Analysis On Wetland Landscape Pattern And Driving Factors At Caizi Lakes,Anhui Province

There is dense population in the middle and lower Yangtze River floodplain.The wetland landscape pattern is particularly affected by human activities.As a representative shallow-water lake,the Caizi Lakes have been extensively developed in natural wetlands such as lake water surfaces and marsh,and the lake wetland landscape has gradually become patchy and fragmented,due to human and social economic activities such as net farming,lake reclamation,and dike engineering.It is very urgent to strengthen the research about the quantitative analysis of wetland landscape change and its driving forces.This study takes the Caizi Lakes wetland in Anhui Province as the research object,selects the four periods of satellite remote sensing image data in 1999,2004,2011 and 2017,and uses ENVI and GIS software to interpret and extract the Caizi Lake wetland landscape information.Transition matrix analysis and landscape pattern index were used to analyze the evolution of wetland landscape in Caizi Lakes wetland.Combining socio-economic statistics,comprehensively using geographic detectors and related analysis methods,discussing the factors such as economic expansion,fishery economic development and population growth,affect the evolution of wetlands.The relevant results obtained are as follows.1.During the study period,the landscape area of the Caizi Lake wetland changed significantly,the overall performance of the natural wetland was shrinking,and the artificial wetland expanded.The area of the natural wetland decreased by 2,835.54 ha,and the area of artificial wetland increased by 2738.07 ha.The area of lake wetland increased by 3100.50 ha,and the area of beach and marsh grassland wetland decreased by 3273.30 ha and 3312.18 ha,respectively,accounting for 47.11% and 54.60% of the original area,respectively.The area of farmland wetland increased from 84.69 ha in 1999 to 2323.62 ha in 2017,with a proportion of9.34% increased from 0.34%.2.It shows that during the study period,the intensity of land use increased,landscape patches gradually became regularized and their connectivity weakened.The advantage of natural wetland landscape has reduced,and the dominance of constructed wetlands has risen.The fragmentation of the overall landscape has intensified,and the spatial heterogeneity has increased.The landscape index of mudflats and the herbaceous marshes basically showed the same trend,the number of patches(NP)increased,and the proportion of patch type area(PLAND)and the largest patch index(LPI)gradually decline;aquaculture ponds landscape index fluctuates,NP,patch density(PD),PLAND,and LPI all reached their maximum in 2011,and then declined significantly.Paddy field landscape NP,PD,PLAND,and LPI increased steadily,landscape advantages degree rises.In the landscape level index,the Shannon Diversity Index(SHDI)and PD increased,while the aggregation index(CONTAG)and patch average subdimension index(FRAC-MN)decreased.3.From 1999 to 2017,the area of human activities and the intensity of disturbance in Caizi Lakes increased significantly.In 1999,human disturbance in the study area was relatively good,with low disturbance accounting for 47.53% of the total grid.From 1999 to2017,the number of low and lower interference grid decreased,with their proportions decreasing by 27.78% and 21.30% respectively.The number of the grid with moderate disturbance increased significantly,increasing by 26.23% compared with that in 1999.The high interference grid experienced a trend of steady increase from scratch,with an increase of8.64%.As a whole,the degree of human disturbance in the wetland gradually decreased from the outside to the inside,and the range of disturbance gradually diffused from the outside to the middle.4.The landscape pattern of Caizi Lake wetland is influenced by human activities and social economy.The results showed that there were significant temporal differences in the influence of farmland,aquaculture,purse seine culture,and enclosure dam on patch number distribution,and the interaction of human activity factors was significantly stronger than that of a single factor,showing enhancement effect.In 1999,aquaculture ponds and enclosures played a leading role in the spatial differentiation of wetland landscape fragmentation,with q values of 25.82% and 21.46%,respectively.In 2004,aquaculture ponds and fence nets played a leading role in the spatial differentiation of wetland landscape fragmentation,with q values of 28.36% and 21.41%,respectively.In 2011,enclosure dam,aquaculture pond,and purse seine culture activities all had a greater impact on landscape spatial differentiation,which were 23.09%,20.04%,and 22.34%,respectively.In 2017,farmland and purse seine culture had a greater influence,accounting for 23.68% and 29.86%,respectively.From 1999 to 2017,the effect of farmland expansion on the spatial and temporal differentiation of NP index in the study area showed a steady increasing trend,and the influence q value increased from 5.74%to 29.86%.And reached the maximum value is 2017,indicating that the effect of farmland factors on the spatial and temporal differentiation of NP index in the study area is becoming more and more prominent.The results of correlation analysis showed that the patch density was significantly positive correlated with the output value of the three major industries,GDP,population,fishery production,cultivated land area,and other socio-economic factors.The patch average subdimension index was negatively correlated with social economy.The aggregation index was significantly negatively correlated with the output value of the secondary industry,the output value of the tertiary industry,the total output value,and the population.Shannon's diversity index was positive correlated with the output value of the primary industry,population,aquatic products,and cultivated land area.This paper described the evolution characteristics of wetland landscape pattern in Caizi Lakes,and elucidated the driving mechanism of landscape changes.The results provide suggestions for the restoration of the wetland landscape connectivity,the restoration of animal and plant habitats,and the protection of biodiversity in Caizi Lake wetland,thereby is help to improve effectively the ecology service function of the wetland.