Use of functional traits to distinguish successional guilds of tree species for restoring forest ecosystems

ABSTRACT: Forest ecosystem restoration involves establishing mixes of tree species representing various successional stages of the reference forest. When selecting species, conceptualizing successional status as a gradient of guilds is more appropriate than the conventional binary classification of pioneer and climax species. Therefore, we tested the hypothesis that functional traits can be used to distinguish successional guilds among tree species, planted to test the framework species method of restoration. Values of 13 non-intercorrelated traits of 28 species, derived from field measurements and databases, were analyzed by cluster analysis and rank scoring. Cluster analysis grouped species into six guilds. For rank scoring, negative (from 0 to -2) and positive scores (from 0 to +2) were assigned to each trait, according to their association with early or late succession, respectively. Seven guilds were distinguished from the total scores. This novel technique placed species evenly along a gradient, with 13 and 15 species attaining negative and positive total scores, respectively. Crossvalidation between the two techniques was high, signifying the robustness of using functional traits to distinguish successional guilds. Functional traits, therefore, provide a powerful tool to inform species selection when planning forest restoration. However, their wider use depends on greater availability of functional trait data for more tree species.