青藏高原植被覆盖对水热条件年内变化的响应及其空间特征

利用1982-2000年NOAA/AVHRR卫星的NDVI数据(时间分辨率旬,空间分辨率8 km×8 km),结合同时期的气温和降水资料,基于时滞互相关方法和GIS工具,分析了青藏高原植被覆盖对水、热条件年内变化的时滞响应及其空间特征。结果如下:①除高寒荒漠、森林外,青藏高原植被NDVI与同期旬均温和旬降水相关性均呈高度正相关。其中,中等覆盖度的植被受水、热影响表现更为强烈。②青藏高原植被NDVI对气温和降水有滞后效应,且滞后水平存在空间差异,高原北部(柴达木盆地、昆仑山北冀)和高原南部植被对降水、和温度的响应比较迟缓,而高原中、东部地区植被对温度和降水的响应比较敏感。③不同植被类型对水热条件的响应程度也存在差异,由高到低依次是草甸、草原、灌丛、高寒垫状植被、荒漠,最后是森林。

Seasonal Time Lag Response of NDVI to Temperature and Precipitation Change and Its Spatial Characteristics in Tibetan Plateau

Today.human activities become more and more intense.How to minimize human disturbance is very important in the study of the relationship between vegetation and climate.The Tibetan Plateau,a8 one of the few extensive regions escaped from human disturbance,provides an ideal site for studies on the response of natural vegetation cover to water/thermal conditions.Based on the trend surface of TN(short for time series of ten-day NDVI),TP(short for time series of ten-day rainfall)and 3T(short for time series of ten-day temperature),which all are multi-year means,ARCGIS9.2 software and lag cross-correlation method are used to analyze the temporal and spatial characteristics of the relationships between water/thermal climate elements and vegetation cover.The main results are as follows:(1)Except high-cold desert vegetation and forest vegetation,the TN has very good correlation with TT and TP on the Tibetan Plateau,especially in the areas with a vegetation cover of moderate density,such as meadow and grassland.(2)NDVI has a hysteresis effect towards temperature and preeipitation and in the northern part(Qaidam Basin and the north of Kunlun Mountains)and southern part of the Tibetan Plateau,the vegetation responds to the water/thermal changes slowly,but in the middle and east parts of the Tibetan Plateau,the vegetation responds to the water/thermal changes quickly;(3)Different vegetation types respond to water/thermal condition differently.The descending order of the responding degree for each vegetation type is:alpine cold meadow,alpine cold grassland,alpine cold brush,periglacial cushion vegetation,desert,and forest.