Functional traits and the growth-mortality tradeoff in tropical trees

Abstract

A trade-off between growth and mortality rates characterizes tree species in closed canopy forests. This trade-off is maintained by inherent differences among species and spatial variation in light availability caused by canopy-opening disturbances. We evaluated conditions under which the trade-off is expressed and relationships with four key functional traits for 103 tree species from Barro Colorado Island, Panama. The trade-off is strongest for saplings for growth rates of the fastest growing individuals and mortality rates of the slowest growing individuals (r 2 ¼ 0.69), intermediate for saplings for average growth rates and overall mortality rates (r 2 ¼ 0.46), and much weaker for large trees (r 2 0.10). This parallels likely levels of spatial variation in light availability, which is greatest for fast-vs. slow-growing saplings and least for large trees with foliage in the forest canopy. Inherent attributes of species contributing to the trade-off include abilities to disperse, acquire resources, grow rapidly, and tolerate shade and other stresses. There is growing interest in the possibility that functional traits might provide insight into such ecological differences and a growing consensus that seed mass (SM), leaf mass per area (LMA), wood density (WD), and maximum height (H max) are key traits among forest trees. Seed mass, LMA, WD, and H max are predicted to be small for light-demanding species with rapid growth and mortality and large for shade-tolerant species with slow growth and mortality. Six of these trait-demographic rate predictions were realized for saplings; however, with the exception of WD, the relationships were weak (r 2 , 0.1 for three and r 2 , 0.2 for five of the six remaining relationships). The four traits together explained 43-44% of interspecific variation in species positions on the growth-mortality trade-off; however, WD alone accounted for .80% of the explained variation and, after WD was included, LMA and H max made insignificant contributions. Virtually the full range of values of SM, LMA, and H max occurred at all positions on the growth-mortality trade-off. Although WD provides a promising start, a successful traitbased ecology of tropical forest trees will require consideration of additional traits.

Community assembly by limiting similarity vs. competitive hierarchies: testing the consequences of dispersion of individual traits

“…This suggests that observations of overdispersion of such traits in communities are unlikely to be related to why such species coexist. On the other hand, in heterogeneous environments with variation in degree of resource limitation and trade-offs among species along the leaf or wood economic spectrum (Wright et al 2004(Wright et al , 2010, variation in growth rate may lead to coexistence through lifehistory trade-offs (Mouquet, Moore & Loreau 2002). These alternative hypotheses could be tested with mechanistic, traitbased demographic models of the type we used here that include more physiological and morphological traits related directly to resource acquisition, as well as incorporate environmental heterogeneity.…”

Influence of functional traits on the demographic rates of 47 arboreal species in a tropical forest in northeastern Brazil

“…Plants with high percentage of fibrous tissues and thick cell walls have very dense wood (Swenson & Enquist, 2007), storing more carbon per unit of volume and lower percentage of conductive vessels, which can result in lower photosynthetic and respiration rates (Weiher et al, 1999), as well as lower rates of biomass accumulation Wright et al, 2010). Survival increases with higher wood density Poorter et al, 2010;Kraft et al, 2010;Martinez-Vilalta et al, 2010;Wright et al, 2010) as dense wood provides greater mechanical stability (Chave et al, 2009) and protection against pathogens, as well as resistance to impacts from other falling trees (Poorter, 2008).…”

“…The opposite behavior is observed among species that require high light intensities and use their available resources rapidly (with low BWD, high SLA, and producing small, spherical seeds) to invest in rapid growth -therefore being good colonizers of disturbed habitats Wright et al, 2010). Despite recent increases in characteristic-based ecological studies, Chaturvedi et al (2011) noted that there had been very few studies of water-limited tropical forests, such as the moist semi-evergreen tropical coastal forests in the northern region of northeastern Brazil (with a six-month dry period) (Schessel et al, 2008).…”

“…The ability to identify and correlate functional characteristics with plant successes represents a useful tool for determining and evaluating ecological strategies (Wright et al, 2010).…”

Biomass Determination Using Wood Specific Gravity from Increment Cores

“…Traditionally an index of wood properties, wood specific gravity (SG) of standing trees has become a fundamental component of biomass determinations in ecosystem studies and a cornerstone of functional trait analysis in community ecology (Fearnside 1997;Chave et al 2009;Baraloto et al 2010;Zanne et al 2010;Wright et al 2010). Many ecological studies use a single SG estimate for an individual tree or a given species.…”