Architecture of 54 Moist-Forest Tree Species: Traits, Trade-Offs, and Functional Groups

Abstract

Tree architecture is an important determinant of the height extension, light capture, and mechanical stability of trees, and it allows species to exploit the vertical height gradient in the forest canopy and horizontal light gradients at the forest floor. Tropical tree species partition these gradients through variation in adult stature (Hmax) and light demand. In this study we compare 22 architectural traits for 54 Bolivian moist-forest tree species. We evaluate how architectural traits related to Hmax vary with tree size, and we present a conceptual scheme in which we combine the two axes into four different functional groups. Interspecific correlations between architecture and Hmax varied strongly from negative to positive, depending on the reference sizes used. Stem height was positively related to Hmax at larger reference diameters (14-80 cm). Species height vs. diameter curves often flattened toward their upper ends in association with reproductive maturity for species of all sizes. Thus, adult understory trees were typically shorter than similar-diameter juveniles of larger species. Crown area was negatively correlated with Hmax at small reference heights and positively correlated at larger reference heights (15-34 m). Wide crowns allow the small understory species to intercept light over a large area at the expense of a reduced height growth. Crown length was negatively correlated with Hmax at intermediate reference heights (4-14 m). A long crown enables small understory species to maximize light interception in a light-limited environment. Light-demanding species were characterized by orthotropic stems and branches, large leaves, and a monolayer leaf arrangement. They realized an efficient height growth through the formation of narrow and shallow crowns. Light demand turned out to be a much stronger predictor of tree architecture than Hmax, probably because of the relatively low, open, and semi-evergreen canopy at the research site. The existence of four functional groups (shade-tolerant, partial-shade-tolerant, and long- and short-lived pioneer) was confirmed by the principal component and discriminant analysis. Both light demand and Hmax capture the major variation in functional traits found among tropical rain forest tree species, and the two-way classification scheme provides a straightforward model to understand niche differentiation in tropical forests.

Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly

“…1999; Poorter et al. 2006). An alternative explanation to competition as the main internal filtering process is that community‐scale internal filtering is nonrandomly affected by site‐specific species (Baldeck et al.…”

Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate

“…Such a strategy is especially beneficial for shade-tolerant species that regenerate in the light-limited understory. Indeed, several other studies also found that shade-tolerant species make wider crowns (Sterck et al 2006;Poorter et al 2006). In contrast, branches made of low-density wood are weaker, and need therefore to be extra thick to provide sufficient strength (Sterck et al 2006).…”

“…Alternatively, no clear asymptote is found because mature undisturbed pine forests are rare in the Mediterranean. Although it is generally assumed that height-diameter relationships should be asymptotic, studies from different forests show that a quarter of the species evaluated do not show such an asymptotic relationship (Thomas 1996;Chave et al 2003;Poorter et al 2006; but also see Aiba and Nakashizuka 2009). Species that do show an asymptote are canopy species from closed forest types, or species from more open woodland.…”

Root architecture and allocation patterns of eight native tropical species with different successional status used in open-grown mixed plantations in Panama

“…Four species (Cedrela, Sterculia, Tabebuia and Hura) have been described in many studies as long-lived shadeintolerant species but not pioneers (Welden et al 1991;Poorter and Hayashida-Oliver 2000;Kitajima 2002;Poorter et al 2006). They are characterised by intermediate growth rates at the seedling stage (see Wright et al 2003) (with the exception of Cedrela, which presents a high growth rate, see Menalled and Kelty 2001) and by seed dry masses above 0.01 g. From these four species, Tabebuia is markedly the most shade tolerant with a d.s.…”

“…Most previous studies analysing survival, establishment and growth patterns of native tropical species (e.g. Condit et al 1996a;Welden et al 1991;Poorter 2006) have been conducted in forest conditions, which can differ considerably from the environment characteristic of open-grown plantations.…”