Leaf economic traits link drought and heat tolerance of woody species in two contrasting hydrothermal habitats

The combined stress of drought and high temperature is posing a growing threat to plants. However, how plants coordinate growth and tolerance to cope with the multiple stresses in natural habitats remains poorly understood. We examined nine traits related to leaf drought and heat tolerance, and leaf economics across 58 species from one dry-hot habitat dominated by deciduous species and one wet-warm habitat dominated by evergreen species. Heat and drought tolerance were only weakly associated, while leaf economics was linked closely with heat and drought tolerance through maximum photosynthetic rate per mass and leaf mass per area, respectively. Heat tolerance was primarily influenced by leaf habit, whereas drought tolerance and leaf economics were affected by both leaf habit and habitat. Leaf economic traits were associated more with drought tolerance within evergreen species, while they were linked more with heat tolerance within deciduous species. This study offers new insights that leaf economics is central to linking drought and heat tolerance, with leaf habit as a key influencing factor. This enhances our understanding of plant adaptation strategies in response to increasing drought and warming climate.