Ramet spacing of Elymus lanceolatus (thickspike wheatgrass) in response toneighbour density

Many plants exploit patchy resources through clonal foraging. Plants establ ished in field plots were used to determine if Elymus lanceolatus ssp. lanc eolatus (Scribner et J.G. Smith) Gould (thickspike wheatgrass) showed a clo nal foraging response to neighbour densities, as it had previously shown to patchy soil nutrients. Neighbours consisted of the rhizomatous E. lanceola tus ssp. lanceolatus and the bunchgrass Elymus lanceolatus ssp. wawawaiensi s (Scribner et Gould) J.R. Carlson et D.R. Dewey (proposed name), which are both native to the semiarid western U.S.A., and their ratios as well as to tal densities varied. Rather than an increase in spacing of exploratory ram ets at high densities, as expected with clonal foraging, there was a decrea se in spacing in both years of the experiment. Fewer target plants produced exploratory ramets at higher densities only in the second year. These redu ctions in exploratory clonal growth at higher neighbour densities, which we re opposite to E. lanceolatus ssp. lanceolatus' response to low-resource pa tches, occurred perhaps because soil resource levels were too low overall t o support rhizome production, and this condition was more pronounced in the second year. Physical resistance from neighbour roots perhaps also reduced rhizome production. However, rhizome growth may not be beneficial in such cases, and plants may be adapted to produce exploratory rhizomes only when some high-resource patches are encountered by the clone.