Clipping effects on growth dynamics of Japanese brome.

Abstract

Japanese brome (Bromus japonicus Thunb.) has invaded many northern mixed prairie communities. Understanding how defoliation affects the life cycle or this species is critical for proper grazing management of communities infested with this annual. The objective of this study was to determine the effect of defoliation on growth of Japanese brome. Treatments included no clipping or clipping to 75- or 150-mm stubble height weekly or biweekly for 65 to 70 days in a greenhouse. Response of Japanese brome tiller numbers, leaf height, and above- and below-ground biomass were measured in 1991, 1992, and 1997. Clipping vegetative plants in 1991 reduced tiller numbers and leaf heights, whereas clipping plants with reproductive shoots in 1992 and 1997 increased tiller numbers and reduced leaf heights. Herbage accumulated during clipping, above-ground and total biomass were similar in 1991 and 1997, but lower in 1992. Accumulated herbage was reduced by reducing stubble height from 150 mm to 75 mm on a biweekly frequency and increasing the frequency of clipping from biweekly to weekly at either the 150-mm or 75-mm stubble height. Reducing the stubble height also reduced above-ground and total biomass. Increasing frequency of clipping did not generally affect total biomass. Some inflorescences were produced with even the most severe clipping treatment.