岷江上游河岸带土地覆盖格局及其生态学解释

 针对岷江上游干流河岸带的土地覆盖状况，将该区沿河流主干分为68个样方，结合空间信息及环境因子，对这些样方及流域内的12种土地覆盖 类型，采用双向指示种分析法（ Two_way indicator species analysis, TWINSPAN）和除趋势典范对应分析法（Detrended canonical correspondence analysis, DCCA）对种类和样方进行分类和排序，以揭示其生态学意义及环境影响因素。结果显示：1）研究区土地覆盖可分 为高植被覆盖、中度植被覆盖和低／非植被覆盖3种类别，各类别在流域不同位置分布状况不同，整个流域以中度植被覆盖为主。2）所取样方 可分为8个类群，各自拥有相似的土地覆盖组成，呈聚集分布。3） 根据土地覆盖特征，河岸带可分为上、中、下3段，流域上段河岸带植被覆 盖度较高；中段以中度植被覆盖类型为主，占总面积最大；下段集中了大部分人工土地覆盖类型。4）气温 、海拔是影响岷江上游干流河岸带 土地覆盖格局的最重要因素，此外降水和人类活动对其也有影响。除干旱河谷区外，顺流自上而下，海拔逐渐降低，水热条件逐渐改善，同时 人类干扰强度也逐渐增加，是造成流域3段截然不同的土地覆盖格局的原因。5）干旱河谷特殊的土地覆盖格局是水、热共同作用造成的。总之 ，岷江上游河岸带土地覆盖呈现出一定的梯度变化特征，自然条件的制约是形成这一格局的主要原因。

INTERPRETING ECOLOGICAL LAND COVER PATTERN FOR THE RIPARIAN ZONE OF THE UPPER MINJIANG RIVER, CHINA

Abstract Aims Riparian zones encompass sharp environmental gradients with an unusually diverse array of landforms, habitats and communities. The land cover pattern of the riparian zone was studied in the upper Minjiang River, China, to determine: 1) the land cover pattern and 2) environmental factors affecting the pattern. Methods Sixty-eight quadrats with 12 classes of land cover were sampled along the main stream of the river. Based on the spatial information and environmental factors, the pattern of land cover was investigated using two-way indicator species analysis (TWINSPAN) and detrended canonical correspondence analysis (DCCA).  Important findings Land cover was classified into high, moderate and low/non－vegetation types. These had different distributions, with the moderate type most predominant. The quadrats were classified into 8 groups, within which each quadrat had similar land cover. Based on land cover, the riparian zone could be divided into three parts: the upper part with mostly high vegetation types, the middle part, which occupied the greatest area, mostly with moderate vegetation types, and the lower part, mostly with the man-made land cover type. Temperature and elevation were the most important environmental factors related to the land cover pattern, followed by precipitation and human distribution. From upper to lower parts of the riparian zone, temperature, precipitation and human activity increase. The overall result is explicitly different land cover patterns in the three parts of the riparian zone. The pattern of dry valley is controlled by the interaction of water and temperature. Ordination was useful in interpreting the land cover pattern of the riparian zone in the upper Minjiang River. Environment factor s had a larger effect on this pattern than human factors.