmen... more available online at www.jpe.oxfordjournals.org CO2 enrichment accelerates successional development of an understory plant community
Background/Question/Methods Rising concentrations of atmospheric carbon dioxide ([CO2]) are likel... more Background/Question/Methods Rising concentrations of atmospheric carbon dioxide ([CO2]) are likely to have effects on terrestrial ecosystems via both direct and indirect effects on understory plant communities. Elevated [CO2] can directly affect understory plant communities through stimulation of photosynthesic responses and overall performance of plant species. Elevated [CO2] can indirectly affect understory plant communities via direct effects on forest structure. Here, we describe how elevated [CO2] affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility. From 2001 to 2003, we estimated species-specific, woody vs. herbaceous, and total aboveground biomass by harvesting subplots within the established understory plant community using four 1 m 0.5 m quadrats in each FACE plot. In 2008, we estimated herbaceous biomass as previ...
Background/Question/Methods Invasive species, such as Tamarix spp. (tamarisk), often alter ecosys... more Background/Question/Methods Invasive species, such as Tamarix spp. (tamarisk), often alter ecosystem properties and reduce native species diversity. However, native and exotic species diversity are often positively correlated within plots sampled across landscapes. Thus, a goal of restoration that removes dominant invasive species should include changing the relationship between native and exotic species by reducing richness and abundance of exotic species while increasing native species. Tamarisk has invaded thousands of hectares of riparian zones in the southwestern US, including ecosystems in Grand Canyon National Park. The National Park Service and partner organizations began a tamarisk management project in 2000, which included a restoration study investigating the effects of tamarisk removal on native plant diversity and composition. Plant species composition and diversity were sampled along transects in tamarisk-dominated stands prior to tamarisk removal. Transects were then ...
Ecological Restoration, 2010
The removal of non-native species is often an important restoration goal in natural areas, includ... more The removal of non-native species is often an important restoration goal in natural areas, including national parks. There is often a positive correlation between non-native and native plant species richness, so that areas with the greatest number of native species support the greatest number of non-natives. This pattern may create both challenges and opportunities for restoration. Native species may be inadvertently damaged or killed during mechanical or chemical treatments targeted toward non-natives. However, greater numbers of native species may better colonize subsequent openings. We used data from an ongoing active management project in Grand Canyon National Park to test three predictions of plant community response to invasive tamarisk (Tamarix spp.) removal. We investigated patterns of native and nonnative species abundance and richness, compositional shifts, and the relationship between native and non-native species before and after treatments. In general, native species richness and abundance did not increase, but species composition following tamarisk removal tended to become more similar to that in uninvaded stands. Native and non-native species richness and abundance were positively correlated before tamarisk removal. While treatment successfully reduced cover of tamarisk after one to three years, our results suggest that it may not increase richness of native species during the same period. Furthermore, investigating native and non-native species relationships may be a useful tool for exploring hypotheses and consequences of restoration via invasive species removal.
New Phytologist, 2004
• Rising atmospheric CO 2 concentrations are likely to have direct effects on terrestrial ecosyst... more • Rising atmospheric CO 2 concentrations are likely to have direct effects on terrestrial ecosystems. Here, we describe effects of elevated concentrations of CO 2 on an understory plant community in terms of production and community composition. • In 2001 and 2002 total and species-specific above-ground net primary productivity (ANPP) were estimated by harvesting above-ground biomass within an understory community receiving ambient [CO 2 ] and elevated [CO 2 ] at Oak Ridge National Laboratory's free-air carbon dioxide enrichment (FACE) facility. • During a wet year, community composition differed between plots receiving ambient [CO 2 ] and elevated [CO 2 ], but total ANPP did not differ. By contrast, during a drier year, community composition did not differ, but total ANPP was greater in elevated than ambient [CO 2 ] plots. These patterns were driven by the response of two codominant species, Lonicera japonica and Microstegium vimineum , both considered invasive species in the southeastern United States. The ANPP of L. japonica was consistently greater under elevated [CO 2 ], whereas the response of M. vimineum to CO 2 enrichment differed between years and mediated total community response. • These data suggest that community and species responses to a future, CO 2enriched atmosphere may be mediated by other environmental factors and will depend on individual species responses.
