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Carbon and nitrogen are supplied by a variety of sources in the desert food web; both vascular and non-vascular plants and cyanobacteria supply carbon, and cyanobacteria and plant-associated rhizosphere bacteria are sources of biological nitrogen fixation. The objective of this study was to compare the relative influence of vascular plants and biological soil crusts on desert soil nematode and protozoan abundance and community composition. In the first experiment, biological soil crusts were removed by physical trampling. Treatments with crust removed had fewer nematodes and a greater relative ratio of bacterivores to microphytophages than treatments with intact crust. However, protozoa composition was similar with...
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The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results...
This dataset is the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3800 observations representing 27 temperature manipulation studies, spanning nine biomes and nearly two decades of warming experiments. Data for this study were obtained from a combination of unpublished data and published literature values. We find that although warming increases soil respiration rates, there is limited evidence for a shifting respiration response with experimental warming. We also note a universal decline in the temperature sensitivity of respiration at soil temperatures >25°C. This dataset includes 3817 observations, from control (n=1812), first (i.e., lowest or sole) level...
Archaea are common and abundant members of biological soil crust communities across large-scale biogeographic provinces of arid North America. Regardless of microbial community development, archaeal populations averaged 2 � 107 16S rRNA gene copies per gram of soil, representing around 5% of the prokaryotic (total calculated bacterial and archaeal) numbers assessed by quantitative-PCR. In contrast, archaeal diversity, determined by denaturing gradient gel electrophoresis fingerprinting and clone libraries of 16S rRNA genes, was very restricted. Only six different phylotypes (all Crenarchaea) were detected, three of which were very dominant. Some phylotypes were widespread, while others were typical of Southern desert...
Composite soil samples from 7 sites on San Nicolas Island were evaluated quantitatively and qualitatively for the presence of cyanobacteria and eukaryotic microalgae. Combined data demonstrated a rich algal flora with 19 cyanobacterial and 19 eukaryotic microalgal genera being identified, for a total of 56 species. Nine new species were identified and described among the cyanobacteria and the eukaryotic microalgae that were isolated: Leibleinia edaphica, Aphanothece maritima, Chroococcidiopsis edaphica, Cyanosarcina atroveneta, Hassallia californica, Hassallia pseudoramosissima, Microchaete terrestre, Palmellopsis californicus, and Pseudotetracystis compactis. Distinct distributional patterns of algal taxa existed...
Greenhouse experiments were undertaken to identify soil factors that curtail growth of the exotic annual grass Bromus tectorum L. (cheatgrass) without significantly inhibiting growth of native perennial grasses (here represented by Hilaria jamesii [Torr.] Benth). We grew B. tectorum and H. jamesii alone (monoculture pots) and together (combination pots) in soil treatments that manipulated levels of soil phosphorus, potassium, and sodium. Hilaria jamesii showed no decline when its aboveground biomass in any of the applied treatments was compared to the control in either the monoculture or combination pots. Monoculture pots of B. tectorum showed a decline in aboveground biomass with the addition of Na2HPO4 and K2HPO4....
The aeolian accumulation of natural atmospheric dust in a desert environment was investigated during a 24-month experiment. Accumulation was measured with marble collectors every month. At the same time, wind speed, dust concentration, dew formation and rainfall were recorded. Atmospheric stability was measured from a 90 m tower several km from the test site. Dust accumulation by day was systematically higher than dust accumulation at night. Also, dust concentration was higher, but the higher concentrations cannot completely explain die higher accumulation values. Both average monthly concentration and accumulation are considerably influenced by the occurrence of high-magnitude dust events, either dust storms or...
Bouteloua gracilis (Kunth) Lag. ex Griffiths (blue grama), Bouteloua eriopoda (Torr.) Torr. (black grama), and Larrea tridentata Coville (creosotebush) are dominant plants on the McKenzie Flats portion of the Llano de Manzano landform within Sevilleta National Wildlife Refuge in central New Mexico, part of the biome ecotone from the Colorado Shortgrass Steppe to the Chihuahuan Desert. In this study, we examine the hypothesis that soil heterogeneity, determined by variation in surface soil depth, carbonate accumulation, and fine-textured fraction, controls relative dominance of the three species. The area is flat, generally <1% slope; however, abrupt soil differences exist even within the flattest parts of the landscape...
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Seedlings of the succulent crassulacean acid metabolism (CAM plant Agave deserti in the northwestern Sonoran Desert were found only in sheltered microhabitats, nearly all occurring under the canopy of a desert bunchgrass, Hilaria rigida. Apparently because soil surface temperatures can reach 71@?C in exposed areas, seedlings were generally located near the center or on the northern side of this nurse plant. Both species have shallow root systems, about half of the roots of H. rigida and all those for seedlings of A. deserti occurring above soil depths of 0.08 m. To examine competition for water between the nurse plant and an associated seedling, a three-dimensional model for root water uptake was developed. The...
The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results...
Aeolian erosion of natural dust on two types of hills located in a rocky desert was investigated by means of wind tunnel simulations and field measurements. The first hill showed an elongated, nearly symmetric shape and was oriented perpendicular to the wind, whereas the second hill was almost perfectly conical. Erosion was measured along three transects: one across the elongated hill (transect parallel to the wind) and two across the conical hill (transects perpendicular to each other and crossing at the summit). In the field, erosion was measured on erosion plots during two wind storms. In the wind tunnel, erosion was measured on topographic scale models. The wind tunnel experiments and field experiments showed...
