Date of Award

Spring 1-1-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geological Sciences

First Advisor

Jason C. Neff

Second Advisor

Kimberly P. Wickland

Third Advisor

Noah Fierer

Abstract

Efflux of carbon dioxide from soils constitutes a large portion of the global terrestrial-atmosphere CO2 flux. However, the magnitude of this flux can be highly variable across the landscape, especially in regions of complex topography. To advance understanding of the spatial variability of soil surface CO2 exchange we explore the variation in CO2 efflux between landscape positions, characterize the relationship between soil properties of temperature and moisture and CO2 efflux, and quantify seasonal and spatial variability at the plot and landscape scale within a topographically complex boreal forest. We find that CO2 efflux does not vary significantly between landscapes, likely due to the extreme plot scale heterogeneity in soil conditions. Efflux is explained by relationships and threshold responses between soil CO2 efflux and soil conditions. Regression tree analysis and the statistical strength of plot based efflux-temperature relations show that temperature is the dominant control on soil CO2 efflux in this watershed, and that soil moisture becomes a more important control on efflux at warmer soil temperatures. Soil moisture is an important factor in explaining seasonal variability in efflux from individual landscape positions, and accurate quantification of soil moisture at the landscape scale is necessary to describe CO2 efflux-soil moisture relations in topographically complex regions.

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