Slope mediates drought sensitivity but does not affect drought recovery for young trees along elevation gradients in temperate planted larch forests

Climate warming causes mountainous species to shift their distributions towards higher elevations. How elevation influences growth–climate relationship in mountain regions has been intensively investigated. However, how microtopography shapes tree growth and its drought resistance along the elevation gradient remains poorly understood. We used a network of Larix principis-rupprechtii tree-ring data comprising 1,918 trees from different age classes and mountain slopes, along an elevation gradient ranging from 970 to 1,869 m, to investigate how slope gradients mediate the growth and drought resilience of larch trees along an elevation gradient in North China. Growing season drought and temperature were the major limiting climatic factors for larch trees across the study region. Larch trees younger than 40 years exhibited a stronger positive correlation between basal area increment (BAI) and elevation on steep slopes (10°–35°) than on flat (0°–5°) or gentle (5°–10°) slopes. At low-elevation steep slopes, the growth of larch trees younger than 40 years showed a stronger correlation with the Palmer drought severity index (PDSI). Both resistance and resilience were found to increase along the elevation gradient on steep slopes for young larch trees but not for old larch trees. No significant differences were observed in the drought recovery ability of larch trees across all age groups at increasing elevation. Our results highlight that drought events may particularly affect the growth of young larch trees on low-elevation steep slopes, with potential repercussions on mortality rates.