美国大陆五个山区集水区的河溪结构分析

摘要

河溪结构及其关联的空间特征,是研究集水区中能量和物质移动规律所不可缺少的内容.利用美国地质调查局的水文数据库和地理信息系统(ARC/INFO),对美国大陆5个主要山地中典型集水区河溪的数量、密度、分布结构以及河溪岸边带的组成,进行了分析和比较.5个山地分别是:西北太平洋沿岸,西部卡斯卡特山,中部落矶山,东部阿巴拉契亚山和南部欧扎克山.发现这5个集水区中的河溪网络结构非常相似,一级河溪大约占河溪总长度的60%左右.东部山地地质历史比较长,其集水区中河溪总长度、密度,高差以及河溪片段数量,都比西部相对年轻的集水区要高.此外,尽管其中河溪边岸域总面积随边岸域宽度线性增长,但它们在面积中的相对比例仍然很小(＜12%).因此,在森林经营中保护河溪边岸植被,并不会对木材生产造成太大的威胁.%Stream geometry and related measurements are the baseline information needed for ecological analysis of materials and energy movements within a watershed landscape.Using the United States Geological Surveys(USGS)hydrography database and a geographic information system(ARC/INFO),we examined and compared the distribution of streams,stream sections,total numbers,density,and riparian zones,in five mountainous watersheds in the continental United States:the Pacific Coastal Range,Cascades,Rockies,Appalachian Mountains,and Ozarks.Stream networks were found to be similar among the watersheds,with first order streams comprising up to 60% of the watersheds,The two watersheds in the eastern US had smaller stream length,basin relief,and higher stream density and section density than western watersheds.The amount of riparian area linearly increased with buffer width and did not account for larger amounts of the land area.Only seven to twelve percent of a total watershed area was included in riparian areas when a 60m buffer width was applied.Riparian zone distribution was related to watershed geomorphology.Emprirical models were developed to predict the proportions of stream,stream density,and changes in riparian areas with stream order within each watershed.Applications of these results in ecosystem analysis at watershed scales and riparian zone management are discussed.