青海省东部农业区植被覆盖时空演变遥感监测与分析

基于象元二分模型,利用MODIS植被指数产品定量估算研究区2000—2009年生长季(4—9月)植被覆盖度,采用相关系数法和有序聚类分析方法对植被覆盖度时空变化趋势及突变进行了分析,并结合DEM分析其对地形因子的响应。结果显示:1)研究区2000—2009年整体植被覆盖度在波动中呈不显著增加趋势,其中2001年是显著突变年份,表明研究区植被覆盖度发生比较显著的变化;2)通过对地形因子的响应分析,植被覆盖度在高程2500m和4100m,坡度4°和26°发生突变;对各高程带、坡度带植被覆盖度年际变化趋势及突变年份进行分析,获得了各带的变化趋势及其突变年份。对研究获得的结果进行讨论,结果表明:研究区降水量的变化及退耕还林措施是植被覆盖度变化的重要影响因素,其中退耕还林措施对植被覆盖度变化的影响较大。

Spatiotemporal variation of fractional vegetation cover and remote sensing monitoring in the eastern agricultural region of Qinghai Province

Based on dimidiate pixel model, the normalized difference vegetation index (NDVI) datasets deduced from MODIS product were used to calculate the fractional vegetation cover (FVC) in the eastern agricultural region of Qinghai Province in vegetation growing season(Apr.-Sep.) from 2000 to 2009. The correlation coefficient method and the ordered clustering analysis method were applied to detect the spatiotemporal trend and identify abrupt change points. In addition, DEM was considered to investigate the influence of terrain factors on fractional vegetation cover. The results indicated that: 1) fractional vegetation cover of the study area showed a slightly upward trend from 2000 to 2009 and the change was not significant; The year of 2001 was a significant abrupt change point, suggesting that the fractional vegetation cover changed significantly. 2) According to the analysis of fractional vegetation cover responding to terrain factors, the abrupt change points of fractional vegetation cover can be found at: 2500 m and 4100 m in the elevation zones, 4 degrees and 26 degrees in the slope zones, respectively. The trend and the abrupt change points in each specific elevation zone and slope zone were obtained through the investigation of interannual variation and abrupt change year between fractional vegetation cover and both elevation and slope zones. Furthermore, the contributing factors to spatiotemporal variation of fractional vegetation cover and its responding to terrain factors were further discussed. It can be conclude that changes in precipitation and returning cultivated land into forest measurs were the important influence factors, but the latter had a greater influence.