金衢盆地丘陵荒山土地退化评价及其时空分异特征——以兰溪市上华试验区为例

ASSESSMENT OF LAND DEGRADATION AND ITS SPATIAL AND TEMPORAL VARIATION IN THE UNRECLAIMED HILLS AND PLATFORMS OF THE JINHUA——QUZHOU BASIN: A CASE STUDY

本文根据联合国土地退化和土地荒漠化定义，结合研究区特点，提出以植被覆盖度、侵蚀地貌形态和地面组成物质作为丘陵荒山土地退化程度的评价指标，既反映了植被的退化和土地表面形态的退化，又反映了土壤的退化。以此为基础，进而通过两期航空相片的解译，完成了研究区５０年代和８０年代丘陵荒山土地退化程度的模糊数学半定量评价和制图。分析表明，不同等级退化土地约占全区土地总面积的３６％，其中严重和剧烈退化的土地约占５％；退化土地的分布具有明显的坡位分异性和地域分异性；区内严重和剧烈退化的“劣地”早在解放以前即已存在，其形成历史可以追溯至明清时期，５０年代到８０年代土地退化的发展主要表现为微度退化土地的明显减少及中度和轻度退化土地的增加。

According to the definition of land degradation/desertification by UN, vegetation coverage, erosional morphology and surface material were chosen as the criteria for asseessing land degradation in this paper.Based on this, assessment, mapping and comparison of land degradation between 1950's and 1980's were carried out by the interpretation of aerial photos of the two periods and by using a Fuzzy model. It was shown that the degraded land caused by water action accounts for 36% of the total studied area, in which severely and very severely degraded land, with the characteristics of bare badland, occupied 5% of it. Moreover, obvious downslope zonation and spatial variation of land degradation were observed in the studied area. It was proved that the severely and very severely degraded land existed even before the foundation of the country and could be traced back to the Ming and Qing Dynasties at least. Development of land degradation manifested itself as drastic reduction of non degraded land and relevant increase of slightly and moderately degraded land from 1950's to 1980's.