Contribution of root and rhizosphere respiration of Haloxylon ammodendron to seasonal variation of soil respiration in the Central Asian desert

Temporal changes in soil CO2 efflux rate was measured by a canopy gap method in a temperate natural shrub forest in the Central Asian Desert. Soil CO2 efflux rate in situ was correlated with key soil biotic (e.g. fungal, bacterial and actinomycetes populations) and abiotic (e.g. soil moisture, temperature, pH and organic carbon concentration) variables. Root and rhizosphere respiration originating from soil organic matter decomposition (Rd) were estimated from Rc (soil respiration under the crowns of Haloxylon ammodendron) and Rg (soil respiration in the gaps between H. ammodendron) of H. ammodendron. Contribution of root and rhizosphere respiration (Rr) to total soil respiration ranged from 13% to 94% during the growing season. Correlations of Rr with soil temperature and moisture were significant, but Rd was not significantly correlated with soil temperature and moisture. Microbial biomass, pH, soil organic carbon (SOC), total nitrogen (TN) and calcium carbonate (CaCO3) were analyzed in the soil. Rd with soil biomass and SOC were significantly correlated, whereas Rr was not significantly correlated with soil biomass and SOC. Effects of pH value, TN and CaCO3 on the two components of soil respiration (Rr and Rd) were not significant. Taken together, the data suggest that factors affecting seasonal changes of respiration were different between the two components of soil respiration: Rr was more sensitive to changes of temperature and moisture than Rd.