中文摘要：

草原综合顺序分类理论自20世纪50年代提出以来,其完善的基本理论构架和定量化潜力已经使其成为草地生态系统研究科学性的代表.在草原综合顺序分类系统第1级——“类”的定量化研究方面取得了丰硕的成果,建立了检索图.但自该体系建立以来,由于数据获取困难,定量技术限制等原因,一直未开展第2级分类的定量化研究.论文以草原综合顺序分类系统的第2级——“亚类”为研究对象,在对亚类的分类指标——地形（地貌）和土壤的发生和分类进行综合分析的基础上,提出了在草地亚类划分中进行定量化分类的方法和原则,并以甘肃省为研究区域,进行了亚类的划分实践.首先,确定在山地使用地形（地貌）因子,在平原使用土壤亚类进行草地亚类划分,具体将甘肃省山地和平原按照坡度＞3°,连续面积达到6 km2以上,划分为山地,其余划分为平原;在SRTM-DEM数据基础上,提取了坡度、海拔、地势起伏度、山地和平原等因子,将甘肃省划分为20个基本地貌类型单元;利用SRTM-DEM提取的地形坡度、坡向、曲率等数据和MODIS数据中MODIS09GA、MODIS13 A2影像提取和反演的土壤亮度、植被指数、水体指数、土壤温度、湿度指数、纹理特征等信息,通过监督分类,将甘肃省的土壤亚类定量划分为36个类型;在此基础上,在山地使用地貌分类指标,在平原使用土壤分类指标将甘肃省草地划分为568个草地亚类.研究结果可以为完善草原综合顺序分类系统,建立类与型之间的桥梁,并最终推进该系统三级分类体系的实用化提供研究思路和方法参考.

英文摘要：

A comprehensive and sequential classification system of grasslands （CSCS）,a well known grassland classification systems proposed in the 1950s in China,represents a theoretical framework and quantitative potentiality for the science of grassland ecosystem study.At the basic level of a quantitative classification study of CSCS,a considerable achievement has been made and an index chart for determining grassland class has been established.However,owing to the limitations of techniques,relevant reports on quantitative subclass study are infrequent.Based on analysis of the classification subclass indexes this dissertation puts forward the quantitative principles and methods of subclass grasslands,and subclasses classified in Gansu Province.1） The quantitative index system and index chart for grassland subclass are established; 2） The basic geomorphologic types are divided into 20 types in Gansu Province by extracting the slope,attitude,roughness,mountain and plain factors from SRTM-DEM data; 3） Using supervised classification,36 soil subtypes have been obtained in Gansu Province by extracting the slope,aspect,curvature factors from SRTM-DEM data and soil brightness,vegetation index,NDWI,NDSI and NDMI from MODIS data; 4） 568 subclasses of grassland have been obtained by operating the grid algebra on the grassland first class map,the basic geomorphologic types map and the soil subtypes map.