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

1 A glasshouse experiment was conducted in which individuals of the rh izomatous grass Calamagrostis canadensis were grown in soil-filled woo den boxes. Directly adjacent to each plant on one side was a control a rea (same conditions as those in which the plant was growing), while i mmediately adjacent on the other side was an area with one of the expe rimental conditions ('shade', 'cool soil', 'cool soil + shade', or 'co ol soil + intraspecific competition'). Rhizomes of each plant were all owed the opportunity to grow simultaneously into both the control and the treated side. 2 Fewer rhizomes grew into the 'cool soil + competit ion' area compared to the number of rhizomes from the same plant growi ng 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 t he control side. 3 Calamagrostis canadensis appears to display an 'opp ortunistic guerrilla' strategy of clonal foraging. Provided with the o pportunity to 'choose' between different microhabitats for clonal expa nsion, plants showed preferential entry into, and exploitation of, fav ourable 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 expl oitation of more favourable microhabitats. This may play an important role in the persistence of this species in a variety of boreal forest habitats.