Research

My research interests focus on two general themes: 1) carbon and nitrogen cycling in streams, rivers and soils (especially in the context of land-water interactions), and 2) watershed-scale carbon cycling and climate change. I am interested in carbon and nitrogen cycling at a range of scales ranging from the molecular composition and microbial use of dissolved organic molecules, to the biogeochemical cycling in streams and soil, to larger scale fluxes from watersheds and trace gas emissions to the atmosphere. A central theme of my research is the role of hydrology, both surface and ground water, in linking ecosystems and governing biogeochemical transformations. A second theme involves the role of permafrost and permafrost thaw in controlling ecosystem structure in boreal forest and arctic ecosystems.

Bonanza Creek Long-Term Ecological Research Program

We are investigating how streams are linked to their catchments, and focuses on how permafrost influences groundwater inputs of nutrients and organic matter to streams. The boreal forest in interior Alaska is underlain with discontinuous permafrost, which has a major affect on watershed hydrology. Where permafrost is present, groundwater flowpaths through catchments are largely restricted to soils, whereas in the absence of permafrost water can infiltrate into deeper bedrock regions of watersheds. In addition to affecting hydrology, permafrost stores a lot of soil organic matter that will potentially be released to streams and the atmosphere with climatic warming and permafrost thaw. This research is particularly exciting in the context of how groundwater inputs of nutrients and organic matter may shift with changing climate and resulting alterations in the extent of permafrost. An interesting sidelight of this research is the role of forest fires and their influences on permafrost. Fire alters the albedo of soil and, as a consequence, can lead to thawing of permafrost. Fire frequency has been increasing in interior Alaska, which has important implications for permafrost and watershed hydrology. This work is funded through the Bonanza Creek Long Term Ecological Program (http://www.lter.uaf.edu/) and is being conducted in the Caribou-Poker Creeks Research Watersheds (CPCRW; located near Fairbanks). CPCRW covers an area of ~100 km2, and has a number of sub-catchments and streams that we have been studying. Of these sub-catchments, we conducted a controlled burn of one watershed in July of 1999, and another sub-catchment was burned extensively in summer 2004 by a wild fire.