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Eighteen different treatments were applied to an area seeded with the native grasses Stipa comata and S. (Oryzopsis) hymenoides. Plots received supplemental water up to annual rainfall levels. Treatments included 30% cover of native grass mulch (Hilaria jamesii); nitrogen and phosphorus fertilizer; cyanobacterial inoculant from an adjacent, undisturbed area; sugar (to stimulate microbial activity); no water; and various combinations of these treatments. Plots were evaluated one year later for number of grass seedlings established, number of grass seedlings eaten, and cover and biomass of the exotics Salsola kali and S. iberica. Different treatments resulted in strikingly different establishment rates of the seeded...
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Summers on the Colorado Plateau (USA) are typified by harsh conditions such as high temperatures, brief soil hydration periods, and high UV and visible radiation. We investigated whether community composition and pigmention might vary in biological soil crusts as a result of such conditions. Representative surface cores were sampled on the ENE, WSW, and top microaspects of 20 individual soil crust pedicels at a single site in Canyonlands National Park, Utah, in spring and fall of 1999. Frequency of major cyanobacterial taxa and pigment concentrations were measured for each core. The frequency of major cyanobacterial taxa was lower in the fall compared to spring. The less-pigmented cyanobacterium Microcoleus vaginatus...
A number of studies have shown that dust delivers essential nutrients that sustain terrestrial productivity over millennia. Dust, however, contains a range of elements ranging from base cations, N and P, to heavy metals. Some of these elements will stimulate primary productivity over the time scale of soil development while others, such as metals, could inhibit biological activity. As dust accumulates, it also influences water flux and availability by altering soil texture. We are examining the ecological impacts of dust accumulation in Canyonlands National Park in Utah. Using magnetic susceptibility as a proxy for far-traveled dust, we have established transects in sandy surficial deposits (50-90% sand) in which...
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From January 1997 through October 1998, research was conducted at Canyonlands National Park to investigate soil traits responsible for distinct spatial patterns of cheatgrass (Bromus tectorum) occurrence. Field experiments were conducted at sites representing a broad range of soil conditions and cheatgrass abundances. Standard physicochemical soil measures in combination with innovative ion-exchange resin capsules and bags were used to describe spatial and seasonal soil variations. Cheatgrass performance varied along a complex, multivariate soil gradient, with the strongest cheatgrass-soil relationship occurring during winter. Biogeochemical principles, soil measures, growth rates, and leaf-tissue analyses support...
In arid and semiarid lands throughout the world, the cover of vegetation is generally sparse or absent. Open spaces between the higher plants are not bare of autotrophic life but usually covered by a community of highly specialized organisms. This soil surface floral community consists of cyanobacteria, green algae, lichens, mosses, microfungi, and other bacteria. Cyanobacterial and microfungal filaments weave throughout the top few millimeters of soil, gluing loose soil particles together to form a biological crust. These crusts occur in all hot, cool, and cold arid and semiarid regions. They may constitute up to 70% of the living cover (Belnap 1994) and have only recently been recognized as having a major influence...
There are many reasons to be concerned about the use of non-native species or non-local genetic material in restoration efforts. An overview of these issues is presented. It is argued that site restoration is more than just successful vascular plant establishment, and that local plant material should be used whenever possible. However, it is recognized that time and money often constrain restoration efforts, and that maintenance of genetic integrity is often an issue of project scale. Published in Wildland Shrub and Arid Land Restoration Symposium, on pages 265 - 266, in 1993.
We conducted a field experiment to assess effects of simulated above-average fall and spring precipitation on monoculture performance and competitive relations of the exotic annual grass Bromus tectorum and the native bunchgrass Stipa hymenoides in southeastern Utah. Between 1 October 1997 and 31 May 1998, "wet" plots received 239 mm and "dry" plots received 119 mm of water representing 175 and 87 percent of average precipitation, respectively. In monoculture, added water increased fall Bromus establishment by a factor of 1.6 but did not affect fall or winter growth. Added water adversely affected Bromus growth during early spring, but enhanced growth as soils dried during mid-spring. Overall, Bromus shoot production...
    map background search result map search result map Components of Spatial and Temporal Soil Variation at Canyonlands National Park: Implications for P Dynamics and Cheatgrass (Bromus tectorum) Performance Temporal variation in community composition and pigmentation of desert cyanobacterial soil crusts Components of Spatial and Temporal Soil Variation at Canyonlands National Park: Implications for P Dynamics and Cheatgrass (Bromus tectorum) Performance Temporal variation in community composition and pigmentation of desert cyanobacterial soil crusts