Competitive Hierarchies in Herbaceous Plant Communities

Using data from eight published competition experiments with diallel designs, and a new method of analyzing such data, we present evidence that competition among herbaceous plants has two general properties: pairwise interactions are predominantly asymmetric, and competitive hierarchies exist, i.e. competitive networks are primarily transitive. This empirical evidence is compared with what is known about the mechanisms of plant competition. Finally we present an hypothesis to explain some of the variability in the degree to which competitive networks display asymmetry and transitivity, and explore some of the consequences of this in terms of developing a predictive theory of plant competition.