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sequestration, and accelerated nutrient cycling. Litter produced by Bromus alters
nearly all aspects of ecosystems and notably increases wildfi re occurrence. Where
Bromus has become dominant, it can decrease soil stability by rendering soils bare
for months following fi re or episodic, pathogen-induced stand failure. Bromus-
invaded communities have lower species diversity, and associated species tend to be
generalists adapted to unstable and variable habitats. Changes in litter, fi re, and soil
properties appear to feedback to reinforce Bromus’ dominance in a pattern that por-
tends desertifi cation.
Keywords Bromus • Annual exotic grasses • Ecosystems • Desertifi cation •
Feedbacks
3.1 Introduction
Exotic annual grasses in the genus Bromus that are invading semiarid and arid land-
scapes in the Western USA (hereafter “ Bromus ”) have signifi cant impacts on eco-
system structure and function where they dominate plant community cover (Fig. 1.1
in Germnio et al. 2015 ). This chapter aims to give an overview of these impacts,
with some treatment of Bromus rubens L. (red brome), B. diandrus Roth (ripgut
brome), and B. hordeaceus L. (soft brome) but a primary focus on B. tectorum L.
(cheatgrass, downy brome). B. tectorum has become the most widespread exotic
annual grass in the Western USA and has also attained the greatest local dominance
of communities, often occurring in vast and nearly monocultural patches (Brooks
et al. 2015 ). Nearly 10 % of the many publications on invasive plant impacts are on
Bromus (specifi cally B. tectorum ; Hulme et al. 2013 ), and an exhaustive review of
the studies on ecosystem impacts of Bromus invaders is beyond the scope of this
chapter. Several previous reviews have suggested ways that Bromus can transform
ecosystem structure and function (Hulbert 1955 ; D’Antonio and Vitousek 1992 ;
Allen et al. 2011 ), particularly B. tectorum (Stewart and Hull 1949 ; Klemmedson
and Smith 1964 ; Mack 1981 ; Billings 1990 ). We begin with a short overview of how
the plant community is altered by Bromus invasion. Then, we describe how distur-
bance interacts with Bromus , focusing on fi re because it is a key disturbance for
most landscapes in western North America and is a key aspect of Bromus invader’s
impacts (Brooks et al. 2004 ). We evaluate Bromus’ impact on fi re frequency and
extent and the infl uence of Bromus on ecosystem characteristics such as site and soil
stability and fl ow or cycling of energy, water, carbon (C), and nutrients. Last, we
discuss impacts on invertebrate and vertebrate communities, including wildlife and
domestic livestock.
We focus on comparisons between native- and Bromus -dominated communities
where there is supporting literature, although few studies can truly separate Bromus
invader effects from those of native species (Stark and Norton 2015 ). Many of the
M.J. Germino et al.