CLONAL FORAGING IN PERENNIAL WHEATGRASSES - A STRATEGY FOR EXPLOITINGPATCHY SOIL NUTRIENTS

1 Foraging by means of plasticity in placement of tillers in response to low-and high-nutrient patches was examined in the rhizomatous wheat grass Elymus lanceolatus ssp. lanceolatus. Its ability to exploit soil nutrient patches was compared to that of the closely related but caes pitose E. lanceolatus ssp. wawawaiensis. 2 Clones of 14 genets of each taxon were planted in boxes consisting of two 30 x 30 cm cells: the ' origin cell' where clones were planted, and the adjacent 'destination cell', with each cell containing soil with either low or high levels o f nutrients. 3 The rhizomatous taxon, which can produce intravaginal, short-rhizome and long-rhizome tillers, preferentially produced short- rhizome and intravaginal tillers in high-nutrient destination cells. E ffects of nutrient status of the origin cell as well as of the destina tion cell on total tiller numbers indicated clonal integration, yet ti ller placement responded to local conditions, 4 Roots of both taxa acc essed nutrients in destination cells (the caespitose subspecies by roo t growth only), and above-ground biomass of both taxa increased to a s imilar extent with high-nutrient destination cells. With the patch siz es used in this experiment, root growth was as important as ramet plac ement in exploiting nutrients in destination cells. 5 There was no rel ationship between degree of plasticity in ramet placement and biomass of the clone when high-nutrient destination cells were present.