CLIPPING AND JAPANESE BROME REDUCE WESTERN WHEATGRASS STANDING CROP

Japanese brome (Bromus japonicus Thunb,) and downy brome (Bromus tecto rum L,), introduced annuals, have invaded many northern mixed-prairie plant communities. This study determined the effect of removing Japane se brome and clipping western wheatgrass [Pascopyrum smithii Rydb, (Lo ve)] on aboveground forage production of a western wheatgrass dominate d northern mixed-prairie community. During early spring 1993, a wet ye ar, and 1995, a drier year, western wheatgrass tillers were clipped to ground level in May or June and Japanese brome seedlings were left un disturbed or removed in circular, 1-m(2) plots on a clay-pan field sit e. Western wheatgrass standing crop and tiller densities were estimate d by clipping and counting in May and June, and these plus community s tanding crops were estimated in all plots after Japanese brome matured in mid July. Year effects were significant for standing crop and till er density due to annual variation in amount and distribution of fall, spring, and early summer precipitation. Conditions were most favorabl e for tiller initiation of western wheatgrass and germination of annua l brome seed in fall 1994 and for herbage production in 1993, Clipping western wheatgrass tillers reduced accumulated standing crop 230 to 3 50 kg ha(-1) and reduced tiller weight by 17 to 58%. Standing crop of western wheatgrass was increased 102 kg ha(-1) with removal of Japanes e brome, while total standing crop was reduced 284 kg ha(-1) with brom e removal. Increased standing crop of western wheatgrass appeared to r esult from increased tiller density rather than increased tiller weigh t. Removal of Japanese brome from northern mixed-prairie plant communi ties may increase production of associated perennial grasses, but mana gers should also expect a short-term decrease in total standing crop.