Journal of Plant Ecology, 2010
Aims Rising concentrations of atmospheric carbon dioxide ([CO 2 ]) may influence forest successio... more Aims Rising concentrations of atmospheric carbon dioxide ([CO 2 ]) may influence forest successional development and species composition of understory plant communities by altering biomass production of plant species of functional groups. Here, we describe how elevated [CO 2 ] (eCO 2) affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility in eastern Tennessee, USA. We asked if (i) CO 2 enrichment affected total understory biomass and (ii) whether total biomass responses could be explained by changes in understory species composition or changes in relative abundance of functional groups through time. Materials and methods The FACE experiment started in 1998 with three rings receiving ambient [CO 2 ] (aCO 2) and two rings receiving eCO 2. From 2001 to 2003, we estimated species-specific, woody versus herbaceous and total aboveground biomass by harvesting four 1 3 0.5-m subplots within the established understory plant community in each FACE plot. In 2008, we estimated herbaceous biomass as previously but used allometric relationships to estimate woody biomass across two 5 3 5-m quadrats in each FACE plot. Important findings Across years, aboveground biomass of the understory community was on average 25% greater in eCO 2 than in aCO 2 plots. We could not detect differences in plant species composition between aCO 2 and eCO 2 treatments. However, we did observe shifts in the relative abundance of plant functional groups, which reflect important structural changes in the understory community. In 2001-03, little of the understory biomass was in woody species; herbaceous species made up 94% of the total understory biomass across [CO 2 ] treatments. Through time, woody species increased in importance, mostly in eCO 2 , and in 2008, the contribution of herbaceous species to total understory biomass was 61% in aCO 2 and only 33% in eCO 2 treatments. Our results suggest that rising atmospheric [CO 2 ] could accelerate successional development and have longer term impact on forest dynamics. Keywords: community composition d FACE d aboveground biomass d woody d herbaceous d sweetgum d Microstegium vimineum d Lonicera japonica
Frontiers in Ecology and the Environment, 2006
Quality and quantity of publications are among the most important measures determining the succes... more Quality and quantity of publications are among the most important measures determining the success of ecologists. The past 50 years have seen a steady rise in the number of researchers and collaborative manuscripts, and a corresponding increase in multi-authored articles. Despite these increases, there remains a shortage of useful and definitive guidelines to aid ecologists in addressing authorship issues, leading to a lack of consistency in what the term "author" really means. Deciding where to draw the line between those who have earned authorship and those who are more appropriately credited in the acknowledgments may be one of the more challenging aspects of authorship. Here, we borrow ideas from other scientific disciplines and propose a simple solution to help ecologists who are making such decisions. We recommend improving communication between co-authors throughout the research process, and propose that authors publish their contributions to a manuscript in a separate byline.
Frontiers in Ecology and the Environment, 2003
Forest Ecology and Management, 2011
Factors influencing the relationship between ecosystem productivity and biological diversity form... more Factors influencing the relationship between ecosystem productivity and biological diversity form the basis of much ecological theory. An understanding of how productivity-diversity relationships are influenced by scale of observation and unique attributes of ecoregions may provide important insights to aid conservation planning for carbon retention and biodiversity. Here we use publically available datasets to investigate patterns of productivity-diversity and explore potential factors influencing these patterns in forests located in five mid-Atlantic and Appalachian states. We used a geographic information system (GIS) to overlay multiple publically available datasets including remotely sensed estimates of productivity from MODIS and tree diversity estimated from the forest inventory analysis (FIA) database. We evaluated productivity-diversity relationships using two scales of observation (among and within ecoregions). We also determined if productivity-diversity relationships might be related to region-wide patterns in land use, and if the relationships varied by forest type, land management zones, and along gradients of mean productivity and diversity. Productivity-diversity relationships depended on scale and varied among ecoregions, and land use was correlated with both productivity and diversity. Mountainous ecoregions were characterized by positive productivity-diversity relationships, whereas coastal ecoregions were characterized by negative productivity-diversity relationships. Forest types and management zones that were on average less productive and more diverse exhibited positive productivity-diversity relationships across stands (the most productive stands were more diverse). In contrast, ecoregions and forest types that were on average more productive and less diverse exhibited negative productivity-diversity relationships (the most productive stands were less diverse). In conclusion, regional and local ecological and anthropogenic factors likely influence productivity-diversity relationships and these relationships appear to change along gradients of productivity and diversity.
Forest Ecology and Management, 2013
We describe and label four types of monitoring-surveillance, implementation, effectiveness, and e... more We describe and label four types of monitoring-surveillance, implementation, effectiveness, and ecological effects-that are designed to answer very different questions and achieve very different goals. Surveillance monitoring is designed to uncover change in target variables over space and time; implementation monitoring is designed to record whether management actions were applied as prescribed; effectiveness monitoring is designed to evaluate whether a given management action was effective in meeting a stated management objective; and ecological effects monitoring is designed to uncover unintended ecological consequences of management actions. Public land management agencies have focused heavily on implementation and effectiveness monitoring and very little on the more ecologically oriented surveillance and ecological effects monitoring. Tradeoffs, in the form of unintended ecological consequences, are important to consider in the management of natural resources, yet lack of ecological effects monitoring data has hindered our ability to fully understand these tradeoffs. Our proposed monitoring classification scheme offers practitioners and stakeholders a framework that explicitly identifies the type of monitoring they are conducting. We also suggest that, as a start, the effectiveness and ecological effects of a particular type of management activity can be approached rapidly and relatively inexpensively through use of a chronosequence approach to learning.
