Contrasting diurnal variations in soil organic carbon decomposition and root respiration due to a hysteresis effect with soil temperature in a Gossypium s. (cotton) plantation

Abstract

To understand the characteristics of the diurnal variation in soil respiration and its response to temperature, we used root exclusion plots, and buried CO 2 sensors in situ during the late growing season in northwestern China. Soil organic carbon (SOC) decomposition and root respiration dynamics were quantified. In our study, we found that the diurnal variations in root respiration and soil organic carbon (SOC) decomposition showed a contrasting diurnal pattern. SOC decomposition peaked in the afternoon and was in phase with an increase in soil temperature at 10 cm; whereas root respiration decreased from 08:00-09:00 and was minimal at~17:00-18:00 despite an increase in soil temperature. Furthermore, an exponential function explained the diurnal variation in total soil respiration and SOC decomposition (r 2 > 0.6, n=504), but not so for root respiration (r 2 < 0.3, n = 504). The fitted Q 10 value of 4.3 for SOC decomposition was significantly higher than the Q 10 value of 3.1 for root respiration. This result suggested that the root respiration rate had a different temperature sensitivity to the microbial respiration rate. In addition, we observed a significant (p<0.001) clockwise hysteretic effect for SOC decomposition with respect to soil temperature at 10 cm over a 24 h period, with higher rates when soil temperature was increasing and lower rates when soil temperature was decreasing. By contrast, the diurnal hysteresis in root respiration with soil temperature at 10 cm was always counterclockwise, with lower rates when soil temperature was increasing than when soil temperature was decreasing. This study emphasizes that root respiration and SOC decomposition have different responses to changing soil temperature. Therefore, modeling the impact of global climate change on soil carbon efflux should consider simultaneously, but separately, the impact of the two components.

Classification of soil respiration in areas of sugarcane renewal using decision tree

“…Zhi-Min et al (2013) observed that the average contribution of root respiration to total soil respiration was about 32 %. Li et al (2011) pointed out mean contribution of root respiration to total soil respiration over 60 %. Another hypothesis may be related to the tendency to dissociate CO 2 to cause acidity in the soil and control the acidity potential, because the carbonic acid produced by dissolving CO 2 in water is an important acidifying agent in natural systems (Reuss and Johnson, 1986;Tossell, 2009).…”

Simulated rain addition modifies diurnal patterns and temperature sensitivities of autotrophic and heterotrophic soil respiration in an arid desert ecosystem

“…Thus, the increased rainfall in arid and semiarid regions in northwestern China under future climate scenarios is expected to modify the Q 10 value (Curiel Yuste et al, 2003;LelleiKovacs et al, 2011;Jiang et al, 2013). Many experimental studies have investigated the response of daily Q 10 to rainfall variability (Liu et al, 2008;Zhang et al, 2010;Bowling et al, 2011;Li et al, 2011;Thomas et al, 2011;Shi et al, 2012;Vargas et al, 2012). However, we are not aware of any studies which distinguished the differential responses of daily Q 10 of R H and R A to rain change.…”

24-h variation in soil respiration after a long dry season in a Sudano-Sahelian region

“…This 24-h variation was obtained in agro-ecosystems in a temperate climate (Shi et al, 2006), an arid climate (Li et al, 2011) and a Mediterranean climate (Xu and Qi, 2001). These authors explain this process as a function of soil temperature because this is a variable that changes considerably in the course of a day (Rayment and Jarvis, 2000).…”