SYMMETRY OF BELOW-GROUND COMPETITION BETWEEN KOCHIA-SCOPARIA INDIVIDUALS

Competition among individual plants is usually asymmetric, i.e. larger plants are able to obtain a disproportionate share of the resources ( for their relative size) and suppress the growth of smaller individual s. There is evidence that the asymmetry of competition is primarily du e to shading, but there is very little information about the symmetry of competition below ground. We grew Kochia scoparia individuals singl y and in pairs in containers for 54 d with dividers above ground so th at competition could occur only below ground. Initial size differences were generated by a 10-d difference in sowing date. There was no evid ence that larger individuals had a disproportionate effect on smaller individuals; the effect of a small neighbor on the growth rate of a pl ant was similar for large and small plants, as was the effect of a lar ge neighbor. The results demonstrate that competition for resources be low ground can be symmetric. When competition is symmetric, it will no t exacerbate initial size differences.