Soil respiration sensitivities to water and temperature in a revegetated desert

Soil respiration in water-limited ecosystems is affected intricately by soil water content (SWC), temperature, and soil properties. Eight sites on sand-fixed dunes that revegetated in different years since 1950s, with several topographical positions and various biological soil crusts (BSCs) and soil properties, were selected, as well as a moving sand dune (MSD) and a reference steppe in the Tengger Desert of China. Intact soil samples of 20cm in depth were taken and incubated randomly at 12 levels of SWC (0 to 0.4m(3)m(-3)) and at 9 levels of temperature (5 to 45 degrees C) in a growth chamber; additionally, cryptogamic and microbial respirations (R-M) were measured. Total soil respiration (R-T, including cryptogamic, microbial, and root respiration) was measured for 2years at the MSD and five sites of sand-fixed dunes. The relationship between R-M and SWC under the optimal SWC condition (0.25m(3)m(-3)) is linear, as is the entire range of R-T and SWC. The slope of linear function describes sensitivity of soil respiration to water (SRW) and reflects to soil water availability, which is related significantly to soil physical properties, BSCs, and soil chemical properties, in decreasing importance. Inversely, Q(10) for R-M is related significantly to abovementioned factors in increasing importance. However, Q(10) for R-T and respiration rate at 20 degrees C are related significantly to soil texture and depth of BSCs and subsoil only. In conclusion, through affecting SRW, soil physical properties produce significant influences on soil respiration, especially for R-T. This indicates that a definition of the biophysical meaning of SRW is necessary, considering the water-limited and coarse-textured soil in most desert ecosystems.