Review: plant functional traits in agroecosystems: a blueprint for research.
Functional trait-based ecological research has been instrumental in advancing our understanding of natural plant community dynamics. However, to date, principles of functional trait ecology have not been widely applied to agricultural research and management. Here, we discuss why and how a functional trait approach - distinct from a traditional agronomic trait approach that focuses strictly on crop yield components - can provide a valuable framework for agricultural research. We illustrate these points with an emphasis on commodity crops. The literature suggests a key role for functional trait-based research in understanding the causes and consequences of changes in agroecosystem structure and function. This includes novel approaches to understanding crop breeding and productivity, agroecosystem dynamics and non-crop biodiversity maintenance, the contributions of agroecosystems to global net primary productivity and other biogeochemical cycles, and agricultural vulnerability to climate change. We propose that a key step in advancing trait-based agricultural research is the consolidation of functional trait data for the world's most common crop and fodder species, the main commodities on ∼1.2 billion ha of land. Using Coffea arabica as an example, we show there is strong potential to populate a comprehensive data base of crop functional trait data. For C. arabica, there exist hundreds of observations for ecologically important 'leaf economics' and 'root economics' traits, either in smaller data bases or peer-reviewed studies, but these have not been consolidated. A similar opportunity for functional trait data consolidation exists for many of the world's most common crops. Synthesis and applications. A unified functional trait data base for just 65 of the world's most common agricultural crops can be used to provide baseline evaluations of the functional diversity across croplands covering ∼8.1% of the Earth's land surface. This functional trait data, and other trait-based research, could further be used to evaluate how changes in interspecific and intraspecific crop diversity are mechanistically linked with alterations in agroecosystem function. Ultimately, trait-based research that examines the causes and consequences of agricultural homogenization may contribute to more ecologically informed management of agricultural diversity, from genetic through to global scales.