Plant functional types in Earth System Models: Progress, plans, and future directions

Background/Question/Methods

Earth System Models simulate natural vegetation distribution and terrestrial carbon, water, and energy exchange in response to climate, soil, disturbance, and their many interactions. These models rely on the concept of plant functional types (PFT) to reduce the complexity of species diversity to a few key plant types. There are, however, competing views on how vegetation distribution and changes over space and time can best be represented in dynamic vegetation models. Central to this debate lies the question of balancing the trade-offs between simplicity in our classification of PTFs, while capturing sufficient complexity in describing differences among PFTs for major ecosystem properties and processes. This is a particular challenge in deciding how Arctic and boreal PFTs should be represented and what level of complexity is required to improve representation of vegetation dynamics in advanced high-resolution land models.

 Results/Conclusions

To address this challenge knowledge gaps must be identified and modelers and field biologists must build on this information and discuss how the improved availability of plant functional trait data can potentially enable a more realistic and empirically-based representation of terrestrial vegetation in Earth System Models. This will include perspectives for how a suite of above- and below-ground processes can be incorporated into PFTs (e.g., phenology, turnover) and the possibilities to incorporate genetic diversity and adaptive plasticity within PFTs through probabilistic representation of key processes. Progress, plans, and recommendations for the incorporation of new approaches to define PFTs will be discussed.