近20年三峡库区(重庆段)森林景观退化特征

Characteristics of Forest Landscape Degradation in the Three Gorges Reservoir Area(Chongqing) in the Past 20 Years

使用2012年2.5m分辨率SPOT-5影像、2002年森林资源二类调查、参与式农村访谈等数据为基础,选取三峡库区典型森林资源大县且属长江生态屏障区的石柱西沱镇为样区,对近20年的森林景观退化的特征、过程与动因进行分析,旨在丰富人们对三峡库区森林景观退化特征的理解.结果表明:1森林景观作为样区主要的景观类型,受大地貌格局控制以原始林和次生林为主,展现强空间异质性;2样区森林景观退化特征在2002年前就已形成,之后基本沿着"森林转型"的轨迹正向演化,总体展现为前期的退化和后期的恢复两个截然相反的过程;3样区森林景观格局演化遵循临级优先原则,在空间分布上具有强异质性,不同时段的主要轨迹和空间分布差异较大;4立地条件是驱动样区森林景观演化的主要影响因素,农户行为追求收益最大化和政府行为退耕还林与天然林保护工程则是主要驱动因素,两者共同作用下便出现2002年前森林景观被开发为耕地和之后又被恢复为森林.

In order to have a better understanding of the characteristics of forest landscape degradation in the Three Gorges Reservoir Area ,the characteristics ,process and driving forces of forest landscape degra‐dation there in the past 20 years were analyzed ,with Xituo town ,Shizhu county ,which is within the Yan‐gtze River Ecological Barrier Zone ,as the sampling area .The following data were used ,i.e. SPOT‐5 im‐age with 2.5 m resolution （2012） ,forest resource inventory （2002） and participatory rural interviews .The forest landscape ,as the main landscape type of the sampling area ,was shown to be characterized by a strong spatial heterogeneity ,and primeval forest and secondary forest were the major forest landscape types under the control of macro‐relief patterns ,their proportion being 77.7% -92.1% of the total forest landscape .The characteristics of forest landscape degradation of the sampling area took shape already in 2002 .A positive forest transition trend was presented thereafter ,a degradation process being dominant in the former phase and a restoration process in the latter phase .Primeval forest and secondary forest de‐creased rapidly at a rate of 9.17% and 0.72% during 1992-2002 ,respectively ,and secondary forest and degraded primeval forest increased speedily at a rate of 23.27% and 143.74% during 2002-2012 ,respec‐tively .The trajectory of forest landscape change of the sampling area followed the priority principle of near types .Moreover ,its main trajectory and spatial distribution presented clear differences in different stages . Primeval forest → degraded primeval forest ,primeval forest → secondary forest and secondary forest →degraded forestland mainly occurred in the Fangdou Mountains and the surrounding areas .Degraded for‐estland → secondary forest was focused in the hilly areas surrounded by the Yangtze River and its tributa‐ries .The site condition was the major driving force for the evolution of forest landscape of the sampling ar‐ea .Farmers’ maximum income‐seeking behaviors and Government behaviors （returning farmland to forest and natural forest protection project ） were the main driving factors .Under their co‐action ,the above‐men‐tioned consequence of forest landscape occurred .