10 research outputs found
Divergent trends in ecosystem services under different climate-management futures in a fire-prone forest landscape
While ecosystem services and climate change are often examined independently, quantitative assessments integrating these fields are needed to inform future land management decisions. Using climate-informed state-and-transition simulations, we examined projected trends and trade-offs for a suite of ecosystem services under four climate change scenarios and two management scenarios (active management emphasizing fuel treatments and no management other than fire suppression) in a fire-prone landscape of dry and moist mixed-conifer forests in central Oregon, USA. Focal ecosystem services included fire potential (regulating service), timber volume (provisioning service), and potential wildlife habitat (supporting service). Projections without climate change suggested active management in dry mixed-conifer forests would create more open forest structures, reduce crown fire potential, and maintain timber stocks, while in moist mixed-conifer forests, active management would
reduce crown fire potential but at the expense of timber stocks. When climate change was considered, however, trends in most ecosystem services changed substantially, with large increases in wildfire area predominating broad-scale trends in outputs, regardless of management approach (e.g., strong declines in timber stocks and habitat for closed-forest wildlife species). Active management still had an influence under a changing climate, but as a moderator of the strong climate-driven trends rather than being a principal driver of ecosystem service outputs. These results suggest projections of future ecosystem services that do not consider climate change may result in unrealistic expectations of benefits
Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States
Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establishment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species, suggesting that reductions in fire severity, and resultant impacts on seed availability, could partially offset expected climate-driven declines in postfire regeneration. Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from 5% in 1981 to 2000 to 26 to 31% by mid-century, highlighting a limited time window over which management actions that reduce fire severity may effectively support postfire conifer regeneration. © 2023 the Author(s)
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Evidence of a trophic cascade among wolves, elk, and aspen in Yellowstone National Park, USA
According to general top-down trophic theory, in the presence of carnivores, herbivore behavior and/or densities could change and result in an overall decrease in herbivory on plant communities. In this dissertation, I examined the potential relationship between gray wolf (Canis lupus) presence and absence on elk (Cervus elaphus) herbivory of aspen (Populus tremuloides). Based on aspen tree cores and an age-diameter relationship, I approximated aspen origination dates both within and outside two elk exclosures to study long-term patterns of aspen recruitment in the Gallatin elk winter range of northwestern Yellowstone National Park, USA. From aspen data, I concluded that while a host of interacting biophysical factors may influence aspen recruitment and growth, the observed pattern of aspen decline is most correlated with elk herbivory, coincident with the presence and absence of wolves.
Outside of the elk winter range, but still within the northwestern portion of the park, I studied growth patterns of clonal upland aspen thickets since wolf reintroduction. Growth patterns were compared in an area burned in the 1988 fires to an adjacent area that was unburned. From the results, I proposed that in addition to any wolf-mediated changes in elk densities, a recoupling of fire with increased elk predation risk in the presence of wolves may improve upland clonal aspen recruitment.
To examine the potential for a trophic cascade from the perspective of elk, I measured vigilance behavior in female elk throughout the park during both winter and summer seasons. After vigilance behavior was recorded, I noted the distance to, and type of, objects that could have impeded observed female elk escape from predators. From my model selection procedure, I concluded elk foraging behavior appeared to vary with physical features in the landscape. This variation in foraging behavior with risk of predation provides a potential mechanism to explain the patchy release of preferred woody browse species within the Park. Therefore, in addition to density-mediated effects, the results are consistent with a behaviorally-mediated top-down trophic cascade between wolves, elk, and aspen
Data from: Climate change, wildfire, and vegetation shifts in a high-inertia forest landscape: Western Washington, U.S.A.
Future vegetation shifts under changing climate are uncertain for forests with infrequent stand-replacing disturbance regimes. These high-inertia forests may have long persistence even with climate change because disturbance-free periods can span centuries, broad-scale regeneration opportunities are fewer relative to frequent-fire systems, and mature tree species are long-lived with relatively high tolerance for sub-optimal growing conditions. Here, we used a combination of empirical and process-based modeling approaches to examine vegetation projections across high-inertia forests of Washington State, USA, under different climate and wildfire futures. We ran our models without forest management (to assess inherent system behavior/potential) and also with wildfire suppression. Projections suggested relatively stable mid-elevation forests through the end of the century despite anticipated increases in wildfire. The largest changes were projected at the lowest and uppermost forest boundaries, with upward expansion of the driest low-elevation forests and contraction of cold, high-elevation subalpine parklands. While forests were overall relatively stable in simulations, increases in early-seral conditions and decreases in late-seral conditions occurred as wildfire became more frequent. With partial fire suppression, projected changes were dampened or delayed, suggesting a potential tool to forestall change in some (but not all) high-inertia forests, especially since extending fire-free periods does little to alter overall fire regimes in these systems. Model projections also illustrated the importance of fire regime context and projection limitations; the time horizon over which disturbances will eventually allow the system to shift are so long that the prevailing climatic conditions under which many of those shifts will occur are beyond what most climate models can predict with any certainty. This will present a fundamental challenge to setting expectations and managing for long-term change in these systems
Recoupling fire and aspen recruitment after wolf reintroduction in Yellowstone National Park, USA
Appendix A. Figures showing proportion of (Fig. A1) dry and (Fig. A2) moist conifer forest available to treat and hectares actually treated under the active management scenario and different climate assumptions.
Figures showing proportion of (Fig. A1) dry and (Fig. A2) moist conifer forest available to treat and hectares actually treated under the active management scenario and different climate assumptions
Linking instream wood recruitment to adjacent forest development in landscapes driven by stand-replacing disturbances: a conceptual model to inform riparian and stream management
Divergent trends in ecosystem services under different climate-management futures in a fire-prone forest landscape
Fine-scale predation risk on elk after wolf reintroduction in Yellowstone National Park, USA
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Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States
Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establishment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species, suggesting that reductions in fire severity, and resultant impacts on seed availability, could partially offset expected climate-driven declines in postfire regeneration. Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from 5% in 1981 to 2000 to 26 to 31% by mid-century, highlighting a limited time window over which management actions that reduce fire severity may effectively support postfire conifer regeneration