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Dust Deposition (dust + deposition)
Selected AbstractsRelationship between road dust and ungulate density in Serengeti National Park, TanzaniaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2008Vedasto G. Ndibalema Abstract We measured the responses of ungulate grazers to roads by recording the density of dust on grasses and compared distance sampling of ungulates in Serengeti National Park (SNP), Tanzania. Data were collected on the east and west side of the Ngorongoro,Seronera main gravel road to test if road traffic and dust were important factors determining distribution patterns amongst grazers. Results indicate that dust increased progressively with traffic speed and volume during dry season. More dust was intercepted on the west than on the east side of the road mainly because of wind effects. Dust deposition (measured as density g grass g,1 dust) was higher on short grasses than on long grasses during the dry and late-dry seasons than during the wet season, when paired perpendicular distances up to 300 m were compared. Mean number of observed grazer species indicated that most fed further from the west side of the road than from the east perhaps to minimize higher density of dust commonly spread on foliage up to 200 m away from the road. Despite that most grazers avoided road side grass shoulders, supporting the ,dust aversion hypothesis', the test predictions from the ,road disturbance' and the ,road attraction' hypotheses did not support the responsive behaviours of grazers toward roads. Résumé Nous avons mesuré la réponse d'ongulés brouteurs à la présence de routes en enregistrant la densité de poussière sur les herbes et en comparant la distance des ongulés dans le Parc National du Serengeti, en Tanzanie. Les données ont été récoltées à l'est et à l'ouest de la principale route en gravier du Ngorongoro Seronera pour voir si le trafic routier et la poussière étaient des facteurs importants qui déterminaient les schémas de distribution des animaux brouteurs. Les résultats indiquent que la poussière augmente progressivement avec la vitesse et le volume du trafic pendant la saison sèche. On a recueilli plus de poussière du côté ouest de la route, surtout à cause des effets du vent. Les dépôts de poussière (mesurés comme la densité g d'herbe/g de poussière) étaient plus abondants sur les herbes courtes que sur les longues pendant la saison sèche et en fin de saison sèche qu'en saison des pluies lorsqu'on comparait deux à deux des distances perpendiculaires allant jusqu'à 300 mètres. Le nombre moyen d'espèces d'animaux brouteurs observées indiquait que la plupart se nourrissaient plus loin du côté ouest de la route que du côté est, peut-être pour minimiser la forte densité de poussière qui se dépose régulièrement sur le feuillage jusqu'à 200 mètres de la route. Bien que la plupart des brouteurs évitent les accotements herbeux de la route, ce qui vient soutenir l'hypothèse de l'aversion pour la poussière, les tests de prédiction concernant les hypothèses de « perturbations par la route » ou d'« attraction par la route » ne supportent pas le comportement réactif des ongulés brouteurs vis-à-vis de la route. [source] Aeolian dust dynamics in agricultural land areas in Lower Saxony, GermanyEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2001Dirk Goossens Abstract The dynamics of fine aeolian dust emitted from agricultural land was investigated over 15 months near Grönheim, Lower Saxony, Germany. The following aspects were studied: airborne dust concentration, the ratio of mineral versus organic dust, the vertical distribution of the particles in the atmosphere, horizontal and vertically integrated horizontal dust flux, vertical dust flux, dust deposition at ground level, grain-size distribution of the mineral dust component, and vertical distribution of organic matter in the dust. Standard meteorological parameters (wind speed and direction, precipitation) were measured as well. Dust activity in Grönheim is high in spring (March,May) and autumn (October,November) and low to very low during the rest of the year. There is a strong relationship between the periods of tillage and the intensity of dust activity. Also, there is high dust activity during wind erosion events. For the year 1999, dust emission due to tillage was 6·6 times higher than dust emission due to wind erosion. A dust transport of 15·8 ton km,1 a,1 was calculated for the first 10 m of the atmosphere in 1999. Total dust transport (in the entire mixing layer) was estimated between 16 and 20 ton km,1 a,1. About 25,30 per cent of this dust is mineral dust, emitted from the fields during tillage or during wind erosion events. In spring and autumn there is a strong vertical stratification in the airborne sediment, with much (coarse) dust in the lower air layers and significantly less (and finer) dust at higher altitudes. In summer and winter, when there is no local dust production, there is no stratification: equal amounts of dust are transported at all heights. The stratification in spring and autumn is exclusively caused by the mineral part of the dust. The organic particles are much better mixed in the atmosphere because of their lower density. Copyright © 2001 John Wiley & Sons, Ltd. [source] Iron limits primary productivity during spring bloom development in the central North AtlanticGLOBAL CHANGE BIOLOGY, Issue 4 2006C. MARK MOORE Abstract We present in situ biophysical measurements and bioassay experiments that demonstrate iron limitation of primary productivity during the spring bloom in the central North Atlantic. Mass balance calculations indicate that nitrate drawdown is iron (Fe)-limited and that aeolian Fe supply to this region cannot support maximal phytoplankton growth during the bloom. Using a simple simulation model, we show that relief of Fe limitation during the spring bloom can increase nitrate drawdown and, hence, new primary production, by 70%. We conclude that the episodic nature of iron supplied by dust deposition is an important factor controlling the dynamics of the spring bloom. From this, we hypothesize that variability in the timing and magnitude of the spring bloom in response to aeolian Fe supply will affect carbon drawdown and food web dynamics in the central North Atlantic. [source] Yellow-brown earth on Quaternary red clay in Langxi County, Anhui Province in subtropical China: Evidence for paleoclimatic change in late Quaternary period,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2008Xue-Feng Hu Abstract In order to investigate the paleoclimatic changes in S China during the late Quaternary and their influence on pedogenesis and soil classification, a yellow-brown earth (YBE),red clay (RC) profile in Langxi County, Anhui Province was studied. The grain-size distribution and the major- and trace-element compositions of the profile indicate that the YBE of the profile shares the same origin with the YBE in Jiujiang and Xuancheng and the Xiashu loess in Zhenjiang, and the underlying RC also has aeolian characteristics and shares the same origin with the Xiashu loess. Grain-size characteristics, molecular ratios of SiO2/Al2O3, SiO2/(Al2O3+Fe2O3), and BA ([CaO+MgO+K2O+Na2O]/Al2O3) and other weathering indices (CaO/TiO2, MgO/TiO2, K2O/TiO2, Na2O/TiO2, and Rb/Sr) of the profile indicate that the RC is more strongly weathered than the YBE. Magnetic susceptibility (,lf) of the uniform red clay (URC) of the profile is significantly enhanced. However, that of the underlying reticulate red clay (RRC) is significantly decreased because of the paleogroundwater movement and cannot indicate its strong weathering properties. The YBE-RC profile in Langxi County recorded a great climatic change during late Quaternary: At that time, the pedogenic development of the RC was terminated and widespread dust deposition occurred. The parent material of the RC may be aeolian deposits which were accumulated before the last interglacial and were strongly weathered and rubified under the subsequent interglacial climate. It is observed that red soils, derived from the RC, and yellow-brown soils, derived from the YBE, coexist in the study area, which is contradictive to the theory of the zonal distribution of soils. Therefore, it is necessary to take into account the history of Quaternary climatic changes when studying pedogenesis. [source] | |||||||||||||