Across much of Europe, climate change has caused a major dieback of Norway spruce (Picea abies L.), an economically important tree species. However, the southeasternmost fringe of this tree species – the Eastern Carpathians – has not yet suffered large-scale dieback. Studying temporal shifts of climate sensitivity (TSCS) over time may elucidate the degree to which Norway spruce may be vulnerable to climate-change induced decline in upcoming decades. Under this framework, we analyzed a regional tree-ring network comprising >3000 trees, with the aim of quantifying TSCS since 1950. We mathematically defined TSCS as the slope parameter of the regression of climate sensitivity (the correlation coefficient) over time. Given the often-observed contrasting shift of climate sensitivity at low versus high elevations, we were particularly interested in studying potentially divergent TSCS along elevational and spatial gradients. Our analyses revealed several indications of TSCS for Norway spruce in the Eastern Carpathians. First, at high elevations (>1100 m a.s.l.), we found that the positive link between summer temperature and spruce growth decreased significantly over the study period. In turn, these trees, over time, featured an increasing positive relationship with late winter temperatures. At low elevations (<800 m a.s.l.), the signal of positive summer Standardised Precipitation-Evapotranspiration Index (SPEI) correlation became more frequent among sites towards 2021, while the strength of the positive winter SPEI correlation from the previous growing season weakened. Our results revealed that TSCS was driven significantly by an elevational climate gradient and a longitudinal continentality gradient. Overall, our findings indicate that Norway spruce is increasingly affected by water limitations under climate change at low elevations, highlighting a potentially rising risk of decline of this species in the Eastern Carpathians.

中文翻译：

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追求变化：挪威云杉气候敏感性沿喀尔巴阡山脉海拔和大陆性梯度的不同时间变化


在欧洲大部分地区，气候变化导致挪威云杉 （Picea abies L.） 严重枯萎，这是一种具有重要经济意义的树种。然而，这种树种最东南的边缘——东喀尔巴阡山脉——尚未遭受大规模的枯死。研究气候敏感性 （TSCS） 随时间的变化可能会阐明挪威云杉在未来几十年内可能受到气候变化引起的衰退的脆弱程度。在这个框架下，我们分析了一个由 >3000 棵树组成的区域树木年轮网络，目的是量化自 1950 年以来的 TSCS。我们在数学上将 TSCS 定义为气候敏感性 （相关系数） 随时间回归的斜率参数。鉴于经常观察到低海拔和高海拔地区气候敏感性的对比变化，我们对研究沿海拔和空间梯度的潜在分歧 TSCS 特别感兴趣。我们的分析揭示了东喀尔巴阡山脉挪威云杉 TSCS 的几个迹象。首先，在高海拔地区（x3E1100 m a.s.l.），我们发现夏季温度与云杉生长之间的正相关关系在研究期间显著下降。反过来，随着时间的推移，这些树木与冬末温度的正相关关系越来越大。在低海拔地区（海拔 3C800 m 处），到 2021 年，夏季标准化降水蒸散指数 （SPEI） 正相关性的信号在站点之间变得更加频繁，而与上一个生长季节的冬季 SPEI 正相关性的强度减弱。我们的结果表明，TSCS 显著受海拔气候梯度和纵向大陆性梯度驱动。 总体而言，我们的研究结果表明，挪威云杉在低海拔地区受到气候变化下水分限制的影响越来越大，这凸显了该物种在东喀尔巴阡山脉下降的风险可能上升。