基于CASA模型的藏北地区草地植被净第一性生产力及其时空格局

Grassland net primary productivity and its spatiotemporal distribution in Northern Tibet:A study with CASA model

基于1981-2004年遥感监测和气象数据，采用CASA（Carnegie-Ames-Stanford Approach）模型模拟分析藏北地区草地植被净第一性生产力（NPP）及其时空变化特征．结果表明：受水热条件的制约，藏北地区草地植被NPP空间分布规律呈水平地带性分布，由东南向西北逐渐由230gC·m^-2·a^-1减少到接近0．藏北地区草地植被NPP整体水平较低，年均草地植被总NPP为21．5×10^12g C·a^-1，多年平均值仅为48．1g C·m^-2·a^-1，明显低于青藏高原和其它草原区．藏北地区坡度小于1°平地和平滩地，以及南坡的草地植被年平均NPP相对较低．藏北主要高寒草地7-9月NPP占全年NPP的64．0％～70．0％．1981-2004年间，藏北地区草地植被总NPP的年际变化较大，并有进一步下降趋势．

Based on the remote sensing data, meteorological data and other related data from 1981 to 2004, the grassland net primary productivity （NPP） and its spatiotemporal distribution in Northern Tibet were analyzed by CASA （Carnegie-Ames-Stanford Approach） model. The results indicated that in the study area, the spatial distribution of grassland NPP was affected by the local water and heat conditions, and represented a horizontal zonality. From southeast to northwest, the grassland NPP reduced from 230 g C·m^-2·a^-1 to near 0 g C·m^-2·a^-1. The overall level of grassland NPP in Northern Tibet was rather low, with the multi-years average value of total NPP being 21.3×10^12 C·a^-1 and the mean value of NPP being 48.1 g C·m^-2·a^-1 , which were obviously lower than those in Qinghai-Tibetan Plateau and other grassland areas of China. The mean values of NPP on fiat land （slope gradient 〈 1°） and south slope were relatively lower. On the main alpine grasslands in Northern Tibet, the NPP from July to September occupied 64. 0%-70.0% of the whole year. From 1981 to 2004, the grassland NPP within the whole Northern Tibet had a greater annual fluctuation, and tended to further reduce.