基于MODIS数据的植被物候时空变化

Spatio-temporal variation of vegetation phenology using MODIS data

植物物候是地表植被对气候变化响应的指示器,研究植物物候时空变化规律对理解其对气候变化的响应机制、预测植被变化具有重要意义.基于2001—2014年MODIS植被物候数据,经过图像拼接和转投影等预处理操作后,分别统计分析了5个自然区的森林、灌木和草原物候的时空变化.结果表明:①在高纬和高海拔地区,我国自然植被物候多年平均生长季节始期(begin of growing season,BGS)较晚,末期(end of growing season,EGS)较早,这一现象很好地反映了地形和气候的地域分异规律;森林、灌木和草原BGS之间的差异在气候温度低的区域大,森林、灌木和草原EGS之间的差异在气候干旱的区域大.②从植被物候的变化趋势来看,灌木的BGS以推迟趋势为主,森林和草原的BGS以提前趋势为主,森林、灌木和草原的EGS均以推迟为主.从平均结果看,我国5个自然区植被BGS呈现提前趋势,植被EGS呈现推迟趋势,但变化速率变缓,仅有16%的像元通过了显著性检验(P<0.1).③植被物候在年际上的波动程度远小于其在空间上的变化.植被BGS时间标准差约1~3 d,植被EGS的时间标准差略大,约为2~6 d.

Vegetation phenology is an indicator of the response of surface vegetation to climate change,so it is important to study the temporal and spatial variation of vegetation phenology for understanding the mechanism of vegetation response to cli-mate change and predicting vegetation change.The temporal and spatial changes of forest,shrub and grassland phenology in five natural regions were analyzed after image mosaic,transparence and other preprocessing operations based on the MODIS vegetation phenology data from 2001 to 2014.The results show that:①In high latitudes and high altitudes regions,the multi-year average BGS(begin of growing season)of natural vegetation phenology in China is later and EGS(end of growing season)is earlier,which well reflects the regional differentiation rule of topography and climate.There is a wide gap between forest,shrub and grassland BGS in regions with low climate temperature,and between forest,shrub and grassland EGS in regions with drought climate.②The BGS of shrub mainly delay,while the BGS of forest and grass mainly advance,and the EGS of forest,shrub and grass mainly delay from the view of the change trend of vegetation phenology.The BGS of vegetations in five natural regions of China show an advance trend,and the EGS of vegetations show a delay trend from the view of average results.But the change rate become slower,only 16%of the pixels pass the significance test(P<0.1).③The annual fluctuation of vegetation phenology is much less than its spatial variation.The annual standard deviation of vegetation BGS is about 1-3 d,and that of vegetation EGS is slightly larger,about 2-6 d.