Abstract In the Mediterranean region, the coupled effect of recent changes in climatic features and an increase in human-related water demand induced a progressive reduction in the water level of many lakes. Consequently, intense withdrawals for public supply can affect the health of lake ecosystems and increase trees’ vulnerability to predicted drought intensification effects. This study aimed to evaluate, through a dendroecological analysis of riparian trees, the strength of the climatic and hydrological signals retained in the tree-ring widths and to detect a critical water-level threshold affecting tree resilience and growth recovery. Our study area is located within the Regional Natural Park of Bracciano-Martignano in central Italy. In recent years, the lake water-level drop observed at Bracciano after intensive water withdrawals raised concerns about the ecological impacts on the ecosystem's vulnerability. The main distinctive pattern in the climate-growth relations was the influence of previous years precipitation and drought conditions up to five years at Bracciano. At Martignano, where lake water withdrawals are absent, long-term climatic signals disappeared after two years. The intensive human water use at Bracciano Lake most likely induced trees to be more dependent on groundwater raising or soil water content stored from the previous rainy periods especially on an annual scale. On the other hand, tree-ring growth was strongly correlated with short-term water-level fluctuations (monthly – seasonal). Tree-rings of riparian species appear to be a useful tool to detect critical water levels after the intensive water withdrawals and the increase in dry conditions occurred in the past few decades. Yearly values ranging from -108 to -139 cm may be considered as potential thresholds affecting riparian species. This finding may support lake water withdrawal regulation for riparian ecosystem protection and conservation under future drought intensification.

中文翻译：

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气候和人为对不同干扰机制下河岸湖泊森林生态系统树木年轮生长的影响

摘要 在地中海地区，近期气候特征变化和人类用水需求增加的耦合效应导致许多湖泊的水位逐渐下降。因此，公共供应的大量取水会影响湖泊生态系统的健康，并增加树木对预测的干旱加剧影响的脆弱性。本研究旨在通过对河岸树木的树木生态学分析，评估树木年轮宽度中保留的气候和水文信号的强度，并检测影响树木恢复力和生长恢复的临界水位阈值。我们的研究区位于意大利中部的 Bracciano-Martignano 区域自然公园内。最近几年，大量取水后在布拉恰诺观察到的湖泊水位下降引起了人们对生态系统脆弱性的生态影响的担忧。气候-增长关系的主要独特模式是前几年在布拉恰诺长达五年的降水和干旱条件的影响。在马蒂尼亚诺，湖水没有取水，两年后长期气候信号消失了。布拉恰诺湖密集的人类用水很可能导致树木更加依赖地下水的增加或以前雨季储存的土壤含水量，尤其是在每年的规模上。另一方面，树木年轮的生长与短期水位波动（每月 - 季节性）密切相关。在过去几十年中大量取水和干旱条件增加后，河岸物种的年轮似乎是检测临界水位的有用工具。年值范围从 -108 到 -139 厘米可被视为影响河岸物种的潜在阈值。这一发现可能支持未来干旱加剧下湖泊取水调节以保护河岸生态系统。