2001-2014年海南岛植被覆盖时空变化特征

Spatiotemporal Variable Vegetation on Hainan Island During 2001-2014

基于2001—2014年MODIS NDVI数据,采用趋势分析法、标准差法、Hurst指数法以及相关系数分析法研究了海南岛植被覆盖变化特征,结合气象数据及统计年鉴数据分析了气候变化及人类活动对植被覆盖变化的影响情况。研究表明:近14年海南岛NDVI呈显著增加趋势,增速为0.02/10a(p<0.01);空间分布上,植被覆盖呈由中心向四周递减的分布格局,高值区分布于中部山区市县;波动变化特征变现为中间波动小,四周波动大,高波动和较高波动区所占的比重为42%,高波动区主要集中于海口、琼海、万宁、东方、乐东等市县沿海区域;在趋势上,海南岛14年间植被覆盖变化以改善为主,轻度改善和中度改善所占比重为53.42%,其中22.65%的区域呈显著增加;Hurst指数表明研究区未来NDVI变化趋势呈持续性和反持续性的比重分别为57.21%和42.71%,其中持续改善和由退化转为改善的面积分别占11.15%和40.90%。海南岛植被生长年际变化受降水影响要强于气温,人类活动也是影响植被覆盖变化的重要因素。

The variation of vegetation indicates the changes of global and regional environment.In this paper,spatial and temporal patterns of vegetation on Hainan Island were explored by using MODIS NDVI data from-2001 to 2014 based on Theil-Sen median method and standard deviation.Then,the future vegetation change tendency was analyzed based on Hurst exponent.Specially,the influence of climate change and human activities were assessed based on temperature,precipitation,and urbanization rate.The results showed that：（1）the annual NDVI values showed a significant increasing trend at an annual rate of 0.02 per year over the study period;（2）the vegetation standard deviation showed obvious characteristics：high at the boundary and low in the middle,and the high variation was apparent across 42% of the land,mainly distributed around the coastal areas of Haikou,Qionghai,Wanning,Dongfang,Ledong;（3）as a whole,the NDVI values of Hainan Island showed an upward trend of improvement,specifically,areas where improvement levels were light and moderate accounted for 53.42% of all area during 2001—2014,significantly improved with 22.65% of the region′s vegetation;（4）the percentage of anti-persistence was 57.21%,and 42.71% for persistence.The four change characteristics of future vegetation were degradation into improvement,continual degradation,improvement into degradation,and continual improvement,and the percentages were 40.9%,34.1%,13.94%,and 11.15%,respectively;（5）the vegetation variation was influenced by precipitation even more than temperature;moreover,in EL Nino years,34.48% of NDVI pixels showed positive anomaly,while 65.52%showed negative anomaly,conversely,63.01% of NDVI pixels showed positive anomaly,while 36.99%showed negative anomaly for La Nina years;（6）the vegetation presented a upward trend based on the increase of afforested area,while urbanization can induce negative effect on vegetation growth.