Carbon absorption capability and morphological traits are crucial for plant leaf function performance. Here, we investigated the five bamboos at different elevations to clarify how the leaf trait responds to the elevational gradient, and drive the photosynthetic capacity variations. We selected five bamboo species located along different elevations in Wuyi Mountain, southeastern China. The Standardized Major Axis Regression (SMA) analyses and the Structural Equation Model (SEM) are applied to identify how the bamboo leaf trait, including the ratio of leaf length to width (W/L), leaf mass per area (LMA), photosynthesis rates (Pn), leaf nitrogen, and phosphorus concentration (Nmass and Pmass) response to elevation environment, and the driving mechanism of Pn changes. Across the five bamboo species, our results revealed the Pmass of Phyllostachys edulis and Oligostachyum oedogonatum decreased with increasing elevation, but the Nmass, and LMA of Indocalamus tessellatus increased. Besides, the Pmass scaled isometrically with respect to W/L, the Nmass scaled allometrically as the 0.80-power of Pmass, and Nmass and Pmass scaled allometrically to Pn, with the exponents of 0.58 and 0.73, respectively. The SEM result showed altitude, morphological trait (W/L and LMA), and physiological trait (Nmass and Pmass) could together explain the 44% variations of Pn, with a standard total effect value of 70.0%, 38.5%, 23.6% to Pmass, Nmass, and W/L, respectively. The five bamboo species along the different elevational share an isometric scaling relationship between their Pmass and W/L, providing partial support for the general rule and operating between morphological and physiological traits. The scaling relationship between Pmass and W/L is insensitive to elevation and species. Further, the leaf W/L and Pmass as the main trait that affects leaf area and P utilization in growth and thus drives bamboo leaf photosynthetic capacity variations in different elevations.

Understanding the scaling between leaf size and leafing intensity is crucial for comprehending theories about light interception and leaf carbon uptake and adjustments in life history strategies. To test whether have the broad scope predictions between leaf size variation and leafing intensity on first year stem in evergreens and deciduous. A comprehensive data set of minimum (Mmin) and maximum (Mmax) leaf mass and total leaf number in twig was compiled, as well as data for the stem volume and mass. The datasets provide measurements of 123 woody species in subtropical mountain forests. Standardized major axis (SMA) analysis was used to determine the effects of the variation in leaf size (i.e., Mmin to Mmax) and the effects of different functional groups on the trade-off between leaf size and leafing intensity, i.e., the leafing intensity based on stem volume (LIV) and stem mass (LIM). Leaf size plasticity variation did not differ between evergreen and deciduous functional groups, but Mmin scaled as the 1.19 power of Mmax. Across the 123 species, the scaling exponents of the pooled data ranged between -1.14 to -0.96 for Mmin and Mmax vs. the leafing intensity based on stem volume (LIV) and from -1.24 to -1.04 for Mmin and Mmax vs. the leafing intensity based on stem mass (LIM). Across the subtropical woody species examined in this study, the results show the scaling relationship between leaf mass and leafing intensity is constrained to be ≤ -1.0. More importantly, the scopes in twig leaf size and the leafing intensity correlate with the biomass allocation to minimum and maximum leaf mass, and not sensitive to plant functional groups in subtropical mountain forests.