| In the context of current global warming and intensified human development activities,Tianjin wetlands’ecosystem functions and properties have undergone drastic changes,which have seriously affected the habitats of wetland waterbirds.The thesis addresses three significant dilemmas in the evaluation and restoration of wetland waterbird habitat suitability:the fracture in spatial and temporal research of waterbird habitat caused by traditional technical methods,the fragmentation of waterbird habitat cognitive logic caused by the lack of systematic cognitive methods,and the multiple problems of waterbird habitat restoration caused by the stripping of restoration methods and scientific basis.This study uses remote-sensing images as the primary database.It integrates theoretical and technical methods from ecology,zoology,geography,landscape planning,and other related disciplines to systematically analyze the evaluation and restoration of waterbird habitats in Tianjin wetlands in the context of spatial and temporal changes.Given the diversity and complexity of the research objects,this research mapped distribution of wetlands in the study area based on the six issues of Landsat TM+/OLI TIRS remote sensing images from 1990 to 2020,land use data,and field sampling data by integrating the system theory of ecology and the habitat cognition laws of waterbirds.Based on the characteristics of habitat selection by wetland waterbirds,we analyzed and discussed the dynamic changes of wetland landscape pattern and simulation prediction,habitat suitability evaluation of wetland waterbirds,and ecological security pattern construction and restoration strategy of wetland waterbirds.First,we use supervised classification and manual visual interpretation methods to study the dynamics of wetland distribution and changes in wetland landscape patterns in Tianjin.Second,we use a future urban land use simulation model to simulate and predict the future wetland landscape in the study area.Thirdly,we select a habitat suitability index model to effectively assess the habitat suitability of waterbirds in Tianjin wetlands and analyze the seasonal and interannual variation characteristics of habitat suitability.Fourthly,we use a Minimum Cumulative Resistance model to construct a model suitable for wetland waterbirds.Finally,the restoration strategy of the core area of Qilihai wetland,a critical habitat for waterbirds in Tianjin wetlands,was discussed based on the preliminary research and data analysis.The main conclusions of this thesis are as follows:1)The wetland types in the study area include offshore and coastal wetlands,constructed wetlands,marsh wetlands,river wetlands,and lake wetlands.1,166.18km~2(25.80%)of the wetland area decreased between 1990 and 2020.The wetland area decreased most sharply between 2002 and 2008,and the loss was mainly due to the fluctuating changes resulting from land reclamation,paddy field,salt field,and aquaculture.The changes in the landscape index indicate that the fragmentation of Tianjin’s wetland landscape is intensifying,the control of dominant patches on the regional wetland landscape is weakening,and the patch types are becoming more diverse.The changes in wetland landscape patterns have significant impacts on wetland waterbird habitats.2)The prediction results of future wetland landscapes show that the total wetland area of Tianjin will further decrease by 442.46 km~2(13.20%)during 2020-2032.Among the natural wetlands,except for the marsh wetland area,the areas of offshore and coastal wetlands,river wetlands,and lake wetlands are reduced by 4.13%,29.50%,and 2.15%,respectively.Suppose appropriate conservation and restoration strategies are not adopted to improve the current condition of wetlands.In that case,the quality of wetlands in Tianjin will further deteriorate,affecting the wetland waterfowl habitat.3)The overall suitability of waterbird habitats in Tianjin wetlands is relatively unfavorable,and the area with the best,good,and fair habitats decreased from9284.86 km~2to 8073.67 km~2between 1990 and 2020,a total decrease of 13.05%;the area with less suitable and unsuitable habitats increased from 3518.31 km~2to 4729.49km~2,a total increase of 34.43%.The area with good suitability is changing to less suitability,and the ranking is decreasing,indicating that the habitat suitability of waterbirds in Tianjin wetlands is influenced by human activities,mainly the expansion of cities and the conversion of land types.In addition,the seasonal changes are also evident,with the overall suitability being higher from July to August and decreasing in other months,which is mainly influenced by the seasonal changes of vegetation.4)The ecological source area of Tianjin wetlands for waterbirds is 2695.06 km~2,which accounts for 21.05%of the city’s total area,with prominent spatially clustered distribution characteristics.Among them,120 ecological corridors are distributed to meet the requirements of ecological source area connectivity,and these ecological corridors traverse most of the nature reserves and wetlands.Based on constructing the ecological security pattern of waterbirds in Tianjin wetlands,the spatial pattern of wetland waterbird conservation is proposed to optimize and restore the corridors for crucial conservation sites,conservation hotspots,and linkages between habitats.5)Using the Qilihai wetland core area,a key conservation site for waterbirds in Tianjin wetlands,as an example,we analyzed the suitability of waterbird habitats in the study area based on the qualitative and quantitative research results.The target waterbirds were selected,and their habitats(habitat type,water body selection,and plant requirements)were analyzed according to the current resource status of the wetland waterbirds and the restoration strategies were proposed(terrain consolidation,water level regulation,and plant selection)as well as the post-restoration monitoring and management methods for the Qilihai wetland core area,taking into account the actual problems of the current site.The study of wetland waterfowl habitat restoration based on the context of spatial and temporal changes has significant value for theoretical and practical applications.It is an effective guide and reference for wetland waterfowl habitat restoration in Tianjin. |
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