Document: SIY-3-58-28

Soil respiration rate (SRR) among patches of a heterogeneous mixed-conifer forest in a Mediterranean climate.

MA, S.* 1, J.CHEN 1, M.NORTH 2 and M.JURGENSEN 1

Michigan Technological University Houghton MI 49931 USA 1
Foresty Science Lab, Fresno CA 93710 USA 2

Abstract:
We investigated the relationship between soil respiration rate (SRR), surface temperature (Tsf) and moisture (Ms) in a Mediterranean climate in Sierra Nevada mixed conifer. From June to August 1999, at the Teakettle Experimental Forest, we took weekly measurements of SRR using a dynamic soil respiration system, in six dominant patch types defined by cluster analysis of vegetation and litter depth measurements. The patch types were (1) bare ground, (2) deep litter layer with high canopy cover, (3) manzanita, (4) ceanothus, (5) rock or shallow soil, and (6) high canopy cover with coarse wood debris (CWD) on the ground. Soil surface temperature and soil moisture at 15 cm were simultaneously measured at the same sampling points. The measured SRR values ranged from 0.42 (bare ground) to 2.23 gCO2/m2/hour (ceanothus). Based on patch types, this study confirmed that both Tsf and Ms affected SRR, but in the hot, dry summer typical of Mediterranean climates, Ms may limit SRR. The correlation coefficients for Tsf and SRR and Ms in bare ground, deep litter layer with high canopy, and manzanita patches was 0.87, 0.66, and 0.43, respectively. For these three patch types, SRR and Ms can be directly assessed with a linear regression model. The relationship, however, between SRR, Ms and Tsf in ceanothus, rocky-shallow soils, and high canopy cover/CWD patches was not significant. Based on year-round microclimatic data in the area, surface soil temperature may be the strongest influence on soil respiration rates in the winter, while respiration rates during the summer months are limited by soil moisture availability.

Keywords: Soil Respiration, Patch type, Mediterranean Climate, Soil temperature, Soil moisture, Regression models

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This abstract is being presented at: 9:15 AM in session:
Oral Session #71: Soil Microbial Biomass and Soil Respiration.