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In 1988, the US Geological Survey began a study of the effects of potential climate change on the water resources of the Gunnison River basin. The Gunnison River, in southwestern Colorado, is an important tributary of the Colorado River, contributing approximately 40% of the flow of the Colorado River at the Colorado/Utah stateline. As part of the study, the sensitivity of annual and seasonal runoff in the East River basin, a sub-basin of the Gunnison River basin, to changes in temperature and precipitation was examined. To perform the sensitivity analyses, hypothetical climate changes were used to alter current time series of temperature and precipitation. The altered time series were then used as inputs to a hydrological...
Double sampling was used to provide a cost efficient estimate of the accuracy of a Landsat Thematic Mapper (TM) classification map of a scene located in the Rocky Mountain National Park, Colorado. In the first phase, 200 sample points were randomly selected to assess the accuracy between Landsat TM data and aerial photography. The overall accuracy and Kappa statistic were 49.5 per cent and 32.5 per cent, respectively. In the second phase, 25 sample points identified in the first phase were selected using stratified random sampling and located in the field. This information was used to correct for misclassification errors associated with the first phase samples. The overall accuracy and Kappa statistic increased...
Microbiotic soil crusts play several important roles in many arid and semiarid ecosystems around the world. Their effects on soil hydrology, however, are poorly understood. It has been speculated that crusts (1) improve soil water availability by "sealing" the soil surface to water loss, or (2) diminish soil water by increasing the latent heat of a soil profile thereby increasing evaporation. In order to distinguish between these two opposing hypotheses, we analyzed water loss and temperature of soil profiles covered by different types of microbiotic soil crust (cyanobacteria, Psora decipiens, Placidium squamulosum) and a bare soil. We conducted experiments under growth chamber and field conditions. After watering...
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This paper discusses several difficulties encountered in detecting and monitoring temporal changes in vegetation using multispectral imagery from airborne or spaceborne sensors. These difficulties are due to (1) temporal change in the vegetation state; (2) temporal change in the soil/rock signature; and (3) difficulty in discriminating vegetation from soil or rock background. The seasonal dynamics of soil and vegetation was investigated over two years on permanent sample plots in a natural fenced-off area in the semi-arid region (200 mm annual average rainfall) of the Northern Negev, Israel. Results show that temporal analysis of natural vegetation in semi-arid regions should take into account three ground features--perennials,...
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This study compared the consistency of nutrient extraction among repeated cycles of ion-exchange resin membrane use. Two sandy calcareous soils and different equilibration temperatures were tested. No single nutrient retained consistent values from cycle to cycle in all treatments, although both soil source and temperature conferred some influence. It was concluded that the most conservative use of resin membranes is single-use. Published in Communications in Soil Science and Plant Analysis, volume 34, issue 1&2, on pages 13 - 20, in 2003.
Thermodynamics predict that in calcareous soils where the equilibrium activity of solution orthophosphate (Pso) is controlled by any calcium-phosphate mineral, calcium oxalate (CaC2O4) precipitation will increase Pso by depressing Ca2+ ion activity in soil solution and enhancing dissolution of the P-controlling mineral. Plants and/or associated microflora capable of imparting effective levels of oxalic acid (H2C2O4) to soil solution, may significantly improve their phosphorus nutrition via this mechanism. In previous work, we presented evidence for calcium oxalate (CaC2O4) formation in the rhizosphere of vesicular-arbuscular mycorrhizal (VAM) western wheatgrass (Agropyron smithii Rydb.). Herein, we report on further...
Soil surface growths dominated by cyanobacteria and the lichen Collema in southeastern Utah are shown to be associated with greater tissue content of several bio-essential elements in two co-occurring seed plants (Festuca octoflora, Poaceae, and Mentzelia multiflora, Loasaceae). The elements N, P, K, Ca, Mg, and Fe were present in significantly greater concentrations in Festuca growing on soils heavily encrusted with cyanobacteria and cyanolichens than in plants on the same soil where foot traffic had destroyed the cryptobiotic crusts. With Mentzelia, N, Mg, and Fe were present in significantly greater concentrations in plants from sites with encrusted soil surfaces than on blow-sand sites. The cryptobiota appeared...
Delayed egg hatching can influence the survival of aquatic insects by reducing exposure to competitors, predators, parasites, or unfavorable environmental conditions. We examined egg development in a Colorado population of the stonefly, Megarcys signata (Plecoptera: Perlodidae), whose larvae inhabit high altitude streams in the Rocky Mountains of western North America. Five-thousand fertilized eggs were collected from 40 different females and incubated in the East River, Gunnison County, Colorado, until late fall, at which time unhatched eggs were transported to incubation chambers in Ithaca, New York. We used three different combinations of photoperiod and temperature (10L:14D, 4 degrees C; 10L:14D, 8 degrees C;...
