Basic ecological theory suggests that a tradeoff between competitiveness and stress tolerance dictates species range limits at regional extents. However, empirical support for this key theory remains deficient because the necessary spatial and temporal coverage and scalability of field observations has rarely been achieved. We harnessed an extensive dendroecological network (> 22 000 tree-ring samples from 816 forest inventory plots) to disentangle competition-limited from climate-limited growth in both overstory and understory trees. Growth synchrony among trees thereby served as an integral metric of climate sensitivity, an approach that we justify in supplementary analyses of growth responses to temperature, precipitation, and the standardized precipitation-evapotranspiration index. Sampling plots were arranged along elevational climate and vegetation gradients throughout the Carpathian Mountains, ranging from mixed-species lowland forests to coniferous forests at high elevations. With mixed-effect modelling, we also identified non-climatic factors (stand characteristics, species diversity, and disturbance history) that modulate spatial patterns in the growth rate and synchrony of European beech Fagus sylvatica and Norway spruce Picea abies. Beech exhibited reduced growth and increased climate sensitivity towards higher elevations but performed better when species diversity was higher. The growth of spruce increased towards its lower range boundary, but understory cohorts grew poorly under interspecific competition. Overall, climate sensitivity was lower in more productive stands with benign climatic conditions and in recently disturbed sites with reduced stand density. These contrasting performances at mid-elevations where the two species overlap (900–1300 m a.s.l.) reflect their evolutionary history, which enables them to be competitive (beech) or cold-stress tolerant (spruce). This history will affect interactions between the two species under climate warming and shape macroecological patterns in the Carpathian ecoregion and likely other parts of Europe. Our findings point to a growing advantage of competitively stronger species in montane and subalpine vegetation zones.

中文翻译：

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气候竞争权衡决定了欧洲山毛榉和挪威云杉沿着喀尔巴阡山脉海拔梯度的范围限制


基本生态理论表明，竞争力和抗逆性之间的权衡决定了区域范围内的物种范围限制。然而，这一关键理论的实证支持仍然不足，因为现场观测所需的时空覆盖范围和可扩展性很少实现。我们利用广泛的树木生态网络（来自 816 个森林清查地块的超过 22,000 个树木年轮样本）来区分林上和林下树木的竞争限制与气候限制生长。因此，树木之间的生长同步性成为气候敏感性的一个整体指标，我们在对温度、降水和标准化降水-蒸散指数的生长响应的补充分析中证明了这种方法的合理性。采样点是沿着整个喀尔巴阡山脉的海拔气候和植被梯度排列的，范围从混合物种的低地森林到高海拔的针叶林。通过混合效应模型，我们还确定了调节欧洲山毛榉和挪威云杉生长速率和同步性空间模式的非气候因素（林分特征、物种多样性和干扰历史）。山毛榉对较高海拔表现出生长减缓和气候敏感性增加，但当物种多样性较高时表现更好。云杉的生长向其较低范围边界增加，但林下群体在种间竞争下生长不良。总体而言，在气候条件良好、生产力较高的林分和最近受到干扰、林分密度降低的林分中，气候敏感性较低。这些对比表现在两个物种重叠的中海拔地区（海拔 900-1300 米）。）反映了它们的进化历史，这使它们具有竞争力（山毛榉）或耐冷胁迫（云杉）。这段历史将影响气候变暖下两个物种之间的相互作用，并塑造喀尔巴阡生态区和欧洲其他地区的宏观生态模式。我们的研究结果表明，在山地和亚高山植被区，竞争较强的物种的优势日益增强。