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


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

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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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    ABSTRACT: A better understanding of the factors affecting interannual variability in litter respiration is critical to precisely understand local carbon cycling, especially under the changing climate. In this study, litter respiration was obtained by subtracting in situ soil respiration in a control (LCK) treatment by that in a litter removal (LR) treatment for the period 2009-2013 in a 30-year-old black locust plantation (Robinia pseudoacacia L.) on a ridge slope in a small watershed of Loess Plateau, China. Annual cumulative litter respiration ranged from 48 ± 15 to 165 ± 36 g C m-2 y-1, with mean value of 113 ± 45 g C m-2 y-1 and coefficient of variation (CV) of 40%; annual contribution rate of litter respiration to total soil respiration (hereafter refer to as litter contribution rate) also exhibited a similar interannual variability (ranged from 8 ± 3% to 20 ± 7%; mean = 15 ± 5%; CV = 31%). Additionally, annual mean soil moisture was highest in 2010 (53.2 ± 8.4% WFPS) and lowest in 2013 (31.4 ± 9.5% WFPS), with mean value of 41.6 ± 7.9% WFPS and CV of 19%; annual litter production rates also exhibited a similar interannual variability (ranged from 379 ± 34 to 565 ± 69 g m-2 y-1; mean = 477 ± 71 g m-2 y-1; CV = 15%). Annual mean soil moisture was mainly affected by the frequency and distribution of precipitation, and annual litter production rates varied with summer precipitation. Annual cumulative litter respiration and litter contribution rate increased linearly with both annual litter production rates and mean soil moisture content. The contribution of soil water to litter respiration was larger than that of litter production rates. Therefore, litter production rates and soil moisture resulted from precipitation needs to be taken into account for precisely predicting litter respiration in the dryland ecosystems, especially under the changing climate.
    Full-text · Article · Feb 2016 · Journal of Arid Environments
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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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    ABSTRACT: Subalpine mixed-conifer ecosystems are dependent on snowfall, which is expected to decrease under projected climate change. Changes in snowpack are likely to have important consequences for water and carbon cycling in these and downstream ecosystems. Particularly within semi-arid environments, snowpack changes will directly influence localized water and carbon dynamics and indirectly influence regional-scale levels of water availability and carbon sequestration. In this study, we monitor soil evaporation (E) and soil respiration (R) and evaluate how snow cover affects these effluxes within a mixed-conifer ecosystem within the Santa Catalina Mountains about 10km north of Tucson, Arizona. Using time-lapse digital photos, we identified areas of consistent short and long snow duration, and we monitored E and R in these areas every 2weeks for 15months. Our primary findings include the following: (1) Dynamics of E are not different between long and short snow season sites, (2) E for both short and long snow seasons has a strong relationship with soil moisture and a poor relationship with soil temperature, (3) dynamics of R vary between long and short snow season sites throughout the year, with short snow season fluxes typically higher than those of long snow season sites, and (4) R for short and long snow seasons has a strong relationship with soil temperature and a poor relationship with soil moisture. Because climate change will only exacerbate both drying-wetting and cooling-warming cycles, detangling these complex relationships becomes increasingly important for understanding shifts in carbon dynamics in these subalpine mixed-conifer ecosystems. Copyright (c) 2013 John Wiley & Sons, Ltd.
    Full-text · Article · Apr 2014 · Ecohydrology
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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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    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.
    Full-text · Article · Sep 2012 · European Journal of Soil Biology
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