城市破碎化和植被恢复型绿色空间对植物物种丰富度的影响
Impacts of Urban Fragmented and Revegetated Greenspace on Plant Species Richness
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摘要: 如何平衡城市发展与生物多样性保护之间的矛盾, 是提升城市生态系统稳定性、多样性和持续性的关键问题, 也是城市生态文明建设的重要内容。城市主要依托绿色空间进行生物多样性保护, 快速城市化导致生物栖息地分裂成破碎化型绿色空间(FGS), 同时不透水面也不断转变为植被恢复型绿色空间(RGS), 但是, FGS和RGS通往生物多样性平衡的过程不同。因此, 需要明确区分不同类型绿色空间对城市生物多样性影响的机制, 从而为城市更新生物多样性的保护与恢复策略提供重要依据。以扬州市广陵区为研究区, 利用2007、2012和2022年遥感数据对绿色空间进行分类; 对FGS和RGS分别开展38和20条植物群落样线调查, 采用Spearman相关性分析和广义线性混合模型识别对植物物种丰富度有显著贡献的景观指数; 运用结构方程模型解析不同绿色空间格局动态变化对植物物种丰富度的直接和间接效应。结果表明, 2012年FGS格局通过斑块数量、连接度和形状指数等景观指数直接主导2022年植物物种丰富度, 同时也支配着2022年FGS基本格局; 相反, 就RGS而言, 植物物种丰富度主要由2022年RGS格局塑造, 周长面积比指数和邻近指数是关键指标。据此, 提出3个建议: (1)识别城市绿色空间动态变化的过程; (2)构建连接FGS和RGS的生态廊道, 建立源-汇动态, FGS是源, RGS是汇; (3)重点监测和防治RGS中的植物入侵风险。Abstract: 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.