432.5.3 Management Strategies for Bromus
in Western Great Plains
Bromus invasions can be p revented and minimized throughout the ecoregion by
conserving intact grasslands and applying reasonable levels of grazing and burning
to maintain their integrity and resistance to invasion. The Western Great Plains eco-
systems are currently most threatened by large- scale disturbances such as conver-
sion to cultivated agriculture, urban development, and oil and gas exploration and
development, all of which may foster Bromus dominance.
Management beyond good stewardship of the ecosystem can focus fi rst on con-
taining and then eliminating Bromus where it occurs. Herbicides that control Bromus
with minimal negative effects on native species can be effectively used alone
(Hewlett et al. 1981 ; Haferkamp et al. 2001 ) or in combination with burning
(Masters et al. 1992 ; Calo et al. 2012 ). Bromus populations can be managed by
reducing seed production through well-timed grazing, mowing, or burning (e.g.,
Fig. 2.13b ) (Vermeire et al. 2008 ; Milchunas et al. 2011 ) or application of growth
regulator herbicides used for broadleaf weed control (Rinella et al. 2010a , b , 2013 ).
2.6 Western Forests
The Western Forests range from the Marine West-Coast Forest to the Northwestern
Forested Mountains Level I EPA ecoregions and are characterized by a very diverse
range of environmental conditions. Collectively, they represent some of the coolest
and wettest conditions in the western United States (Fig. 2.3 ). Soil temperature
regimes are generally cryic or frigid in the east and north, but can also be mesic and
even thermic to the west and south. These conditions combined with high precipi-
tation are conducive to the growth of forests with relatively high canopy and sur-
face cover of perennial vegetation and high accumulations of litter and duff.
Shrublands or grasslands occur as early successional patches following distur-
bances that remove forest canopy cover, and where productivity levels are rela-
tively low due to shallower soils or warmer and drier soil temperature and moisture
regimes (Fig. 2.15 ).
Bromus species are generally not considered among the highest priority invasive
plants in the Western Forests. In fact, one recent review of the impacts of exotic
invasive species in US forests did not even mention Bromus (Moser et al. 2009 ). The
exception are patches of chaparral and grasslands (Fig. 2.15 ) within ponderosa pine
and Jeffrey pine mixed conifer forests (Pierson and Mack 1990 ; Keeley and
McGinnis 2007 ). In these situations, soils are more frequently exposed to sunlight
and warmer and drier conditions facilitate establishment, growth, and reproduction
of Bromus. Bromus tectorum is the most widespread and abundant Bromus in these
ecoregions, but B. diandrus can also occur within grassland and chaparral forest
openings.
2 Exotic Annual Bromus Invasions: Comparisons Among Species and Ecoregions...