Rainfall pulses modify soil carbon emission in a semiarid desert

Abstract

Modifications of rainfall patterns are expected to accompany global climate changes. It has been suggested that in dry regions changes in soil carbon emission induced by precipitation will affect soil carbon storage and atmospheric CO2 concentration. However, our understanding of the responses of soil carbon emission [often as soil respiration (RS)] to rainfall pulses is still limited regarding changes in soil respiration components [heterotrophic respiration (RH) and autotrophic respiration (RA)] and under different precipitation patterns in arid and semiarid ecosystems. To evaluate the variations in soil carbon emission in response to rainfall pulses, we measured RS and its components in situ before/after precipitation in the Mu Us Desert, China. Rates of RS and its components were significantly enhanced by rainfall pulses, but gradually reverted thereafter. Moreover, the magnitudes of diel hysteresis for RS, RH, and RA with respect to soil temperature (TS) were modified by precipitation, and the effects of rainfall pulses on RS were influenced by antecedent soil water availability. In addition, the ratio of respiration components was changed by individual precipitation events, with an increase in the amount of each rainfall pulse causing a decrease in the proportion of RH to RS. Our results indicate that rainfall pulses in desert ecosystems have a major impact on soil carbon emission via changes in the magnitude and ratio of respiration components. We accordingly suggest that greater carbon emission and alterations in respiration components may occur with more extreme precipitation in desert ecosystems.