农林复合生态系统氮素生物地球化学循环及其环境影响研究

对长江上游典型农林复合生态系统N素收支平衡及其污染特征研究结果表明 ,农林复合生态系统旱地N素盈余相对较多 ,水田基本平衡 ,而林地有较大亏缺。N素收支平衡评价表明其旱地平衡合理 ,水田平衡略高 ,但整个农田N素已由 2 0世纪 6 0年代严重亏缺达到目前的较合理水平 ;大规模造林以及水保耕作措施对农田N素合理分配均产生重要影响。但化肥施用量剧增已导致农田气态N素释放量增加和水体非点源污染风险加大。

N biogeochemical cycle and its impacts on environments in an agro-forest ecosystem

The N balance and its pollution characteristics on enviro nments in a typical agro -forestry ecosy stem in the upper reaches of the Yangtze River were studied.The results show tha t in ecosystem,there is relatively high N surplus in croplands,almost N balance in paddies and high N deficit in forest. N balance appraisals show the N balance rate of croplands is reasonable but that of paddies shows a little higher.Howeve r,N balance of the whole arable lands ha s changed greatly from heavy deficit of 1960s to reasonable balance of nowadays. Forest and cultivations play the importa nt roles in the N balance changes of eco system.But the great increases of chemic al N fertilizer usages lead to the incre asing of the gas N emissions and N non -p oint source pollutions risk of water bod ies.