Abstract: Drying-rewetting (D/R) cycle of soil induced by discontinuous rainfall events is an important factor influencing soil respiration in desert ecosystems. In this study, two patterns of precipitation (same in total precipitation but different in frequency) were applied to two typical biologically-crusted soils in the revegetation area in the southeast fringe of the Tengger Desert, and laboratory incubation experiment with a constant-temperature of 25 ℃ was adopted, to investigate the response of soil CO₂ efflux to repeated D/R cycles with different frequencies. The results showed that as drying and rewetting proceeded, the peak and average respiration rates, accumulated carbon release and average soil water content showed a tendency of decrease, and the decreasing rate declined with the extension of drought. The cumulative carbon emissions of both two biologicallycrusted soils under 10 days interval D/R cycling were less than under 20 days interval D/R cycling. Under the same precipitation pattern, the cumulative carbon emission of moss overlying soil was significantly higher than that of the algae overlying soil. These findings indicate that land cover types and precipitation frequency are both the important factors influencing the response of soil CO₂ efflux to dryingrewetting cycle in desert ecosystems.

Key words: Quercus variabilis, population structure, spatial pattern, geographical gradient