| Since the reform and opening up,the urbanization process of Shenzhen has brought about great changes in urban landscape structure and ecosystem,and the policies put forward by the government in different periods have restricted the changes of urban ecological structure to some extent.In this paper,Landsat image combination index of Shenzhen in 1986,1996,2006 and 2016 was selected to analyze the dynamic change process of landscape pattern and connectivity in Shenzhen from 1986 to 2016,and principal component analysis was used to evaluate the ecological resilience of Shenzhen from 2006 to 2016.Finally,the following research results were obtained:(1)At the level of type,the patch area CA and landscape percentage PLAND of construction land increased from 57357.76ha to 85982.58ha from 1986 to 2016,and the PLAND increased from 29.36%to 44.01%.Forestland,agricultural land,other land and water area showed a decreasing trend on the whole,indicating that the area of land used for urban construction in Shenzhen continued to expand,while forest land,agricultural land,other land and water area gradually decreased under the influence of urban development.The number of patches(NP),patch density(PD)and landscape shape index(LSI)of construction land increased slowly from 1986 to 1996,but decreased significantly from 1996 to 2016.On the contrary,the maximum patch index(LPI),average patch AREA(AREA-MN),aggregation degree(AI)and cohesion degree(COHESION)showed that construction land had transformed from fragmentation into a continuous and integrated pattern.The NP,PD and LSI of forest land,agricultural land and other land showed a continuous increase in the fragmentation of landscape pattern from 1986 to 2006,and a gradual aggregation after the effect of ecological construction from 2006 to 2016.During the past 30 years from 1986 to 2016,the water patch in Shenzhen was continuously damaged and fragmented.(2)From the perspective of landscape level,NP and PD indexes showed an upward trend from slow to rapid from 1986 to 2006,and a sharp decline from 2006 to 2016.LSI,edge density ED,integral dimension of perimeter surface PAFRAC,separation DIVISION,Shannon homogeneity SHEI and Shannon diversity SHDI increased slightly from 1986 to 1996,but showed a downward trend from 1996 to 2016,while the change curves of LPI,AI,COHESION and contagion index(CONTAG)were on the contrary.From 1986 to 1996,the shape complexity increased and the landscape fragmentation degree was higher.From 1996 to 2006,the fragmentation of patches slowed down and gradually approached the aggregation state.From 2006 to 2016,the patches became aggregated after the regulation of Shenzhen Municipal policies.(3)From 1986 to 2016,the ecological land in Shenzhen was mainly composed of a large number of small patches and a small number of giant patches.The landscape distribution was uneven and the patch area showed polarization.Overall connectivity index(ⅡC),possible connectivity index(PC)and landscape coincidence probability(LCP)increased first and then decreased.During 1986-1996,IIC increased from 0.08 to 0.10,PC from 0.36 to 0.47,and LCP from 0.50 to 0.51.From 1996 to 2016,ⅡC decreased from 0.10 to 0.05,PC decreased from 0.47 to 0.23,and LCP decreased from 0.51 to 0.28.The results showed that the landscape connectivity of ecological land was good from 1986 to 1996,and the patch connectivity became worse from 1996 to 2016,but the decline began to slow down after 2006.(4)Among the top 100 patches of ecological land importance value(dPC)in Shenzhen,the number of medium-sized patches accounted for the largest proportion from 1986 to 2006,and then the number of small patches gradually became equal to that of medium-sized patches from 2006 to 2016.Although the area of giant patches fluctuated from 1986 to 2016,they still played an important role in the landscape and played an important ecological function.Most of the top 10 patches in dPC importance of ecological land in Shenzhen were giant patches.Most of them were distributed in Wutong Mountains,Maluan Mountains and Dapeng Peninsula in the southeast during 1986-2016,while the other areas were basically unchanged.They all fell within the range of basic ecological control line of Shenzhen,and embodied huge ecological benefit value under the protection of policies.(5)From 2006 to 2016,the ecological resilience of Shenzhen increased steadily from 0.096 to 0.863 during the period from 2006 to 2008.From 2008 to 2011,there was a sharp decrease from 0.863 to-0.933.From 2011 to 2016,it increased from-0.933 to 0.651.It showed that the coordination and balance ability of the ecosystem was not stable.The change trend of the first principal component and the ecological resilience index were roughly the same,and the water resource index was the main driving factor of the ecological resilience of Shenzhen.Vegetation and soil indexes,air temperature indexes and illumination indexes also had potential influence on the change of ecological resilience. |
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