Terrestrial plant competition for nutrients and the race for fish.
Craine, Joseph*,1, 1 Univeristy of Minnesota, Saint Paul, MN, USA
ABSTRACT- The allocation of resources among organs represents the largest transfer of resources a plant makes and should be under strong selection pressure. Yet, perennial grasses have two orders of magnitude greater root length density (RLD) than prairie legumes, seemingly much more than necessary to have high productivity. As such, there must be something about relying on an external nitrogen supply that favors plants to have high allocation of resources to roots. I tested two competing hypotheses regarding allocation and maximization of net resource benefit: the high RLD in grasses is due to either the slow diffusion of inorganic N or competition among plants for N. I used a fine-scale raster-based model of nutrient movement and uptake in soils to assess the costs and benefits of different allocation strategies. In the absence of competition, plants only need a RLD equivalent to that of legumes (0.25 cm cm-3) to maximize net resource benefit over the course of a year. Yet, in the presence of a competitor, uptake by a plant is determined by its fraction of the total root length in soil as described by the supply preemption hypothesis. Hence, when competing for N, plants needed to produce higher root length density than competitors, which leads to high root allocation. In all, competition for nutrients needs to be considered when extrapolating from individuals to stands and has had profound effects on the evolution of plants.
Key words: Roots, Allocation, Nutrients, Competition
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