宁夏自2000年后实施退耕还林以来,局部地区的生态环境得到明显改善,为探求近15来年宁夏地区植被的动态变化及其影响因子,本文以MOD13Q1为数据源,结合DEM数据、土地利用分类图,采用Sen+Mann-Kendall非参数检验方法和Hurst模型,分析了宁夏不同行政区、不同海拔、不同坡度、不同坡向及不同植被类型生长季NDVI的空间变化特征及未来变化趋势;并利用重心迁移模型和转移矩阵分析宁夏2000-2014年间植被覆盖的时空演变特征。结果表明:(1)从空间分布看,宁夏南部六盘山、北部贺兰山及引黄灌溉区植被长势较好,中部干旱地区植被长势较差;且植被NDVI与海拔高程和坡度呈显著正相关。(2)从植被覆盖的转移矩阵看,较高植被覆盖的面积占比从2000年的17.29%增长到2014年的31.55%,主要是由较低植被覆盖转化而来的。(3)从重心迁移方向看,中度植被覆盖和较高植被覆盖的重心迁移最为明显,分别向东北方向偏移了129.49 km和向东南方向偏移了89.49km。(4)从变化趋势看,生长季植被NDVI整体呈上升趋势,明显改善的面积占总面积的59.63%,轻微改善区域占31.72%;林地和水田显著改善的面积分别占总面积的71.50%和70.80%;显著改善的面积比例随海拔高程和坡度的增加均先增加后减少,且南部各行政区植被改善的面积均高于北部。(5)从可持续性看,植被恢复的持续性较强,89.24%的植被NDVI呈现持续改善的趋势;南部地区的持续改善的面积大于北部地区。
In order to ascertain the dynamics of vegetation and its impacting factors in the period of 2000-2014,based on MOD13Q1, the DEM data, and the land use classification map, this study analyzed the characteristics of the spatiotemporal distribution and future trends of the administrative areas of Ningxia Autonomous Region at different altitudes and slopes, as well as with different types of vegetation, using the Sen + Mann-Kendall nonparametric test, the Hurst index, and other methods. Based on the center of gravity migration model and transition matrix, this study analyzed the temporal change of vegetation patterns from 2000 to 2014. The results are as follows:(1) NDVI values were high in the north and the south, but low in the central area, due to its arid condition; NDVI values were significantly positively correlated with elevation and slope.(2) The transition matrix of vegetation coverage shows that the percentage of area of higher vegetation grew from 17.29% in 2000 to 31.55% in 2014, which was mainly developed from lower vegetation coverage in the beginning of the period.(3) The center of gravity migration direction indicates that moderate and higher vegetation cover centers moved:the moderate vegetation cover center migrated toward the northeast by 129.49 km, and the higher vegetation cover center migrated toward the southeast by 89.49 km.(4) The trends of NDVI show that overall, NDVI of Ningxia improved from 2000 to 2014. The area where the values of NDVI significantly increased accounted for59.63% of the total area, while the slightly improved area accounted for 31.72% of the total. The significantly improved area of woodland and paddy accounted for 71.50% and 70.80% of the total woodland and paddy areas.The significantly improved area of NDVI firstly increased and then decreased with the increase of elevation and slope. The area in the south with increased NDVI was larger than that in the north.(5) The trend of NDVI change indicates that vegetation restoration in Ningxia is susta