Article / Book
View introductory chapter of the book, Exotic brome-grasses in arid and semiarid ecosystems of the western US: causes, consequences, and management implications.
The spread and impacts of exotic species are unambiguous, global threats to many ecosystems. A prominent example is the suite of annual grasses in the Bromus genus that originate from Europe and Eurasia but have invaded or are invading large areas of the Western USA. This book brings a diverse, multidisciplinary group of authors together to synthesize current knowledge, research needs, and management implications for Bromus. Exotic plant invasions are multifaceted problems, and understanding and managing them requires the biological, ecological, sociological, and economic perspectives that are integrated in this book. Knowing how well information from one geographic or environmental setting can transfer to another is a key need for broadly distributed Bromus species especially given ongoing climate change.
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Heavy late-fall grazing by sheep following spring deferment improves deteriorated sagebrush-grass ranges by reducing sagebrush and increasing the production of grasses and forbs. Fall grazing as a method for range improvement is more effective and practical than complete protection from grazing and is less expensive than mechanical or chemical means of sagebrush control. Heavy spring grazing damages good-condition ranges by increasing sagebrush and reducing herbaceous production.
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The objective of this study was to investigate how climate, land use and community structure may explain these patterns of species dominance. We found that differences in summer precipitation and winter minimum temperature, land use intensity, and shrub size may all contribute to the dominance of annual species in the Great Basin, particularly cheatgrass. In particular, previous work indicates that summer precipitation and winter temperature drive the distribution of cheatgrass in the Great Basin. As a result, sites with wet summers and cold springs, similar to the Chinese sites, would not be expected to be dominated by cheatgrass. A history of more intense grazing of the Chinese sites, as described in the literature, also is likely to decrease fire frequency, and decreases litter and shrub dominance, all of which have been demonstrated to be important in cheatgrass establishment and ultimate dominance. Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.
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Sage-grouse obtain resources for breeding, summer, and winter life stages from sagebrush communities. Grazing can change the productivity, composition, and structure of herbaceous plants in sagebrush communities, thus directly influencing the productivity of nesting and early brood-rearing habitats. Indirect influences of livestock grazing and ranching on sage-grouse habitat include fencing, watering facilities, treatments to increase livestock forage, and targeted grazing to reduce fine fuels. To illustrate the relative value of sagebrush habitats to sage-grouse on year-round and seasonal bases, we developed state and transition models to conceptualize the interactions between wildfire and grazing in mountain and Wyoming big sagebrush communities. In some sage-grouse habitats, targeted livestock grazing may be useful for reducing fine fuels produced by annual grasses. We provide economic scenarios for ranches that delay spring turnout on public lands to increase herbaceous cover for nesting sage-grouse. Proper rangeland management is critical to reduce potential negative effects of livestock grazing to sage-grouse habitats.
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The key to grazing that will enhance watershed dynamics is encompassed in the basic ingredients of watershed management, i.e., managing for water efficiency. These ingredients, which have been stated by Barrett (1990), are to CAPTURE, STORE, and SAFELY RELEASE water on watersheds.
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Time-controlled, short-duration, high intensity sheep or cattle grazing for several days in early spring removes substantial amounts of alien annual plant seed while it is still in inflorescence and opens up the sward canopy to allow light to penetrate to young, short-statured seedling perennials. This grazing event must be timed to allow perennial grass regrowth, flowering and seed set before spring soil moisture is exhausted. It must be intense enough to graze off the grass inflorescences of most alien annual grasses. The result is increased live crown cover for mature perennial grasses, reduced decadent dead-center growth forms in bunchgrasses, and improved light availability to tiller bases which promotes basal bud activation and new vegetative and reproductive tiller formation. These perennial grass responses constitute what managers term improved plant vigor.
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Fire risk in western North America has increased with increasing cover of cheatgrass, an invasive alien annual grass. The relationship between cheatgrass cover and fire risk was determined in a historically burned shrub-steppe community where cheatgrass cover ranged from 5 to 75%. Fire risk ranged from about 46% with an average of 12% cheatgrass cover to 100% when cheatgrass cover was greater than 45% based on prediction confidence limits. Reflectance of the green and red bands of aerial photographs, were related to senescent cheatgrass cover to create fine resolution cheatgrass cover and fire risk maps. This assessment technique will allow land managers to prioritize lands for restoration to reduce fire risk in the shrub-steppe.
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Several wildfire prevention programs in southern Europe are currently using livestock grazing for the maintenance of fuelbreaks. This silvopastoral management is valued for being sustainable and effective in reducing fuel loads, but few studies have analyzed other impacts linked to fuelbreak grazing. This paper reports on an experiment performed within the wildfire prevention program in Andalusia (southern Spain) with the aim of clarifying and quantifying the effect of fuelbreak grazing on herbage biomass, ground cover, herbage species composition, and growth of holm oak saplings.
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The experience Squaw Valley Ranch has had with fire, livestock grazing, and sage grouse centers on management strategy and flexibility. Squaw Valley Ranch and the BLM Elko District have a monitoring program that allows for year-to-year adaptations of the grazing plan, as well as long-term
planning for goals and assessment of goal achievement.
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The widespread abundance of cheatgrass on the foothill and semidesert ranges of the Intermountain Great Basin region causes concern to range managers of this area. During the past 20 years, crested wheatgrass has been used to replace cheatgrass on some of the more favorable sites. However, many soils supporting extensive areas of cheatgrass are so low in productivity it is believed that they should be managed as an annual grass type and used for the most effective purpose which appears to be spring range for livestock.