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Abstract The potential effects of climate change on the hydrology and water resources of the Colorado River basin are assessed by comparing simulated hydrologic and water resources scenarios derived from downscaled climate simulations of the U.S. Department of Energy/National Center for Atmospheric Research Parallel Climate Model (PCM) to scenarios driven by observed historical (1950–1999) climate. PCM climate scenarios include an ensemble of three 105-year future climate simulations based on projected `business-as-usual'(BAU) greenhouse gas emissions and a control climate simulation based on static 1995 greenhouse gas concentrations. Downscaled transient temperature and precipitation sequences were extracted...
Invasion by Tamarix (L.) can severely alter riparian areas of the western U.S., which are globally rare ecosystems. The upper Verde River, Arizona, is a relatively free-flowing river and has abundant native riparian vegetation. Tamarix is present on the upper Verde but is a minor component of the vegetation (8% of stems). This study sought to determine whether riparian vegetation characteristics differed between sites where Tamarix was present and sites where Tamarix was absent during the invasion of the upper Verde. We hypothesized that herbaceous understory and woody plant communities would differ between Tamarix present and absent sites. Our hypothesis was generally confirmed, the two types of sites were different....
Bog vegetation, which is dominated by Sphagnum mosses, depends exclusively on aerial deposition of mineral nutrients. We studied how the main mineral nutrients are distributed between intracellular and extracellular exchangeable fractions and along the vertical physiological gradient of shoot age in seven Sphagnum species occupying contrasting bog microhabitats. While the Sphagnum exchangeable cation content decreased generally in the order Ca2+ ? K+, Na+, Mg2+ > Al3+ > NH4+, intracellular element content decreased in the order N > K > Na, Mg, P, Ca, Al. Calcium occurred mainly in the exchangeable form while Mg, Na and particularly K, Al and N occurred inside cells. Hummock species with a higher cation exchange...
N limitation to primary production and other ecosystem processes is widespread. To understand the causes and distribution of N limitation, we must understand the controls of biological N fixation. The physiology of this process is reasonably well characterized, but our understanding of ecological controls is sparse, except in a few cultivated ecosystems. We review information on the ecological controls of N fixation in free-living cyanobacteria, vascular plant symbioses, and heterotrophic bacteria, with a view toward developing improved conceptual and simulation models of ecological controls of biological N fixation. A model (Howarth et al. 1999) of cyanobacterial fixation in lakes (where N fixation generally increases...
The effects of elevated metals on stream periphyton in the Eagle River, a mining impacted river in central Colorado, were assessed in 1991 and 1992 using assemblage information (taxa richness, community similarity) and non-taxonomic measures (biomass, chlorophyll a, autotrophic index). The number of periphyton genera collected ranged from 2 at a site adjacent to abandoned mining operations to 21 at a downstream site, but was not significantly correlated with dissolved metals concentrations. Fragilaria and Achnanthes were the dominant genera at all sites, with Fragilaria dominating the less impacted sites and Achnanthes dominating at the more impacted sites. Taxonomic similarity was greatest among those sites receiving...
We integrated soil models with an established ecosystem process model (SIPNET, simplified photosynthesis and evapotranspiration model) to investigate the influence of soil processes on modelled values of soil CO2 fluxes (RSoil). Model parameters were determined from literature values and a data assimilation routine that used a 7-year record of the net ecosystem exchange of CO2 and environmental variables collected at a high-elevation subalpine forest (the Niwot Ridge AmeriFlux site). These soil models were subsequently evaluated in how they estimated the seasonal contribution of RSoil to total ecosystem respiration (TER) and the seasonal contribution of root respiration (RRoot) to RSoil. Additionally, these soil...
We observed a large peak of absorbance when methanol extracts of dorsal skin from four species of fish were scanned in a spectro-photometer. There appeared to be a direct relation between the amount of this skin component and the period of time in which each species of fish developed UVB-induced sunburn. Published in Environmental Science and Pollution Research, volume 2, issue 1, on pages 30 - 32, in 1995.
The primary hypothesis for the astonishing success of many exotics as community invaders relative to their importance in their native communities is that they have escaped the natural enemies that control their population growth ? the `natural enemies hypothesis'. However, the frequent failure of introduced biocontrols, weak consumer effects on the growth and reproduction of some invaders, and the lack of consistent strong top-down regulation in many natural ecological systems indicate that other mechanisms must be involved in the success of some exotic plants. One mechanism may be the release by the invader of chemical compounds that have harmful effects on the members of the recipient plant community (i.e., allelopathy)....
In arid lands, where vegetation is sparse or absent, the open ground is not bare but generally covered by a community of small, highly specialized organisms. Cyanobacteria, algae, microfungi, lichens, and bryophytes aggregate soil particles to form a coherent skin - the biological soil crust. It stabilizes and protects the soil surface from erosion by wind and water, influences water runoff and infiltration, and contributes nitrogen and carbon to desert soils. Soil surface disturbance, such as heavy livestock grazing, human trampling or off-road vehicles, breaks up the fragile soil crust, thus compromising its stability, structure, and productivity. This book is the first synthesis of the biology of soil crusts...
