庐山森林景观格局变化的长期动态模拟

Abstract

Forest succession is a naturally occurring process of reorganization which occurs constantly in forest ecosystems; the term refers to the process of one plant community being replaced by another over time. The process of forest vegetation ecological succession is driven by underlying natural conditions and anthropogenic disturbance. We can infer dynamic changes of landscape patterns and corresponding ecological processes of forest succession using forest landscape dynamic analysis based on vegetation patterns. Research related to vegetational succession provides a foundation for the understanding of dynamic changes of forest landscape patterns. The changes of forest landscape pattern also influence nutrient cycling and energy flows in forest ecosystems while restricting a variety of ecological processes. As a result,the study on forest landscape patterns explains very important dynamic processes of forest succession.The natural laboratory of Mount Lushan provides a unique site for studying ecological succession as it relates to vegetation and restoration ecology. The study of forest succession is the foundation of recovery and restoration activities. This type of research depends on the study of ecological succession of vegetation which can provide a basis for understanding the dynamics of landscape change. Using the spatially explicit landscape simulation model( LANDIS),this paper analyzes forest vegetation on Mount Lushan,by stimulating the dynamics of the vegetation's ecological succession in the next 300 aunder undisturbed natural conditions,and determines the representative landscape pattern indices of each patch. This process includes measures of the proportion of the landscape covered by each type of patch area as well as determining the values for the aggregation,fractal dimension,diversity and evenness indices. This process allows the analysis of the spatial distribution pattern of dominant tree species,which helps reveal the factors regulating vegetation succession and helps predict the future trends in variation of the forest landscape. Finally,the theoretical basis for successfully realizing sustainable development of forest resources is discussed. The results indicate:( 1) Over the next 300 a,the extent of a stable populations of broad-leaved tree species will tend to increase; ecological succession in the entire Mount Lushan forest ecosystem is moving in the direction of the reformation of a complex zonal evergreen broad-leaved forest system.( 2) The aggregation index for broad-leaved tree species exhibits a pattern of slow growth in the next 150 a,and then stabilizes after 150 a. The aggregation index of fir remained steady for the entire 300 a while the degree of aggregation for moso bamboo declined steadily throughout the entire simulation until it stabilized during the end stage of the simulation.( 3) The fractal dimension of all dominant tree species is between 1 and 1. 1,illustrating that the edge of each patch is relatively inerratic and experiences small changes during natural forest vegetation succession.( 4) The diversity index of the research region initially tended to increase and later maintained a slow rate of decline. Also,the evenness index initially declined,then rose and went into a slow decline at the end of the simulation. The results of the simulation indicate that the Mount Lushan ecosystem is trending toward an optimal climax community based on the natural forces of ecological succession occurring in the forest community. During this natural ecological succession,various species predominate before the climate evergreen broad-leaved forest stage becomes dominant. In the next 300 years,the reforestation program implemented in the 1960s will not have an obvious influence on climax forest landscape patterns in Mount Lushan. Our research provides a scientific foundation for current and future forest landscape management practices on Mount Lushan. In the long run,we should continue to implement a strict policy of protecting hillside forest habitat to facilitate ongoing afforestation efforts.