Mixed Planting Can Improve Leaf Gas Exchange by Diversifying Plant Water Absorption Strategy

ABSTRACT Plants with diverse neighbors often exhibit significant variation in water absorption strategies, yet the responses of leaf gas exchange traits to water absorption strategies remain complex and uncertain. Therefore, we examined Robinia pseudoacacia and Quercus acutissima forests in the warm temperate zone, quantifying the water absorption strategies and leaf gas exchange traits across seasons to assess the impact of water absorption strategies dynamics. Our results demonstrate that mixed planting significantly enhanced the net photosynthetic rate compared to pure planting across all seasons, with a particularly pronounced effect for Q. acutissima . Furthermore, mixed planting promoted instantaneous water use efficiency in R. pseudoacacia while reducing transpiration and leaf midday water potential in Q. acutissima . The relationship between leaf gas exchange traits and water absorption strategies varies seasonally: in spring, a significant positive correlation was found between net photosynthetic rate and water absorption strategy; in summer, a similar correlation was observed between transpiration rate and water absorption strategy; in autumn, a significant positive correlation was noted between instantaneous water use efficiency and water absorption strategy, whereas a significant negative correlation was found between leaf midday water potential and water absorption strategy. These findings reveal that the seasonal responses of leaf gas exchange traits to water absorption strategies reflect key adaptive mechanisms of R. pseudoacacia and Q. acutissima . This study provides critical scientific guidance for optimizing forest restoration and management strategies, particularly in enhancing productivity and mitigating water competition in warm temperate zones.