中文摘要：

依据自然雪被分布的差异，在青藏高原东缘高寒草甸中设置3条样带（即深雪、中等厚度雪被和浅雪），于2008年的秋冬过渡期，连续监测各样带中的雪被厚度和土壤温度，并采用原位培养法测定每月的土壤氮素氨化、硝化和矿化速率，以研究不同厚度雪被对高寒草甸土壤氮矿化的影响．结果表明，月均土温、每月日最高土温均值分别与雪被厚度极显著相关，二次函数关系拟合较好（R^2=0．576，0．685），且根据每月日最高土温均值与雪被厚度的二次函数关系方程可知，25cm厚的雪被可以起到较好的隔绝效果；土壤含水量受雪被厚度和土壤温差两个因素的显著影响．在秋冬过渡期末，浅雪梯度下土壤硝态氮含量显著降低，且雪被下的净氮矿化速率与月均土温、每月日最高土温均值、每月日最低土温均值都分别呈极显著相关，二次函数关系拟合较好（R^2=0．589，0．541，0．601）．研究表明，不同厚度的雪被对土壤温度和含水量影响显著，从而显著地影响着土壤氮的矿化，深雪更有利于氨化、硝化和氮矿化．图7表2参36

英文摘要：

Transects of three snow cover regimes with different snow depths and duration, which included a shallow and short duration snowpack （SS）, a moderate snow depth and medium duration snowpack （MS）, as well as a deep and long duration snowpack （DS）, were laid out in an alpine meadow on the eastern Tibetan Plateau of China based on the natural snow distribution pattern. The soil temperature and moisture under different snow conditions were measured continuously, and the soil net ammonification rate, net nitrification rate and net N mineralization rate, as well as the soil ammonium and nitrate contents were measured monthly with in-situ incubation method for the different snow regimes during the autumnwinter transition. The results indicated that the relationship between daily mean, maximum soil temperature in each month and snow depth was significant and well fitted with quadratic regression respectively （R2 = 0.576, 0.685）. Mean values of daily maximum soil temperatures were highly correlated with snow cover depths, and 25 cm depth of snow cover effectively decoupled the soil temperature from air temperature. Soil moisture markedly affected snow depth and soil temperature. At the end of the autumn-winter transition, nitrate content declined significantly under SS. Furthermore, net N mineralization rate was significantly correlated to mean values of daily mean, maximum and minimum soil temperature in each month under snow cover respectively （R2 = 0.589, 0.541, 0.601）. The results showed that seasonal snow cover affected soil nitrogen mineralization significantly resulting from its marked effect on the soil temperature and moisture, and deeper snowpack could lead to faster rates of net ammonification, nitrification and N mineralization. Fig 7, Tab 2, Ref 36