Sand Solidified by Gemsbok Urine as Selected Burrow Sites by Gerbils

No Abstract

Microclimate and activity of the lizard Angolosaurus skoogi on a dune slipface

The lizard Angolosaurus skoogi inhabits the surface and subsurface environments of sand dunes of the northern Namib Desert. We have related posture, locomotion, and other aspects of surface activity to the microclimate prevailing above and below the surface. Globe temperature was the best microclimatic correlate of surface activity. From our analysis, we concluded that surface thermoregulatory behaviour of A. skoogi is facultative, and aimed at maintaining a body temperature compatible with foraging and other obligatory surface activities

The lead-glass electromagnetic calorimeters for the magnetic spectrometers in Hall C at Jefferson Lab

The electromagnetic calorimeters of the various magnetic spectrometers in Hall C at Jefferson Lab are presented. For the existing HMS and SOS spectrometers design considerations, relevant construction information, and comparisons of simulated and experimental results are included. The energy resolution of the HMS and SOS calorimeters is better than $\sigma/E \sim 6$, and pion/electron ($\pi/e$) separation of about 100:1 has been achieved in energy range 1 -- 5 GeV. Good agreement has been observed between the experimental and simulated energy resolutions, but simulations systematically exceed experimentally determined $\pi^-$ suppression factors by close to a factor of two. For the SHMS spectrometer presently under construction details on the design and accompanying GEANT4 simulation efforts are given. The anticipated performance of the new calorimeter is predicted over the full momentum range of the SHMS. Good electron/hadron separation is anticipated by combining the energy deposited in an initial (preshower) calorimeter layer with the total energy deposited in the calorimeter.Comment: 22 pages, 33 figure

Major-ion chemistry and ground-water salinization in ephemeral floodplains in some arid regions of Namibia

Ground-water quality in drinking water sources within ephemeral flood plains in the Namib Desert and north central Namibia displays seasonal and spatial variations. The monthly variation in total dissolved solids (TDS) in individual sources ranges between 5% and 65% in north central Namibia and between 0.5% and 85% in the Namib Desert. A higher monthly TDS variation, close to 500%, is recorded in slightly deeper as well as over-pumped freshwater sources in both study sites. The lowest TDS values are recorded after the rains for north central Namibia sources and only after flood events for sources in the lower rainfall Namib Desert. Ground-water salinization in both sites is generally characterized by a shift from 'fresh' to 'very saline' ground-water, and a chemical evolution from Na and Ca-HCO3 waters towards Na-Cl ones. The dominant processes that determine these hydrochemical shifts are refreshing by recharge waters, concentration by evaporation, dissolution of saline sediments (mainly evaporites), and mixing with older and more saline ground-water. © 2003 Elsevier Ltd. All rights reserved.Articl

Ecological correlates of locomotion speed, morphometries and body temperature in three Namib desert tenebrionid beetles

No Abstract

The effects of desert pavements (gravel mulch) on soil micro-hydrology

The effect of desert pavements (gravel mulch) on near surface soil micro-hydrology has been inadequately studied. Micro-hydrology in arid ecosystems occurs due to a daily non rainfall atmospheric water cycle, consisting of an input phase (dew, fog, vapour adsorption) and an evaporation phase. A winter comparative study between a bare soil (control) and gravel mulch using the automated microlysimeter approach was conducted in Stellenbosch, South Africa in 2008. Results showed that dew deposition and direct water vapour adsorption were significantly higher into bare soil compared to gravel mulch. In contrast, however, soil moisture from rain persists for a longer time under gravel mulch compared to bare soil. This result suggests that the greatest impact of gravel mulch on soil micro-hydrology is towards conserving moisture and could explain why the treatment is used in dry-land agriculture in Mediterranean regions. © 2011 Springer Basel AG

A method for direct assessment of the "non rainfall" atmospheric water cycle: Input and evaporation from the soil

"Non rainfall" atmospheric water (dew, fog, vapour adsorption) supplies a small amount of water to the soil surface that may be important for arid soil micro-hydrology and ecology. Research into the direct effects of this water on soil is, however, lacking due to instrument and technical constraints. We report on the design, development, construction and findings of an automated microlysimeter instrument to directly measure this soil water cycle in Stellenbosch, South Africa during winter. Performance of the microlysimeter was satisfactory and results obtained were compared to literature and fell within the expected range. "Non rainfall" atmospheric water input into bare soil (river sand) was between 0.88 and 1.10 mm per night while evaporation was between 1.39 and 2.71 mm per day. The study also attempted to differentiate the composition of "non rainfall" atmospheric water and results showed that vapour adsorption contributed the bulk of this input. © 2011 Springer Basel AG