Environmental Entomology, 2004
Rising levels of atmospheric [CO 2 ] will directly affect the responses and community composition... more Rising levels of atmospheric [CO 2 ] will directly affect the responses and community composition of plants. However, few studies have examined how these changes to plant communities will alter insect communities that rely on them. Here, we report on a study that examined the community-level responses of plants, herbivores, detritivores, predators, parasitoids, and omnivores to increased [CO 2 ] at a Free Air Carbon Enrichment (FACE) facility at Oak Ridge National Laboratory. We found that aboveground net primary productivity for the Þve dominant plant species in the understory community, C:N ratios of leaf tissue for four of the Þve dominant understory taxa, amounts of herbivory, and arthropod abundance and richness across all trophic groups did not differ between ambient and elevated CO 2 plots. Abundance and richness of particular trophic groups were higher in ambient than in elevated CO 2 plots. There were also strong temporal effects on community composition, but no distinct treatment effects. These results, although preliminary, suggest that community-level responses to future atmospheric [CO 2 ] are likely to be species-and trophic-group speciÞc. KEY WORDS insect communities, plant communities, global change, invasive species, CO 2 enrichment
Ecology, 2008
Research examining the relationship between community diversity and invasions by nonnative specie... more Research examining the relationship between community diversity and invasions by nonnative species has raised new questions about the theory and management of biological invasions. Ecological theory predicts, and small-scale experiments confirm, lower levels of nonnative species invasion into species-rich compared to species-poor communities, but observational studies across a wider range of scales often report positive relationships between native and nonnative species richness. This paradox has been attributed to the scale dependency of diversity-invasibility relationships and to differences between experimental and observational studies. Disturbance is widely recognized as an important factor determining invasibility of communities, but few studies have investigated the relative and interactive roles of diversity and disturbance on nonnative species invasion. Here, we report how the relationship between native and nonnative plant species richness responded to an experimentally applied disturbance gradient (from no disturbance up to clearcut) in oakdominated forests. We consider whether results are consistent with various explanations of diversity-invasibility relationships including biotic resistance, resource availability, and the potential effects of scale (1 m 2 to 2 ha). We found no correlation between native and nonnative species richness before disturbance except at the largest spatial scale, but a positive relationship after disturbance across scales and levels of disturbance. Post-disturbance richness of both native and nonnative species was positively correlated with disturbance intensity and with variability of residual basal area of trees. These results suggest that more nonnative plants may invade species-rich communities compared to species-poor communities following disturbance.
Ecology, 2009
Whether biological diversity within communities is limited by local interactions or regional spec... more Whether biological diversity within communities is limited by local interactions or regional species pools remains an important question in ecology. In this paper, we investigate how an experimentally applied tree-harvesting disturbance gradient influenced local-regional richness relationships. Plant species richness was measured at three spatial scales (2 ha ¼ regional; 576 m 2 and 1 m 2 ¼ local) on three occasions (one year pre-disturbance, one year post-disturbance, and 10 years post-disturbance) across five disturbance treatments (uncut control through clearcut) replicated throughout the southern Appalachian Mountains, USA. We investigated whether species richness in 576-m 2 plots and 1-m 2 subplots depended on species richness in 2-ha experimental units and whether this relationship changed through time before and after canopy disturbance. We found that, before disturbance, the relationship between local and regional richness was weak or nonexistent. One year after disturbance local richness was a positive function of regional richness, because local sites were colonized from the regional species pool. Ten years after disturbance, the positive relationship persisted, but the slope had decreased by half. These results suggest that disturbance can set the stage for strong influences of regional species pools on local community assembly in temperate forests. However, as time since disturbance increases, local controls on community assembly decouple the relationships between regional and local diversity.
