A comparative approach to examine competitive response of 48 wetland plantspecies

Competitive ability can be separated into competitive effect (ability to su ppress neighbours) and competitive response (ability to tolerate suppressiv e effect from neighbours), but little is known about the competitive respon se of plants. A screening trial was conducted in outdoor plant pots where c ompetitive response was measured for 48 wetland species during four months grown with seven established sward species: Acorus calamus, Carer crinita, Eleocharis smallii, Lythrum salicaria, Penthorum sedoides, Scirpus acutus a nd Typha angustifolia. Competitive response was calculated as 100 (x(1)-x(2 ))/x(1), where x(1) is the weight of the target plant grown alone and x(2) the weight of the target plant grown in the swards. Despite significant dif ferences in biomass and survivorship of the target plants between the sward species, the correspondence, W, of the rank order of the competitive respo nse of target plants grown in the seven sward species was 0.70 (P < 0.001). The competitive response values were not significantly correlated with ind ependent measures of competitive effect, relative growth rate or functional classification. Published competitive effect values, however, were signifi cantly positively correlated with RGR. The results suggest a different appr oach towards the study of competitive response, with a conceptual model inc luding three different response types: (1) escape; (2) foraging; and (3) pe rsistence.