The Biogeochemistry Lab is part of the Forest Soils focus group within the University of Washington’s School of Environmental and Forest Sciences. Our research focuses on the following areas below. To see a list of our current projects, click here.

Moss

The impact of anthropogenic N deposition: The evidence from fire chronosequences, and from experimental nitrogen addition studies (Gundale et al. 2011) suggest that N fixation in the feather moss layer is down-regulated under conditions of enhanced nitrogen availability. We extend this work to look at the potential effects of anthropogenic N deposition on boreal N fixation. Under increasing N deposition, do boreal forest mosses retain to the capacity to build N capital? We also have limited understanding of the fate of N fixed by the cyanobacteria. We expect that much of it is conserved in the moss layer, with most of the fixed N liberated only occasionally during disturbance events such as fire. How is N fixed by feathermoss-cyanobacterial communities cycled and taken up by higher plants?

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Carbon and nitrogen dynamics of natural and disturbed ecosystems: Soil and understorey CO2, CH4, and N2O greenhouse gas (GHG) fluxes are directly influenced by stand age and associated N fertility conditions in boreal forests (Ball et al.2007). As yet, there is no direct evidence of the influence of N fixation on green house gas emissions in boreal forests, but soil NO3- accumulation and increased net nitrification after fire has been observed for up to 30 years (DeLuca et al. 2002DeLuca et al. 2006).

MPingree_Fire

Fire as a driver of ecosystem processes in forest ecosystems:  Recurrent, low to moderate severity fires in temperate and part of the soil O horizon. Depending on severity, a portion of the total ‘ecosystem N capital’ contained within plant and soil material is lost to combustion. After fire, there is an associated increase in inorganic N availability, with the amount of N in throughfall elevated after fire, then decreasing as succession progresses. Organic N resources lost through combustion during severe wildfire events are eventually recovered through feathermoss-cyanobacterial N-fixation.

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