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3.2.1 Changes to Above- and Belowground Community
Structure
Invasion of Bromus in the absence of fi re often occurs through establishment in bare
soil interspaces between perennials, creating a homogeneous herbaceous layer, such
as for B. tectorum in grazed sagebrush steppe (Reisner et al. 2013 ). However, greater
establishment under shrubs or trees than interspaces is also evident in some com-
munities, such as for B. rubens in the Mojave Basin and Range (Brooks 1999 ;
Fig. 3.1 Photos of a Wyoming big sagebrush site that had no B. tectorum before fi re ( top left ) and
the resulting “clean burn” typical of such sites ( top right ), a site dominated by B. tectorum before
fi re ( middle left ), and the resulting “dirty burn” and dense Bromus litter ( middle right ). The bottom
panel shows a close-up view of the charred but incompletely combusted Bromus litter occluding
the soil. Postfi re photos were taken approximately 1 month after summer wildfi re. Photo credits:
top row , M. Germino; lower three, A. Halford
M.J. Germino et al.