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annual grasses, B. hordeaceus has short-lived seeds and transient seed banks that
experience high rates of mortality (Marshall and Jain 1967 ), yet seed banks remain
large because of prolifi c seed production (Wainwright et al. 2012 ). Bromus
hordeaceus also has invaded serpentine grasslands in Northern California
(Bartolome et al. 1980 ) where herbicide applications have been relatively effective
at reducing its percentage cover (Aigner and Woerly 2011 ).
12.2.2 Bromus diandrus
Seeds of Bromus diandrus Roth (ripgut brome) have a short-lived innate dormancy
(Gill and Blacklow 1985 ), and similar to B. hordeaceus , seed banks are essentially
transient (Cheam 1986 ). In California coastal prairie ecosystems, growth of B. dian-
drus is favored in nitrogen-rich patches (Maron and Connors 1996 ). Compared to
B. hordeaceus , B. diandrus also responds favorably to increased nutrient availabil-
ity and is likely less adapted to lower soil nutrient availability in oak woodlands of
California (Rice and Nagy 2000 ). However, experimentally reducing soil nitrogen
in California coastal prairie did not reduce the competitive ability of B. diandrus
relative to the native grass, Bromus carinatus L. (California brome), suggesting that
restoration will require more than manipulating soil resources (Kolb and Alpert
2003 ). Additional control methods include carefully timed grazing and prescribed
fi re to reduce B. diandrus biomass and spikelet production (Skaer et al. 2013 ). For
example, B. diandrus is considered more susceptible to burning than other California
annual grassland species (DiTomaso et al. 2006 ), and seeds have higher mortality
when exposed to direct fl ames during burn experiments (Sweet et al. 2008 ).
Consequently, in the absence of fi re, B. diandrus reaches high abundance (Kyser
and DiTomaso 2002 ), allowing it to deplete soil moisture early in the growing sea-
son and reduce the abundance of the native bunchgrasses in California annual grass-
lands (Moyes et al. 2005 ).
12.2.3 Bromus arvensis
The winter annual grass Bromus arvensis L. (fi eld or Japanese brome; syn. B. japon-
icus Thunb.) occurs throughout the Western USA, but is most problematic in mixed-
grass prairies of the Northern Great Plains where it lowers forage production and
reduces native ungulate use (Haferkamp et al. 2001 ). In this region, B. arvensis also
alters several ecosystem properties, including net annual productivity, aboveground
litter decomposition, and soil moisture content (Ogle et al. 2003 ). The contribution
of annual grasses to annual biomass production in this region can range from 6 % to
96 % depending on precipitation, and B. arvensis invasion is enhanced by wet
autumn conditions and the presence of dense ground litter (Haferkamp et al. 1993 ).
Bromus arvensis tends to become more abundant as soil moisture increases and
temperatures become cooler (Hulbert 1955 ), and similar to B. diandrus , fi re
T.A. Monaco et al.