RHIZOME PLASTICITY AND CLONAL FORAGING OF CALAMAGROSTIS-CANADENSIS IN RESPONSE TO HABITAT HETEROGENEITY

1 A glasshouse experiment was conducted in which individuals of the rhizomatous grass Calamagrostis canadensis were grown in soil-filled wooden boxes. Directly adjacent to each plant on one side was a control area (same conditions as those in which the plant was growing), while immediately adjacent on the other side was an area with one of the experimental conditions ('shade', 'cool soil', 'cool soil + shade', or 'cool soil + intraspecific competition'). Rhizomes of each plant were allowed the opportunity to grow simultaneously into both the control and the treated side. 2 Fewer rhizomes grew into the 'cool soil + competition' area compared to the number of rhizomes from the same plant growing into the control side and those that did were shorter, showed less branching, had shorter intermodes, and produced fewer shoots. Rhizomes entering the 'cool soil' area (with or without shade) showed reduced growth compared to rhizomes from the same individual which grew into the control side. 3 Calamagrostis canadensis appears to display an 'opportunistic guerrilla' strategy of clonal foraging. Provided with the opportunity to 'choose' between different microhabitats for clonal expansion, plants showed preferential entry into, and exploitation of, favourable microhabitats (i.e. warm soil, unshaded, free of competition). 4 For individuals faced with considerable environmental heterogeneity, plasticity of rhizome growth and development allows for greater exploitation of more favourable microhabitats. This may play an important role in the persistence of this species in a variety of boreal forest habitats.