区域城市扩张对森林景观破碎化的影响——以粤港澳大湾区为例

森林生境丧失与景观破碎化是引起生物多样性下降，生态系统功能降低的重要原因。量化森林景观破碎化的时空特征及其与城市扩张格局的关系是开展区域生态修复与功能提升的重要基础。本文以快速城市化的典型区域——粤港澳大湾区为研究对象，基于遥感解译的1980年、1990年、2000年、2010年和2018年土地覆盖/利用专题图，通过多尺度的景观格局分析和统计分析，定量解析森林景观破碎化的时空演变特征及其与城市扩张格局间的关系。研究结果显示：1）1980-2018年，大湾区林地覆盖面积缩减1，274 km²，林地转变为建设用地的面积占林地丧失总面积的比例从1980-1990年的11%增长至2010-2018年的42%，表明城市扩张已成为林地丧失的主导因素；2）森林景观破碎化程度加剧，表现为林地斑块密度提高，平均斑块面积减小，但破碎类型与程度具有地域差异；3）城市扩张幅度与空间格局显著影响林地破碎化，其中，城市扩张幅度对林地破碎化的影响更为重要。基于森林景观破碎化与城市扩张的现状，落实城市增长边界划定、关键斑块-廊道识别与生态网络构建等措施，有助于保护与连通重要生态空间，保障和提升生态功能。

Forest fragmentation and its relationship with urban expansion in Guangdong-Hong Kong-Macao Great Bay Area, China

Urban expansion is fragmenting the forest landscape, with the consequence of biodiversity loss and ecosystem degradation. Characterizing the forest loss and fragmentation over time and examining its relationship with the urban expansion is crucial for regional ecological restoration. Previously, several studies have focused on how the urban expansion impacts the forest loss and fragmentation by land cover change and landscape dynamics along the urban-rural gradient or in the entire study area over time in an individual city or a region. Results from these studies usually neglected the spatial pattern relationships between forest fragmentation and urban expansion. Since the urban megaregion has become the major form of urbanization in China, the conclusions from a single scale analysis, such as city or regional level, concealed the spatial differences of forest fragmentation change in the regional processes. Here, Guangdong-Hong Kong-Macao Great Bay Area, a rapidly urbanized region in southern China, was selected as a study area and the relationships between forest fragmentation and urban expansion at multiple scales were explored. Firstly, the spatio-temporal dynamics of forest loss and fragmentation were characterized at the region- and city-level by the landscape metrics based on the land cover and land use maps derived from the remotely sensed imagery in 1980, 1990, 2000, 2010, and 2018. The relationships between the forest fragmentation and the urban expansion at the county-level were then quantified by Pearson correlation analysis. Results showed that 1) The forest area decreased from 33,304 km² in 1980 to 32,030 km² in 2018, with a decrease of 1,274 km² in the past four decades. The percentage of forest being converted to developed land increased from 11% in 1980-1990 to 42% in 2010-2018, suggesting the urban expansion has become the major factor of the forest loss. 2) Forest landscape became fragmented shown by the increment of the patch density and decrement of the mean patch size at the regional level. The landscape metrics change at the city level revealed the type and degree of forest fragmentation varied from different regions. 3) Both the cover percentage of developed land and its spatial pattern, including patch density and mean patch size, had significant impacts on the forest fragmentation. But compared to the spatial pattern, the area increment of the developed land was the major factor. The results from this study suggest that the measures, including delimiting urban growth boundary and constructing ecological network via patch-corridor-matrix paradigm, will help connect the fragmented habitat and restore the ecosystem function.