DOES ABUNDANCE REFLECT COMPETITIVE ABILITY - A FIELD-TEST WITH 3 PRAIRIE GRASSES

Two field experiments were conducted in a tallgrass prairie remnant to determine whether the relative abundance of three perennial grasses ( Andropogon gerardii > Sorghastrum nutans > Dichanthelium oligosanthes) was directly related to their relative competitive ability. In the fi rst experiment, performance of transplanted seedlings was measured in monocultures (1, 5, 10, 15 and 20 seedlings) and in pairwise species m ixtures. Three different planting proportions (2:18, 10:10, 18:2 seedl ings) were used for each pairwise species mixture. Neighbours reduced biomass and tiller production of seedlings significantly while surviva l was largely unaffected. The performance of a species grown in mixtur e versus in monoculture at an equivalent density did not differ signif icantly in almost all cases. In the second experiment, neighbours were removed experimentally from a 1 m radius around established target pl ants of each species. Tiller production increased significantly follow ing neighbour removal. The three species responded about equally to ne ighbour removal, indicating that common and less common species were a bout equally suppressed by neighbours. Results of both experiments ind icate that competitive ability and abundance are not significantly rel ated for these three grasses.