Impacts of Urban Fragmented and Revegetated Greenspace on Plant Species Richness

The reconciliation between urban development and biodiversity conservation is a pivotal issue for enhancing the stability, diversity, and sustainability of urban ecosystems, constituting an integral component of constructing urban ecological civilization. Cities primarily depend on greenspaces for biodiversity conservation. Fragmentation processes usually dominate greenspace formation during rapid urbanization, a process whereby a large and intact habitat is split into many small and isolated patches (fragmented greenspace, FGS). Revegetation occurs when an established city invests in greenspaces, a process to create greenspaces by replanting, transforming disturbed unplanted urban areas such as impervious surfaces into habitats covered with vegetation (revegetated greenspace, RGS). But, the way species richness approaches diversity equilibrium is different for greenspaces established by fragmentation or revegetation. Therefore, understanding the distinct impacts of fragmentation and revegetation on urban biodiversity paves the way for improving current conservation and restoration strategies. Taking the Guangling District of Yangzhou City as the research area in this study. Remote sensing data from 2007, 2012 and 2022 was used to classify greenspaces. A total of 38 and 20 plant transect lines were surveyed in FGS and RGS, respectively. Spearman correlation analysis and a general linear mixed model were employed to identify landscape indices that significantly contributed to plant species richness. Furthermore, a structural equation model was utilized to determine both the direct and indirect effects of dynamic changes in the different greenspace patterns on plant species richness. The results indicate that the current plant species richness was influenced by the number of patches, proximity index and shape index in FGS from the previous 10 years, which also dominated the current FGS basic pattern. On the contrary, plant species richness was predominantly affected by the perimeter-area ratio and contiguity index in the current RGS. Accordingly, three suggestions have been put forward: (1) We must correctly identify how the urban greenspace changed dynamically, either via fragmentation or revegetation. (2) The construction of ecological corridors to connect FGS and RGS is crucial to maintaining urban biodiversity. Purposefully connected greenspaces generated by different processes can establish source-sink dynamics, in which FGS serves as the source and RGS is the sink. (3) Monitoring and controlling the risk of invasive plant species in revegetated greenspaces is needed.