Article

Precipitation drives interannual variation in summer soil respiration in a Mediterranean-climate, mixed-conifer forest

University of California at Santa Cruz Department of Environmental Studies 1156 High Street Santa Cruz CA 95060 USA
Climatic Change (Impact Factor: 3.43). 01/2008; 92(1):109-122. DOI: 10.1007/s10584-008-9475-0

ABSTRACT

Predictions of future climate change rely on models of how both environmental conditions and disturbance impact carbon cycling at various temporal and spatial scales. Few multi-year studies, however, have examined how carbon efflux is affected by the interaction of disturbance and interannual climate variation. We measured daytime soil respiration (R
s) over five summers (June–September) in a Sierra Nevada mixed-conifer forest on undisturbed plots and plots manipulated with thinning, burning and their combination. We compared mean summer R
s by year with seasonal precipitation. On undisturbed plots we found that winter precipitation (PPTw) explained between 77–96% of interannual variability in summer R
s. In contrast, spring and summer precipitation had no significant effect on summer R
s. PPTw is an important influence on summer R
s in the Sierra Nevada because over 80% of annual precipitation falls as snow between October and April, thus greatly influencing the soil water conditions during the following growing season. Thinning and burning disrupted the relationship between PPTw and Rs, possibly because of significant increases in soil moisture and temperature as tree density and canopy cover decreased. Our findings suggest that R
s in some moisture-limited ecosystems may be significantly influenced by annual snowpack and that management practices which reduce tree densities and soil moisture stress may offset, at least temporarily, the effect of predicted decreases in Sierran snowpack on R
s.

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    • "Secondly, the low interannual variation in annual mean soil temperature with a CV of only 6% contributes little to annual litter respiration and contribution rate (Asensio et al., 2007; Ma et al., 2007; Concilio et al., 2009). The results of this study clearly showed that annual cumulative litter respiration and contribution rate were not related to annual mean soil temperature (P > 0.05). "
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    • "Moisture provided from snowmelt has also been shown to persist throughout the summer (e.g. Hu et al., 2010), the presence of which tends to elevate summer soil respiration in these subalpine mixed-conifer ecosystems within semi-arid regions (Hogberg et al., 2001; Concilio et al., 2009). Few field-based research studies have evaluated how ecohydrological processes will be impacted by climate change, especially with respect to changes in winter precipitation dynamics. "
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    • "Seasonal patterns of R S have been attributed to soil temperature [5] [18], soil moisture [10] [19], precipitation, productivity [20], or combinations of these factors [11]. Inter-annual variation of R S is usually controlled by productivity [21], soil water condition [22], or precipitation amount [23] and pattern [10]. Therefore, sampling schedule (in terms of both frequency and pattern) that captures these factors is important for adequately capturing the temporal variation of R S [8] [20] and estimating annual R S . "
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