Climate change is altering forest ecosystems worldwide, particularly in steppe landscapes, where the rare tree communities are challenged with steadily increasing droughts. In the steppe of Eastern Europe, amid dry conditions, Quercus robur occupies mostly riverine habitats and ravines. Here we study the climate sensitivity and drought vulnerability of a Q. robur population located at the rear edge of the species range, in the steppe of Ukraine. The population occupies two adjacent but clearly contrasting in their microclimatic conditions sites: a river floodplain and a steep-sloping river bank. We develop tree earlywood, latewood, and total ring width site-level chronologies and evaluate their relationship with regional climate variables and the local river's water level using response function analysis. We find that trees growing in the floodplain and at the steep river bank have exhibited slightly different growth patterns. The trees at the flooded site have benefited from water proximity, which facilitated their earlywood growth. These trees have responded positively to the current May and previous September precipitation and previous and current May temperatures. At the non-flooded site, the trees have experienced warm temperatures and the lack of precipitation in June. The extreme drought episodes have triggered a decrease in the latewood and total ring width in trees from both sites. We established that oak growth in the floodplain had been depressed by an unknown stressor around 1900, therefore limiting our ability to identify the more beneficial steppe habitat for Q. robur conclusively. Nevertheless, our results provide a dendrochronological evidence of Q. robur survival in a dry steppe environment and lend new insights into local microclimatic factors contributing to it.

气候变化正在改变世界范围内的森林生态系统，尤其是在草原景观中，在这些景观中，稀有树木群落面临着不断增加的干旱挑战。在东欧草原上，干燥的干旱条件下，栎属居群主要占据河流栖息地和沟壑。在这里，我们研究了Q. robur的气候敏感性和干旱脆弱性种群位于该物种的后缘，在乌克兰的草原上。人口在其微气候条件下占据两个相邻但明显相反的地方：河漫滩和陡峭的河岸。我们开发树木早木，晚木和总环宽站点级别的年表，并使用响应函数分析评估它们与区域气候变量和当地河流水位的关系。我们发现在洪泛区和陡峭河岸生长的树木表现出略有不同的生长方式。淹水地点的树木得益于水的接近，从而促进了早材的生长。这些树木对当前的5月和9月的降水以及5月以前和当前的温度有积极的响应。在非淹没地点，树木在6月经历了温暖的温度和缺乏降水。极端干旱事件触发了两个地点的树木的胶合木和总环宽度的减少。我们确定，在1900年左右，洪涝平原的橡树生长因未知的压力源而受到抑制，因此限制了我们识别更有利的草原栖息地的能力。Q. robur的结论是。然而，我们的结果提供了旱地草原环境中罗氏梭菌存活的树状年代学证据，并为造成这种现象的当地微气候因素提供了新的见解。