On detecting and measuring competition in spatially structured plant communities

Citation
Rp. Freckleton et Ar. Watkinson, On detecting and measuring competition in spatially structured plant communities, ECOL LETT, 3(5), 2000, pp. 423-432
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
ECOLOGY LETTERS
ISSN journal
1461-023X → ACNP
Volume
3
Issue
5
Year of publication
2000
Pages
423 - 432
Database
ISI
SICI code
1461-023X(200009)3:5<423:ODAMCI>2.0.ZU;2-P
Abstract
Recent models have shown that the development of spatial structure in plant mixtures may make strong competitive interactions between species hard to detect owing to spatial segregation of the competing species. Here we addre ss the issue of measuring interspecific competition using a simulation base d on a neighbourhood population model which assumes that both dispersal and competitive interactions are localized. Using known parameter combinations we use the model to test the power and efficiency of two approaches for de tecting and measuring competition. The first approach is based on measuring the response of communities to the removal of neighbours. Measures of inte rspecific competition based on this approach are extremely biased by spatia l segregation of species, although this bias may be partially overcome by a ltering the spatial scale at which the effects of removals are recorded. Th e second approach is based on multiple regression of per capita population growth rates on local densities of the interacting species. When dispersal is restricted, the regression approach provides accurate estimates of inter specific competition coefficients when the scale of the sampling unit (i.e. the quadrats within which plants are counted) is large compared to the sca le at which interactions and dispersal occur. When seeds disperse globally the removal method performs best; the regression method fails because sampl ing units do not form closed dynamic systems. Our results highlight the imp ortance of tailoring methods for detecting competition to the characteristi cs of the species in question. They also indicate that rapid nonmanipulativ e estimates of competition coefficients may be the best approach in communi ties where dispersal is restricted and competitive interactions localized, which is likely to be the case for the majority of plants.