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 have proportionately higher growth rates than smaller individuals, owing to their 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 use of the maximum likelihood approach different hypotheses concerning the asymmetric competition parameter can be tested. As input data the model allows non-destructive sampling as well as random destructive sampling. The model is exemplified on field data of oilseed rape (Brassica napus L.) from two consecutive years. In the first year, where there was relative intense competition, the hypothesis of no asymmetric competition could be rejected and overall the degree of asymmetric competition was higher in that year.