Document: ROB-3-38-28

Detecting and measuring plant competition: An analytical perspective.

FRECKLETON, R.* and A.RWATKINSON

University of East Anglia, Norwich NR47TJ, UK ¹

Abstract:
A range of approaches exist for measuring competition between plant species, yet these are rarely evaluated critically with respect to their performance under field conditions. We contrast two approaches to detecting and measuring competition under field conditions: The first centers on plant removals, whereby the response of focal plants to the removal of competitors is monitored, and simple indices of competitive intensity are generated; the second uses regressions of local rates of population change on population densities and generates per capita competition coefficients (in the sense of classic competition models). We contrast the ability of these techniques to measure competition when communities are spatially segregated through localized dispersal, when micro- environmental heterogeneity affect species distributions and when reserves of dormant seed lead to a storage effect. Our models show that the regression method generally outperforms the removal method and has the further advantage that communities can be monitored over long timer periods without intervention, although for short-term studies a combination of the two methods may be more powerful. The power of either technique depends, however, on the life-histories of the species being studied, and we therefore advise that techniques are explored both analytically and through simulation prior to analysis in order to generate power statistics.

Keywords:

This abstract is being presented at: 8:45 AM in session:
Oral Session #72: Plant Competition.