Leaf Functional Traits Are Related to Tree Size and Location in Cotton Trees Bombax malabaricum

Exploring intraspecific variation of functional traits of different sizes and ecogeographical regions is important to understand the adaptation strategies of tree populations to their environments. In this study, we explored the variation and bivariate relationships of 16 functional traits of 30 trees of Bombax malabaricum across 5 geographical regions in Hainan Island and between large- and small-sized tree populations. Principal component analysis showed that leaf thickness (LTh), guard cell length, and lower epidermis (LE) thickness were the key functional traits implicated in varying ecological strategies of B. malabaricum. A significant variation was found in the key functional traits including LE thickness, LTh, and guard cell (GCL) in populations across different ecogeographical regions. However, the LE and LTh vary significantly between the large- and small-sized trees. The LTh and LE thickness also showed an allometric relationship across different geographical regions and tree sizes. Hence, it was concluded that trees vary their ecological strategy according to their ontological developments across environments. Moreover, adaptation strategies of large-sized trees differing from small-sized ones highlight the fact that priority should be taken to conserve the trees with high age.