Study On The Change Characteristics And Optimization Of Landscape Pattern In Poyang Lake Region Under The Background Of Water Level Fluctuation

With the growth of population and progress of science and technology,human activities are becoming more and more intensive.Various types of ecosystems on the earth are affected more or less by human activities,the impacts are more extensive and strongin recent decadesespecially.For a particular ecosystem,it will be disturbed by varying degrees of interference,such as natural factors and human activities,in its own process of development and evolution.At the same time,landscape patterns and other natural features will be changed.Therefore,understanding the relationship between landscape pattern and is of great significance for a certain region to protect and rationally utilize the water and soil resources and to formulate the regional development strategy for the government.This paper was to provide some reference for achieving healthy,stability and sustainable development of regional ecosystem.With the help of GIS and RS technologies and theory of landscape ecology,we acquired four scenes of satellite images in 1994,2001,2007,2014 and hydrological data of Poyang lake.Variation characteristics of hydrological rhythm and landscape pattern and landscape pattern optimistic were analyzed with Mann-Kendall,landscape pattern index and accumulative cost distance model.The objective of this paper is to provide a theoretical reference for the effective protection and scientific management of the ecosystem in the Poyang Lake.Results showed that:1)There are some key hydrological stations located in the main lake of Poyang Lake,such as Xingzi,Hukou,Duchang,Kangshan.The four hydrological stations are interrelated and influenced.With the Gray Relational Analysis method,it is found that Xingzi station can represent the water level of other hydrological stations to the greatest extent,and reflect the hydrological characteristics of the Poyang Lake.The statistical analysis of the waterlevel data of Xingzi station shows that the annual average waterlevel,the highest waterlevel and the lowest waterlevel are descendingin the last 25 years(1991-2015),and the average descending rate is 0.74m/10 a,1.25 m/10 a,0.50 m/10 a,respectively.The M-K test method shows that 2003 was the waterlevel mutation time point,which was related to the operation of the Three Gorges.2)According to the actual situation of Poyang Lake area,the landscape of the study area was divided into seven types: cultivated land,forest land,grassland,water body,beach land,construction land and unused land.Landscape pattern index was calculated by Fragstats 4.2 to analysis the characteristics of landscape pattern.The results show that the landscape pattern of Poyang Lake area has changed obviously in the past 20 years.The degree of landscape reunification is decreasing,the connectivity is reduced,the degree of fragmentation is strengthened,the spatial heterogeneity is increased,the irregularity of the landscape shape is increased and the complexity is increased.The seasonal variations of the overall landscape pattern in Poyang Lake region were obvious.Compared with the high water period,the patch in the low water period was more broken,the shape was more complex,the aggregation degree was lower,the level of heterogeneity was higher.Analyzed from patch types,the change of bottomland was the most obvious in the landscape pattern.3)On the basis of the seasonal variation of landscape pattern,the ecological components including source,corridor(three types),node sin high and low water periods of Poyang Lake region were identified and constructed with the Minimum Accumulative Resistance model and GIS spatial analysis module,an ecological function network of "Patch-Corridor-Matrix" model was formed.And through the comparison and analysis of ecological component sin different hydrographic periods,the major ecological components which play an important role in maintenance of landscape pattern and function were chosen to build a reasonable landscape pattern optimization program.This program aimed to enhance the connectivity of landscape network and operation of ecological flows,strengthen the stability and sustainability of ecological system,and provide the reference for the ecological planning and management in Poyang Lake region.