利用CASA模型估算黑河流域净第一性生产力

陆地生态系统是维系生物圈乃至人类存在与发展的生命支持系统。该系统净第一性生产力估算研究有助于寻找陆地植被从大气中固定碳的数量及影响其时空分布的驱动因子。基于CASA(Carnegie Ames Stanford Approach)模型,结合多光谱遥感数据和气候数据,模拟干旱半干旱典型区黑河流域1998~2002年净第一性生产力的时空分布,并分析和探讨了上、中、下游NPP的驱动因子。研究结果证明CASA模型适用于内陆河流域范围内NPP研究;通过分析黑河流域上、中、下游的NPP变化与气温、降水、太阳辐射和NDVI的相关关系,发现上游山区NPP与热量相关性显著,中游地区由于人工绿洲对水资源的截留用于作物灌溉,NPP相对稳定,下游的NPP受热量和水分因素共同复杂控制。

Estimation of Heihe Basin Net Primary Productivity Using the CASA Model

The terrestrial ecosystem is the supporting system for the biosphere as well as for human being’s survival and development. The research of net primary productivity will help in understanding the amount of carbon fixed by terrestrial vegetation and its influencing factors. The purpose of this paper was to find out the NPP spatial and temporal dynamic distribution in the Heihe Basin during 1998 to 2002, and analyze vegetation’s feedback on climatic conditions. The CASA (Carnegie Ames Stanford Approach) was selected to calculate NPP. The SPOT/VEGETATION, land use/land cover, meteorologic data and soil attribute were collected. The results validate the CASA’s applicability in inland watershed scale. The 5 years NPP variation in the Heihe Basin was monitored by the model. The upper, middle and lower reaches of the Heihe Basin contributed ~50％,~30％ and ~20％ to the total NPP of the basin respectively. From 1998 to 2000 the NPP decreased and then increased from 2000 to 2002. The NPP in the upper reaches of the basin was mainly controlled by heat because the vegetation seldom faced the problem of moisture shortage, and the NPP increased when temperature increased. The NPP in the middle reaches of the basin also had good relationship with heat. The reason was that the cropland plants could get adequate water supply when necessary because there were many reservoirs set up for irrigation system and factories. The NPP variation in the lower reaches of the basin was larger than upper and middle, and had weak relationship with meteorologic factors. The vegetation endured drought throughout the year and high temperature in summer. It seldom obtained water supply, even from the oasis along the river because of water interception by the middle reaches reservoirs. Desert plants mainly lived on groundwater to survive in case of drought.