Skip to main content
U.S. flag

An official website of the United States government

Ecosystem impacts of exotic annual invaders in the genus Bromus

January 23, 2016

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) transform 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 productivity and cover are less stable across seasons and years when Bromus dominates, due to a greater response to annual climate variability. Bromus’ “flash” 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 sequestration, and accelerated nutrient cycling. Litter produced by Bromus alters nearly all aspects of ecosystems and notably increases wildfire occurrence. Where Bromus has become dominant, it can decrease soil stability by rendering soils bare for months following fire 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, fire, and soil properties appear to feedback to reinforce Bromus’ dominance in a pattern that portends desertification.

Publication Year 2016
Title Ecosystem impacts of exotic annual invaders in the genus Bromus
DOI 10.1007/978-3-319-24930-8_3
Authors Matthew J. Germino, Jayne Belnap, John M. Stark, Edith B. Allen, Benjamin M. Rau
Publication Type Book Chapter
Publication Subtype Book Chapter
Index ID 70156725
Record Source USGS Publications Warehouse
USGS Organization Forest and Rangeland Ecosystem Science Center; Contaminant Biology Program