Effects of temperature and moisture on nitrogen mineralization in Inner Mongolia grassland, China

In the present study, laboratory incubation with different temperature and moisture were conducted to imitate the effects of soil temperature and moisture on soil N mineralization using soil samples from Stipa krylovii grassland of Inner Mongolia, China. Five different temperatures (9, 14, 22, 30 and 40 ℃) and five different moisture (13%, 26%, 39%, 52%, 66% VWC ) levels were included with a full-factorial design. Results showed that soil mineral N production and net N mineralization rate were positively related to temperature (P0.01). There was no significant difference between soil mineral N production under different temperature levels (P0.05). There were significant difference between net N mineralization rate under different temperature levels during the early and middle stage of incubation (P0.05). Both mineral N production and net N mineralization rate had a quadratic correlation with moisture because both of them decreased rapidly at 52%~66% VWC (P0.01). The difference between moisture levels were significant for net N mineralization rate (P0.05) except the later incubation stage. There were significant effects of the interactions between soil temperature and moisture on nitrogen mineralization (P0.01). Environmental stress in the late incubation stage improved nitrogen immobilization which resulted in that interactions between soil temperature and moisture had no significant effects on net N mineralization rate.