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Desert Region (desert + region)
Selected AbstractsThe role of playas in pedogenic gypsum crust formation in the Central Namib Desert: a theoretical modelEARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2001F. D. Eckardt Abstract The formation of Namibia's extensive pedogenic gypsum crusts (CaSO4·2H2O) is interpreted in a new light. It is suggested that gypsum primarily precipitates at isolated points of evaporitic concentration, such as inland playas, and that deflation of evaporitic-rich gypsum dust from these playas contributes to the formation of pedogenic gypsum duricrusts on the coastal gravel plains of the Namib Desert surrounding these playas. This study establishes the nature, extent and distribution of playas in the Central Namib Desert and provides evidence for playa gypsum deflation and gravel plain deposition. Remote sensing shows the distribution of playas, captures ongoing deflation and provides evidence of gypsum deflation. It is proposed that, following primary marine aerosol deposition, both inland playas and coastal sabkhas generate gypsum which through the process of playa deflation and gravel plain redeposition contributes to the extensive pedogenic crusts found in the Namib Desert region. Copyright © 2001 John Wiley & Sons, Ltd. [source] Is the Sonoran Desert losing its cool?GLOBAL CHANGE BIOLOGY, Issue 12 2005Jeremy L. Weiss Abstract Freezing temperatures strongly influence vegetation in the hottest desert of North America, in part determining both its overall boundary and distributions of plant species within. To evaluate recent variability of freezing temperatures in this context, minimum temperature data from weather stations in the Sonoran Desert are examined. Data show widespread warming trends in winter and spring, decreased frequency of freezing temperatures, lengthening of the freeze-free season, and increased minimum temperatures per winter year. Local land use and multidecadal modes of the global climate system such as the Pacific decadal oscillation and the Atlantic multidecadal oscillation do not appear to be principal drivers of this warming. Minimum temperature variability in the Sonoran Desert does, however, correspond to global temperature variability attributed to human-dominated global warming. With warming expected to continue at faster rates throughout the 21st century, potential ecological responses may include contraction of the overall boundary of the Sonoran Desert in the south-east and expansion northward, eastward, and upward in elevation, as well as changes to distributions of plant species within and other characteristics of Sonoran Desert ecosystems. Potential trajectories of vegetation change in the Sonoran Desert region may be affected or made more difficult to predict by uncertain changes in warm season precipitation variability and fire. Opportunities now exist to investigate ecosystem response to regional climate disturbance, as well as to anticipate and plan for continued warming in the Sonoran Desert region. [source] Diversity of the rodent communities in the Turan Desert regionINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 4 2006Valery M. NERONOV Abstract We assessed the diversity of rodent communities in the deserts of Russia, Kazakhstan, and Central Asia using geographic information system technology. There are 66 species of rodents, belonging to eight faunistic complexes, inhabiting this area. We discuss the geographical changes occurring in taxonomic and zoogeographic diversity at both species and community levels. Communities of gerbils and jerboas dominate in the Turan Desert region (66% of the area). Steppe communities of susliks penetrate the deserts from the north. Farming in deserts causes the replacement of native rodent communities with mouse communities or completely eradicates rodents in their main habitats. [source] Non-random patterns in the Yellowstone ecosystem: inferences from mammalian body size, order and biogeographical affinityGLOBAL ECOLOGY, Issue 2 2007Judsen E. Bruzgul ABSTRACT Aim, Our aim was to investigate how the environment, species characteristics and historical factors at the subcontinental scale affect patterns of diversity. We used the assembly of the Yellowstone biota over the past 10,000 years as a natural experiment for investigating the processes that generate a modern non-volant mammal species pool. Location, The data represent species from throughout North America with special attention to the non-volant mammals of Yellowstone National Park, USA. Methods, We used digitized range maps to determine biogeographical affinity for all non-volant mammals in the Rocky