I work at the interfaces of biological, geological and climatological sciences. The overall objective of my research is to understand patterns and mechanisms of long-term ecosystem dynamics under changing climatic conditions. To achieve this objective, I use the natural  experiments of the past; that are archived in geological deposits. These deposits offer a longterm holistic perspective into past environmental conditions, some of which do not exist today but may be analogs of different climatic conditions in the future. In pursuing my research interests. I integrate traditional paleo-ecological analyses and state-of-the-art analytical tools (e.g., genomic, isotopic, and numerical-modeling techniques). My students and I have conducted field research from the tropics to the Arctic to address a wide array of global change questions. We have authored more than 100 scholarly articles in top-tier disciplinary and interdisciplinary journals.

The lab is an interdisciplinary group of working at the interfaces of biology, geology, and climatology. Projects in the lab broadly examine ecosystem dynamics in relation to past climatic change at various spatial and temporal scales. Our investigations are primarily based on proxy records preserved in geological deposits (lake sediment and peat). We use a wide array of methods in our research, including the analyses of pollen, charcoal, stable isotopes (O, C, and N), organic compounds, and molecular-genetic markers. Our field study sites are located in Alaska, western Canada, the American midwest, Pacific northwest, and Russia.

Current projects address the following questions:
  --Do abrupt climatic changes occur in a predictable fashion, and how do they affect grassland, forest, and peat land ecosystems?
  --How do geomorphic factors interact with climatic change to control ecosystem development and soil carbon cycling?
  --What are the relative roles of climate and vegetation composition in determining forest fire regimes?
  --What can geographic patterns of chloroplast, mitochondrial, and nuclear DNA markers tell us about full-glacial refugia and postglacial migration of trees in North America?
  --How do habitat fragmentation, climatic constraints, and stand invisibility control tree migration on heterogeneous landscapes?