中文摘要：

为了解氮沉降对黄土高原典型草原土壤氮矿化的影响,通过人工氮肥添加模拟试验,采用埋置PVC管的树脂芯方法原位测定了土壤氮素净氨化、净硝化和净矿化量的季节变化规律,探讨了氮素添加初期对氮矿化/固持贡献量和硝态氮淋溶损失量的影响.结果表明：黄土高原典型草原土壤氮矿化以硝化作用为主,夏季净硝化速率显著高于秋季.氮添加初期改变了半干旱草地氮矿化的季节模式,夏季表现为氮固持,秋季表现为氮矿化,并增加了氮矿化/固持的变异度,氮添加和季节因素对土壤氮矿化/固持有显著的交互作用.氮添加初期高氮添加未抑制氮的矿化过程.夏秋2季树脂硝态氮的含量随模拟氮沉降强度增加而显著增加,但硝态氮淋失量小,仅占施氮量的1.72％～4.74％.

英文摘要：

To understand the effects of nitrogen deposition on the soil nitrogen mmerahzatlon ot typical grassland in Loess plateau, the resin core method （buried PVC pipe） was employed to determine the sea- sonal pattern of in-situ net ammonification, nitrification and net mineralization, explore the effects of ni- trogen addition on the contribution of net nitrogen mineralization/immobilization and the amount of nitrate nitrogen leaching at the beginning of nitrogen addition. The results showed that the nitrification was the main mineralization progress in the typical grassland of Loess plateau, and the net nitrification rate was significant higher in summer than that in autumn. The seasonal pattern of nitrogen mineralization was changed in semi-arid grassland at the beginning of nitrogen addition. Nitrogen transformation presented ni- trogen immobilization in summer and nitrogen mineralization in autumn, the variation of nitrogen minerali- zation-immobilization was increased. There was significant interaction between seasonal factor and nitrogen addition on nitrogen mineralization-immobilization. Nitrogen mineralization wasn＇t inhibited under high N addition at the beginning of nitrogen addition. The content of nitrate nitrogen in resin significantly in- creased with the increase of nitrogen addition rate, but the values were small and only accounted for 1.72~4.74~ of nitrogen application rate.