Biological soil crusts of arid and semiarid lands contribute significantly to ecosystem stability by means of soil stabilization, nitrogen fixation, and improved growth and establishment of vascular plant species. In this study, we examined growth and nutrient content of Bromus tectorum, Elymus elymoides, Gaillardia pulchella, and Sphaeralcea munroana grown in soil amended with one of three levels of biological soil crust material: (1) a low-fertility sand collected near Moab, Utah; (2) sand amended with a 1-cm top layer of excised soil crust; and (3) crushed crust material. In addition, all plants were inoculated with spores of the arbuscular mycorrhizal fungus, Glomus intraradices. Plants were harvested after...
Rainfall simulation experiments were performed on 25 plots of varying microphytic crust cover in a wooded semiarid rangeland in eastern Australia. Under a rainfall intensity of 45 mm h-1, steady-state infiltration ranged from 5 mm h-1 to 41 mm h-1, but there was no effect of cover on this or any of the other soil hydrological variables measured. When disturbed plots with low cover (<15% cover) were excluded from the analyses, significant increases in time to ponding were associated with increases in crust cover. Despite some significant relationships, however, crust cover was an insignificant predictor of soil hydrological status at this site. We attribute this to the well-structured nature of the soils at the site,...
The measurement of soil carbon dioxide (CO2) respiration is a means to gauge biological soil fertility. Test methods for respiration employed in the laboratory vary somewhat, and to date the equipment and labor required have limited more widespread adoption of such methodologies. A new method to measure soil respiration was tested along with the traditional alkali trap and titration method. The new method involves the Solvita gel system, which was originally designed for CO2 respiration from compost but has been applied in this research to soils with treatments of increasing dairy manure compost. The objectives of this research are to (1) examine the relationship between the CO2 release after 1 day of incubation...
Recovery of soil properties from World War II-era military training exercises in the Mojave Desert was measured approximately 55 years following disturbance. Tracks from military vehicles were still visible, particularly in areas of desert pavement. Soil penetrability was much lower in visible tracks than outside the tracks. Soils in tracks had fewer rocks in the top 10cm of the soil profile than adjacent untracked soils. Larger particles (> 4.8mm) formed a moderately well-developed pavement outside of the tracks, while smaller, loose particles ( h 4.8mm) dominated the surface of the tracks. The time required to restore the desert pavement is likely to be measured in centuries. Based on biomass estimates, the cyanobacterial...
Cryptobiotic soil crusts are an important component of semiarid and arid ecosystems. An important role of these crusts is the contribution of fixed nitrogen to cold-desert ecosystems. This study examines the residual effects of various intensities and combinations of different surface disturbances (raking, scalping, and tracked vehicles) on nitrogenase activity, chlorophyll content, and chlorophyll degradation in these soil crusts. Nine months after disturbance chlorophyll content of disturbed soils was not statistically different from undisturbed controls, except in the scalped treatments, indicating recovery of this characteristic is fairly quick unless surface material is removed. Differences in chlorophyll degradation...
We evaluated and optimized three rapid methods for extraction of high-quality DNA from carbonate-encrusted microbial communities using modern calcifying oncolites built by cyanobacteria and diatoms in a high-calcium freshwater river. Pulverization, acid (HCl) dissolution, and chelator-mediated (EDTA) dissolution of the carbonate matrix were used and optimized to liberate microbial cells from their mineral encasing. This was followed by cell lysis and DNA extraction and isolation. HCl dissolution yielded no measurable DNA, probably due to hydrolysis, whereas pulverization and EDTA dissolution yielded averages of 3.5 and 7.8 Î&frac14;g per gram of sample, respectively, of high molecular weight DNA. These DNA isolates...
Phenolic acids (caffeic, CAF; protocatechuic, PCA; p-coumaric, COU; and vanillic, VAN), catechol (CAT), poly-galacturonic acid (PGA), and citric acid (CIT) were compared for their effectiveness in phosphorus (P) mobilization in three soils differing in chemical properties. The addition of organic ligands at 100 ?mol g- 1 soil increased the concentrations of resin P (Pr), water-extractable P (Pw), and bicarbonate-extractable inorganic P (Pbi), thus improving the phosphorus availability. The magnitude of P mobilization in the calcareous soil can be expressed in the following order: CAF > CAT > PCA = CIT > VAN > COU > PGA, which was consistent with the number of phenolic hydroxyl groups they contained and the position...
The Colorado River is one of the most highly regulated and extensively utilized rivers in the world. Total reservoir storage is approximately four times the mean annual runoff of -17 times 109 m3 year-1. Reservoir storage and regulation have decreased annual peak discharges and hydroelectric power generation has increased daily flow variability. In recent years, the incidental impacts of this development have become apparent especially along the Colorado River through Grand Canyon National Park downstream from Glen Canyon Dam and caused widespread concern. Since the completion of Glen Canyon Dam, the number and size of sand bars, which are used by recreational river runners and form the habitat for native fishes,...
    map background search result map search result map Temporal dynamics of soil and vegetation spectral responses in a semi-arid environment Repeated Use of Ion-Exchange Resin Membranes in Calcareous Soils Repeated Use of Ion-Exchange Resin Membranes in Calcareous Soils Temporal dynamics of soil and vegetation spectral responses in a semi-arid environment