Leaf functional traits vary with the adult height of plant species in forest communities

Aims Within-community variation accounts for a remarkable proportion of the variation in leaf functional traits. Plant height may be used to explain within-community variances of leaf traits because different microenvironments, especially light intensity, may occur at differ ent heights. This study determines whether or not leaf nitrogen (N) and phosphorus (P) contents as well as leaf mass per area (LMA) are interspecifically correlated with the adult height of forest woody species. We also discuss these relationships with respect to community structure and functions of the ecosystem. Methods A total of 136 dicotyledonous woody species from 6 natural forests (3 evergreen and 3 deciduous ones) in East China (latitude: 18°44′ – 45°25′ N, longitude: 108°50′–128°05′ E) were investigated. For each of the 157 species–site combinations, 6 traits were measured: plant adult height relative to the forest canopy (H R), leaf N and P contents per unit area (N area and P area), N and P contents per unit dry mass (N mass and Pmass) and LMA. The total variances of each leaf trait across sites were partitioned in a hierarchical manner. The relationships between leaf traits and H R within forest communities were then analyzed using both standardized major axis regression and Felsenstein’s phylogenetic independent contrasts. Relationships between evergreen and deciduous forests were compared by linear mixed models. Important Findings HR is a robust predictor of leaf N area, Parea and LMA, explaining 36.7, 39.4 and 12.0% of their total variations across forests, respectively. Leaf Narea, Parea and LMA increased with H R in all of the studied forests, with slopes that were steeper in evergreen forests than in deciduous ones. Leaf N mass and Pmass showed no significant relationship with H R generally. The increase in leaf Narea, Parea and LMA with HR across species is assumed to maximize community photosynthesis and may favor species with larger H R.