松嫩平原中南部黑土氮流失程度及分布特征研究

对松嫩平原中南部黑土区20世纪80年代以及目前土壤中氮含量数据资料分析结果显示，近40年来研究区土壤氮的流失率达到5.02%.总体上呈现出土壤氮含量丰富-较丰富的一级、二级土地面积大量减少，而土壤中氮含量中等-缺乏的三级、四级和五级土地面积逐渐增大.对研究区不同土地利用方式土壤氮含量变化特征统计结果显示，研究区人为活动影响较强的水田和旱田两种主要土地利用方式土壤中氮含量丰富区的土地所占面积比例分别减少了20.9和6.1个百分点；人为活动影响相对较弱的沼泽湿地、草地和林地3种土地利用方式土壤氮含量丰富区的面积有所增加.对不同行政区市县土壤氮含量变化特征空间分析结果表明，研究区有6个市县土壤氮流失达到重度程度，建议作为黑土氮流失治理的重点地区；有8个市县（区）土壤氮流失达到中度程度，应作为土壤氮流失防与治兼顾的重点地区.

NITROGEN LOSS DEGREE AND DISTRIBUTION CHARACTERISTICS OF BLACK SOIL AREA IN SOUTH-CENTRAL SONGNEN PLAIN

The analysis of nitrogen content data in the black soil area of south-central Songnen Plain in 1980s and at present shows that the soil nitrogen loss rate is up to 5.02% over the past 40 years, generally with the grades 1 and 2 land area of rich-relatively rich soil nitrogen content greatly reducing and the grades 3, 4, and 5 land area of moderate-deficient nitrogen content gradually increasing. The statistics of variation characteristics of soil nitrogen content by land use types indicate the proportions of paddy field and upland field strongly affected by human activities with high nitrogen content have decreased by 20.9 and 6.1 percentage points respectively, while the areas of marsh wetland, grassland and forest less affected by human activities rich in soil nitrogen content have increased. The spatial analysis on variation of soil nitrogen content in different administrative regions reflects the soil nitrogen loss in 6 cities and counties has reached severe degree, which should be the key areas of black soil nitrogen loss control as suggested. The soil nitrogen loss in other 8 cities and counties/districts is moderate, regarded as the key areas for both prevention and control of soil nitrogen loss.