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: 3.63). 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

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the context of an ongoing monitoring study of the Cabo de Gata-Níjar Natural Park (SE of Spain), we explored the use of soil respiration as an indicator of ecosystem functioning reflecting changes in ecological processes in semiarid environments. With this purpose, we measured soil CO2 efflux in six different and representative ecosystems of the Natural Park, with different land uses (forest and agricultural sites) and under different soil covers (under plant and bare soil) in two distinctive periods of the year: summer (dry period) and spring (growing season). We also measured the main soil properties and environmental variables. Soil CO2 efflux ranged from 0.40 μmol m−2 s−1 in the dry period to 1.93 μmol m−2 s−1 in the growing season. Soil CO2 efflux showed a large spatial variability, with different behaviour between the measured periods. Whereas in the dry period differences among ecosystems were larger (CVs 75–80%) than within them (CVs 40–55%), in the growing season the CVs were smaller (40–50%) and no differences were observed between or within ecosystem. The factors controlling soil CO2 efflux also differed in the two measurement occasions. Whereas in the dry period soil CO2 efflux was mainly the result of transport processes in the soil and therefore related to local factors (OC content, CN ratio, clay, rock outcrop, etc.) assigned to ecosystem conditions, in the growing season soil CO2 efflux was dominated by soil CO2 production and thus related only to organic carbon content and plant cover. In the growing season environmental variables explained ca. 10% of the variation in soil CO2 efflux. In order to capture these different processes in different times of the year, i.e., diffusion versus production processes we calculated a new index, normalised seasonal difference in soil respiration (SDSR), which is proposed as a good indicator of the state and functioning of the ecosystem.
    Ecological Indicators 03/2012; 14(1):40–49. · 3.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Optimizing a manual measurement schedule (both frequency and pattern) for estimating annual soil respiration (RS) is an important but unresolved issue. We hypothesized that (i) an optimal sampling setup can be found to obtain a reliable annual RS, and (ii) if the desired outcome is a multi-year mean annual RS, a lower sampling frequency might be adequate. Here we explored these issues using a three-year chamber-based dataset, with a sampling frequency of twice per week (defined as control), in an exotic slash pine (Pinus elliottii Englem.) plantation in subtropical China. The results showed that RS during 9:00–11:00 a.m. represented diurnal mean RS well. In order to obtain an annual RS as reliable as the control (deviation within ±5%), the optimal measurement strategy is a biweekly sampling across a year and not a trade-off sampling pattern (monthly sampling combined with weekly sampling depending on the seasons). Furthermore, despite an obvious inter-annual variability in RS (548.4–757.5 g C m−2 year−1, CV = 16.3%), a monthly sampling was sufficient to obtain an unbiased multi-year mean annual RS (deviation within ±5%). Such findings are useful when easy looking for estimates of annual ecosystem carbon budgets. However, the generality needs to be examined in other ecosystems.
    European Journal of Soil Biology 09/2012; 52:41–47. · 1.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The interannual variation of the Bowen ratio, through its effect on the warming extent of available energy to the ecosystem land surface air, heavily influences the ecosystem microclimate and affects the hydrological cycle at both regional and global scales. Although the precipitation amount in southeast China is not expected to change greatly as a result of climate change, the precipitation frequency may be altered in the future. We explored the interannual variation of the Bowen ratio and its affecting mechanisms based on eddy covariance measurements in a subtropical plantation in southeast China during 2003-2012. The results indicated that the annual mean Bowen ratio was 0.35±0.06, with a range of 0.29-0.45. The Bowen ratio during the dry season (July-October) positively correlated with the annual Bowen ratio (R(2) = 0.85, p<0.001). The effective precipitation frequency during the dry season, through its positive effect on shallow soil water content, indirectly and negatively affected the annual Bowen ratio. Between 2003 and 2012, the annual Bowen ratio exhibited a marginally significant decreasing trend (p = 0.061), meanwhile the effective precipitation frequency and shallow soil water content during the dry season increased significantly (p<0.001). The annual Bowen ratio may decrease further if the effective precipitation frequency and shallow soil water content during the dry season follow similar trends in the future. The warming effect of available energy to the surface air of our studied plantation may decline with the decreasing annual Bowen ratio.
    PLoS ONE 01/2014; 9(2):e88267. · 3.53 Impact Factor

Full-text (2 Sources)

Available from
Jun 3, 2014