Document: PAU-3-33-19

Modeling plant competition for soil nutrients.

LEADLEY, P.*

University of Paris at Orsay ¹

Abstract:
Most models of nutrient competition have assumed that nutrients and roots are uniformly distributed throughout the soil. Relaxing this assumption tends to reduce competitive interactions between plants. We have been simulating nitrogen competition in semi-natural grasslands using a model of nutrient mineralization, diffusion through the soil, and uptake by roots. This work suggests that nutrient uptake kinetics and root diameter do not play an important role for ammonium or nitrate competition in these ecosystems, due to diffusion limitations in the soil. Root length per unit soil volume is by far the most critical determinant of competition. Inter-specific competition is strongly reduced by the aggregation of roots of individual species, even when this aggregation occurs at millimeter scales. Agricultural systems with annual plants where nitrogen comes predominantly from inorganic fertilizers behave very differently from semi-natural systems in which most of the nitrogen comes from mineralization of soil organic matter. In particular, root growth into unexplored soil plays a critical role in nutrient uptake and competition in fertile agricultural systems. These and other examples will be used to illustrate the importance of explicitly treating fine scale spatial heterogeneity and diffusion limitations in models of nutrient competition.

Keywords: Competition, nitrogen, diffusion

This abstract is being presented at: 8:30 AM in session:
Oral Session #61: Plant Responses to Nutrients.