RESPONSES OF CO2 AND N2O EMISSIONS TO CARBON AND PHOSPHORUS ADDITIONS IN TWO CONTRASTING ALPINE MEADOW SOILS ON THE QINGHAI-TIBETAN PLATEAU

A 45-day incubation experiment in laboratory was conducted to examine the effects of the carbon (C) and phosphorus (P) additions on carbon dioxide (CO2) and nitrous oxide (N2O) emissions from two alpine meadow soils sampled on the Qinghai-Tibetan Plateau: one with acid pH and high organic carbon content (HM), and the other one with alkaline pH and low organic carbon content (CM). The concentrations of DOC, NO3--N, NH4+-N and DTN in soils were measured at the end of the incubation. Addition of C significantly increased soil CO2 and N2O emissions in both alpine meadow soils. No significant effect of P addition on CO2 and N2O emission was detected in both soils. Data analysis revealed a significant positive correlation between the cumulative CO2 emissions and the soil DOC concentration, and a significant negative correlation between the cumulative N2O emissions and soil NO3--N concentration. These results suggest that soil CO2 and N2O emission is directly linked to the availability of soil C, while P is not the limiting factor for soil microbial activity in alpine meadow soils.