基于草地综合顺序分类法的CASA模型改进

An Improved CASA Model Based on Comprehensive and Sequential Classification System of Grasslands

将任继周等提出的草原综合顺序分类法的草原分类气候指标>0℃年积温(Σθ)和湿润度指标(K)引入CASA模型,对水分胁迫因子的计算进行改进,避免了复杂的土壤参数,仅用>0℃年积温和K值就可计算水分胁迫因子,极大地简化了模型。同时调整了CASA模型最大光能利用率的固定取值,使之成为适合中国草地净第一性生产力(NPP)估算的模型。改进的CASA模型实现了草地NPP模拟与草地综合顺序分类系统的耦合,能更好地反映草地类型与草地NPP的关系,为研究草地NPP的区域分布和全球分布提供了理论依据。

The 0℃ average annual cumulative temperature（Σθ） and grassland moisture index（K） in Ren Jizhou＇s Comprehensive and Sequential Classification System of Grasslands were introduced in CASA model to account water stress factor in this study.The water stress factor can be calculated only by Σθ and K in the improved model,complex soil parameters were avoided,so it was greatly simplified.The maximum light use efficiency was adjusted to make it suitable to estimate the grassland NPP in China.The improved CASA model implements the coupling of simulating grassland NPP and Comprehensive and Sequential Classification System of Grasslands.So,it can reflect the relationship between rangeland type and grassland NPP better,and it provides a theoretical basis for identifying the regional and global distribution of grassland NPP.