Abstract: Global change factors (e.g. climate warming and altered precipitation regimes) and island area are widely known to affect the leaf economic traits of island-dwelling plants in various ways, such as through changes to aboveground plant species richness and belowground soil properties. However, our understanding of the relative importance of factors shaping the leaf economics trait pattern remains limited. In this study, we selected 20 representative tropical islands in the South China Sea that varied in area and climate conditions, and then measured plant community composition, several leaf economic traits associated with plant growth strategies (i.e. the specific leaf area, leaf dry matter content and leaf thickness), and a series of soil physicochemical properties. We found that the mean annual temperature and precipitation significantly influenced the community-level specific leaf area by affecting the soil total nitrogen and phosphorus content. Likewise, climatic factors and island area directly impacted the community-level leaf dry matter content, with additional indirect effects mediated through plant species richness and the soil total potassium content. Similarly, in addition to the direct impact of mean annual temperature and island area, mean annual temperature could significantly affect community-level leaf thickness by altering soil total potassium content. Overall, our findings highlight the importance of plant species richness and soil properties in shaping leaf economic trait dynamics among island-dwelling plant species and also provide critical insights into shifts in plant growth strategies under global change scenarios.

Key words: growth-defense trade-off, island biogeography, leaf dry matter content, plant diversity, soil nutrients, specific leaf area