© Springer International Publishing Switzerland 2016 61
M.J. Germino et al. (eds.), Exotic Brome-Grasses in Arid and Semiarid
Ecosystems of the Western US, Springer Series on Environmental Management,
DOI 10.1007/978-3-319-24930-8_3
Chapter 3
Ecosystem Impacts of Exotic Annual Invaders
in the Genus Bromus
Matthew J. Germino , Jayne Belnap , John M. Stark ,
Edith B. Allen , and Benjamin M. Rau
Abstract An understanding of the impacts of exotic plant species on ecosystems is
necessary to justify and guide efforts to limit their spread, restore natives, and plan
for conservation. Invasive annual grasses such as Bromus tectorum , B. rubens ,
B. hordeaceus , and B. diandrus (hereafter collectively referred to as Bromus ) trans-
form the structure and function of ecosystems they dominate. Experiments that
prove cause-and-effect impacts of Bromus are rare, yet inferences can be gleaned
from the combination of Bromus -ecosystem associations, ecosystem condition
before/after invasion, and an understanding of underlying mechanisms. Bromus
typically establishes in bare soil patches and can eventually replace perennials such
as woody species or bunchgrasses, creating a homogeneous annual cover. Plant pro-
ductivity and cover are less stable across seasons and years when Bromus domi-
nates, due to a greater response to annual climate variability. Bromus’ “fl ash” of
growth followed by senescence early in the growing season, combined with shallow
rooting and annual habit, may lead to incomplete use of deep soil water, reduced C
M. J. Germino (*)
US Geological Survey , Forest and Rangeland Ecosystem Science Center ,
Boise , ID 83706 , USA
e-mail: [email protected]
J. Belnap
US Geological Survey , Southwest Biological Science Center , Moab , UT 84532 , USA
e-mail: [email protected]
J. M. Stark
Department of Biology, and the Ecology Center , Utah State University ,
Logan , UT 84322-5305 , USA
e-mail: [email protected]
E. B. Allen
Department of Botany and Plant Sciences , University of California, Riverside ,
Riverside , CA , USA
e-mail: [email protected]
B. M. Rau
US Department of Agriculture, Forest Service , Southern Research Station ,
Aiken , SC 29803 , USA
e-mail: [email protected]