Ecological Applications, 2012
Human-caused changes in disturbance regimes and introductions of nonnative species have the poten... more Human-caused changes in disturbance regimes and introductions of nonnative species have the potential to result in widespread, directional changes in forest community structure. The degree that plant community composition persists or changes following disturbances depends on the balance between local extirpation and colonization by new species, including nonnatives. In this study, we examined species losses and gains, and entry of native vs. exotic species to determine how oak forests in the Appalachian Mountains might shift in species composition following a gradient of pulse disturbances (timber harvesting). We asked (1) how compositional stability of the plant community (resistance and resilience) was influenced by disturbance intensity, (2) whether community responses were driven by extirpation or colonization of species, and (3) how disturbance intensity influenced total and functional group diversity, including the nonnative proportion of the flora through time. We collected data at three spatial scales and three times, including just before, one year postdisturbance, and 10 years post-disturbance. Resistance was estimated using community distance measures between pre-and one year post-disturbance, and resilience using community distance between pre-and 10-year post-disturbance conditions. The number of colonizing and extirpated species between sampling times was analyzed for all species combined and for six functional groups. Resistance and resilience decreased with increasing timber-harvesting disturbance; compositional stability was lower in the most disturbed plots, which was driven by colonization, but not extirpation, of species. Colonization of species also led to increases in diversity after disturbance that was typically maintained after 10 years following disturbance. Most of the community-level responses were driven by postdisturbance colonization of native forbs and graminoids. The nonnative proportion of plant species tended to increase following disturbance, especially at large spatial scales in the most disturbed treatments, but tended to decrease through time following disturbance due to canopy development. The results of this study are consistent with the theory that resources released by disturbance have strong influences on species colonization and community composition. The effects of management activities tested in this study, which span a gradient of timber-harvesting disturbance, shift species composition largely via an increase in species colonization and diversity.
Biological Invasions, 2008
Dominant tree species influence community and ecosystem components through the quantity and quali... more Dominant tree species influence community and ecosystem components through the quantity and quality of their litter. Effects of litter may be modified by activity of ecosystem engineers such as earthworms. We examined the interacting effects of forest litter type and earthworm presence on invasibility of plants into forest floor environments using a greenhouse mesocosm experiment. We crossed five litter treatments mimicking historic and predicted changes in dominant tree composition with a treatment of either the absence or presence of nonnative earthworms. We measured mass loss of each litter type and growth of a model nonnative plant species (Festuca arundinacea, fescue) sown into each mesocosm. Mass loss was greater for litter of tree species characterized by lower C:N ratios. Earthworms enhanced litter mass loss, but only for species with lower C:N, leading to a significant litter 9 earthworm interaction. Fescue biomass was significantly greater in treatments with litter of low C:N and greater mass loss, suggesting that rapid decomposition of forest litter may be more favorable to understory plant invasions. Earthworms were expected to enhance invasion by increasing mass loss and removing the physical barrier of litter. However, earthworms typically reduced invasion success but not under invasive tree litter where the presence of earthworms facilitated invasion success compared to other litter treatments where earthworms were present. We conclude that past and predicted future shifts in dominant tree species may influence forest understory invasibility. The presence of nonnative earthworms may either suppress of facilitate invasibility depending on the species of dominant overstory tree species and the litter layers they produce.
ABSTRACT Background/Question/Methods Understanding the role fire historically played in maintaini... more ABSTRACT Background/Question/Methods Understanding the role fire historically played in maintaining local and landscape composition and biodiversity remains an active research front. In many forest types, fire suppression and land use have altered the structure and composition of forests. In response to altered conditions, various management strategies have been used to restore forest structure, biological diversity, and the ecological role of fire. Fire regimes of forests that historically burned with frequent, low-severity fires are widely studied and provide a useful guide for ecological restoration. In contrast, setting goals for ecosystem management and restoration targets in mixed-severity fire regimes, where the frequency, severity, and effects of fires historically varied in time and space has proven more difficult. Variability in forest conditions and fire severity in space and time make active treatments in forests of mixed severity fire regimes controversial. There, target conditions for forest restoration may be based on limited historical evidence, and relationships between spatially-complicated patterns and processes are not fully understood. We surveyed the literature, burn severity data at local and landscape scales, and our own experiences in collaborative forest restoration to provide conceptual and empirical overview of mixed severity fire regimes. Results/Conclusions Drivers of fire severity vary by scale of observation, with fuel loading, weather, and topography predicting fire severity at small scales, and vegetation, climate and landform influencing fire severity at larger scales. Variability in spatial composition of fire severity among forest fires in the western U.S. appears to be continuous without clear classification thresholds. Thus, classifying fire regimes using a categorical approach, while convenient, may be less helpful than understanding the mechanisms driving fire severity across forest types. Variability in temporal patterns of fire severity (variation in fire return intervals) may also reflect interactions between topographic and climatic drivers and create challenges to understanding and applying historical range of variability. This variability in space and time leads to controversy in prioritizing restoration using mechanical or prescribed fire treatments. Predictions of future impacts of climate change and increasing residential development in fire-prone forests have led collaborations of diverse stakeholders to begin supporting treatments in complex forest types where landscape restoration objectives are not clearly defined. We suggest restoration be conducted with mechanistic understanding of fire’s role in maintaining species diversity and landscape resilience. Where socially and economically feasible, treatments should be implemented using experimental approaches with collaborative input to facilitate collective learning within an adaptive management framework.
Understanding relationships between ecosystem productivity and species diversity may lead to impr... more Understanding relationships between ecosystem productivity and species diversity may lead to improved management for carbon sequestration and biodiversity. Few ecologists have yet investigated whether land management alters the relationship between productivity and diversity ...