Competition for moisture among seedlings of annual and perennial grasses as influenced by root elongation at low temperature.
TL;DR: The results suggest that in areas where root growth occurs at low temperatures and where lands are infested with B. tectorum and T. asperum, seedlings of A. desertorum would be more successful than seedlingsof A. spicatum.
Abstract: Rapidly elongating Bromus tectorum and Taeniatherum asperum roots penetrated the soil ahead of Agropyron spicatum roots and used available moisture. In contrast, Agropyron desertorum roots penetrated the soil almost as rapidly as B. tectorum and T. asperum and remained in favorable moisture. These differences in root penetration resulted in lower leaf water potentials and poorer survival in A. desertorum. The results suggest that in areas where root growth occurs at low temperatures and where lands are infested with B. tectorum and T. asperum, seedlings of A. desertorum would be more successful than seedlings of A. spicatum. See full-text article at JSTOR
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TL;DR: In this article, the authors conducted a study in Artemisia tridentata ecosystems at two Great Basin locations examining differences in resource availability and invasibility of Bromus tectorum over elevation gradients and in response to direct and interacting effects of removal of perennial herbaceous vegetation and fire.
Abstract: Ecosystem susceptibility to invasion by nonnative species is poorly understood, but evidence is increasing that spatial and temporal variability in resources has large-scale effects. We conducted a study in Artemisia tridentata ecosystems at two Great Basin locations examining differences in resource availability and invasibility of Bromus tectorum over elevation gradients and in response to direct and interacting effects of removal of perennial herbaceous vegetation and fire. We monitored environmental conditions, soil variables, and B. tectorum establishment and reproduction over two years. Soil water (measured as the number of days soil matric potential was .� 1.5 MPa) and nitrate availability (measured as micromoles of NO3 � sorbed to resin capsules per day in the ground) decreased with decreasing elevation. Lower-elevation sites had greater annual variability in soil water availability than upper-elevation sites did. Soil nitrate levels were highest at all elevations when soils were wettest; nitrate availability was not more variable at lower elevations. Removal of herbaceous perennials increased soil water and nitrate availability, but burning without removal had only minor effects. Bromus tectorum had low establishment, biomass, and seed production on high-elevation sites and on a mid-elevation site during a cold, short, growing season probably due to ecophysiological limitations resulting from cold temperatures. Establishment, biomass, and seed production were variable at low elevations and best explained by soil characteristics and spatial and temporal variation in soil water. Removal and fire had minor effects on emergence and survival, but biomass and seed production increased two to three times following removal, two to six times after burning, and 10-30 times following removal and burning. Our data indicate that invasibility varies across elevation gradients and appears to be closely related to temperature at higher elevations and soil water availability at lower elevations. High variability in soil water and lower average perennial herbaceous cover may increase invasion potential at lower elevations. Soil water and nitrate availability increase following either fire or removal, but on intact sites native perennials typically increase following fire, limiting B. tectorum growth and reproduction. Following resource fluctuations, invasibility is lowest on sites with relatively high cover of perennial herbaceous species (i.e., sites in high ecological condition).
587 citations
Cites background from "Competition for moisture among seed..."
...Annual grasses are effective competitors for soil water in these ecosystems and can deplete soil water and depress the moisture status of native shrubs and grasses (Harris and Wilson 1970, Melgoza et al. 1990, Booth et al. 2003)....
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Book•
01 Dec 1996TL;DR: In this paper, the physical and biological characterization of the four North American deserts and a description of the primary adaptations of plants to environmental stress are described, along with a synthesis of the adaptations and resource requirements of North American desert plants.
Abstract: This book begins with the physical and biological characterization of the four North American deserts and a description of the primary adaptations of plants to environmental stress. In the following chapters the authors present case studies of key species representing dominant growth forms of the North American deserts, and provide an up-to-date and comprehensive review of the major patterns of adaptations in desert plants. One chapter is devoted to several important exotic plants that have invaded North American deserts. The book ends with a synthesis of the adaptations and resource requirements of North American desert plants. Further, it addresses how desert plants may respond to global climate change.
381 citations
Cites background from "Competition for moisture among seed..."
...Instead, it appears that Bromus is poised to extract water, grow rapidly, and complete its life cycle early in the spring, whereas the more slowly elongating roots of seedlings of perennials such as Pseudoroegneria are forced to develop in dry soil at the onset of the summer dry season, which results in high seedling mortality of the bunchgrass (Harris and Wilson 1970)....
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01 Jun 2004
TL;DR: Schroeder et al. as mentioned in this paper presented an unbiased assessment from an ecological perspective of the current status and the potential factors that influenced the long-term conservation of greater sage-grouse populations and the sagebrush ecosystems on which they depend.
