Anthropogenically induced climate change largely affects the functioning of vegetation communities worldwide. In the world's largest land biome, the boreal forest, a persistent decoupling of tree growth from rising summer temperatures has been recorded in recent decades. This so-called ‘Divergence Problem’ (DP) has been studied over the past 30 years, yet the causes and spatial patterns within the boreal forest zone are not well understood. Here, we present tree-ring evidence on varying DP in Larix gmelinii from the globally northernmost forest island on Taymyr Peninsula and Larix sibirica from the southern taiga in central Siberia. Tree-ring width and maximum latewood density data reveal DP to be substantially stronger in the south indicating that growth-climate relationships in Siberian larch passed beyond a tipping point under warmer climate and increased anthropogenic pressure. In the north, the temperature signal remained strong and temporally stable underscoring the skill of tree-ring chronologies for long-term climate reconstructions. These findings highlight the heterogeneity of tree growth responses to global warming within the boreal forest zone, from which spatially varying consequences for carbon and water cycle dynamics must be expected. Our study emphasizes the importance of updating tree-ring chronologies in remote regions within boreal forest zone to foster understanding of spatiotemporal patterns in biomass allocation, permafrost degradation, and DP across this large biome.

中文翻译：

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西伯利亚中部森林苔原和南部针叶林非平稳树木生长反应的评估


人为引起的气候变化在很大程度上影响了全球植被群落的功能。在世界上最大的陆地生物群落——北方森林中，近几十年来，树木生长与夏季气温上升的持续脱钩已经被记录下来。这种所谓的“分歧问题”（DP） 已经研究了 30 年，但北方森林区的原因和空间模式尚不清楚。在这里，我们提供了来自全球最北端的泰米尔半岛森林岛屿的 Larix gmelinii 和来自西伯利亚中部南部针叶林的 Larix sibirica 中不同 DP 的树木年轮证据。树木年轮宽度和最大晚材密度数据显示，南部的 DP 要强得多，这表明在气候变暖和人为压力增加的情况下，西伯利亚落叶松的生长-气候关系超过了临界点。在北部，温度信号仍然很强且时间稳定，这凸显了树木年轮年表对长期气候重建的技能。这些发现突出了北方森林区内树木生长对全球变暖的反应的异质性，必须预期对碳和水循环动态的空间变化影响。我们的研究强调了更新北方森林区偏远地区树木年轮年表的重要性，以促进对这一大型生物群落中生物量分配、永久冻土退化和 DP 的时空模式的理解。