基于MODIS植被指数的浑善达克沙地植被物候变化

基于近20a MODIS的2种植被指数数据，利用Logistic曲线曲率极值法和动态阈值法，对浑善达克沙地植被物候进行了提取，分析其时空变化，并利用研究结果数据，分析植被物候对高程和气象因子的响应.结果表明，2000~2019年间研究区的植被物候呈微弱波动趋势，浑善达克沙地植被返青期（SOS）主要集中在110~140d，枯黄期（EOS）主要集中在250~280d，整体呈微弱推迟趋向（0.28d/a），生长季长度（LOS）主要集中在120~170d，整体呈微弱延长趋向（0.23d/a）.在空间分布上，占研究区51.51%的区域植被SOS呈提前趋势；占研究区67.02%的区域植被EOS呈提前趋势，并且占研究区32.98%的区域植被EOS呈推迟趋势.占研究区62.71%的区域植被LOS呈延长趋势.在海拔900~1500m区间，随着海拔升高，SOS显著推迟，EOS不显著提前，LOS显著缩短.前一年11、12月和当年1、2、4月降水量对SOS有提前作用.6、7、8、9月份气温和降水都对EOS推迟有明显的作用.总的来说，浑善达克沙地植被物候与气候因子的相应规律比较复杂，表现出季节性的差别及地形的差异性.

Research on vegetation phenological changes in the Otindag sandy land Based on MODIS NDVI and EVI

Based on the MODIS NDVI and EVI data in recent 20 years, the vegetation phenology in Otindag sandy land was extracted by using the extreme curvature method of logistic curve and dynamic threshold method, and its temporal and spatial changes were analyzed. The response of vegetation phenology to elevation and meteorological factors was analyzed by using the research result data. The results indicated that the vegetation phenology in the study area showed a slight fluctuation trend from 2000 to 2019. The start of growth season (SOS) was concentrated in 110~140 Julian day, while the end of growth season (EOS) was in 250~280 Julian day and was delayed (0.28d/a). The length of growth season (LOS) was in 120~170 Julian day and was lengthened (0.23d/a). For the trend, SOS was showed a decreasing trend which occupied 51.51% of the total study area. EOS was showed an increasing trend in 32.98% of the study area while the rest decreased. LOS of the area accounted for 62.71% of the study area was showed a prolonged trend. In the altitude range of 900~1500m, SOS was significantly delayed, EOS was not significantly advanced, and LOS was significantly shortened as the altitude increased. The precipitation had an advance effect on SOS in January, February, April and November, December of the previous year. The temperature and precipitation had an obvious effect on the delay of EOS from June to September. On the whole, the responses of phenology to meteorological factors in Otindag sandy land were complex, showing obvious seasonal differences and topographical variability.