Abstract: Population declines of greater sage-grouse (Centrocercus urophasianus) and alterations and loss of sagebrush (Artemisia spp.) have prompted petitions to the U.S. Fish and Wildlife Service to list the species under the Endangered Species Act. Our objectives were to present an unbiased assessment from an ecological perspective of the current status and the potential factors that influenced the long-term conservation of greater sage-grouse populations and the sagebrush ecosystems on which they depend. We reviewed the primary literature, and conducted new analyses and presented results on data collected for greater sage-grouse populations and sagebrush habitats. Our approach was large-scale, and was intended to identify regional patterns of disturbances, land use practices, and population trends. A blind review of this document was conducted by the Ecological Society of America. In addition, members of the National Sagegrouse Conservation Planning Framework Team and representatives from each state and province in the current range of greater sage-grouse reviewed the document for completeness and technical accuracy. In this chapter, we present the background, objectives, perspective, and geographical and temporal scope for the Conservation Assessment. Because 70% of the lands dominated by sagebrush cover are managed by public agencies, we summarized the primary legislation directing the historical disposition and governing the use of public lands. We also presented information on the administrative jurisdiction of sagebrush habitats because many of the stressors on sagebrush ecosystems involve land use and management practices. However, we did not provide management recommendations. Rather, this document was intended as an objective scientific presentation of the individual and cumulative influences on greater sage-grouse and sagebrush habitats. Range-wide Conservation Assessment Background and Rationale Historically, greater sage-grouse occurred in parts of 12 states within the western United States and 3 Canadian provinces (Fig. 1.1) (Schroeder et al. 2004). Greater sage-grouse populations have declined throughout much of their former range and have been extirpated from Nebraska, and British Columbia (Connelly and Braun 1997, Schroeder et al. 1999, Schroeder et al. 2004). The historical distribution of greater sage-grouse in Arizona currently is being questioned. Estimates of regional declines ranged from 17 to 47% (Connelly and Braun 1997). Greater sage-grouse currently occupy 670,000 km, or 56%, of their potential pre-settlement range, which once covered approximately 1,200,000 km (Schroeder et al. 2004). Current distributions of “fringe” populations are fragmented and increasingly disjunct from core regions of the distribution (e.g., Mono Lake, California; eastern Washington; southern Utah) (Schroeder et al. 1999). Despite widespread concerns regarding the species’ status and declining numbers, there has been no definitive range-wide assessment of sage-grouse populations and habitats. The greater sage-grouse is entirely dependent on sagebrush ecosystems that dominate much of western North America. The sagebrush biome, comprised primarily of 20 taxa encompassing 11 major Artemisia species and subspecies groups (McArthur and Plummer 1978, McArthur and Sanderson 1999), covers approximately 480,000 km (118.6 million acres) and Conservation Assessment of Greater Sage-grouse and Sagebrush Habitats Connelly et al. Introduction 1 2 includes 14 states (Washington, Oregon, California, Idaho, Nevada, Utah, Arizona, Montana, Wyoming, Colorado, New Mexico, Nebraska, South Dakota, and North Dakota) (sagebrush habitats in Oklahoma and Kansas were outside of the pre-settlement range of greater sage-grouse were not included in this assessment) and 3 provinces (Alberta, British Columbia, Saskatchewan) (Fig. 1.2). Vegetation and wildlife communities vary greatly across the range covered by sagebrush as a function of differences in underlying soils, climate, elevation, and geographic location (Miller and Eddleman 2001). The relatively simple structure and floristic characteristics of sagebrush landscapes (West 1996, West and Young 2000) mask complex community dynamics, disturbance regimes, and system resiliency. Three fundamental characteristics of the landscape that early European explorers once described as a vast sea of sagebrush (Fremont 1845) have been altered from pre-settlement conditions. First, the total land area dominated by sagebrush has been reduced in many regions of the sagebrush biome. For example, approximately 75% of the shrubsteppe habitats occurring on deep, loamy soils in the state of Washington and virtually all of the basin big sagebrush (Artemisia tridentata ssp. tridentata) habitats in southern Idaho have been converted to agricultural croplands (Hironaka et al. 1983, Noss et al. 1995, McDonald and Reese 1998, Vander Haegen et al. 2000). Second, the composition of sagebrush communities has been changed, primarily through alterations in the understory vegetation and soils. Replacement of native perennial