I study past and present global change and its impacts on Earth’s ecosystems, at scales ranging from the regional (with a focus on dryland ecosystems of the western United States) to the global. The tools I use include remote sensing, dendrochronology (the science of tree rings), and empirical/process-based modeling.

Most of my research investigates the impacts of climate variability/change on the growth, phenology and carbon uptake of terrestrial vegetation. A particular focus is understanding the effects of coupled ocean-atmosphere circulation systems, such as the El Niño–Southern Oscillation, on the timing and magnitude of vegetation activity, which may allow forecasting of ecological processes months before the growing season even starts. An additional emphasis is understanding how the seasonality and variability of precipitation affects ecosystem processes, particularly in the context of a warmer and more variable hydroclimate.

In addition to my work on climate–ecosystem interactions, I also use and develop methods for monitoring land use and land cover change with remote sensing, with the goal of separating climate influences on ecosystems from the effects of land cover composition. To date, most of this work has focused on the southeastern United States, where ongoing changes in forest cover and composition are rapidly changing the climate, hydrology, and ecosystem services of the region. However, I am also interested in using these methods for other systems and applications, such as monitoring woody encroachment in arid and semiarid regions, modeling health effects of land cover change, and quantifying the impacts of surface mining operations on land-atmosphere CO2 exchange.