乡村路网对三峡库区社区水平森林结构的影响

道路作为人为扰动介质被认为是短时空尺度森林景观演化或用途转换的主要驱动力之一,体现为明显的“通道-阻隔”效应。论文以重庆市石柱县西沱镇为例,以3期遥感影像和调研数据为基础,利用ArcGIS的缓冲叠加功能,基于路网动态变化角度,从类型、林龄、起源等主要森林结构方面分析路网变化对森林结构变化的影响。结果表明：1）研究区道路数量先增加后减少,道路质量以等外公路和村级公路的改善为主。2）道路对森林景观干扰性明显。森林从类型、起源、林龄三方面在道路缓冲区内的破碎度均高于非缓冲区内的破碎度。1992—2002年及2002—2014年两个时期相比,前一时期其他灌木林、幼龄林以及萌生林大幅减少,基本表现为道路缓冲区内减少量大于非缓冲区内减少量。后一时期乔木林、中龄林以及萌生林有所增加,其他灌木林和成熟林轻微减少,其中,乔木林在道路缓冲区内增加量大于非缓冲区内增加量,中龄林及萌生林则表现为道路缓冲区内增加量弱于非缓冲区内增加量。3）道路影响域范围内,在无政策性干预条件下,道路的增加和质量的提高很大程度上导致森林景观的退化,低级路段的消失则有助于森林景观的恢复。

The Effects of Rural Roads on Forest Structure at the Community Level in Three Gorges Reservoir Area

Road as an artificial disturbance medium is considered as one of the main driving forces of the evolution of forest landscape and the conversion of forest usage at small spatial and temporal scales. It shows obvious “Channel-barrier” effect. Xituo town of Shizhu County in Chongqing city was selected as a research area. We used the buffer and overlay function in ArcGIS based on three phase remote sensing images and servey data to analyze the effects of road evolution on the changes of types, ages and origins of forest landscape. Results showed that: 1) The number of roads firstly increased and then decreased, and the road quality was most improved in substandard roads and village roads. 2) The disturbance of roads on forest landscape is obvious. The fragmentation of forest type, forest age and forest origin was higher in buffer zones of roads than in non-buffer zones of roads. Comparing the two periods of 1992-2002 and 2002-2014, the shrub forest, young forest and coppice forest reduced significantly in the first period, and the reduction were higher in buffer zones of roads than in non-buffer zones of roads. In the latter period, arbor forest, middle and old age forest increased, but shrubs and mature forests slightly reduced, among which the increase of arbor forest in buffer zones of roads was greater than in non-buffer zones of roads and the increase of middle age forest and coppice forest were lower in buffer zones than in non-buffer zones. 3) In the influence area of roads, if there is no intervention of policies, the increase of new roads and the improvement of road quality degraded the forest landscape, while the disappearance of low level roads was benefit to the restoration of forest landscape.