PARENT SESSION
Oral Session #76: Plant Ecology: Nutrient Uptake, Movement, Use. Presiding: J. Schade.
Friday, August 10, 2001. 8:00 AM to 11:45 AM. Hall of Ideas G.

Steady-state resource preemption: a new hypothesis for nutrient competition.

Craine, Joseph¹, ¹

ABSTRACT- To effectively model plant competition for nutrients, it is important to understand the factors that are important for nutrient supply, transport, and uptake by roots under competitive circumstances. For nutrient-limited plants growing in the absence of competition, long-term nutrient uptake is constrained by nutrient supply as individual roots have to wait for nutrients to arrive at the root surface. When root systems of two plants are competing for nutrients, partitioning of the nutrient supply is most dependent on and proportional to the relative amounts of root length of the two individuals. Each additional unit of root length for an individual acquires a greater proportion of the nutrient supply by preempting nutrients from arriving at the roots of its competitor (i.e. steady-state resource preemption). The steady-state resource preemption theory differs fundamentally from the R* theory of resource competition. The steady-state resource preemption theory focuses on the supply of the limiting nutrient in solution, while the R* model of competition states that competitive superiority is dependent on the level of nutrient's concentration. Since soil solution nutrient concentrations are not necessarily correlated with nutrient supply or uptake, and plants can acquire nutrients at concentrations much lower than average nutrient concentrations in the soil solution, it appears that steady state resource preemption should explain competition for nutrients better than R* theory.

KEY WORDS: competition, nutrients, roots