大气氮沉降对黄土高原土壤氮特征的影响

为了解氮沉降对土壤氮特征的影响，通过人工氮肥添加模拟试验，分析在不同氮添加梯度下黄土高原典型草原土壤全氮（TN）和轻组有机氮（LFON）含量的变化特征。结果显示，氮添加对黄土高原典型草原土壤0～40 cm土层TN含量没有显著影响(P>0.05)；但是显著增加了土壤表层（0～10 cm）的LFON含量和LFON/TN(P<0.05)。氮添加对10～20和20～40 cm的LFON含量和LFON/TN没有显著影响(P>0.05)。本研究表明，在黄土高原典型草原实施氮添加的初期，LFON含量和LFON/TN比TN含量能更早地显示出土壤氮特征的变化。

Influence of nitrogen deposition on soil nitrogen characteristics in the typical steppe on Loess Plateau

To study the influence of nitrogen addition on soil nitrogen characteristics in the steppe on Loess Plateau, six levels of nitrogen (N) treatments, 0, 1.15, 2.3, 4.6, 9.2 and 13.8 g·m-2 were conducted in the experiment. Based on the field sampling and laboratory analysis, the responses of soil total nitrogen (TN) and light fraction organic nitrogen (LFON) contents to the N addition were examined. The results showed that the early N addition had no significant effect on the TN content in the 0-40 cm soil layer. However, the early N addition significantly increased LFON content and LFON/TN in the 0-10 cm soil layer. There were no obvious changes of LFON and LFON/TN in the 10-20 cm and 20-40 cm layer among treatments. LFON and LFON/TN were more influenced by the early N addition than TN. Therefore, LFON and LFON/TN were sensitive indictors of soil N dynamics to the early N addition in the steppe on the Loess Plateau.