The mineralization of soil nitrogen and its influenced factors under alpine meadows in Qilian Mountains

The alpine meadows soil nitrogen mineralization and its relationship with soil temperature,soil water content,soil depth and altitude in Qilian Mountains were analyzed by soil incubation in an orthogonal experiment.Based on the range of soil nitrogen mineralization,the impacts of soil temperature and soil water content on soil nitrogen mineralization were the highest of the impacts of different factors,while the impacts of altitude,soil depth or interaction between soil temperature and soil water content were the lowest.Based on the range of soil nitrogen mineralization ratios,the impacts of soil temperature and altitude on soil nitrogen mineralization were also the highest impacts,but the impacts of soil water content was relatively lower than the impacts of soil temperature,and that of soil depth was the lowest.The impacts of soil temperature and soil water content on soil nitrogen mineralization were significant at the 10% level,and the impacts of soil temperature were significant at the 5% level.Additionally,the impacts of different factors on the ratio of soil nitrogen mineralization were not significant at the 10% level.At 5%,soil nitrogen mineralization at 35℃ was higher than that at 25,15 and 5℃ and it was also higher at 25℃ than at 5℃,but it was not significantly different between 5 and 15℃ or between 15 and 25℃.At the 10% level,it was higher at 15,25,or 35℃ than at 5℃,and it was also higher at 35℃ than at 15 or 25℃.The difference of soil nitrogen mineralization ratios were not significantly different at the 5% level,but at the 10% level,the soil nitrogen mineralization ratio at 35℃ was higher than at 15℃.The difference of soil nitrogen mineralization and its ratio were not significantly different among different soil water contents,while soil nitrogen mineralization was higher at a water content of 40% than at 60%,and the ratio of soil nitrogen mineralization was lower at a soil water content of 60% than at 40% or 20% at the 10% level.The difference of soil nitrogen mineralization and its ratio among different interactions of soil temperature and soil water content were not significant.The difference of soil nitrogen mineralization was not significant between different altitudes,although the soil nitrogen mineralization ratio was lower at an altitude of 3 800 m than at 3 700,3 600 or 3 500 m at the 5% level.Based on the soil nitrogen mineralization rate,the Q10 ranged from 1 to 3,and it was higher from 5 to 15℃ than at 15 to 25℃ or from 25 to 35℃,which was almost same as from 15 to 25℃ and from 25 to 35℃.Based on the soil nitrogen mineralization rate ratio,Q10 ranged from 0.5 to 2,and it was lower from 5 to 15℃ than from 15 to 25℃ or from 25 to 35℃.It was about 2 from 15 to 25℃ or from 25 to 35℃.The results showed that alpine meadow soil nitrogen would be greatly influenced by soil temperature change.