In this talk I will argue for the need for a broader theory designed to resolve the often complex strategies by which plants allocate photosynthetic carbon to acquire belowground resources. While this is a long-standing hard problem in ecology, progress has been hampered by the demand that any first-principle theory must marry the biophysical perspective of individual trees competing for resources with two additional perspectives: (i) the dramatic influence caused by root-microbe symbioses (chiefly nitrogen fixation and different mycorrhizal strategies) on plant-plant competition, and on emergent ecosystem nutrient economies; and (ii) the emergence of plant-soil feedbacks that over time can reshape the very ecosystem and soil environment that plants compete within. A further challenge is that the resulting assembly of functional properties within plant communities depends on the local selection of alternative strategies -- a Darwinian process that plays out over both ecological and evolutionary time.
Results/Conclusions
I will present our nascent effort to build a new theory that marries first-principle biophysical properties of the plant-soil system with assembly rules that emerge at both ecological and evolutionary timescale. Central to this approach is the consideration of traits that influence local plant-plant competition, and the role of trait evolution in context of plant-resource feedbacks that emerge at the ecosystem scale. I will address two dimensions of progress: one organized around plant-root symbioses and their role in the prediction of emergent ecosystem processes including nitrogen fixation, and a second organized around the biophysical rules of trait organization within the rooting system itself. While our work still is in its infancy, I will show results that indicate the promise of this approach for predicting fundamental emergent properties at the ecosystem scale, including aspects of biodiversity and community assembly, carbon storage in soils, and the assembly of biomes over deep evolutionary timescales.