Effect of temperature and humidity on the alpine meadow soilcarbon mineralization under different management in Naqu prefecture in Tibet

Soil carbon mineralization rate is affected by many factors. A laboratory incubation experiment was conducted in the present work with strictly controlled temperature and water levels to determine the effect of temperature and moisture on soil carbon mineralization rate of grazing prohibited and freely-grazing alpine meadows in Naqu,Tibet. Combined with determined soil-related indicators revealed mechanism of temperature and humidity on soil carbon mineralization.The incubation experiment consisted offive temperature treatments(5,10,15,20,and25℃) and two water treatments(40% and60% of water holding capacity,WHC).The soi lcarbon mineralization rate was found to be mainly affected by temperature and humidity. At low temperatures and 60% soil water holding capacity,there was no significant differencein soilcarbon mineralization rate for grazing prohibited and freely-grazing meadows,and the soil carbon mineralization rate increased significantly with the increase intemperature (P<0.05). At the same temperature and 40% soil water holding capacity,the soil carbon mineralization rate offreely-grazing meadow was significantly higher than grazing prohibited meadows (P<0.05).The average carbon mineralization rate in soilunder freely�grazing meadow at 40% soil water holding capacity was (0.66 ± 0.30)μmol·g-1·s-1,73.7% higher than at 60% soil water holding capacity. The average carbon mineralization rate of soiling razing prohibited area at 60% soil water holding capacity was (0.27±0.01)μmol·g-1·s-1,3.8% higher than at 40% soil water holding capacity. Other than the direct effects of temperature and humidity,the density and activity of soil microbial community,soil physical and chemical indicators also affected soil carbon mineralization rate. With the increase in temperature, the microbial biomass carbon was not changed at the early stage of incubation and the later stage, but the microbial biomass carbon increased significantly (P<0.05) at the medium stage. The change of soil dissolvable or ganic carbon was not consistent under different management methods.