Climate change alters the bioclimatic conditions during the growing period of trees directly, but also indirectly by causing shifts in spring and autumn leaf phenology that lead to changes in the timing and length of the growing period. Several studies researched the ecological consequences of direct climate change effects on bioclimatic conditions during the growing period of trees. However, the complementary and indirect effects through phenological shifts on these conditions have been insufficiently investigated. We analysed 49088 leaf unfolding and leaf colouring dates of six major European tree species from Switzerland, observed between 200 and 1900 m a.s.l. during 1961–2018. We estimated phenological trends, the resulting changes in bioclimatic conditions during the growing period, and the relative contributions of phenological shifts towards these changes. Our results show that climate change advanced leaf unfolding by up to –3.0 days/decade since 1985. Leaf colouring was mainly delayed at low elevations and was advanced or delayed at high elevations with species-specific rates between –3.1 and +4.0 days/decade. While the length of the growing period and growing degree-days increased for most species after 1985, precipitation during the growing period predominantly decreased by up to –43.6 mm/decade. Furthermore, drought intensity during the growing period (based on the number of days with negative water balance) increased significantly for most species, reaching +6.7 days/decade at low elevations. Phenological shifts amplified the trends towards drier conditions by up to +81% at low elevations for beech, rowan, and sycamore, but weakened them by up to –84% at high elevations for beech, rowan, sycamore, and larch. These findings indicate widely increased drought stress, especially at lower elevations. Further, we conclude that future forest net ecosystem productivity in Central Europe will depend strongly on elevation and species composition, despite a general lengthening of the growing period for trees.

气候变化会直接改变树木生长期间的生物气候条件，但也会通过引起春季和秋季叶片物候的变化而间接改变，从而导致生长期时间和长度的变化。多项研究研究了气候变化对树木生长期间生物气候条件的直接影响的生态后果。然而，通过物候变化对这些条件的补充和间接影响尚未得到充分研究。我们分析了来自瑞士的六种主要欧洲树种的 49088 叶展开和叶着色日期，这些树种在 1961 年至 2018 年期间在 200 至 1900 米之间观察到。我们估计了物候趋势，生长期生物气候条件的变化，以及物候变化对这些变化的相对贡献。我们的结果表明，自 1985 年以来，气候变化使叶子展开最多 –3.0 天/十年。叶子着色主要在低海拔地区延迟，在高海拔地区提前或延迟，物种特异性比率在 –3.1 至 +4.0 天/十年之间. 虽然 1985 年后大多数物种的生长期长度和生长期日数增加，但生长期的降水主要减少了 –43.6 毫米/十年。此外，大多数物种在生长期的干旱强度（基于负水平衡的天数）显着增加，在低海拔地区达到 +6.7 天/十年。物候变化将山毛榉、罗文、和美国梧桐，但在山毛榉、罗文、美国梧桐和落叶松的高海拔地区削弱了高达 –84%。这些发现表明干旱压力普遍增加，尤其是在低海拔地区。此外，我们得出结论，尽管树木的生长期普遍延长，但中欧未来的森林净生态系统生产力将在很大程度上取决于海拔和物种组成。