Revegetation of semi-desert rangeland is dependent on rainfall, weather, and soil factors affecting seed germination and seedling establishment. To aid in predicting seed zone temperature and moisture following rainfall, a weather driven one-dimensional computer model was developed to simulate the simultaneous flow of heat and water within a bare semi-desert soil. The Newton-Raphson method was used to solve the surface energy budget equation for surface temperature. The coupled soil heat and water flow equations were then solved numerically using the weighted average finite-difference method to calculate the subsurface temperature (T(s)) and water content (θᵥ) profiles. Weather data and soil thermal and hydraulic properties were the only required inputs to the model. The model was tested using two data sets collected in the Altar Valley of Arizona during the summer rainy season of 1988. Data set 1, collected from calendar day (CD) 198 to 205, was used to calibrate the model. Calibration tests revealed that the model markedly underestimated T(s) when measured values exceeded 37°C. Underestimation of T(s) was found to be related to overestimation of latent heat flux. Therefore, the modelled latent heat flux was reduced as a linear function of air temperature (Tₐᵢᵣ) when Tₐᵢᵣ > 30°C. Also, soil thermal conductivity values predicted by the de Vries model had to be reduced 80% in order to achieve acceptable agreement between measured and modelled T(s). Data set 2, from CD 191 to 195, was then used to validate the calibrated (modified) model. Results obtained with data set 2 indicated that the modified model accurately simulated T(s) at 0.01 m depth even when the measured T(s) at that depth exceeded 50°C. Simulated T(s) values for the soil profile were generally within ± 3°C of the measured values. Results also showed good agreement between modelled and measured net radiation flux densities. In addition, the modified model predicted surface layer (0-0.03 m) moisture content remained wet enough for seed germination, i.e. θᵥ > 0.09 m³ m⁻³, about 24 to 36 hours longer than indicated by measured (resistance block) θᵥ values.

A petrographic study of upper Devonian sandstones (Endicott and Hammond Terranes), Philip Smith Mountains and Arctic quadrangles, Brooks Range, Alaska, shows that the sand-sized detritus was derived from two petrographic provenances. Detrital modes, calculated from point counts of thin sections, show that the provenance for the Devonian clastic wedge (Endicott Terrane) was a recycled orogenic belt with major components of quartz, chert, and lithic fragments. Three petrofacies are distinguished. Their distribution indicates compositional changes vertically and laterally which reflect changing compositions in the source area. A petrographically different provenance supplied the sandstones that overlie the Skajit Limestone (Hammond Terrane). Characterized by high feldspar and abundant volcanic rock fragments, this petrofacies indicates first-cycle deposition close to the source area. A magmatica arc provenance is suggested.

Presence and composition of Eragrostis Lehmanniana was measured on 75 permanent transects every 3-8 years between 1958-1989 on the Santa Rita Experimental Range, Arizona. The number of transects occupied and average composition increased rapidly over this period. A repeated measures analysis of two soil groups with different water holding capacity and permeability revealed that the rate of increase of E. Lehmanniana was different between the groups. Repeated measures analysis of five grazing intensities revealed that the rate of E. Lehmanniana increase was different among intensities. It appears that the highest intensity had the highest rate of increase. The influence of grazing on E. Lehmanniana spread was also expressed by the lack of difference in relative composition measured in 1989 between ten livestock enclosures and adjacent grazed areas. This research suggests that E. Lehmanniana will spread and dominate with an average of 89 mm of summer precipitation in 40 days; a lower regime than estimated by other research.

This study evaluated the influence of Lehmann lovegrass (Eragrostis lehmanniana Nees) on the densities and spatial distributions relative to mesquite (Prosopis velutina Woot.) of two native grasses, Arizona cottontop (Digitaria californica (Benth.) Henr.) and Rothrock grama (Bouteloua rothrockii Vasey), in the semi-desert grassland. Also evaluated were the affects of independent variables range site, elevation, and proportion mesquite cover on these relationships. General Linear Model analyses showed no association between Lehmann lovegrass and either the densities or the distributions of the native species. Arizona cottontop showed an affinity for mesquite cover, while Rothrock grama and Lehmann lovegrass both showed an aversion to mesquite canopy. The relationship of Rothrock grama to mesquite cover was affected by range site. The relationship of Lehmann lovegrass to mesquite cover became less averse with increasing elevation and as its density increased. These results contradict suggestions that Lehmann lovegrass is associated with declines in native grasses.

