The response of CO2 flux to rain pulses at a saline desert

As the substantial component of the ecosystem respiration, soil CO2 flux is strongly influenced by infrequent and unpredictable precipitation in arid region. In the current study, we investigated the response of soil CO2 flux to rain pulses at a saline desert in western China. Soil CO2 flux was measured continuously during the whole growing season of 2009 at six sites. We found that there were remarkable changes in amplitude or diurnal patterns of soil CO2 flux induced by rainfall events: from bimodal before rain to a single peak after that. Further analysis indicated that there is a significant linear relationship (P?<?0.001) between soil CO2 flux and soil temperature (Tsoil). However, a hysteresis between the waveform of diurnal course of CO2 flux and Tsoil was observed: with soil CO2 flux always peaked earlier than Tsoil. Furthermore, a double exponential decay function was fitted to the soil CO2 flux after rainfall, and total carbon (C) releases were estimated by numerical integration for rainfall events. The relative enhancement and total C release, in association with the rain pulses, was linearly related to the amount of precipitation. According to the size and frequency of rainfall events, the total amount of C release induced by rain pulses was computed as much as 7.88?g C.m2 in 2009, equivalent to 10.25% of gross primary production. These results indicated that rain pulses played a significant role in the carbon budget of this saline desert ecosystem, and the size of them was a good indicator of rain-induced flux enhancement. Copyright (c) 2012 John Wiley & Sons, Ltd.