岷江上游景观格局及生态水文特征分析

基于1994年岷江上游TM遥感影像分类,结合6个不同集水区1992、1993、1995年植被生长季降雨、径流及同期NOAA/AVHRR的N DVI数据,构建了植被保水指数作为表征植被生态水文功能分析的指标。并用此对岷江上游6个不同集水区景观格局与生态水文特征进行分析。结果表明:不同集水区植被组成及景观结构有显著差异;不同集水区植被保蓄降雨能力即保水指数有明显差异;不同集水区景观结构指数与保水指数之间具有很高相关性,其中边界密度、多样性指数与保水指数呈负相关,聚集度指数与保水指数呈正相关。保水指数的构建对植被建设具有一定的科学意义

Analysis on landscape pattern and eco-hydrological characteristics at the upstream of Minjiang River

The relationships among vegetation, precipitation and runoff are important issues in eco-hydrological study. There have been a lot of researches working on eco-hydrological function of forest at small scale of a catchments or an ecosystem, while less effort is made at large scale of a landscape or watershed. At the same time, there are few studies addressing the relationship between landscape indices and ecological functions, which indicates potential interaction of landscape patterns and landscape processes. The upstream of Minjiang River is situated at the south-east edge of Tibetan sub-Alpine and the topography is characterized with deep valley and steep slop. The complicated landscape patterns resulted from land use and land cover change might create different eco-hydrological functions at the upstream of Minjiang River. The study pursues two objectives: (1) to characterize vegetation and landscape patterns, to analyze dynamics of the precipitation, runoff and NDVI in the different catchments at the upstream of Minjiang River; (2) to explore the eco-hydrological responses of the targeted catchments to the corresponding landscape pattern, which infers landscape pattern-function relationship. Based on the three scenes of Landsat 5 Thematic Mapper (TM) satellite images acquired on June 26, 1994, which include path 130 rows 37~39. Twelve land cover types were identified by the supervised classification techniques. With the reference to the global position system (GPS) points and GIS coverage for vegetation (1:1,000,000) acquired from the Institute of Botany, Chinese Academy of Science. Landscape pattern was analyzed by the software FRAGSTATS. The precipitation, runoff and NDVI data of different catchments were accumulated from April to September in the year of 1992, 1993 and 1995. Spatial surfaces for monthly precipitation were produced based on 51-gauged precipitation points by the thin plate smoothing spline techniques. The precipitation statistic data in the different catchments were made by ARCVIEW. A new eco-hydrological index, which is expressed by the difference 1between precipitation and runoff divided by the product of precipitation and NDVI, was used in this research to represent the eco-hydrological functions of different catchments. The results are as following: (1) the selected 6 catchments at the upstream of Minjiang River were different in landscape patterns in terms of landscape type and cover . There were higher contagion, lower edge density and diversity index in the Shouxi catchments, and lower contagion, higher edge density and diversity index in the Zagunao catchments. (2) Eco-hydrological indexes had remarkable differences among different catchments. The highest eco-hydrological index was found in the Shouxi catchments, indicating higher precipitation holding capacity of vegetation therein, while the lower eco-hydrological index was found in the Zagunao catchments, indicating its lower precipitation holding capacity of vegetation. (3) High correlation was detected between the landscape indexes and eco-hydrological indexes. Eco-hydrological index was positively correlated with landscape contagion in contrast with the negative correlation with landscape diversity and edge density.