岷江上游大沟流域驱动植被退化的人为干扰体研究

研究了岷江上游大沟流域内的人为干扰体，分析了干扰的类型、强度、频率及其时空变化特征，揭示了不同干扰类型及其特性对植被退化的作用、干扰体与人口增长、植被退化等的关系．结果表明：大沟流域人为干扰类型多达８种，但优势的干扰类型是砍伐薪材和牲畜放牧．从近３０ａ的干扰强度变化看，以８０年代初的干扰强度最大，并在近２０ａ内保持很高的干扰强度水平；干扰强度的年内变化表现为春末、夏、秋大而冬、早春小．近４０ａ来的干扰频率愈趋增高，年内表现为春秋季干扰频率最高，夏季中等，而冬季最小．人为干扰的空间差异十分明显，反映出人为干扰的现状及其对植被的破坏强度差异，即由村寨向沟尾和高海拔区、由近及远、由低到高，形成“钟形”干扰格局．认为大沟流域植被的严重退化是所有人为干扰长期共同驱动的结果，与该区人口及其需求迅速增长密切相关．结果还表明，不同性质的干扰对植被的影响作用具协同性，同一干扰体长期连续对植被的影响具累加和放大的作用

HUMAN-INDUCED DISTURBANCE REGIME IN THE DAGOU VALLEY IN THE UPPER REACHES OF THE MINJIANG RIVER

Studies on human induced disturbance regime, as a main driving force of vegetation degradation, could help understand the process and mechanism of vegetation degradation and restore the degraded vegetation, but until now not enough attention has been paid to and few studies found on this subject. This paper highlights the studies on human induced disturbance regime in the Dagou valley in the upper reaches of the Minjiang River, presents analyses of the types, strength, frequency and variations of the anthrogenic disturbances, and reveals the effects of different types of the disturbances on vegetation degradation and the relations of the human induced disturbances with population and vegetation degradation. The results indicate that in the Dagou valley there are 8 types human induced disturbances, of which fire wood cutting and grazing are the major and strong disturbances. In recent 30 a the strongest disturbance intensity taking place at the beginning of 1980s has lasted for about 20 a. In a year the disturbances were strong in late spring, summer, and autumn, but weak in winter. The frequency of human induced disturbances became higher and higher in recent 30 a, and it was found the highest in spring and autumn and the lowest in winter in a year. Generally speaking, the disturbances displayed apparent spatial pattern, that is, the closer from the village and the higher elevation from about 1 750 m was, the stronger the disturbances were, which the vegetation degradation displayed differences along the disturbances pattern. Vegetation degradation was just seriously caused by the human induced disturbance regime and connected closely with population increase and their demands. The study also showed the disturbances with different characteristics had coordination effects on vegetation and had an intensification and amplification on vegetation degradation for long period.