Soil moisture modifies the response of soil respiration to temperature in a desert shrub ecosystem

Abstract

Abstract.The current understanding of the responses of soil respiration (Rs) to soil temperature (Ts) and soil moisture is limited for desert ecosystems. Soil CO 2 efflux from a desert shrub ecosystem was measured continuously with automated chambers in Ningxia, northwest China, from June to October 2012. The diurnal responses of Rs to Ts were affected by soil moisture. The diel variation in Rs was strongly related to Ts at 10 cm depth under moderate and high volumetric soil water content (VWC), unlike under low VWC. Ts typically lagged Rs by 3-4 h. However, the lag time varied in relation to VWC, showing increased lag times under low VWC. Over the seasonal cycle, daily mean Rs was correlated positively with Ts, if VWC was higher than 0.08 m 3 m −3 . Under lower VWC, it became decoupled from Ts. The annual temperature sensitivity of Rs (Q 10 ) was 1.5. The short-term sensitivity of Rs to Ts varied significantly over the seasonal cycle, and correlated negatively with Ts and positively with VWC. Our results highlight the biological causes of diel hysteresis between Rs and Ts, and that the response of Rs to soil moisture may result in negative feedback to climate warming in desert ecosystems. Thus, global carbon cycle models should account the interactive effects of Ts and VWC on Rs in desert ecosystems.

Mitigating the Stress of Drought on Soil Respiration by Selective Thinning: Contrasting Effects of Drought on Soil Respiration of Two Oak Species in a Mediterranean Forest

“…In the reduced rainfall treatment, we observed some campaigns with soil moisture higher than 8%, but SR of these campaigns were still lower than the SR in the control treatment of the same campaigns. The reduction of Q 10 due to drought has been found in many studies [71][72][73][74]. As the apparent Q 10 in this study was calculated as annual Q 10 , the low Q 10 in the reduced rainfall treatment could be attributed by the diminished seasonal amplitude of SR, especially SR under Q. cerrioides.…”

Diurnal Freeze-Thaw Cycles Modify Winter Soil Respiration in a Desert Shrub-Land Ecosystem

“…Further research is suggested to include more replicates representing spatial heterogeneity sufficiently for more accurate estimate. Q10 derived for the whole winter varied from 2.8 to 19 among microsites with an average value of 8.9, much higher than the growing-season value of 1.5 [3]. High Q10 values in winter have been reported previously.…”

“…However, they are particularly vulnerable to climate change [2]. In order to accurately predict global C cycling under a changing climate, it is necessary to know how dryland soil respiration (R s ), the primary path by which CO 2 fixed by plants returns to atmosphere [3], responds to variations in climate. Currently, the R s of dryland ecosystems and its responses to environmental factors are studied to a much lesser extent compared to other ecosystems [4].…”

“…For instance, biocrusts were reported to affect R s by constraining microsite factors, such as T s and SWC [16]. But these reports were explored mostly during the growing season [3]. We have little knowledge about the influence of biocrusts on soil temperature and moisture during winter.…”

Soil moisture influence on the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

“…Soil moisture is the most significant limiting factor for underground physiological processes in dry and semi-dry ecosystems (Balogh et al, 2011;Cable et al, 2011;Wang et al, 2014). Soil water availability may indirectly affect Q 10 by influencing the diffusion of substrates because the diffusion of extracellular enzymes produced by microorganisms and available substrates must occur in the liquid phase (Davidson et al, 1998;Illeris et al, 2004), but the response of Q 10 to soil water availability is extremely complex and controversial (Davidson et al, 2000;McCulley et al, 2007).…”