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.