My research uses remote-sensing and field-based approaches to understand shifts in forest structure, species composition, and landscape pattern due to disturbance and climate change. Through my research, I try to increase our understanding of:
- The factors that influence fire regimes: the frequency, intensity, severity, extent, and spatial pattern of fires in a given ecosystem.
- How ecosystems respond after fire: which species become more or less abundant, how the structure (the vertical and horizontal arrangement of vegetation and the diversity of different forms of vegetation) changes, and what is likely to happen as post-fire succession continues.
To address these questions, I use concepts and analytical methods from a variety of sub-disciplines in ecology, such as landscape ecology, forest ecology, and plant community ecology. I also use data collected at a variety of different scales, from tree-level data collected on intensively measured forest plots to regional-scale remote-sensing data and modeled climate.
Impacts of disturbance and climate change on alpine treeline ecotones.
Upper treeline environments have been hypothesized to be some of the most sensitive to changes in climate but research has shown that environmental variation and biotic feedbacks at local scale often override the influence of regional climate on seedling germination, survival, and recruitment. Additionally, climate change is likely to affect the occurrence and magnitude of disturbances process in these ecosystems.
Current projects assessing disturbance in alpine treeline ecotones include:
- A regional assessment of trends in the area burned and severity of fire in treeline ecotones in the Pacific Northwest and Northern Rocky Mountains.
- A field study of the influence of pre-fire ecotone vegetation structure on fire severity, and post-fire vegetation structure and composition.
- A field study on the biological and biophysical constraints on post-fire tree regeneration.
- A focused review of the literature on the impacts of disturbance in alpine treeline ecotones worldwide.
Quantifying fire spatial patterns at regional scales and their relationship with climatic and biophysical controls.
I use remotely sensed burn-severity (e.g. Landsat) and forest structure (e.g. LIDAR) data to address research questions about how fire regime attributes, such as fire size, severity, and the spatial pattern of burn severity, are influenced by the interaction between large-scale climatic drivers and smaller-scale variation in topography and fuels.
I have conducted (see CV) or am currently conducting research on pattern of burn severity in the Pacific Northwest and Yosemite National Park, and on the role of fire refugia (i.e., unburned areas within fires). I am actively pursuing grant opportunities to apply methods that have been developed in regional studies at large scales (e.g., the western U.S.) using consistent methods and nested hierarchical analysis extents.
Basic and applied fire ecology research focusing on stand-level assessments of fire effects, fuels management, and post-fire succession.
My research in this area has focused on conifer forests with mixed-severity fire regimes, particularly in reference ecosystems that have intact fire regimes or have seen little human disturbance. I have collaborated on past projects in the Bob Marshall Wilderness (western larch and ponderosa pine forests), and am an active collaborator at the Yosemite Forest Dynamics Plot (www.yfdp.org), a 25.6 ha long-term research plot in old-growth sugar pine – white fir forests at Yosemite National Park.
Resilience and state change in forest ecosystems in response to disturbances and climate change.
Feedbacks between disturbance and vegetation–such as between wildfire and post-fire tree establishment and structural development–will attenuate or amplify the climate-driven relationships we are currently observing. For example, post-fire shifts in vegetation reflecting new climate may increase or decrease the frequency and severity of fires. How this will play out is likely ecosystem dependent and thus spatially variable.
I am currently developing a theoretical modeling study to test ideas about resilience and state change in response to disturbance and climate change. The goal is to assess how long-term equilibrium with climate is impacted by different levels of disturbance and rates of recovery (i.e., a sensitivity analysis).I am also interested in developing collaborations on this topic that capitalizing on existing data sets, such as networks of ecological monitoring plots, dendroecological data, and time series of remotely sensed data, to address spatial variability in the strength and direction of fire-vegetation feedbacks so we can predict the resistance of ecosystems to rapid and difficult-to-reverse changes.