Mountains, Deserts and Great Plains biogeographical regions of North America. This biogeographical affinity, along with taxonomic order and body size class, was used to test whether non-random patterns exist in the assemblage of Yellowstone non-volant mammals. These characteristics were also used to investigate the strength of non-random processes, such as habitat or taxon filtering, on particular groups of species or individual species. Results, Our results indicated that the Yellowstone fauna is composed of a non-random subset of mammals from specific body size classes and with particular biogeographical affinities. Analyses by taxonomic order found significantly more Carnivora from the Rocky Mountains region and significantly fewer Rodentia from the Deserts region than expected from random assembly. Analyses using body size classes revealed deviations from expectations, including several significant differences between the frequency distribution of regional body sizes and the distribution of those species found within Yellowstone. Main conclusions, Our novel approach explores processes affecting species pool assembly in the Yellowstone region and elsewhere, and particularly identifies unique properties of species that may contribute to non-random assembly. Focusing on the mechanisms generating diversity, not just current diversity patterns, will assist the design of conservation strategies given future environmental change scenarios. [source] Shiny Cowbird parasitism of a low quality host: effect of host traits on a parasite's reproductive successJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2009Andrea A. Astié ABSTRACT The reproductive success of parasitic cowbirds (Molothrus spp.) varies among host species and is influenced by the degree of synchronization in timing of egg laying, the duration of parasite and host incubation periods, and the ability of hosts to incubate and rear parasite young. We studied the reproductive success of Shiny Cowbirds (Molothrus bonariensis) that parasitized the nests of Creamy-bellied Thrushes (Turdus amaurochalinus) in the Monte desert region of Argentina. Shiny Cowbirds frequently parasitized Creamy-bellied Thrush nests (60%), and most cowbirds synchronized egg laying with that of thrushes (79%). Most parasitic eggs (80%) hatched within 1 d of the hatching of the first host egg, and more than 91% of the eggs survived until the end of the incubation. However, only 60% of the cowbird eggs hatched and 52% of young survived. The proportion of Shiny Cowbirds eggs laid in Creamy-bellied Thrush nests that resulted in fledged young was 0.03, including eggs and young lost due to predation or desertion. Despite this low reproductive success, Creamy-bellied Thrushes were heavily parasitized by Shiny Cowbirds in our study area. Shiny Cowbirds may continue to parasitize these thrushes because of diffuse selection or because Shiny Cowbird chicks are more likely to fledge from Creamy-bellied Thrush nests in years or areas with greater food availability when brood reduction does not occur. SINOPSIS El éxito reproductivo del los tordos parásitos (Molothrus spp.) varía entre sus especies hospedadoras y está afectado por el grado de sincronización en el momento de la puesta de huevos, la duración de los períodos de incubación del hospedador y el parásito y la habilidad del hospedador para incubar y criar a los pichones parásitos. Nosotros estudiamos el éxito reproductivo del Tordo Renegrido (Molothrus bonariensis) en nidos del Zorzal Chalchalero (Turdus amaurochalinus) en la región del desierto del Monte de Argentina. El Tordo Renegrido parasita frecuentemente los nidos del Zorzal Chalchalero (60%) y la mayoría de los tordos sincroniza su puesta con la de los zorzales (79%). La mayoría de los huevos parásitos (80%) eclosionan entre 1 día antes y un día después del primer huevo del hospedador y más del 91% de los huevos sobreviven hasta el final de la incubación. Sin embargo, solo el 60% de los huevos de tordo eclosionan y el 52% de los pichones sobreviven. La proporción de huevos de Tordo Renegrido puestos en nidos de Zorzal Chalchalero que resultan en volantones fue 0.03, incluyendo los huevos y los pichones perdidos por depredación o abandono. A pesar de este bajo éxito reproductivo, el Zorzal Chalchalero es intensamente parasitado por el Tordo Renegrido en nuestra área de estudio. Es posible que el Tordo Renegrido continúe parasitando a estos zorzales debido a un proceso de selección difusa o porque los pichones de tordo tienen mayores posibilidades de llegar a volantones en nidos de Zorzal Chalchalero en años o en áreas con mayor disponibilidad de alimento, donde no ocurra reducción de nidada. [source] | ||||||||||