大气氮沉降与森林生态系统的氮动态

由于人类活动的影响，若干年代以来大气氮沉降明显增加。在森林地区，大气氮沉降的空间变异性由林分的位置、结构和组成树种所决定。除降雨之外，干沉降和隐藏降水也是大气氮沉降的重要形式。

ATMOSPHERIC NITROGEN DEPOSITION AND NITROGEN DYNAMICS OF FOREST ECOSYSTEMS

Atmospheric nitrogen deposition has been increasing significantly over the last decades because of the influence of human activities. In forest areas, spatial variability of the nitrogen deposition depends on the stand position, structure and species composition. Besides the rainfall, dry deposition and occult precipitation are also important forms in atmospheric nitrogen deposition.Some forest canopies can absorb the deposited nitrogen to a certain extent, but the throughfall nitrogen flux increase obviously with the nitrogen inputs of bulk precipitation.When the nitrogen deposition is more than 15 kg N/hm2. a, not only do most forest canopies not absorb the nitrogen in rainwater, but also large amounts of nitrogen are leached out from the canopies. In the long run, there is no obvious correlation between forest vegetation nitrogen increment and atmospheric nitrogen deposition. The increase in atmospheric nitrogen input can induce nitrification regardless of hardwood forest, mixed hardwood-coniferous forest, or coniferous forest. When the nitrogen deposition is large, the leaching of nitrogen from forest soils shows a obvious increase trend with the increase of the deposition. As a whole, there is no clear correlation between net nitrogen accumulation in forest ecosystems and atmospheric nitrogen deposition, and it is logical to coincide with the conclusion of no obvious correlation between forest vegetation nitrogen increment and atmospheric nitrogen deposition.