Plant functional types: an alternative to taxonomic plant community description in biogeography?

This article critically reviews the concept of plant functional types as an alternative to the traditional taxonomic species-based approach to plant community description in biogeography and ecology. Originally formulated in the last century, there has been an acceleration in interest in the concept over the last decade. Plant functional types are nonphylogenetic groupings of species that show close similarities in their response to environmental and biotic controls. Functional classifications often cut across taxonomic classifications and may be more meaningful in terms of plant response, in addition to overcoming certain problems associated with the traditional taxonomic species-based approach. Plant functional types are derived from traits based on species morphology, physiology and/or life history, depending on the aims and scale of the research. Whilst some traits can be measured in the field, others require more detailed laboratory measurement and experimentation. A trade-off exists between the time and efficiency gained from using simple traits and those requiring more elaborate analysis, although certain 'key traits' may act as easily measured surrogates for others. Practical applications of plant functional types in biogeography and ecology are also reviewed. Plant functional types can aid in the understanding of ecological processes, such as the assembly and stability of communities and succession, and facilitate the detection and prediction of response to environmental change at a range of scales. Despite its potential, the plant functional type approach is probably best viewed as a complementary approach to description using traditional taxonomy.