Abstract

a b s t r a c t High levels of available nitrogen (N) and carbon (C) have the potential to increase soil N and C mineralization. We hypothesized that with an external labile C or N supply alpine meadow soil will have a significantly higher C mineralization potential, and that temperature sensitivity of C mineralization will increase. To test the hypotheses an incubation experiment was conducted with two doses of N or C supply at temperature of 5, 15 and 25 C. Results showed external N supply had no significant effect on CO 2 emission. However, external C supply increased CO 2 emission. Temperature coefficient (Q 10 ) ranged from 1.13 to 1.29. Significantly higher values were measured with C than with N addition and control treatment. Temperature dependence of C mineralization was well-represented by exponential functions. Under the control, CO 2 efflux rate was 425 g CO 2 eC m À2 year À1 , comparable to the in situ measurement of 422 g CO 2 eC m À2 year À1 . We demonstrated if N is disregarded, microbial decomposition is primarily limited by lack of labile C. It is predicted that labile C supply would further increase CO 2 efflux from the alpine meadow soil.