INTENSITY AND ASYMMETRY OF COMPETITION BETWEEN PLANT PAIRS OF DIFFERENT DEGREES OF SIMILARITY - AN EXPERIMENTAL-STUDY ON 2 GUILDS OF WETLAND PLANTS

Using predictions from existing competition theory, we designed an experiment to test if competition intensity or asymmetry varied with the similarity of the interacting plants. Competition intensity and asymmetry were measured after one growing season for six species of plants grown in an additive pairwise design. Similarity was measured using a guild classification and was assigned to three levels: intraspecific, intra-guild and inter-guild interactions. The guild classification was based upon 27 ecological traits associated with both niche properties (e.g. rooting depth) and competitive ability (e.g. plant height). The six species represented two distinct guilds of wetland plants: obligate and facultative annuals. The results confirmed two key predictions: The intensity of competition increased with increasing similarity between interacting plants, as predicted by the niche control paradigm. The asymmetry of competition decreased with increasing similarity, as predicted by the dominance control paradigm. Guild identity, as defined in our study, was not a good predictor of competitive ability.