A test of asymmetric competition in plant monocultures using the maximum likelihood function of a simple growth model

Competition between plants is called asymmetric when larger individuals hav e proportionately higher growth rates than smaller individuals, owing to th eir competitive superiority. Plant competition is here modelled by a growth function of a number of competitively interacting plants, where the degree of asymmetric competition is summarised by a single parameter. With the us e of the maximum likelihood approach different hypotheses concerning the as ymmetric competition parameter can be tested. As input data the model allow s non-destructive sampling as well as random destructive sampling. The mode l is exemplified on field data of oilseed rape (Brassica napus L.) from two consecutive years. In the first year, where there was relative intense com petition, the hypothesis of no asymmetric competition could be rejected and overall the degree of asymmetric competition was higher in that year. (C) 1999 Elsevier Science B.V. All rights reserved.