1836.4 Management Implications
A number of Bromus grasses that have been introduced into the Western United
States have become natural area invaders, crop weeds, and ruderal weeds
(Table 6.5 ). This suggests that the introduction of additional species of Bromus
grasses should be carefully evaluated and possibly regulated or prohibited.
Monitoring and management of Bromus species in the Western United States may
help to limit new invasions and prevent or reduce damage to additional habitat.
Cultivars of introduced species should be used in ways that minimize movement
into natural habitats. Today land managers often prefer to use native Bromus species for
revegetation and restoration of natural habitats (Bugg et al. 1997 ; May et al. 1999 ;
Tilley et al. 2006 ; Wood et al. 2015 ). Use of introduced species like B. inermis f o r
revegetation in natural and seminatural areas should be avoided if possible. Substitution
of less aggressive species and cultivars for hay and forage should also be considered.
6.5 Research Needs
In the past, the time and labor required to collect large amounts of data have been
barriers to the use of comparison studies with large numbers of species. Today, the
increasing availability of large collections of data on the Internet and the develop-
ment of tools and data collections that integrate data from multiple sources make
analyses of large datasets easier. Using the Bromus database, we were able to show
that species traits such as annual life span, long awns, and polyploidy are correlated
with invasiveness. In most cases, the correlations that we saw supported existing
hypotheses about the relationships between invasiveness and plant traits.
Unfortunately, many types of data that would be useful for comparison studies are
hard to fi nd, especially for less common and noninvasive species. For example,
information on soil type, pH, and nutrient requirements is often vague or unavail-
able for many species.
Much of the research on annual Bromus species has focused on the highly inva-
sive Genea species B. tectorum. There is less information available for other weedy
and invasive annual species. Research that improves our understanding of the fac-
tors that have limited their distribution and evaluates their invasive potential can
contribute to prediction and prevention of future invasions. For example, fi ve of the
seven species other than B. tectorum in section Genea are present in the United
States and are crop, ruderal, and environmental weeds. The other two species,
B. fasciculatus and B. sericeus , seem to be confi ned to their native Eurasian ranges
and may be adapted to specifi c types of environments (Sales 1994 ; Acedo and
Llamas 2001 ; Oja 2002 ; Fortune et al. 2008 ). Little information about these two
species is available. Bromus sericeus is another species that is little studied but
could have serious negative impacts if it is introduced because it is very similar to
B. tectorum and is sometimes considered to be conspecifi c ( Bromus tectorum ssp.
lucidus Sales) (Sales 1991 ). Many species in the annual section Bromus are weeds
6 Attributes That Confer Invasiveness and Impacts Across the Large Genus Bromus...