Plant functional types: are we getting any closer to the Holy Grial?

LAVOREL, S; DÍAZ, S; CORNELISSEN, H; GARNIER, E; HARRISON, SP; MCINTYRE, S; PAUSAS, JG; PÉREZ-HARGUINDEGUY, N; URCELAY, C

Terrrestrial Ecosystems in a Changing World

Springer-Verlag

Lugar: New York; Año: 2007; p. 149 - 160

Plant functional type research has soared for over ten years under the impetus of GCTE. The requirement from large scale ecosystem models to group plants according to similarity in response to changes in their environment and effects on ecosystem structure and processes has proved to be the ‘Holy Grail’ of plant functional type research. One first achievement has been the production of standardised lists of the most significant and easily measurable and well understood traits. Based on these and large data bases, and on large efforts to synthesise the literature, it has been possible to identify and explain plant functional response traits associated with response to resource gradients (esp. nutrients) and widespread disturbances such as grazing and fire. Current research is focusing on the links between these and effects on biogeochemistry, confirming the relevance of fundamental trade-offs that constrain the way plants manage their resources (Grime 2001). This progress and the remaining challenges for ecosystem level plant functional research can be summarised in a series of confirmed or hypothetical linkages between individual plant traits and processes at different levels of organisation (Table 13.2). Significant remaining challenges not only concern further understanding the significance of particular traits, fundamental trade-offs among them, or how short a minimal trait list can be. First, understanding the mechanisms through which species traits, as determined by environmental factors, determine community structure is a priority that will require theoretical, experimental and modeling approaches. Second, our understanding of how these response traits also determine (or not) effects on ecosystems, remains very preliminary. Significant challenges to be addressed regard effects of plant disturbance response on biogeochemical cycles and on disturbance regimes. For this, and also to further resolve the effects of plant resource response on biogeochemistry, it is essential to recognize that simultaneous effects on multiple, linked ecosystem processes are involved (Chapin 2003). Progress in this area will call upon multi-factorial manipulations (see Norby et al. 2007, Chap. 3 of this volume), biodiversity experiments (Hooper et al. 2005; Naeem et al. 2003 and the further development of ecosystem models that directly use those plant traits that can be easily measured for large numbers of species. Current approaches to defining PFTs that emphasize the importance of classifying plants according to welldefined, readily observable and usually continuous plant traits with known responses to particular environmental factors (CO2 concentration, soil resources, climate, and different types of disturbances) should encourage the development of a new generation of DGVMs that explicitly represent key features of this global classification. Model development, however, needs to be paralleled by the global collection of trait data following unified protocols, and by the development of an internally-consistent modern (actual) vegetation map explicitly based on plant functional properties (Nemani and Running 1996). “The same happens to all of us. One hears about the Grail and one thinks one is the only one who will find it” (U. Eco, Baudolino). Rather, the last decade of plant functional research has taught us that, if “There is much to be done. There is also a real hope that we may be getting somewhere” (Westoby et al. 2002), getting somewhere will require continued collaboration across those multiple fields that span from ecophysiology to global modeling.