His studies focus on the interactions between terrestrial carbon cycling and climate change. One of his major research interests is to understand feedbacks to atmospheric CO2 from warming temperature, thawing permafrost and changing fire regimes in high latitudes ecosystems. He has received new investigator awards from NASA and the Andrew W. Mellon Foundation for his work on carbon and nutrient cycling in terrestrial ecosystems, and a CAREER grant from the National Science Foundation for research and education centered on the use of radiocarbon in ecology and earth system science.