23Bromus rubens has also been shown t o effectively compete with native annual
(Brooks 2000 ; DeFalco et al. 2003 ) and perennial plants in the Mojave Desert
(DeFalco et al. 2007 ). These competitive effects can infl uence community dynamics
and resilience following disturbance (Brooks and Chambers 2011 ). For example,
during the fi rst 3 years following the 2005 Southern Nevada Fire Complex woody
plant seedlings were almost nonexistent except where densities of exotic annuals,
primarily B. rubens and Erodium cicutarium (L.) L’Hér. ex Aiton (redstem stork’s
bill), were exceedingly low (Klinger et al. 2011a ). Reduced resilience of native
perennials is a key element of the process by which a grass/fi re cycle becomes
established (Brooks 2008 ). The reduced productivity and diversity of native annuals
and loss of the habitat structure provided by perennial shrubs can negatively affect
wildlife, such as the federally Threatened Gopherus agassizii Cooper ( dese rt tortoise)
(Brooks and Esque 2002 ).
2.2.3 Management Strategies for Bromus in Warm Deserts
Bromus are already so wide ranging in the Warm Deserts that early detection and
eradication is not a relevant management strategy for these taxa. Even when direct
control efforts such as herbicide use are implemented, they are typically economi-
cally feasible to implement for only a couple of years and in relatively small areas.
In addition, even if dominance of one Bromus species is effectively reduced, other
exotic species may fi ll the void if there is no plan for facilitating the growth of other
more desirable species to compete with them. In one dramatic case from the riparian
zone in Zion Canyon of SW Utah at the regional ecotone between the Warm Deserts,
Cold Deserts, and Western Forests, an herbicide treatment effectively controlled
B. diandrus , but inadvertently led to dominance of B. tectorum by the following
year (Fig. 2.7 ). This is an important reminder that any effort to reduce abundance of
Fig. 2.6 ( a ) 7-year post-fi re scene dominated by a carpet of B. rubens following a stand-replacing
fi re in a blackbrush shrubland that burned once in 1939 (photo by A. Croft, 12 May 1946). ( b ) A
63-year post-fi re scene showing B. rubens persisting with early successional shrubs following a half
century of no additional fi re (photo by D. Oldershaw, 9 May 2002). The view is looking southwest
inside the mouth of Horse Spring Basin in the northeastern Mojave Desert, Lincoln County, NV
2 Exotic Annual Bromus Invasions: Comparisons Among Species and Ecoregions...