Variability in CO2 exchange in a topographically complex boreal black spruce forest

Graduate Thesis Or Dissertation

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/n296wz38r

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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