I received a Bachelor's degree in Chemistry from Yale University in 1987 and a Masters (1994) and PhD (1997) in Environmental Sciences from the University of Virginia. I had a post-doctoral position from 1997-1999 at the US Environmental Protection Agency in Corvallis, Oregon, and a second post-doctoral position from 2000-2001 at the Max Planck Institute for Biogeochemistry in Jena, Germany, before joining Complex Systems Research Center.

The main focus of my work has been using stable isotopes at natural abundance levels to understand carbon and nitrogen cycling in forest ecosystems. I am particularly interested in understanding the importance of mycorrhizal fungi in forests, both as a carbon sink and as a source for nitrogen. Mycorrhizal fungi are ubiquitous root symbionts that supply the majority of nutrients to forest vegetation, protect tree roots against pathogens, and filter out potentially toxic metals such as aluminum. Mycorrhizal fungi appear heavily affected by atmospheric nitrogen deposition in Europe, and we suspect that the same processes are starting to operate in the northeastern US, with possibly deleterious consequences for forest health. In culture work with Jan Colpaert (Limburgs Universitair Centrum, Belgium), we are studying how nitrogen availability affects carbon and nitrogen allocation in mycorrhizal pines, and whether nitrogen isotope measurements can be used as a marker of carbon allocation to mycorrhizal fungi.

We have shown that nitrogen and carbon isotopes (15N, 13C, and 14C) can be used to distinguish between mycorrhizal and free-living (saprotrophic) fungi. Such isotopic methods appear to be a promising way to determine relative biomass of these two important functional groups in the field. These measurements will be combined with modeling to assess the importance at ecosystem scales of mycorrhizal symbioses. We are currently testing other, more direct measures of allocation to mycorrhizal fungi at field sites in the Northeast and the Arctic.

I am director of the UNH Stable Isotope Laboratory http://www.isotope.unh.edu.