基于MODIS-NDVI的2000—2018年中国北方土地沙化敏感性时空变化

选择植被覆盖度、湿润指数、大风日数、土壤表层砂粒含量和坡度5个因子作为评价指标,基于多源数据开展了中国北方14省（区）2000—2018年土地沙化敏感性空间分布格局及其动态变化研究,并按土地易起沙尘程度的高低依次划分为极易起沙尘和高度易起沙尘（高敏感等级）、中等易起沙尘（中敏感等级）、轻度易起沙尘和不易起沙尘（低敏感等级）。结果表明：2000—2018年中国北方14省（区）处于土地沙化高敏感等级的面积从48.1%下降至40.4%,处于土地沙化低敏感等级的面积从30.3%上升至38.8%,整体呈土地沙化高敏感等级向中、低敏感等级过渡的趋势。与2000年相比,2018年内蒙古科尔沁、浑善达克和毛乌素沙地及其周边区域极易起沙尘和高度易起沙尘的土地面积明显减小,植被覆盖度的增加和大风日数的减少是这种变化的重要原因。

Spatio-temporal change of land desertification sensitivity in Northern China from 2000 to 2018 based on MODIS-NDVI

Analysis of land desertification sensitivity is an important part of the wind break and sand-fixation ecological function assessment. The spatial distribution pattern and dynamic change of land desertification sensitivity in 14 provincial-level regions of Northern China from 2000 to 2018 were evaluated with the vegetation coverage, moisture index, days of strong wind, slope and sand content in surface soil as evaluation indexes. Five classes of land desertification sensitivity ranging from extreme to low were generated, namely extreme sensitivity zone and high sensitivity zone (high-sensitive desertification grade), moderate sensitivity zone (moderate-sensitive desertification grade), low sensitivity zone and non-sensitivity zone (low-sensitive desertification grade). Results showed that the land area of high-sensitive desertification grade decreased from 48.1% to 40.4% with a decline of 0.4% per year, and the land area of low-sensitive desertification grade increased from 30.3% in 2000 to 38.8% in 2018, showing the tendency of transition from high-sensitive desertification grade to middle and low-sensitive desertification grade in Northern China. The spatial distribution pattern of land desertification sensitivity in 2000, 2010 and 2018 showed that area of high-sensitive desertification grade was mainly distributed in the desert aggregation zone and its adjacent areas in the western and Northern China, with low vegetation coverage, and dry and windy climate; area of low-sensitive desertification grade was mainly distributed in Da and Xiao Hinggan Mountains, Changbai Mountains and Qinling Mountains with high vegetation coverage and relatively humid climate; area of moderate-sensitive desertification grade was located in the buffer areas of the two. Compared with 2000, the sensitivity of land desertification in the desert aggregation zone in the western and Northern China remained stable, however, the land area of high-sensitive desertification grade in Mu Us sandy land, Horqin sandy land and Hunshandake sandy land, which were located in Inner Mongolia, Ningxia and their surrounding area, decreased significantly in 2018. The remarkable increase of vegetation coverage caused by the temperature rising, precipitation increasing and a series of ecological protection engineering as well as the decrease of strong wind days were important factors for this change.