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- Here, we develop a new approach that links functional attributes
- of tree species with studies of forest recovery and regional
- land-use transitions (Chazdon et al. 2007). Grouping species according
- to their functional attributes or demographic rates provides
- insight into both applied and theoretical questions, such as selecting
- species for reforestation programs, assessing ecosystem services, and
- understanding community assembly processes in tropical forests
- (Diaz et al. 2007, Kraft et al. 2008).
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- Since we have data on leaf
- and wood functional traits for only a subset of the species in our
- study sites, we based our functional type classification on information
- for a large number of tree species obtained through vegetation
- monitoring studies.
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- Our approach avoided preconceived notions of successional
- behavior or shade tolerance of tree species by developing an objective
- and independent classification of functional types based on vegetation
- monitoring data from permanent sample plots in mature and
- secondary forests of northeastern Costa Rica (Finegan et al. 1999,
- Chazdon et al. 2007).We apply an independent, prior classification
- of 293 tree species from our study region into five functional types, based on two species attributes: canopy strata and diameter growth
- rates for individuals Z10 cm dbh (Finegan et al. 1999, Salgado-
- Negret 2007).
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- Our results demonstrate strong linkages between functional
- types defined by adult height and growth rates of large trees and
- colonization groups based on the timing of seedling, sapling, and
- tree recruitment in secondary forests.
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- These results allow us to move beyond earlier conceptual
- frameworks of tropical forest secondary succession developed
- by Finegan (1996) and Chazdon (2008) based on subjective groupings,
- such as pioneers and shade-tolerant species (Swaine &
- Whitmore 1988).
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- Reproductive traits, such as dispersal mode, pollination mode,
- and sexual system, were ultimately not useful in delimiting tree
- functional types for the tree species examined here (Salgado-Negret
- 2007). Thus, although reproductive traits do vary quantitatively in
- abundance between secondary and mature forests in our landscape
- (Chazdon et al. 2003), they do not seem to be important drivers of
- successional dynamics of trees Z10 cm dbh. For seedlings, however,
- dispersal mode and seed size are likely to play an important
- role in community dynamics during succession (Dalling&Hubbell
- 2002).
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- Our classification of colonization groups defies the traditional
- dichotomy between ‘late successional’ shade-tolerant and ‘early successional’
- pioneer species. Many tree species, classified here as
- regenerating pioneers on the basis of their population structure in
- secondary forests, are common in both young secondary forest and
- mature forests in this region (Guariguata et al. 1997), and many are
- important timber species (Vilchez et al. 2008). These generalists are
- by far the most abundant species of seedlings and saplings, conferring
- a high degree of resilience in the wet tropical forests of NE
- Costa Rica (Norden et al. 2009, Letcher & Chazdon 2009). The
- high abundance of regenerating pioneers in seedling and sapling
- size classes clearly shows that species with shade-tolerant seedlings
- can also recruit as trees early in succession. For these species, early
- tree colonization enhances seedling and sapling recruitment during
- the first 20–30 yr of succession, due to local seed rain. Species
- abundance and size distribution depend strongly on chance colonization
- events early in succession (Chazdon 2008). Other studies
- have shown that mature forest species are able to colonize early in
- succession (Finegan 1996, van Breugel et al. 2007, Franklin & Rey
- 2007, Ochoa-Gaona et al. 2007), emphasizing the importance of
- initial floristic composition in the determination of successional
- pathways and rates of forest regrowth. On the other hand, significant
- numbers of species in our sites (40% overall and the majority
- of rare species) colonized only after canopy closure, and these species
- may not occur as mature individuals until decades after agricultural
- abandonment.
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- Classifying functional types
- based on functional traits with low plasticity, such as wood density
- and seed size, could potentially serve as robust proxies for demographic
- variables (Poorter et al. 2008, Zhang et al. 2008).
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- CONDIT, R., S. P. HUBBELL, AND R. B. FOSTER. 1996. Assessing the response of
- plant functional types in tropical forests to climatic change. J. Veg. Sci.
- 7: 405–416.
- DALLING, J. S., AND S. P. HUBBELL. 2002. Seed size, growth rate and gap microsite
- conditions as determinants of recruitment success for pioneer species.
- J. Ecol. 90: 557–568.
- FINEGAN, B. 1996. Pattern and process in neotropical secondary forests: The first
- 100 years of succession. Trends Ecol. Evol. 11: 119–124.
- POORTER, L., S. J. WRIGHT, H. PAZ, D. D. ACKERLY, R. CONDIT, G.
- IBARRA-MANRI´QUEZ, K. E. HARMS, J. C. LICONA, M.MARTI´NEZ-RAMOS,
- S. J. MAZER, H. C. MULLER-LANDAU, M. PEN˜ A-CLAROS, C. O. WEBB,
- AND I. J. WRIGHT. 2008. Are functional traits good predictors of demographic
- rates? Evidence from five Neotropical forests. Ecology 89:
- 1908–1920.
- ZHANG, Z. D., R. G. ZANG, AND Y. D. QI. 2008. Spatiotemporal patterns and
- dynamics of species richness and abundance of woody plant functional
- groups in a tropical forest landscape of Hainan Island, South China.
- J. Integr. Plant Biol. 50: 547–558.
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- Therecent growth of large functional trait data
- bases has been fuelled by standardized protocols forthe
- measurement of individual functional traits and intensive
- efforts to compile trait data(Cornelissen etal. 2003; Chave etal. 2009). Nonetheless, there remains no consensusfor
- the most appropriate sampling design so that traits can be
- scaled from the individuals on whom measurements are
- made to the community or ecosystem levels at which infer-
- ences are drawn (Swenson etal. 2006,2007,Reich,Wright
- & Lusk 2007;Kraft,Valencia & Ackerly 2008).
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- However, the fast pace of
- development of plant trait meta-analyses also suggests that
- trait acquisition in the field is a factor limiting the growth of
- plant trait data bases.
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- We measured
- traits for every individual tree in nine 1-ha plots in tropical
- lowland rainforest (N = 4709). Each plant was sampled for
- 10 functional traits related to wood and leaf morphology and
- ecophysiology. Here, we contrast the trait means and variances
- obtained with a full sampling strategy with those of
- other sampling designs used in the recent literature, which we
- obtain by simulation. We assess the differences in community-
- level estimates of functional trait means and variances
- among design types and sampling intensities. We then contrast
- the relative costs of these designs and discuss the appropriateness
- of different sampling designs and intensities for
- different questions and systems.
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- With regard to estimating mean trait values, strategies
- alternative to BRIDGE were consistently cost-effective. On
- the other hand, strategies alternative to BRIDGE clearly
- failed to accurately estimate the variance of trait values. This
- indicates that in situations where accurate estimation of plotlevel
- variance is desired, complete censuses are essential.
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- Isso significa que estudos de característica de história de vida compensam? Ver nos m&m.
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- We suggest that, in these studies,
- the investment in complete sampling may be worthwhile
- for at least some traits.
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- Falar que isso corrobora nossa sugestão de utilizar poucas medidas, mas que elas sejam confiáveis.
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