Contribution of Root Respiration to Total Soil Respiration in a Cotton Field of Northwest China
2013-06-27
Root respiration (Rr) in soils is a significant component of the global carbon balance, but its relative contribution remains uncertain. The contribution of each component to total carbon balance needs to be clarified in order to achieve a better understanding of the environmental factors affecting soil carbon cycling and sequestration.
Previous studies have shown that Rr and respiration originating from decomposition (Rd) are differentially affected by increasing temperature, exhibiting different temperature response values at 10° intervals (Q10). The different Q10 values for Rr and Rd possibly alter the net C efflux from soils as well as the potential for C sequestration, thus providing a significant contribution to climate-related change.
Furthermore, the difference between the responses of Rr and Rd to environmental factors such as temperature may change with the variation of the environment itself. So, it is important to separately characterize the Rr and Rd, and identify the different environmental factors controlling their dynamics.
To measure the contribution of Rr to total soil respiration (Rt) in arid cotton fields, eighteen plots (nine for girdling and nine for controlling) were built in an arid cotton field in the Aksu National Experimental Station of Oasis Farmland Ecosystem, Xinjiang of China. Given the difference of soil respiration between girdled plots and non-girdled control plots, the components of soil respiration, Rr and respiration originating from decomposition (Rd) were divided. The temperature sensitivities of Rr and Rd were analyzed, respectively.
The results showed that the average contribution of Rr to Rt in arid cotton field was about 32% during the study period. The temperature-response curve of Rr differed from that of Rd. The dynamic variation of Rd was more related to the change of soil temperature as compared to Rr. Rr and Rd had different responses to the variation of environment, and thus new models capable of differentiating between Rr and Rd are needed for evaluating the different factors controlling these two components of soil respiration in arid cotton field.
The result was published in Pedosphere in April 2013, 23(2): 223-228.