Lehmann lovegrass (Eragrostis lehmanniana Nees.), a perennial bunchgrass, has established itself well since its introduction from South Africa. Arizona cottontop (Digitaria californica (Benth.) Henr.) is a native perennial bunchgrass that sometimes appears on the same sites and soils as Lehmann lovegrass. In a greenhouse, emergence was evaluated using line-source irrigation which simulated natural summer precipitation on two soil types collected from the Santa Rita Experimental Range (SRER). Density and cool-season growth of each species were monitored along transects located at the SRER on three different soils. I found that although Lehmann lovegrass and Arizona cottontop emerge similarly on two soils, Arizona cottontop un-emerged caryopses had a better percent survival rate. Also, Lehmann lovegrass plants had more green above-ground biomass from November to May than Arizona cottontop, and Lehmann lovegrass was able to greenup more rapidly following rain. This study showed these species have similar emergence characteristics, but that their cool-season greening differs.

No description available.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / This paper presents a simple, cost-effective solution that permits the antenna in a telemetry/tracking system to be placed at distances even greater than 20 km with virtually no signal degradation. By using a wideband, microwave fiberoptic link to pass the RF telemetry and tracking signals directly, the telemetry receivers can all be installed at the operator's location. In essence, the only RF equipment that needs to be installed at the antenna site is the low maintenance fiberoptic transmitter which can be placed in a ruggedized housing at the pedestal. The actual system described herein uses a hybrid approach with some telemetry receivers at the antenna site and some remoted over the fiberoptic link. It is shown that the fiberoptic link used met and exceeded the system requirements. In addition, the design of the fiberoptic link is discussed and it is shown that the dynamic range acheivable with this fiberoptic link is considerably higher than the system requirements in this case.

Photocopy of typescript. / Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

The vegetation of Canyonlands National Park, Utah, has been described from 157 samples located throughout the Park. Species frequency, density and cover were recorded along with measurements of soil thickness, slope, aspect, elevation and geologic substrate at each site. Measurements of soil texture, pH, and electrical conductivity were taken for a representative subsample. A map of the vegetation of the Park was made by relating the sample points to their corresponding spectral signatures on vertical aerial photographs and locating boundaries between vegetation units by means of changes in photo signatures. Vegetation in these arid to semi-arid environments appears to be strongly related to particular combinations of regolith thickness, bedrock composition and depth to water table. Elevation and slope exposure control vegetation patterns to a much smaller extent. Vegetational units are distinct, and can be readily visualized. The six units mapped, in order of relative importance, (area covered) were: blackbrush, juniper-pinyon woodlands, semi-desert grasslands, sagebrush-fourwing saltbush shrublands, salt-desert shrublands and riparian tall shrublands. These vegetational units are related to specific combinations of environmental factors. Boundaries between units are sharp vegetationally and environmentally. Moisture availability appears to be the key factor, but effective soil moisture is largely controlled by regolith/bedrock relationships. Grasslands predominate at all elevations where regolith is over 50 cm in thickness and there is no access of plant roots to the water table. Regolith that is uniformly thinner than 50 cm supports vegetation dominated by blackbrush (Coleogyne ramosissima). Sandy areas that provide immediate root access to the water table support thickets of Salix, Tamarix, and other riparian shrubs. Shrublands dominated by Atrinlex canescens and Artemisia tridentata occur on thicker sand deposits with seasonal root access to capillary water. Where competent bedrock is exposed and joints are developed, Pinus edulis, Juniperus osteosperroa and various upland shrubs dominate. Several species of Atrinlex dominate the salt-desert shrublands where clayey shales crop out. Historical grazing use by domestic livestock has altered the composition and cover in grasslands, chiefly in the southern part of the Park. Elsewhere, grassland modification is slight because of more difficult access. other vegetation types have experienced less obvious changes. The many abandoned roads within the Park date chiefly from extensive mineral exploration in the early 1950's. Secondary succession on these disturbed areas is extremely slow.