Urban forests, vital for providing ecosystem services in cities, face challenges from climatic factors, particularly in heterogeneous urban environments. Kyiv, one of Europe’s largest and most populated cities, boasts a varied topography, with about 55 % of its area covered by forests, where Quercus robur predominates. In this study we investigate the sensitivity of Q. robur trees to climatic factors within Kyiv's urban forest, utilizing tree ring widths as a proxy. Employing dendrochronological approaches, we built nine site-mean ring-width chronologies and identified the growth pointer years and their frequency. Using moving windows in daily correlation analysis, we examined Q. robur response to climatic variations over the last 135 years. Additionally, linear mixed-effects models (LMMs) were applied to the site-specific characteristics such as slope steepness, altitude a.s.l., soil type, soil mechanical composition, soil pH, forest type and coefficient of soil saturated hydraulic conductivity, to identify which of them exert a significant influence on studied trees’ sensitivity to precipitation and temperature. Our results showed that the frequency of negative or positive pointer years in Q. robur growth coincides with extremely dry or wet years. The precipitation amount falling from the dormant period to the early growing season emerges as the key factor for Q. robur trees' radial growth. The trees' sensitivity to this factor was found to be significantly influenced by the slope steepness. Our findings contribute valuable insights into the complex interplay between urban heterogeneity, climatic factors, and the climatic sensitivity of Q. robur in urban areas. This research contributes to a deeper understanding of urban forests’ dynamics, proposing management strategies for slope stability, soil water retention, and natural tree regeneration.

中文翻译：

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地形的陡峭程度决定了城市橡树林对气候变化的敏感性


城市森林对于提供城市生态系统服务至关重要，但面临气候因素的挑战，尤其是在异质城市环境中。基辅是欧洲最大、人口最多的城市之一，拥有多样的地形，约 55% 的面积被森林覆盖，其中栎属 （Quercus robur） 占主导地位。在这项研究中，我们以树木年轮宽度为代表，调查了 Q. robur 树木对基辅城市森林内气候因素的敏感性。采用树木年代学方法，我们建立了 9 个站点平均环宽年表，并确定了生长指针年份及其频率。在每日相关性分析中使用移动窗口，我们研究了过去 135 年中 Q. robur 对气候变化的反应。此外，线性混合效应模型 （LMM） 应用于特定地点的特征，例如坡度、海拔高度、土壤类型、土壤力学成分、土壤 pH 值、森林类型和土壤饱和水力传导系数，以确定其中哪些对研究树木对降水和温度的敏感性产生重大影响。我们的结果表明，栎树生长中负或正指针年份的频率与极度干燥或潮湿的年份相吻合。从休眠期到生长初期的降水量成为栎树径向生长的关键因素。发现树木对这一因素的敏感性受到坡度的显著影响。我们的研究结果为城市异质性、气候因素和城市地区 Q. robur 的气候敏感性之间的复杂相互作用提供了有价值的见解。 这项研究有助于更深入地了解城市森林的动态，为边坡稳定性、土壤保水和自然树木再生提出管理策略。