Influence of Japanese brome on western wheatgrass yield

Abstract

Japanese brome (Bromus japonicus Thunb.) has invaded many northern mixed-prairie plant communities. Understanding interactions of population dynamics of this and associated species is critical for proper management of communities infested with this annual. Objectives of this study were to determine the effect of Japanese brome removal on aboveground forage production and daily plant water relations of western wheatgrass [Pascopyrum smithii Rydb. (Love)] and Japanese brome in a western wheatgrass dominated northern mixed grass prairie community. During early spring of 1991, a wet year, and 1992, a dry year, 2 treatments, undisturbed and complete (total) removal of Japanese brome seedlings, were applied by hand at silty clay loam and clay field sites in circular, 1-m2 quadrats. Vegetation in additional quadrats was left undisturbed or Japanese brome was removed to assess plant water relations at each site in 1992. Total standing crop was reduced 500 kg ha-1 with removal of Japanese brome, while standing crop of western wheatgrass was increased 220 kg ha-2 with Japanese brome removal. Increased standing crop of western wheatgrass appeared to result from increased tiller density of 153 tillers m-2 rather than increased weight per tiller. Western wheatgrass water relations were essentially unaffected by Japanese brome removal in 1992. Removal of Japanese brome from Northern Great Plains plant communities may increase production of associated perennial grasses, but managers should also expect a short-term decrease in total standing crop.