基于轨迹分析的2003-2010年华东地区土地覆被变化对土壤水分的影响研究

目的]分析华东地区土地覆被变化过程对土壤水分的影响,以期能够揭示土地覆被变化对土壤水分的影响机理.方法]应用MODIS三级土地覆被产品MCD12Q1,采用轨迹分析方法描述20032010年耕地和林地轨迹变化过程;选择基于AMSR-E土壤水分数据的降尺度反演结果作为描述土壤水分变化的数据,研究华东地区土地覆被变化对土壤水分的影响.结果](1)每种土地覆被类型均有3种轨迹变化形式:研究年限内面积增加的轨迹、面积减少的轨迹、研究年限内未发生面积变化的轨迹;(2)在耕地和林地3种轨迹变化过程中,土壤水分含量均表现出下降的趋势.(3)在林地的3种轨迹变化过程中,土壤水分含量大小顺序为:未发生轨迹变化的林地＞林地面积增加的轨迹＞林地面积减少的轨迹;在耕地的3种轨迹变化过程中,土壤水分含量大小排序为:耕地面积减少的轨迹＞耕地面积增加的轨迹＞未发生轨迹变化的耕地;(4)耕地、林地轨迹变化过程对土壤水分的影响均与时间年限有关,至少需要7 a林地土壤水分含量达到最大值,此时耕地土壤水分含量达到最小值.结论]作为华东地区主要的土地覆被类型,耕地和林地在2003-2010年的所有变化轨迹过程中,土壤水分均呈现下降趋势,且土壤水分随着育林年限和耕种年限的增长分别增加和减小,并在第7 a分别达到最大和最小.

Impacts of Land Cover Change on Soil Moisture in 2003-2010 Based on Trajectory Analysis

Objective] Studying the links of the change process of vegetation cover and soil moisture in East China, to reveal the impact mechanism of the former to the later.Methods] This research described the variation of cropland and forest by trajectory analysis using MODIS MCD₁₂Q₁ and researched the soil moisture variation caused by land cover change on the basis of AMSR-E soil moisture data with high spatial resolution.Results] (1) All kinds of land cover existed three forms:afforestation trajectory; deforestation trajectory; permanent trajectory. (2) Soil moisture showed decreasing tendency in all the trajectories of cropland and forest. (3) For forest trajectories, the order of soil moisture was:permanent forest trajectory > afforestation forest trajectory > deforestation forest trajectory; while for cropland trajectory, the rank was deforestation cropland trajectory > afforestation cropland trajectory > permanent cropland trajectory. (4) The variation of soil moisture caused by land cover was affected by their ages. E.g., soil moisture under forest would take for more than 7 years to reach its maximum capacity, while in cropland, it was minimum at this age.Conclusion] As the main land cover types in East China, forest and farmland''s trajectory in years of 2003-2010 had a downward trend of soil moisture. With the prolonging of forest growth and cultivation, soil moisture of forest and cropland were increased and decreased, respectively,and reached their maximum and minimum values after 7 years of growth and cultivation, respectively.