Functional traits and its variation linked to species’ degree of isohydry in subtropical regions with high heterogeneity

Purpose The degree of species’ isohydry determined by the stringency degree of stomatal regulation is commonly used to classify species’ drought response strategies. The aim of our study is to determine the linkages of plant functional traits and their variations to species’ degree of isohydry in subtropical regions with high heterogeneity. Methods In subtropical plantations with high heterogeneity, 13 woody species were selected and determined for 23 above- and below-ground functional traits both in the pure soil (rich) and soil-rock mixed (poor) patches. Results The less isohydric species tend to allocate more to leaves, stems and roots construction than the more isohydric species to resist droughts, while the more isohydric species were more efficient in accessing resources. Consistently, the less isohydric species adapt to the environmental change by altering the traits relating to nutrient absorption efficiency (e.g. changing their leaf C/N, first-order root diameter, and root branching intensity), while the more isohydric species tend to change their drought resistance ability (e.g. changing their wood density and leaf water potential at the turgor loss point). Moreover, the more isohydric species decreased the relative growth rate (RGR), while the less isohydric species increased the RGR when their growth conditions changing from rich patches to poor patches. Conclusions Our results showed that the degree of species’ isohydry results from complex coordination and integration of a series of traits at the whole-plant level, and highlighted the importance of intraspecific variation in traits in determining species’ degree of isohydry in subtropical regions with high heterogeneity.