Abstract: The soil nitrogen mineralization is crucial to the primary productivity of terrestrial ecosystem, but it is affected by many factors, among which temperature and moisture are most important. The research of response of sandy grassland soil nitrogen mineralization to the temperature and moisture plays an important role to predict impact of global change on sandy grassland ecosystem structure and function. Therefore, in this paper, we did the in situ cultivation of sandy grassland soil in Horqin through the method of Open Top Chamber (Open Top Chamber, OTC) simulation of raising temperature and artificial regulation of field moisture capacity, then we analyzed the influence of temperature and moisture on soil nitrogen mineralization. Our results showed that no matter how the temperature changed, the sandy grassland soil net mineralization/nitrification rate increased significantly with the increase of field capacity. The net nitrification rates and net mineralization rates of soil N reached their maximums at the moisture of 9.5% and significantly decreased at the moisture of 12.5%. Raising temperature can make significant changes in sandy grassland soil nitrogen mineralization, but there were some correlations between the effect of raising temperature and the field moisture capacity. Net nitrification rates and net mineralization rates of soil N were significantly accelerated by simulation of raising temperature by OTC under the condition of relatively suitable for field capacity(between 6.5% and 12.5%). However, there were no significant response of net nitrification rates and net mineralization rates of soil N to the increase of temperature under the relatively low or too high condition of field moisture capacity. This implies that effect of raising temperature on soil N mineralization is significant only at the appropriate moisture conditions in the Horqin Sandy Grassland.

Key words: simulated warming, field moisture capacity, inorganic nitrogen, nitrogen nitrification rate, nitrogen mineralization rate