Categories: Publication; Types: Book Citation, Citation; Tags: Springer
Tortula ruralis is a homoiochlorophyllous-desiccation-tolerant (HDT) moss that retains all pigments when dehydrated and rapidly recovers physiological function upon rehydration. This moss forms extensive cover in exposed and shaded areas in the sandy semi-arid grasslands of Central Europe. We hypothesized that contrasting drying regimes between these microhabitats would affect-plant N status, constraints to gas exchange and growth, as well as result in altered pigment concentrations and ratios, and photochemical light-response dynamics. Furthermore, we believed T. ruralis's HDT habit would limit its ability to acclimate to altered light environment. We found that sun plant T. ruralis had lower plant mass, as well...
The soil emission rates (fluxes) of nitrous oxide (N2O) and nitrogen oxides (NO + NO2 = NOx) through a seasonal snowpack were determined by a flux gradient method from near-continuous 2-year measurements using an automated system for sampling interstitial air at various heights within the snowpack from a subalpine site at Niwot Ridge, Colorado. The winter seasonal-averaged N2O fluxes of 0.047-0.069 nmol m-2 s-1 were ~15 times higher than observed NOx fluxes of 0.0030-0.0067 nmol m-2 s-1. During spring N2O emissions first peaked and then dropped sharply as the soil water content increased from the release of snowpack meltwater, while other gases, including NOx and CO2 did not show this behavior. To compare and contrast...
Prolonged use of broad-spectrum antibiotics has led to the emergence of drug-resistant pathogens, both in medicine and in agriculture. New threats such as biological warfare have increased the need for novel and efficacious antimicrobial agents. Natural habitats not previously examined as sources of novel antibiotic-producing microorganisms still exist. One such habitat is the rhizosphere of desert shrubs. Here, we show that one desert shrub habitat, the rhizosphere of desert big sagebrush (Artemisia tridentata) is a source of actinomycetes capable of producing an extensive array of antifungal metabolites. Culturable microbial populations from both the sagebrush rhizosphere and nearby bulk soils from three different...
This volume covers the fields of origin, evolution and phylogenesis from prokaryotic to eukaryotic cells. The eminent authors, experts in their fields, review the three kingdoms of life (Archea, Eubacteria and Eukarya) from molecular evolutionary levels to ecological aspects in enigmatic habitats, including general reviews of puzzling pro-and eukaryotic organisms and their domains. We discuss dry habitats, thermophilic (cells in hot springs and undersea thermal vents up to 110�C), psychrophilic (cryophiles) and halophilic (high salt concentrations) niches which among the harshest conditions found on Earth where microbial life is frequently detected. Some chapters deal with the organisms which grow in extreme pH...
Categories: Publication; Types: Book Citation, Citation; Tags: Springer
We studied the bacterial communities in biological soil crusts (BSCs) from the Colorado Plateau by enrichment and cultivation, and by statistically analyzed denaturing gradient gel electrophoresis (DGGE) fingerprinting of environmental 16S rRNA genes, and phylogenetic analyses. Three 500-m-long transects, tens of km apart, consisting of 10 equally spaced samples each, were analyzed. BSC communities consistently displayed less richness (10-32 detectable DGGE bands per sample) and Shannon diversity (2.1-3.3) than typical soil communities, with apparent dominance by few members. In spite of some degree of small-scale patchiness, significant differences in diversity and community structure among transects was detectable,...
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A survey of nitric oxide (NO) emission from Chihuahuan desert soils found mean NO fluxes <0.1 ng NO-N cm-2 h-1 during the dry season. These fluxes were at the lower end of the range reported for temperate grassland and woodland ecosystems. NO fluxes from wet or watered soils were higher (0.1-35 ng NO-N cm-2 h-1 ). Watering of black grama grassland soils produced an initial pulse of 12 ng cm-2 h-1 (12-h after 1-cm watering) with high fluxes sustained over 4 days with repeated watering. Initial pulses from shrubland soils were lower (maximum 5 ng cm-2 h-1 ), and fluxes declined with repeated watering. Repeated watering of creosotebush soils depleted the soil NH4 + pool, and NO emissions were directly related to soil...
Summary This study examines the effect of moonlight intensity on deermouse (Peromyscus maniculatus) vulnerability to predation by short-eared owls (Asio flammeus). Three nocturnal light intensities, labeled new moon, quarter moon, and full moon, were simulated in a flight chamber. Deermouse activity was observed and measured by an index of tracking intensity in the chamber's sand floor. The mice were then exposed to predation by a short-eared owl in each light intensity and search time, chase time, capture time, and the number of escapes/chase were measured. The results reveal the adaptive significance of deermouse activity suppression in full moon light as an anti-predator response. The deermice reduced activity...
map background search result map search result map Environmental Controls on Nitric Oxide Emission from Northern Chihuahuan Desert Soils The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin USGS 1:24000-scale Quadrangle for Springer, NM 1965 USGS 1:24000-scale Quadrangle for Springer, OK 1964 USGS 1:24000-scale Quadrangle for Springer, OK 1964 USGS 1:24000-scale Quadrangle for Springer, OK 1964 USGS 1:24000-scale Quadrangle for Springer, NM 1965 USGS 1:24000-scale Quadrangle for Springer, OK 1964 USGS 1:24000-scale Quadrangle for Springer, OK 1964 USGS 1:24000-scale Quadrangle for Springer, OK 1964 Environmental Controls on Nitric Oxide Emission from Northern Chihuahuan Desert Soils The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin