The Research Of Soil C Mineralization And Temperature Sensitivity In Inner Mongolia

With the increasing global climate change, the carbon cycle plays an important role. Carbon stock of soil carbon sequestration, especially grassland soil, is an important condition for ensuring the stability of soil carbon stock. Our study selected different grassland types, including long-term fenced Stipa grandis grassland (FG) and grazing Stipa grandis grassland (GG) in Inner Mongolia, grassland transect of Inner Mongolia and adding nitrogen soil investigating the impact of different grassland types on the temperature sensitivity and the priming effects of soil microbial respiration by incubating soils in the laboratory. The conclusions as following:1. The amount of soil C mineralization was higher in GG than that in FG duration the6-weeks incubation. The rates of soil C mineralization increased significantly with increasing incubation temperature for both GG and FG (temperature coefficient (Q10) values ranged from1.1to1.9), however, the Q10values for GG and FG were not significantly different. After mixed-litter addition, the rates of soil C mineralization not only in GG but also in FG increased significantly, and showed the apparent "priming effects" of C mineralization. Compared with long-term fenced grassland (FG), grazing grassland (GG) had higher priming effects, which even after only7d were6.38times higher. Moreover, the priming effects increased with increasing incubation temperature in the first week, although these effects were the highest at15℃duration the42d of incubation. These findings suggest that, on a longer time scale, medium temperatures should promote soil C mineralization. On the whole, long-term grazing exclusion depressed the priming effect of soil microbial respiration and resulted in less C emission under the same mixed litter input. This is probably one of the mechanisms underlying the capacity of long-term fenced grasslands to sequester CO2in Inner Mongolia.2. The effect of zonality of soil C mineralization and temperature sensitivity of soil respiration was significantly. However the linear correlation was not significant. The water was the main limiting factor of soil respiration at the same incubation temperature. Different types of soil with different physical properties, had a direct impact on soil C mineralization and temperature sensitivity. There was a positive correlation between accumulation of soil C mineralization and soil organ carbon but a negative correlation soil acidity. With different incubation water, Q10had different correlation with the soil organ carbon and soil acidity.3. Soil organ carbon of grassland increased significantly because of artificial fertilization. And another result was that the soil acidification. It was a more negative correlation between soil carbon mineralization and temperature sensitivity and the soil acidity at low temperature after N adding. But the relationship between them was not significant. The effects of N addition on temperature sensitivity of soil respiration were significant especially the C/N value of different grassland. The addition of N reduced the soil respiration and promoted the grassland soil carbon sequestration effect in short term. And the soil carbon stock was increased.