中文摘要：

利用系统物质平衡模型,对1995—2005年江西省陆地生态系统的N收支平衡进行了核算,并分析了不同来源N收支量的时间序列特征以及N盈余强度的空间分布特征,探讨了自然灾害和政策实施对N平衡的影响.结果表明：江西省陆地生态系统的N输入量变化范围是（155.5~184.2）×107k.ga-1,平均值为168.5×107kg.a-1.在N输入源中,以生物固N为主,占N输入总量的43.1%;氮肥施用是氮输入的第二大来源,占N输入量的30.9%;大气硝态氮沉降和人畜排泄分别占N输入总量的17.0%和9.1%.人类活动来源的N输入量是自然来源N输入量的2.3~2.9倍.N盈余量变化范围是（39.6~59.0）×107kg.a-1,平均值为47.3×107kg.a-1.系统内N持续发生盈余,必然会导致系统内的N发生累积并最终达到饱和状态,从而增加系统中养分随地表径流和地下水流失和淋失的风险.N盈余强度较高的地区位于环鄱阳湖区,这与该地区农业生产和人口密集、施肥强度高有密切关系,直接威胁到鄱阳湖水体的水质.

英文摘要：

Estimate of the nitrogen（N） mass balance of a terrestrial ecosystem in Jiangxi province for the period 1995—2005 has been made by using the mass balance model.Spatial distributions of the surplus intensities of N are displayed using a geographical information system.Results indicate that the mean annual N inputs vary between 155.5×107 and 184.2×107 kg·a-1,with a mean value of 168.5×107 kg·a-1.Diffuse sources show that biological N fixation constituted the largest source of total N inputs accounting for about 43.1%,while chemical N fertilizer is the second largest contributor,accounting for about 30.9% of the total N inputs.Atmospheric nitrate N deposition and manure N application（including domestic animal and human） account for 17.0% and 9.1% of total N inputs,respectively with N surplus ranging from 39.6×107 to 59.0×107 kg·a-1,showing a stable trend.The surplus intensities of N are highest in the region around the Poyang Lake owing to high intensity agricultural activities,high population intensity and fertilizer utilization.The continuous surplus of N is likely to lead to N saturation in the aquatic ecosystem thus resulting in eutrophication.The study concludes that anthropogenically enhanced N inputs into the ecosystem are about 2~3 times that from natural sources.