EMERGENCE DATE EFFECTS ON RESOURCE PARTITIONING BETWEEN DIFFUSE KNAPWEED SEEDLINGS

Diffuse knapweed (Centaurea diffusa Lam.) has reduced forage productio n, watershed quality, and biodiversity, and increased soil erosion on millions of hectares of rangeland, Diffuse knapweed has evolved mechan isms that allow it to dominate sites in nearly monotypic stands. Under standing these mechanisms may provide useful information in developing weed management strategies. Objectives of this study were to investig ate interference, growth rates, and resource partitioning between earl y and late emerging,diffuse knapweed seedlings, Seeds of diffuse knapw eed were planted 21 March (early emerging) and 14 April (late emerging ) 1993 in addition series mixtures with total stand densities ranging from 1,000-7,000 plants m(-2). Shoots were harvested on 1 and 2 June 1 993. The greatest interference was among co-emerging seedlings, Resour ce partitioning ratios (51 and 1398) indicated substantial partitionin g between seedlings having different emergence dates, Continuous seedl ing emergence may allow diffuse knapweed to occupy all available safe sites.