Climatic and landscape influences on soil moisture are primary determinants of soil carbon fluxes in seasonally snow-covered forest ecosystems

Clare M. Stielstra, Kathleen A. Lohse, Jon Chorover, Jennifer McIntosh, Greg A Barron-Gafford, Julia N. Perdrial, Marcy Litvak, Holly R. Barnard, Paul Brooks

Research output: Contribution to journalArticle

36 Scopus citations

Abstract

A changing climate has the potential to mobilize soil carbon, shifting seasonally snow-covered, forested ecosystems from carbon sinks to sources. To determine the sensitivity of soil carbon fluxes to changes in temperature and moisture, we quantified seasonal and spatial variability of soil carbon dioxide (CO<inf>2</inf>) fluxes (N = 746) and dissolved organic carbon (DOC) in leachate (N = 260) in high-elevation, mixed conifer forests in Arizona and New Mexico. All sites have cold winters, warm summers, and bimodal soil moisture patterns associated with snowmelt and summer monsoon rainfall. We employed a state factor approach, quantifying how distal controls (parent material, regional climate, topography) interacted with proximal variability in soil temperature (−3 to 26 °C) and moisture (2–76 %) to influence carbon effluxes. Carbon loss was dominated by CO<inf>2</inf> flux (250–1220 g C m<sup>−2</sup> year<sup>−1</sup>) rather than leached DOC (7.0–9.4 g C m<sup>−2</sup> year<sup>−1</sup>). Significant differences in mean growing season CO<inf>2</inf> flux were associated with parent material and aspect; differences appear to be mediated by how these distal controls influence primarily moisture and secondarily temperature. Across all sites, a multiple linear regression model (MLR) relying on moisture and temperature best described growing season CO<inf>2</inf> fluxes (r<sup>2</sup> = 0.63, p < 0.001). During winter, the MLR describing soil CO<inf>2</inf> flux (r<sup>2</sup> = 0.98, p < 0.001) relied on distal factors including snow cover, clay content, and bulk carbon, all factors that influence liquid water content. Our findings highlight the importance of state factors in controlling soil respiration primarily through influencing spatial and temporal heterogeneity in soil moisture.

Original languageEnglish (US)
Pages (from-to)447-465
Number of pages19
JournalBiogeochemistry
Volume123
Issue number3
DOIs
StatePublished - Apr 1 2015

Keywords

  • Carbon cycle
  • Climate
  • Forests
  • Soil moisture
  • Soil respiration

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology
  • Earth-Surface Processes

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