How tree architecture varies across coexisting tropical tree species and relate to ecological strategies?

Architecture refers to the overall shape of a tree and the spatial position of its components. Tree height determines the position in the forest canopy and access to light, while the amount and spatial distribution of the foliage depend on the depth and the width of the crown. The aim of this study is to understand how tree architecture varies across coexisting tropical tree species and relates to ecological strategies. Forty five coexisting tree species were sampled in the semi-deciduous forests of Northern Congo. Species were classified according to ecological strategies, specifically regeneration guilds: shade bearers (27 species), non-pioneers light demanding (14 species) and pioneers (4 species). For each species, 14–72 trees (968 trees in total) were measured over a large range of diameter (10–162 cm). At the tree level, we measured the diameter (D in cm), height (H in m), crown radius (Cr in m) and crown depth (Cd in m) and crown exposure index (CEI) was visually estimated. At species level, architectural traits were estimated at juvenile tree with diameter of 10 cm (H10, Cr10 and Cd10) and at adult stature with maximum diameter (Hmax, Crmax and Cdmax), life history traits (dispersal mode, phenology and regeneration guild) and functional traits (wood density and light requirement) were obtained. Our results showed a significant variation in tree allometry between coexisting species. The interspecific variation was related to light requirement (H-D allometry), dispersal mode (Cr-D allometry) and liana infestation (Cd-D allometry). Large-statured tree species were light demanding, deciduous and wind dispersed, while small-statured tree species were evergreen, dense wooded, and animal dispersed. Architectural traits strongly differed between regeneration guilds.