“城中田”生物多样性维持功能测度——以重庆市永川区为例

Assessment of Biodiversity Maintenance Functions in "Urban Farmland": Taking Yongchuan District, Chongqing City as an Example

关键词:  风景园林  城中田  生物多样性维持  InVEST模型  生态网络

Key words:  landscape architecture  urban farmland  biodiversity maintenance  InVEST model  ecological network

摘要:

随着城市化进程加速，“城中田”将成为大部分城市中广泛存在的绿色空间类型。维护和利用“城中田”多元生境空间首先需要清晰认知其对生物多样性的维持功能。以重庆市永川区为例，基于生境质量和景观连通性复合视角，综合InVEST模型、生态网络情景模拟等多种方法，定量测度了“城中田”斑块的生物多样性维持功能。结果显示：1)“城中田”对城市综合生境质量的贡献仅次于林地与水体；2)“城中田”可显著提升城市景观格局的总体连通性；3)永川区生物多样性维持功能较高的“城中田”斑块集中分布于研究区中部和北部地区，面积占比达“城中田”总面积的61.86%，多沿永川河消落带分布。研究结果提供了一个量化识别“城中田”生物多样性维持功能的综合分析框架，有助于深入了解城市生态资源，并为城市生物多样性保护提供支撑。

Abstract:

As urbanization accelerates globally, residual green spaces within cities have become critical for biodiversity conservation. "Urban farmland", referring to agricultural land persisting within urban built-up areas - often preserved through policies such as the "opening skylights" method for permanent basic farmland - represents a prevalent yet underexplored form of urban green space. While theoretical studies suggest that such farmland may contribute to urban ecological functions, empirical and quantitative assessments of its biodiversity maintenance capacity remain limited. This study addresses this gap by quantitatively evaluating the biodiversity maintenance functions of urban farmland patches in Yongchuan District, Chongqing, China, from an integrated perspective of habitat quality and landscape connectivity. The research employs a multi-method framework combining the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model with ecological network scenario simulations. First, the InVEST habitat quality model is used to assess the contribution of different land use types to overall urban habitat quality. Second, two ecological network scenarios are simulated using circuit theory: one excluding urban farmland as a potential source habitat (Scenario I), and another including it (Scenario II). The comparison between these scenarios reveals the role of urban farmland in enhancing landscape connectivity. Finally, a two-dimensional evaluation matrix integrating normalized least-cost corridor values (NLCC) and centrality metrics is constructed to classify urban farmland patches into five levels of biodiversity maintenance function: low, relatively low, medium, relatively high, and high. Results indicate that urban farmland plays a significant role in urban ecological systems. In terms of habitat quality, urban farmland ranks third among eleven land use types in its contribution to overall urban habitatquality, surpassed only by woodland and water bodies. Its contribution rate is nearly equivalent to that of water bodies, underscoring its substantial ecological value. Regarding landscape connectivity, incorporating urban farmland into the ecological network increases the number of corridors from 229 to 281, reduces average corridor length from 404.5 m to 271.0 m, and raises the proportion of short-distance corridors (<500 m) from 69.4% to 81.1%, indicating a marked improvement in overall landscape connectivity. Spatial analysis reveals that approximately 61.86% of urban farmland patches with relatively high or high biodiversity maintenance functions are concentrated in the central and northern parts of Yongchuan District, predominantly along the riparian zones of the Yongchuan River. These findings suggest that proximity to water bodies and integration into riparian ecological systems enhance the ecological performance of urban farmland. Conversely, patches with lower functional ratings are scattered in the western and southern peripheries, often isolated by industrial or urban construction land. This study provides a comprehensive analytical framework for quantifying the biodiversity maintenance functions of urban farmland, offering scientific support for urban ecological planning and the sustainable management of intra-urban agricultural spaces. It demonstrates that even small-scale agricultural patches can serve as vital components of urban ecological networks, particularly when strategically located and ecologically enhanced. The methodology and insights apply to other cities facing similar challenges in balancing urban development with biodiversity conservation.