There may be no more conspicuous example of a conflict between society and technology than a wind energy landscape. The fastest growing renewable energy resource in the world, wind energy has evoked a cool public response. Through the use of interviews, the published literature, governing legislation, and personal experience, this article examines this conflict near Palm Springs, California. Its purpose is to summarize and explain the opposition that developed there from the earliest days, what has been done to mitigate it, and how the local experience is reflected in similar developments elsewhere. This particular conflict between society and technology has the potential, with proper guidance, controls, and sensitivity,...
Biological soil crusts (BSCs) are the dominant living cover in many drylands of the world. They possess many features that can influence different aspects of local hydrologic cycles, including soil porosity, absorptivity, roughness, aggregate stability, texture, pore formation, and water retention. The influence of biological soil crusts on these factors depends on their internal and external structure, which varies with climate, soil, and disturbance history. This paper presents the different types of biological soil crusts, discusses how crust type likely influences various aspects of the hydrologic cycle, and reviews what is known and not known about the influence of biological crusts on sediment production and...
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Biological soil crusts (BSCs) are an integral part of dryland ecosystems and often included in long-term ecological monitoring programs. Estimating moss and lichen cover is fairly easy and non-destructive, but documenting cyanobacterial level of development (LOD) is more difficult. It requires sample collection for laboratory analysis, which causes soil surface disturbance. Assessing soil surface stability also requires surface disturbance. Here we present a visual technique to assess cyanobacterial LOD and soil surface stability. We define six development levels of cyanobacterially dominated soils based on soil surface darkness. We sampled chlorophyll a concentrations (the most common way of assessing cyanobacterial...
In desert ecosystems a large proportion of water and nitrogen is supplied in rain-induced pulses. It has been suggested that competitive interactions among desert plants would be most intense during these pulse periods of high resource availability. We tested this hypothesis with three cold desert shrub species of the Colorado Plateau (Gutierrezia sarothrae, Atriplex confertifolia, and Chrysothamnus nauseosus), which differ in their distribution of functional roots. In a three-year field study we conducted a neighbor removal experiment in conjunction with simulated 25-mm precipitation events and the addition of a nitrogen pulse in either spring or summer. We measured predawn water potential (?), gas exchange, leaf...
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Many soils in southeastern Utah are protected from surface disturbance by biological soil crusts that stabilize soils and reduce erosion by wind and water. When these crusts are disturbed by land use, soils become susceptible to erosion. In this study, we compare a never-grazed grassland in Canyonlands National Park with two historically grazed sites with similar geologic, geomorphic, and geochemical characteristics that were grazed from the late 1800s until 1974. We show that, despite almost 30 years without livestock grazing, surface soils in the historically grazed sites have 38-43% less silt, as well as 14-51% less total elemental soil Mg, Na, P, and Mn content relative to soils never exposed to livestock disturbances....
Microbial activity in semiarid and arid environments is closely related to the timing, intensity, and amount of precipitation. The characteristics of the soil surface, especially the influence of biological soil crusts, can determine the amount, location, and timing of water infiltration into desert soils, which, in turn, determines the type and size of microbial response. Nutrients resulting from this pulse then create a positive feedback as increases in microbial and plant biomass enhance future resource capture or, alternatively, may be lost to the atmosphere, deeper soils, or downslope patches. When rainfall intensity overwhelms the water infiltration capacity of the plant interspace or the plant patch, overland...
Fire risk in deserts is increased by high production of annual forbs and invasive grasses that create a continuous fine fuel bed in the interspaces between shrubs. Interspace production is influenced by water, nitrogen (N) availability, and soil texture, and in some areas N availability is increasing due to anthropogenic N deposition. The DayCent model was used to investigate how production of herbaceous annuals changes along gradients of precipitation, N availability, and soil texture, and to develop risk-based critical N loads. DayCent was parameterized for two vegetation types within Joshua Tree National Park, California, USA: creosote bush (CB) and pi�on?juniper (PJ). The model was successfully calibrated in...
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Landscape Conservation Cooperatives (LCCs) are public-private partnerships composed of states, tribes, federal agencies, non-governmental organizations, universities, international jurisdictions, and others working together to address landscape and seascape scale conservation issues. LCCs inform resource management decisions to address broad-scale stressors-including habitat fragmentation, genetic isolation, spread of invasive species, and water scarcity-all of which are magnified by a rapidly changing climate. For further information go to https://www.fws.gov/science/catalog. The previous 2011 LCC Network Areas data is available at https://www.sciencebase.gov/catalog/item/52f2735ee4b0a6f0bd498c2f
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Landscape Conservation Cooperatives (LCCs) are public-private partnerships composed of states, tribes, federal agencies, non-governmental organizations, universities, international jurisdictions, and others working together to address landscape and seascape scale conservation issues. LCCs inform resource management decisions to address broad-scale stressors-including habitat fragmentation, genetic isolation, spread of invasive species, and water scarcity-all of which are magnified by a rapidly changing climate. For further information go to https://www.fws.gov/science/catalog. The previous 2011 LCC Network Areas data is available at https://www.sciencebase.gov/catalog/item/52f2735ee4b0a6f0bd498c2f


map background search result map search result map Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah Multi-Decadal Impacts of Grazing on Soil Physical and Biogeochemical Properties in Southeast Utah Visually assessing the level of development and soil surface stability of cyanobacterially dominated biological soil crusts Interactions Between Seedlings of Agave Deserti and the Nurse Plant Hilaria Rigida Interactions Between Seedlings of Agave Deserti and the Nurse Plant Hilaria Rigida Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah Multi-Decadal Impacts of Grazing on Soil Physical and Biogeochemical Properties in Southeast Utah Visually assessing the level of development and soil surface stability of cyanobacterially dominated biological soil crusts