青藏高原1982—2007年植被降水利用效率空间格局特征分析

Spatial Characteristics of Precipitation Use Efficiency on the Qinghai-Tibet Plateau From 1982 to 2007

植被降水利用效率(PUE)是指植物光合作用生产的干物质即净初级生产力(NPP)与年降水量之比,是反映生态系统水碳循环相互关系的重要指标.利用气象数据、植被类型数据和归一化植被指数数据,应用改进型CASA模型,模拟出了青藏高原地区1982—2007年的NPP,并进而计算出青藏高原地区的PUE数据,分析了近26年来青藏高原地区PUE的空间格局特征.结果表明:青藏高原PUE基本呈东部高,中西部低的空间格局,26年来青藏高原地区平均PUE为0.751 gC·m^(-2)·mm^(-1).青藏高原各植被类型PUE均值大小顺序为:阔叶林>栽培植物>草甸>针叶林>灌丛>草原>荒漠>高山植被.青藏高原地区PUE均值受到海拔高度和植被类型的共同影响,当海拔高度相同时,PUE大小受到植被类型的影响要大,但当植被类型相同时,PUE随海拔高度的升高而递减.

Precipitation use efficiency （PUE）, a ratio between the net primary productivity （NPP） and the annual precipitation, can be regarded as a key index to reflect the ecosystem water-carbon coupling. The data of PUE on Qinghai-Tibet Plateau during 1982-2007 were simulating by fully applying meteorological data, remote sensing data （NOAA AVHRR and SPOT VEGETAION） and vegetation information using the advanced CASA model. Then based on the 26-year data, the sphtial distribution of vegetation＇s PUE, the distribution and variability of main vegetation types＇ PUE were calculated at full length. The results show that, the PUE on Qinghai-Tibet Plateau decreased from East to Midwest; the mean PUE of vegetation during the 26 years was 0. 751 gC · m^-2 · mm^-1. Furthermore, the PUE values of various vegetation types in Qinghai-Tibet Plateau ranked from large to small as follows： broad-leaved forest, cultivated plants, mixed broadleaf-conifer forest, swamp, meadow, coniferous forest, shrub, tussock, grasslands, desert, and mountain vegetation. PUE on Qinghai-Tibet Plateau is affected by both altitude and vegetation type. When the altitude is the same, PUE is were influenced by type of vegetation, and when the vegetation type is the same, PUE would decrease while altitude increases.