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).

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.

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).

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.

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).

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).

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.

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).

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.

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).

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.

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.

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.

We suggest that, in these studies,

the investment in complete sampling may be worthwhile

for at least some traits.