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: 4.62). 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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    • "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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    • "Consequently, temperature is still regarded as the key factor for predicting soil respiration because it directly controls plant and microorganism metabolisms on a daily time scale and is indirectly related to the seasonal supply of photosynthesis-derived substrate (Ma and others 2004; Campbell and Law 2005). Timber harvest activities can influence forest soil respiration by altering soil carbon input (Johnson 1992; Johnson and Curtis 2001; Li and others 2007; Jandl and others 2007), organic matter in the soil (Mallik and Hu 1997), forest structure and microclimate (Chen and others 1999; Xu and others 2002), microbial biomass and microorganism community structure (Ponder and Tadros 2002; Fraterrigo and others 2006; Chatterjee and others 2008), litter depth (Concilio and others 2005; DeForest and others 2009), and root distribution and biomass (Henderson 2007). Most previous soil respiration studies have addressed the effects of clearcutting (Weber 1990; Striegl and Wickland 1998) or thinning (Ma and others 2004; Tang and others 2005), whereas comparisons of both silvicultural strategies in the same forest type are rare. "
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