下辽河平原降雨中氮素的动态变化

Dynamic changes of nitrogen in precipitation in lower reach of Liaohe River Plain

为了了解降雨中氮对农田生态系统的影响,分析了2004—2006年下辽河平原连续3年定位收集的降雨观测资料与历史资料。结果表明:降雨中氮输入量季节变化显著,夏季最高,这主要与降雨量及空气中NH4+-N浓度变化有关;降雨中DON量与NO3--N含量相当,均接近24%,是雨水中氮的重要组分;与1985年相比,近3年降雨输入到该地区农田生态系统的年氮通量已有较大提高,降雨较多的2005年输入的无机氮量更是20年前的2倍以上;2004—2006年随降雨输入农田生态系统的氮平均占可利用肥料氮的28.3%,对农田生态系统有着重要影响。

To understand the effects of nitrogen （N） in precipitation on agroecosystems, the precipitation samples at the Shenyang Ecological Station located in lower reach of Liaohe River Plain were collected from 2004 to 2006, and their N forms and amounts were measured. The results showed that the N amount in precipitation had an obvious seasonal change, being the highest in summer due to the higher concentrations of NH4 ^＋ -N in precipitation and atmosphere. The proportions of dissolved organic nitrogen （DON） and NO3^ - -N to total nitrogen （TN） in precipitation were all about 24%, and the annual N flux imported to the agroecosystems by wet deposition was more abundant in recent three years than 20 years ago. The N amount in precipitation in 2005 was increased by one time, compared with that in 1985. On average, the N import from precipitation in 2004-2006 accounted for 28.3% of the applied fertilizer N, suggesting that the N input from precipitation had greater effects on agroecosystem.