bunchgrasses by cheatgrass (Bromus tectorum), an exotic annual, has profoundly altered the fire regime and led to extensive loss of large expanses of sagebrush habitats (d’Antonio and Vitousek 1992, West and Young 2000, Brooks and Pyke 2001). Finally, the configuration of sagebrush habitats within the larger context of the landscape has been changed. The increased edge in landscapes fragmented by roads, power-lines, fences, and other linear features promote spread of exotic invasive species (Gelbard and Belnap 2003), facilitates predator movements (Tewksbury et al. 2002), and isolates wildlife populations (Saunders et al. 1991, Trombulak and Frissell 2000). Changes in quantity, composition, and configuration of sagebrush habitats have consequences on the ecological processes within the sagebrush ecosystem and the resources available to support wildlife (Wisdom et al. 2002). Few pristine and intact sagebrush ecosystems remain (Noss and Peters 1995, Noss et al. 1995, West 1996, Mac et al. 1998). Over 350 species of flora and fauna depend on sagebrush habitats for all or part of their existence; a high proportion of the endemic and imperiled species in the western United States are found within the sagebrush distribution. The Great Basin ecoregion contains the second highest number of imperiled endemic species in the United States (Chaplin et al. 2000:166). The Columbia Basin population of pygmy rabbits (Brachylagus idahoensis) and Gunnison sagegrouse (Centrocercus minimus) are highly dependent on sagebrush habitats and currently are candidate species for federal listing under the Endangered Species Act (U.S. Fish and Wildlife Service 2000, U.S. Fish and Wildlife Service 2003). The current range occupied by Gunnison sage-grouse has been reduced to 5,000 km from its pre-settlement distribution of 45,000 km Conservation Assessment of Greater Sage-grouse and Sagebrush Habitats Connelly et al. Introduction 1 3 primarily because of habitat loss and alteration (Oyler-McCance et al. 2001, Schroeder et al. 2004). Petitions filed to list the greater sage-grouse under the Endangered Species Act are based on concerns for long-term conservation because of potential threats to the species and the sagebrush habitats on which it depends (Wambolt et al. 2002). Public perception has progressed beyond the prediction that the “much-maligned sagebrush will be regarded with increasing favor by land managers” (McArthur and Plummer 1978) to genuine concern about these ecosystems (Braun et al. 1976, Knick 1999) to requests for legal action (Chapter 2). A decision to give the greater sage-grouse protected status across its entire range has significant consequences for management and use of a large part of the western United States. Less than 1% of the 668,412 km currently occupied by greater sage-grouse, and very little sagebrush habitat is legally protected (Caicco et al. 1995, Stoms et al. 1998, Scott et al. 2001, Wright et al. 2001, Knick et al. 2003). Multiple-use management dominates approximately 70% of the sagebrush habitats, which are owned publicly (Box 1990, Poling 1991). Consumptive uses that potentially influence sagebrush habitats include livestock grazing, mining, energy development, conversion to agriculture, and urbanization. Non-consumptive uses, such as use of off-road vehicles for recreation, also have the potential to influence habitats and populations of sage-grouse. Greater sage-grouse also are legally hunted in 10 states, and some populations are also subject to subsistence hunting by Native Americans. Objectives and Perspective of the Conservation Assessment Our primary objective was to document the current status and the potential factors that influence the long-term conservation of greater sage-grouse populations and the sagebrush ecosystems on which they depend. We based our analysis throughout this document on an ecological perspective of the dynamics inherent in sagebrush ecosystems and the requirements of greater sage-grouse. In contrast, land-use perspectives have goals to maximize a particular function that may have objectives competing with other resource use. For example, evaluation of sagebrush communities primarily based on their ability to provide forage for livestock may result in extensive alterations that are unsuitable for greater sage-grouse and other species dependent on sagebrush habitats (Schneegas 1967, Klebenow 1970, Braun et al. 1976, Reynolds and Trost 1981, Crawford et al. 2004). An ecological perspective is critical to providing a common denominator within which land uses can be evaluated in relation to disturbance and resiliency of the system. We have used ecological terms to describe population or habitat patterns and processes rather than value-laden terms which may have alternate connotations. Commonly used terms, such as “decadent” or “catastrophic” evoke an attitude that somet
357 citations
TL;DR: B. tectorum competes with native species for soil water and negatively affects their wate status and productivity, but the competition for water does not affect water use efficiency of the native species.
