Wu Dong, Huang Zhi-Lin, Xiao Wen-Fa, Zeng Li-Xiong, Han Li-Yang
Key Laboratory of Forest Ecology and Environment, State Forestry Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University , Nanjing 210037, China.
Huan Jing Ke Xue. 2016 Aug 8;37(8):2940-2946. doi: 10.13277/j.hjkx.2016.08.015.
The nitrogen (N) output in Lanlingxi watershed of Three Gorges Reservoir Area in 2015 was monitored and the current land use map was investigated. Cluster analysis and correlation analysis were used to identify the major sources of pollutants and to discriminate the source and the sink land use types. The effects of land use on N exports were quantitatively analyzed by stepwise regression analysis. The results showed that: ① After the returning farmland to forest project the land use structure of this area changed dramatically. The area proportions of forest land and garden plot increased to 76.85% and 13.87% respectively, and the proportion of cultivated land dropped to 1.16%. Cultivated lands were stellate distributed and garden plots in some catchments were flake distributed. ② The content of TN in some monitoring points surpassed the Class V standard of the national groundwater environmental quality. The ammonium-N (NH-N) concentrations ranged 0.089-0.214 mg·L, 2.925-13.203 mg·L for nitrate-N (NO-N) and 3.561-14.572 mg·L for total-N (TN). And NO-N accounted for more than 80% of TN. ③ There were significant positive correlations between garden plot, residential land and N loss, and negative correlations between forest land, unutilized land and N export, which indicated that the former were N sources and the latter were sinks. ④ Forest land area should be increased and garden plot should be controlled, and the area ratio of residential land should be kept below 5% when adjusting land use structure of this watershed. Moreover, forest-tea and forest-fruits modes should be applied to change single land use type of garden plot in some catchments.
对三峡库区兰陵溪流域2015年的氮（N）输出进行了监测，并调查了当前的土地利用图。采用聚类分析和相关性分析来识别污染物的主要来源，并区分源和汇土地利用类型。通过逐步回归分析定量分析了土地利用对氮输出的影响。结果表明：①退耕还林工程实施后，该地区土地利用结构发生了显著变化。林地和园地面积比例分别增加到76.85%和13.87%，耕地比例降至1.16%。耕地呈星状分布，部分流域的园地呈片状分布。②部分监测点的总氮含量超过国家地下水环境质量Ⅴ类标准。铵态氮（NH-N）浓度范围为0.089 - 0.214mg·L，硝态氮（NO-N）为2.925 - 13.203mg·L，总氮（TN）为3.561 - 14.572mg·L。且硝态氮占总氮的80%以上。③园地、居民用地与氮流失之间存在显著正相关，林地、未利用地与氮输出之间存在负相关，这表明前者是氮源，后者是氮汇。④在调整该流域土地利用结构时，应增加林地面积，控制园地面积，居民用地面积比例应保持在5%以下。此外，应采用林茶、林果模式改变部分流域园地单一的土地利用类型。
