松嫩平原西部草地的时空变化特征

Spatio-Temporal Variation of Grassland in Western Songnen Plain

本文以遥感信息作为主要数据源，以地理信息系统为主要手段，首次对松嫩平原西部地区不同覆盖度的草地资源以及草地内部结构的时空变化进行了深入分析，得出了1989年。2001年间高、中、低覆盖草地之间以及与其它土地利用类型之间的相互转化数量和特征。结果表明，12年间研究区3种草地类型的面积均有不同程度的减少，其中，它们转化为旱田的比例分别占转移总面积的77．78％、70．13％和36．57％，说明人类对草地的持续开发是造成草地面积减少的主要原因。从与盐碱地之间的相互转化关系来看，3种草地类型转化为盐碱地的面积比例随着草地覆盖率的减少而增大，比例分别为0％、4．62％和32．81％，可见植被覆盖率对于草地盐碱化的发生起决定作用。从草地内部结构的动态变化来看，呈现高覆盖向中覆盖再向低覆盖的运级退化特征，而且这种演替规律在当前人类活动下基本上为不可逆过程，草地的退化在空间上主要集中在镇赉县的北部、洮南市的南部、通榆县的北部以及乾安县的西部。本文最后从合理利用研究区现有的草地资源、综合进行草地盐碱化的治理出发，提出了生态环境修复和草地可持续发展的对策。

This paper analyzed temporal and spatial variation of various vegetation fractions and inner configuration of the grassland in western Songnen Plain where ecological environment was fragile based on the remote sensing data and classification of grassland resource with the support of GIS technology. It educes the quantities and characteristics of transformation among higher-coverage grassland, mid-coverage grassland, and lower-coverage grassland and other land use types from 1989 to 2001. The results indicate that the areas of three kinds of grassland are decreasing during 12 years. The transformation proportions to glebe are 77.78%, 70.13% and 36.57% respectively, which illuminate that the main reason for the decrease of grassland is human＇ s durative exploitation of grassland. The transformation proportion from grassland to saline-alkalized land increases with the decrease of grassland＇ s vegetation fraction and is 0%, 4.62%, and 32.81% for higher-coverage grassland, mid-coverage grassland and lower-coverage grassland, respectively. It shows that a crucial factor for saline-alkalized grassland is vegetation fraction. From the dynamic changing of grassland＇ s inner configuration, we conclude that degenerative characteristic of grassland is from higher-coverage to mid-coverage and from mid-coverage to lowercoverage; moreover, the evolution is almost non-reversible under the current human activities. The degraded grassland is mostly located at the north of Zhenlai County, the south of Taonan City, the north of Tongyu County and the west of Qian＇ an County. Analysis of saline-alkalized grassland show that the most important reason causing saline-alkalized grassland is the continuous impact of human activities, and the status of mid-coverage grassland is the key affecting holistic quantity of grassland and the outspread speed of saline-alkalized grassland. Therefore, the only way for socio-economic and ecological environmental sustainable development is to utilize grassland resource soundly and restore the saline-alkalized grassland synthetically. At the end, the authors put forward the measures of ecological environmental restoration and grassland＇ s sustainable development based on rational utilization of existing grassland resource and integrative prevention and rehabilitation of saline-alkalized grassland in research area.