Rapid urbanization has caused significant changes along the urban-rural gradient, leading to a variety of landscapes that are mainly shaped by human activities. This dynamic interplay also influences the distribution and characteristics of trees outside forests (TOF). Understanding the pattern of these trees will support informed decision-making in urban planning, in conservation strategies, and altogether in sustainable land management practices in the urban context. In this study, we employed a deep learning-based object detection model and high resolution satellite imagery to identify 1.3 million trees with bounding boxes within a 250 ​km2 research transect spanning the urban-rural gradient of Bengaluru, a megacity in Southern India. Additionally, we developed an allometric equation to estimate diameter at breast height (DBH) from the tree crown diameter (CD) derived from the detected bounding boxes. Our study focused on analyzing variations in tree density and tree size along this gradient. The findings revealed distinct patterns: the urban domain displayed larger tree crown diameters (mean: 8.87 ​m) and DBH (mean: 43.78 ​cm) but having relatively low tree density (32 trees per hectare). Furthermore, with increasing distance from the city center, tree density increased, while the mean tree crown diameter and mean tree basal area decreased, showing clear differences of tree density and size between the urban and rural domains in Bengaluru. This study offers an efficient methodology that helps generating instructive insights into the dynamics of TOF along the urban-rural gradient. This may inform urban planning and management strategies for enhancing green infrastructure and biodiversity conservation in rapidly urbanizing cities like Bengaluru.

中文翻译：

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揭示特大城市班加罗尔城乡梯度沿线森林外树木的城市化影响


快速的城市化导致了城乡梯度的重大变化，导致了主要由人类活动塑造的各种景观。这种动态相互作用还影响了森林外树木 （TOF） 的分布和特征。了解这些树木的模式将有助于在城市规划、保护策略以及城市环境中的可持续土地管理实践中做出明智的决策。在这项研究中，我们采用基于深度学习的对象检测模型和高分辨率卫星图像来识别 250 平方公里研究横断面内 130 万棵带有边界框的树木，横跨印度南部大城市班加罗尔的城乡梯度。此外，我们开发了一个异速生长方程，从检测到的边界框得出的树冠直径 （CD） 来估计胸径 （DBH）。我们的研究重点是分析沿该梯度的树木密度和树木大小的变化。研究结果揭示了不同的模式：城市地区显示出较大的树冠直径（平均值：8.87 m）和胸径（平均值：43.78 cm），但树木密度相对较低（每公顷 32 棵树）。此外，随着距市中心距离的增加，树木密度增加，而平均树冠直径和平均树木基部面积减少，显示出班加罗尔城乡地区树木密度和大小的明显差异。本研究提供了一种有效的方法，有助于对 TOF 沿城乡梯度的动态产生指导性见解。这可能会为城市规划和管理策略提供信息，以加强班加罗尔等快速城市化城市的绿色基础设施和生物多样性保护。