Currently I am working with collaborators on a project to validate and improve model predicting post-fire tree mortality. The management tools that use these models—e.g., FOFEM, CONSUME, and FVS—are heavily used by managers to determine prescribed fire burn windows, and to inform decisions about post-fire management activities. To date, model accuracy has not been assessed for many of the species included in the above computer programs. We are addressing this problem through an analysis of a database of >150,000 individual tree records, which we assembled using records from data contributions from >30 federal and academic researchers.
We are also developing post-fire tree mortality models that integrate the impacts of climatic drought stress with tree injury. Research has only just begun to demonstrate how pre-fire stress from drought can increase post-fire mortality rates above what would be expected from to fire-caused injuries alone, and none of the previous empirical work has been at an individual-species scale. We are assessing the influence of drought-related climate variables—e.g., climatic water deficit, vapor pressure deficit, precipitation—on post-fire survival and mortality of individual species. Ultimately this project will provide managers tools or guidelines that allow them to address the complex problem of predict post-fire effects under novel, non-stationary climate conditions.
This project is funded by Joint Fire Science Program Project 16-1-04-8, and updates can be found on Research Gate at the “Mortality reconsidered: Testing and extending models of fire-induced tree mortality across the US. JFSP Project ID 16-1-04-8” project page.
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. Currently, I am involved at two ongoing collaborations focusing on burn severity in the Pacific Northwest: one comparing modern and historical fire regimes among forested vegetation types, and a second project funded by Joint Fire Science Program ("Landscape Evaluations and Prescriptions for Post-Fire Landscapes. JFSP Project 16-1-05-24") focusing on post-fire management after the 2014 and 2015 mega-fires in Washington State.
I am a collaborator on a long-term research plot in old-growth sugar pine - white fir forest in Yosemite National Park. The 25.6 ha Yosemite Forest Dynamics Plot (YFDP; www.yfdp.org) is part of the Forest Global Earth Observatory (ForestGEO), overseen by the Western Forest Initiative, a collation of researchers working to improve our understand of climatic and other causes of change in forests in western North America, primarily through research conducted on large forest demography plots. My current research at YFDP is focused on post-fire forest fuel consumption and tree mortality caused by 2013 wildfire, the Rim Fire.
Upper treeline environments are some of the most sensitive to changes in climate, but climate change is also likely to affect the occurrence and magnitude of disturbances in these ecosystems. Currently, I am working with a team of international collaborators on a review of the global literature to assess whether disturbances cause changes in the rate or direction of alpine and latitudinal treelines in responses to climate change.
My research focuses on the impacts of wildfire and climate change on forest and mountain ecosystems. Through my research, I try to increase our understanding of:
1. The factors that influence fire regimes: the frequency, intensity, severity, extent, and spatial pattern of fires in a given ecosystem.
2. 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 during post-fire succession.
In previous research I investigated the influence of climate and topography on fire regimes in the northern Cascade Range of Washington, USA using remotely sensed burn severity data from 125 fires. I conducted field validation of categorical burn-severity images, spatial analysis of burn-severity pattern, and statistical modeling of climatic and topographical relationships to fire size, fire severity, and the spatial complexity of burn-severity patterns. In other subsequent research with collaborators, we examined the spatial pattern of unburned and low severity areas, and biophysical controls on fire severity on post-fire forest structure.
My past research focused on fire effects and post-fire succession in alpine and subalpine parkland in the Pacific Northwest and Northern Rockies. I conducted studies at three scales: (1) a regional assessment of trends in the area burned and severity of fire in treeline ecotones, (2) a study of forest-to-non-forest conversion and changes in the pattern of individual treeline ecotones, and (3) an analysis of changes in species composition and regeneration dynamic at the scale of individual field plots.
Throughout the United States, and across the West in particular, the interactions between climate change and disturbance regimes, particularly wildfire, are one of the principal forces of change in forest ecosystems. Western U.S. wildfire area burned has increased dramatically over the last half-century. How contemporary extent and severity of wildfires compares to the pre-settlement patterns to which ecosystems are adapted is hotly contested. Quantitative predictions of the effects of fires, future disturbance regimes, and the feedbacks between changing fire regimes and other ecosystem changes are necessary to inform management. Changes from historical fire regimes threaten ecosystem resilience, potentially drive undesirable ecosystem transformations, and provide further support for management.