Browsing by Autor "David D. Ackerly"

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ARE FUNCTIONAL TRAITS GOOD PREDICTORS OF DEMOGRAPHIC RATES? EVIDENCE FROM FIVE NEOTROPICAL FORESTS
(Wiley, 2008) Lourens Poorter; S. Joseph Wright‬; Horacio Paz; David D. Ackerly; Richard Condit; Guillermo Ibarra‐Manríquez; Kyle E. Harms; Juan Carlos Licona; Miguel Martínez‐Ramos; Susan J. Mazer
A central goal of comparative plant ecology is to understand how functional traits vary among species and to what extent this variation has adaptive value. Here we evaluate relationships between four functional traits (seed volume, specific leaf area, wood density, and adult stature) and two demographic attributes (diameter growth and tree mortality) for large trees of 240 tree species from five Neotropical forests. We evaluate how these key functional traits are related to survival and growth and whether similar relationships between traits and demography hold across different tropical forests. There was a tendency for a trade-off between growth and survival across rain forest tree species. Wood density, seed volume, and adult stature were significant predictors of growth and/or mortality. Both growth and mortality rates declined with an increase in wood density. This is consistent with greater construction costs and greater resistance to stem damage for denser wood. Growth and mortality rates also declined as seed volume increased. This is consistent with an adaptive syndrome in which species tolerant of low resource availability (in this case shade-tolerant species) have large seeds to establish successfully and low inherent growth and mortality rates. Growth increased and mortality decreased with an increase in adult stature, because taller species have a greater access to light and longer life spans. Specific leaf area was, surprisingly, only modestly informative for the performance of large trees and had ambiguous relationships with growth and survival. Single traits accounted for 9-55% of the interspecific variation in growth and mortality rates at individual sites. Significant correlations with demographic rates tended to be similar across forests and for phylogenetically independent contrasts as well as for cross-species analyses that treated each species as an independent observation. In combination, the morphological traits explained 41% of the variation in growth rate and 54% of the variation in mortality rate, with wood density being the best predictor of growth and mortality. Relationships between functional traits and demographic rates were statistically similar across a wide range of Neotropical forests. The consistency of these results strongly suggests that tropical rain forest species face similar trade-offs in different sites and converge on similar sets of solutions.
Relationships Among Ecologically Important Dimensions of Plant Trait Variation in Seven Neotropical Forests
(Oxford University Press, 2006) Ian J. Wright; David D. Ackerly; Frans Bongers; Kyle E. Harms; Guillermo Ibarra‐Manríquez; Miguel Martínez‐Ramos; Susan J. Mazer; Helene C. Muller‐Landau; Horacio Paz; Nigel C. A. Pitman
The dimensions represented by SLA, seed/fruit size and leaf size were essentially independent and thus conveyed largely independent information about plant strategies. To a lesser extent the same was true for plant height and WD. Our tentative explanation for negative WD-leaf size relationships, now also known from other habitats, is that the traits are indirectly linked via plant hydraulics.