PARENT SESSION
Oral Session # 83: Ecological Theory II: Modeling; Competition.
Presiding: C Brassil
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.
Competition for light between plant species with different foliage profiles: Analysis.
Nevai, Andrew*,1, Vance, Richard 2, 1 University of California at Los Angeles, Los Angeles, California, USA2 University of California at Los Angeles, Los Angeles, California, USA
ABSTRACT- Two coexisting plant species that deploy their foliage at different heights above the ground experience contrasting benefits and costs. By placing its leaves high above the ground, the taller species intercepts full sunlight that produces rapid photosynthesis, but at the cost of growing and then supplying maintenance metabolic energy for tall stems. The shorter species, by contrast, requires less energy for stem growth and maintenance, but its leaves intercept less light and consequently experience slower photosynthesis. Can this height difference by itself make stable coexistence of these competing species possible? How does extensive overlap in foliage profiles affect the outcome of competition? To find out, we examined a two-species Kolmogorov competition model whose specific growth rate functions incorporate realistic descriptions of plant structure and function. The differential equations do not yield explicit equations for the two species nullclines, but implicit arguments reveal nullcline placement and hence the outcome of competition. Depending upon the magnitude of the species height differences and the amount of vertical foliage overlap, four outcomes are possible: the tall species persists alone, the short species persists alone, neither species persists, or the two species persist together at stable equilibrium abundances. This last result appears to occur throughout a large portion of parameter space. Founder-controlled competitive exclusion is not possible. These findings establish that, at least in principle, a difference in foliage height can promote stable competitive coexistence of plant species that differ in no other way.
Key words: light, Kolmogorov, competition, community