Temperature and Moisture Effects on Soil Respiration in Alpine Grasslands

The Tibetan Plateau, the low-latitude and high-altitude cold region, has a variety of soils rich in organic carbon (C). Climate change will have large impacts on soil carbon dioxide (CO2) efflux in the region. These impacts will subsequently affect global-scale climate and C cycle links. However, the magnitude of this feedback is still uncertain. Here we use a laboratory incubation experiment to investigate how soil temperature and moisture affected the rate and temperature sensitivity of heterotrophic respiration of three alpine ecosystems (alpine meadow [M], alpine shrubland [SB], alpine swamp [SP]) on the Tibetan Plateau. Soil samples were incubated under three temperature (0 degrees C, 15 degrees C, and 30 degrees C) and two moisture (50% and 100% water-holding capacity) conditions. The response of soil respiration to temperature and moisture varied with ecosystems. Soil respiration in SP was the most temperature sensitive, and higher moisture increased its temperature sensitivity (Q(10)). The respiration and Q(10) depended on total nitrogen in soils. Moreover, high moisture increased the dependence of Q(10) on total nitrogen. Our results suggest that rising temperature in Tibetan Plateau may cause a positive feedback to the soil C cycle, particularly coupled with increasing precipitation and N addition.