Perspectives in Plant Ecology, Evolution and Systematics 14 (2012) 89–96 Contents lists available at SciVerse ScienceDirect Perspectives in Plant Ecology, Evolution and Systematics j o ur nal homepage: www.elsevier.de/ppees Research article Functional diversity changes during tropical forest succession Madelon Lohbeck a,b , Lourens Poorter a , Horacio Paz b , Laura Pla c , Michiel van Breugel d , Miguel Martínez-Ramos b , Frans Bongers a,∗ a Forest Ecology and Forest Management Group, Centre for Ecosystem Studies, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands b Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Campus Morelia, Antigua Carretera a Patzcuaro 8701, Ex-hacienda de San Jose de la Huerta, 58190 Morelia, Michoacan, Mexico c Department of Agricultural Technology, Universidad Francisco de Miranda, Complejo Docente Los Perozos, 4101 Coro, Venezuela d Smithsonian Tropical Research Institute – CTFS Unit 0948, APO, AA 34002-0948, USA a r t i c l e i n f o Article history: Received 7 January 2011 Received in revised form 19 July 2011 Accepted 15 October 2011 Keywords: Chiapas Chronosequence Mexico Functional redundancy Secondary forests Species diversity Specific leaf area Wood density a b s t r a c t Functional diversity (FD) ‘those components of biodiversity that influence how an ecosystem operates or functions’ is a promising tool to assess the effect of biodiversity loss on ecosystem functioning. FD has received ample theoretical attention, but empirical studies are limited. We evaluate changes in species richness and FD during tropical secondary forest succession after shifting cultivation in Mexico. We also test whether species richness is a good predictor of FD. FD was calculated based on a combination of nine functional traits, and based on two individual traits important for primary production (specific leaf area) and carbon sequestration (wood density). Stand basal area was a good predictor of successional changes in diversity and FD, in contrast to fallow age. Incidence-based FD indices increased logarithmically with stand basal area, but FD weighted by species’ importance values lacked pattern with succession. Species richness and diversity are strong predictors of FD when all traits were considered; linear relationships indicate that all species are equally functionally complementary, suggesting there is little functional redundancy. In contrast, when FD was calculated for individual traits and weighted for abundances, species richness may underestimate FD. Selection of functional trait(s) critically determines FD, with large consequences for studies relating bio- diversity to ecosystem functioning. Careful consideration of the traits required to capture the ecosystem process of interest is thus essential. © 2011 Elsevier GmbH. All rights reserved. Introduction Functional traits are important for the response of species to their environment, and for the effects that species have on ecosys- tem processes (e.g. Lavorel and Garnier, 2002; McGill et al., 2006; Cornwell et al., 2008; Lavorel et al., 2010). Functional diversity has been defined as the value, range, and distribution of func- tional traits in a given ecosystem (Díaz et al., 2007a) or as those components of biodiversity that influence how an ecosystem oper- ates or functions (Tilman, 2001b). Many researchers recognize that functional diversity is more important to local scale ecosystem functioning than taxonomic diversity (Grime, 1998; Tilman, 2001b; Micheli and Halpern, 2005), because functional diversity may be a good indicator of ecosystem resource dynamics, stability and pro- ductivity (Tilman, 2000; Díaz and Cabido, 2001; Cardinale et al., 2006; Díaz et al., 2007b). ∗ Corresponding author. Tel.: +31 317486217. E-mail address: Frans.bongers@wur.nl (F. Bongers). Two main index types have been proposed for measuring functional diversity, those based on species incidence (presence/ absence) and those based on species abundance. Incidence-based indices, which are comparable to functional richness measures (e.g. Walker et al., 1999; Petchey and Gaston, 2002), emphasize the full range of functional strategies present in the commu- nity, proposing that both dominant and rare species contribute equally to functional diversity. The rationale underlying this idea is that each species may strongly influence ecosystem function- ing and that rare species are especially important contributors to long-term ecosystem resilience (Walker et al., 1999; Hooper et al., 2005). In contrast, indices based on species abundance emphasize the role of dominant species (e.g. Mason et al., 2003; Mouillot et al., 2005) in a similar way as the biomass- ratio hypothesis (Grime, 1998), which also states that dominant species have a greater effect on ecosystem functioning than rare species. Processes that are mostly influenced by the trait values of dominant species are, for example, specific primary productivity and decomposition (Garnier et al., 2004; Cornwell et al., 2008). Thus, the type of index useful in a particular 1433-8319/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.ppees.2011.10.002