December 1, 2004:

The hypothesis that ecosystem function depends on biological diversity has been part of ecological theory for more than 100 years. Interestingly enough, while the consequences of species extinction have been hotly debated our knowledge of the causes of biodiversity are limited. For plants, one accepted proposition is that the spatial variability of soil resources is a major determinant of coexistence, but the knowledge of how nutrient uptake by roots interact with the spatial distribution of soil nutrients to affect species diversity is also limited. In this seminar I will discuss some physical aspects of how the spatial distribution of soil nutrients and the branching architectures of root systems interact to minimize nutrient flow resistance and/or maximizes nutrient access, within the local constraints imposed by the soil environment and the global constraints imposed by environmental and species characteristics. The working hypothesis for the talk is that: (1) root branching is the result of an optimization process designed to provide easy access to soil nutrients subjected to the global constraints of plant growth and the local constraints of nutrient diffusion and mass flow; and (2) plant community diversity and production are driven in part by combinations of root branching architectures that maximized uptake while minimizing root competition.