汶川地震前后龙溪-虹口自然保护区景观多样性的遥感评估

Landscape Diversity Assessment in Longxi-Hongkou Nature Reserve Before and After the Wenchuan Earthquake Based on Remote Sensing

本文以植被类型与土地利用类型为主要依据,建立四川龙溪-虹口自然保护区景观分类体系,对汶川地震前后的两期Landsat TM影像进行了解译,得到其地震前后的景观空间格局,并对研究区地震前后景观变化特征进行分析,得到:(1)震后研究区景观斑块总数增加了2.36倍,景观破碎化严重。阔叶林与针叶林组成的森林景观呈片段化,优势度下降;阔叶林、稀疏植被,以及草甸成为新的优势景观。(2)震后Shannon多样性指数与周长-面积分维数分别上升11%和7%,说明研究区景观异质性与多样性增多,景观结构更复杂。优势度指数和聚集度指数下降30%,表示研究区内大的景观斑块减少,景观类型聚集度下降,连通性下降。(3)研究区生境破碎,生物多样性维持功能减弱;植被覆盖度降低,边缘生境增加,水源涵养功能减弱、水土流失风险加剧;景观结构受损,生态屏障功能减弱。其表明地震及其次生灾害作为自然干扰因子,改变了研究区景观的结构与格局,破坏了珍稀动植物的适宜生境,对研究区珍稀濒危物种与自然生态系统造成了严重威胁,将对区域生态环境与生物多样性造成重要影响。

Landscape diversity is the result of natural disturbance,human activity and the internal succession of vegetation.It also is a major level of biodiversity.In this paper,the authors established a landscape classification system for Longxi-Hongkou Nature Reserve,Sichuan Province,with vegetation types and land-use being the main classify basis,interpreted two different phases of Landsat TM images before and after the Wenchuan Earthquake of the reserve,developed the landscape spatial pattern of the study area,and analyzed the characteristics of landscape changes before and after the earthquake.The results showed that： 1） After the earthquake,the total number of patches（NP） in the study area increased by 2.36 times,so landscape became more fragmentation;after the earthquake,forest landscape（broad-leaf and coniferous） went into smaller pieces,implying the weakness of its dominant position.Broad-leaf,meadow and rare landscape turned into the new dominant landscape.2） The SHDI and PAFRAC of the study area increased 11% and 7% respectively.It implied the diversity and heterogeneous of the study area strengthened,and landscape structure was more complex.The Dominance and CONTAG both decreased 30%.It explained that the number of large patches decreased,the landscape contagion of the study area fell and its connection declined.3） The habitats fragmented,the ability of maintain biodiversity was cut down.Vegetation cover dropped,and edge habitats grew in number,leading to a weaker ability of maintain water,a raising risk of soil erosion,landscape structure destroyed and the protective screen function slipped.Therefore,Wenchuan Earthquake and its secondary disasters as natural disturbance factors have changed the landscape structure and landscape pattern of the study area,undermined the suitable habitats of rare animals and plants,posed a threat to endangered species and natural ecosystems,all those would change the biodiversity and ecology environment of the region.