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 CO2 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 m3 m−3. Under lower VWC, it became decoupled from Ts. The annual temperature sensitivity of Rs (Q10) 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.
Highlights
Soil respiration (Rs) is receiving widespread attention as a key component of the global C cycle (Schimel, 1995)
This study reports on findings of continuous soil respiration (Rs) measurements from a desert shrub ecosystem in northwest China, and especially its temporal variation in relation to soil temperature (Ts) and moisture over diel and seasonal cycles
Rs was mainly controlled by Ts, but the response of diel Rs to Ts was adjusted by volumetric soil water content (VWC)
Summary
Soil respiration (Rs) is receiving widespread attention as a key component of the global C cycle (Schimel, 1995). In addition to soil temperature (Ts), volumetric soil water content (VWC) is of primary importance for predicting the evolution of soil carbon stock and fluxes. This is because it strongly controls the decomposition of soil organic matter (Jassal et al, 2008; Liu et al, 2009; Moyano et al, 2012), root respiration (Palta and Nobel, 1989; Bouma et al, 1997), and microbial activity (Linn and Doran, 1984; Skopp et al, 1990; Hallett and Yong, 1999; Drenovsky et al, 2004). VWC is predicted to change at the global scale in the following decades related to global climate change (Wetherald and Manabe, 2002)
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