基于MODIS数据的白芨滩自然保护区人工植被恢复区植被指数研究

Vegetation index of artificial vegetation restoration area in Baijitan Nature Reserve based on MODIS data

基于白芨滩国家级自然保护区2000—2019年的中分辨率成像光谱仪(MODIS)的归一化植被指数(NDVI)和增强植被指数(EVI)时序数据,结合实地踏查和遥感数据,选取了6个研究地区(P1-P6)。通过物候提取和趋势分析等方法,多方面探索了研究区域植被物候变化规律和植被覆盖的时空格局等特征。结果表明:基于NDVI与EVI平均值得出的植被季节物候变化曲线呈现单峰状态,且植被生长季长度略有不同。NDVI与EVI的年最大值及年均值呈波动上升趋势,植被指数的年最大值增长较快,但波动性较大,年均值增长较慢,但波动性较小。因此,在研究该地区植被长期生长变化趋势时,可选择植被指数年均值,以减小误差。2000—2019年研究区域的NDVI与EVI均呈波动上升趋势,各研究区域的NDVI均高于EVI,且NDVI的上升趋势明显,拟合程度更好,并未出现随植被生长而达到饱和状态的现象。这说明在研究小尺度荒漠地区植被生长变化趋势时,NDVI比EVI更敏感且更稳定。

6 study areas(P1-P6)across Baijitan Nature Reserve were selected as the research object,and time series data of NDVI and EVI during 2000—2019 from Moderate Resolution Imaging Spectroradiometer(MODIS)images as well as field survey and remote sensing data were analyzed via phenological index extraction and trend analysis.Seasonal phenological dynamic curves based on multi⁃year averages of NDVI and EVI both demonstrated single peak despite minor differences on length of season(LOS).The annual maxi⁃mum value and mean value of NDVI and EVI both showed a fluctuating upward trend;the annual maximum values of NDVI and EVI increased rapidly with severe fluctuation,while the annual average value increased slowly with subtle fluctuation,indicating the appli⁃cability of annual average value of vegetation index on studying long⁃term growth trend of vegetation coverage in this area for the sake of less error.NDVI and EVI data both showed a fluctuating upward trend during 2000—2019 in the study areas;NDVI generally had greater values and steeper growth than those of EVI for each study area,indicating that NDVI had greater fitting degree,and it had not reached saturation with vegetation growth.Therefore,NDVI was likely to be more sensitive and stable than EVI when studying the change trend of vegetation growth in small⁃scale desert areas.