Abstract: Causes for the widespread abundance of the alien grass Bromus tectorum (cheatgrass) after fire in semiarid areas of western North America may include: (1) utilization of resources freed by the removal of fireintolerant plants; and (2) successful competition between B. tectorum and individual plants that survive fire. On a site in northwestern Nevada (USA), measurements of soil water content, plant water potential, aboveground biomass production, water use efficiency, and B. tectorum tiller density were used to determine if B. tectorum competes with either of two native species (Stipa comata and Chrysothamnus viscidiflorus) or simply uses unclaimed resources. Soil water content around native species occurring with B. tectorum was significantly lower (P<0.05) than around individuals without B. tectorum nearby. Native species had significantly more negative plant water potential when they occurred with B. tectorum. Aboveground biomass was significantly higher for native species without B. tectorum. However, the carbon isotope ratio of leaves for native species with B. tectorum was not significantly different from individuals without B. tectorum. Thus, B. tectorum competes with native species for soil water and negatively affects their wate status and productivity, but the competition for water does not affect water use efficiency of the native species. These adverse effects of B. tectorum competition on the productivity and water status of native species are also evident at 12 years after a fire. This competitive ability of B. tectorum greatly enhances its capability to exploit soil resources after fire and to enhance its status in the community.
322 citations
Cites background from "Competition for moisture among seed..."
...tecIorum effectively competes with seedlings of perennial species (Hull 1963; Harris 1967; Evans et al. 1970; Harris and Wilson 1970)....
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TL;DR: In this paper, the authors used cover, density, and frequency data for vascular plants sampled on 79 permanent plots nine times during 45 years to assess longterm changes in abundance and distribution of major species and life forms, assess changes in species richness and plot similarity, and test the hypotheses that plant cover and stability of cover are positively associated with species richness, and that invasibility is inversely relate.
Abstract: Increasing demands on arid and semiarid ecosystems, which comprise one-third of Earth's terrestrial environment, create an urgent need to understand their biodiversity, function, and mechanisms of change. Sagebrush (Artemisia) steppe, the largest semiarid vegetation type in North America, is endangered because of losses to agriculture, excessive grazing, and invasive species. Establishment in 1950 of what is now designated as the Idaho National Engineering and Environmental Laboratory (southeastern Idaho, USA) created the largest existing reserve of this extensive vegetation type. We used cover, density, and frequency data for vascular plants sampled on 79 permanent plots nine times during 45 years to (1) assess long-term changes in abundance and distribution of major species and life forms, (2) assess changes in species richness and plot similarity, and (3) test the hypotheses that plant cover and stability of cover are positively associated with species richness and that invasibility is inversely relate...
266 citations
References
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28 citations
TL;DR: Crested wheatgrass seeds were tested for their ability to carry on phosphorylation reactions at low water potentials and it was indicated that someosphorylation occurred at a water potential of -880 atmospheres.
Abstract: Crested wheatgrass seeds [Agropyron desertorum (Fisch. ex Link) Schult.] were tested for their ability to carry on phosphorylation reactions at low water potentials. Seeds were treated with (32)P labeled sodium phosphate and incubated in air having different controlled relative humidities. Ion exchange chromatography and radioassay of phosphate esters indicated that some phosphorylation occurred at a water potential of -880 atmospheres. Seeds did not incorporate (32)P in nicotinamide adenine dinucleotide, adenosine triphosphate, and uridine diphosphate hexose until they were moistened to a water potential of -130 atmospheres.
15 citations
TL;DR: The remaining range lands, heavily used for more than a hundred years, are still important to the economy of the West, first because of the tremendous acreage involved; second because the roughages produced on these wild lands can be profitably used by livestock; third because the range lands are adjacent to ranches producing livestock in small irrigated valleys where hay for winter feeding can be produced.
Abstract: America’s wide open spaces, the range lands of the West, are beginning to receive some long deserved attention. Large areas of this country’s original range lands have been diverted to uses other than grazing. They were first used by native game and native Americans, then crossed by explorers, missionaries, and livestock growers. Finally permanent settlers came to plow up and dry farm or irrigate large tracts of range land. Although some plowed areas have been abandoned, range lands are still decreasing in acreage because of new reclamation projects and the expansion of highways, cities and industrial sites. ’ The remaining range lands, heavily used for more than a hundred years, are still important to the economy of the West, first because of the tremendous acreage involved; second because the roughages produced on these wild lands can be profitably used by livestock; third because the range lands are adjacent to ranches producing livestock in small irrigated valleys where hay for winter feeding can be produced; and fourth range lands are often watersheds for irrigation projects and are also used for recreation and by big game animals. / Many attempts to domesticate range plants have failed, largely because the methods used were too direct. They were based on collections of seed where abundant, and direct seeding of such seeds into range areas without intermediate testing. Under the rigorous and droughty climatic conditions the seed produced on native stands and vigor of seedlings from native seed were seldom good. Cultural practices were not known. The wide variation among ecotypes of many species made improbable the selection of the right strain for optimum establishment. After heavy use almost to the extinction of some species, native grasses have finally caught the attention of plant collectors,
5 citations