Variation in functional traits and allometric relationships of Laguncularia racemosa leaves across developmental stages and canopy vertical positions

We measured 12 leaf functional traits of Laguncularia racemosa across three canopy vertical positions (upper, middle, and lower) and two developmental stages (young and mature leaves). Variation patterns and allometric relationships of these traits were analyzed, and the contributions of canopy vertical position and developmental stage to leaf trait variation were quantified using redundancy analysis (RDA).Key results: Developmental stage was the dominant factor driving leaf trait variation, explaining 24.26% of the total variation, much higher than the 3.13% explained by canopy vertical position.

Young leaves had significantly smaller leaf morphological traits than mature leaves, with mature leaves exhibiting fresh weight and dry weight 1.8 and 1.6 times those of young leaves, respectively. Allometric analysis revealed that both leaf area and leaf thickness exhibited negative allometry relative to specific leaf area, indicating that the rates of leaf area expansion and thickening were faster than the rate of change in specific leaf area.

Leaf dry weight showed isometric or positive allometry with leaf area, suggesting that the rate of dry matter accumulation was not lower than that of area expansion. RDA further revealed that young and mature leaves were completely separated along RDA1, while canopy vertical positions were distributed continuously along RDA2 in an upper–middle–lower sequence, indicating that leaf traits varied continuously with decreasing light intensity across canopy vertical positions rather than diverging independently among positions.Conclusions: L. racemosa achieves functional optimization by adjusting leaf traits across developmental stages and canopy vertical positions, and its high leaf trait plasticity underpins its rapid growth.