Exotic Brome-Grasses in Arid and Semiarid Ecosystems of the Western US

Invasions by exotic grasses, particularly annuals, rank among the most extensive and intensive ways that humans are contributing to the transformation of the earth's surface. The problem is particularly notable with a suite of exotic grasses in the Bromus genus in the arid and semiarid regions that dominate the western United States, which extend from the dry basins near the Sierra and Cascade Ranges across the Intermountain Region and Rockies to about 105° longitude. This genus includes approximately 150 species that have a wide range of invasive and non-invasive tendencies in their home ranges and in North America. Bromus species that became invasive upon introduction to North America in the late 1800's, such as Bromus tectorum and B. rubens, have since became the dominant cover on millions of hectares. Here, millenia of ecosystem development led to landscapes that would otherwise be dominated by perennial shrubs, herbs, and biotic soil crusts that were able to persist in spite of variable and scarce precipitation. This native ecosystem resilience is increasingly coveted by land owners and managers as more hectares lose their resistance to Bromus grasses and similar exotics and as climate, land use, and disturbance-regime changes are also superimposed. Managers are increasingly challenged to glean basic services from these ecosystems as they become invaded. Exotic annual grasses reduce wildlife and livestock carrying capacity and increase the frequency and extent of wildfi res and associated soil erosion. This book uses a unique ecoregional and multidisciplinary approach to evaluate the invasiveness, impacts, and management of the large Bromus genus. Students, researchers, and practitioners interested in Bromus specifically and invasive exotics in general will benefit from the depth of knowledge summarized in the book.

Contenu
Part I: Environmental Impacts of Bromus Species.- Annual Brome invasions and their Impacts: Comparisons among ecoregions in the Western United States.- Impacts Impacts of Bromus tectorum and other annual bromes on ecosystem integrity.- Part II: Invasiveness of Bromus species (emphasis on biological attributes of Bromus).- Evolutionary relationships, mating systems and genetic diversity of Bromus tectorum and other species within section Genea.- Attributes that confer invasiveness and impacts across the large Bromus genus: lessons from the Bromus REEnet database.- Part III: Understanding environmental controls and Bromus distribution (invasibility).- Abiotic controls on annual brome distribution at the regional, landscape, local, and microsite scale.- Future range shifts of Bromus rubens and Bromus tectorum with climate change a review of model projections.- Community ecology of fungal pathosystems on Bromus tectorum and implications for management.- Community resistance to Bromus.- Part IV: Relating the science to human uses and restoration of western rangeland landscapes.- Interactions among fire, land uses, and invasion ecology and human dimensions.- Human dimensions of invasive grasses.- Economic modelling and the management of brome grasses: accounting for ecosystem dynamics, ecological thresholds, and spatial interdependencies.- State-and-transition models: conceptual vs. simulation perspectives, usefulness and breadth of use, land management applications.- Restoration and management tools for rangelands impacted by exotic bromes: new perspectives for the future.- Index.