Search results for "Desert climate"
showing 10 items of 12 documents
Change in dominance determines herbivore effects on plant biodiversity
2018
Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis—that herbivore-induced changes in the competitive environment determine the response …
Opposite trends in the genus Monsonia (Geraniaceae): Specialization in the African deserts and range expansions throughout eastern Africa
2017
The African Austroerate Flora stands out by its important species richness. A distinctive element of this flora is Monsonia (Geraniaceae), mostly found in the Namib-Karoo but also in the Natal-Drakensberg, the Somalian Zambezian and the Saharo-Arabian regions. Here, we reconstruct the evolution and biogeographic history of Monsonia based on nuclear and plastid markers, and examine the role of morphological and niche evolution in its diversification using species distribution modeling and macroevolutionary models. Our results indicate that Monsonia first diversified in the Early Miocene c.21 Ma, coinciding with the start of desertification in southwestern Africa. An important diversification…
Evolution of leaf anatomy in arid environments – A case study in southern African Tetraena and Roepera (Zygophyllaceae)
2015
The dry biomes of southern Africa (Desert, Nama Karoo and Succulent Karoo) are home to a rich and diverse xerophytic flora. This flora includes two morphologically diverse clades of Zygophyllaceae, Tetraena and Roepera (Zygophylloideae), which inhabit some of the most arid habitats in the region. Using a plastid phylogeny of Zygophylloideae we assess whether the evolution of putatively adaptive traits (leaf shape, vasculature, mode of water storage and photosynthetic type: C3 versus C4) coincides with the successful colonisation of environments with different drought regimes within southern Africa. Our results show general niche conservatism within arid habitats in Tetraena, but niche shift…
Consequences of the discovery of Stenasellus (Crustacea, Isopoda, Asellota) 2 in the underground waters of Oman (Arabian Peninsula)
1999
An overview of the present knowledgeof the family Stenasellidae (Asellota: Aselloidea) is presented, focusing on the success of recent investigations of the underground waters of Oman (S.E. Arabian Peninsula). We take up the discovery of four new species of the genus Stenasellus: small species adapted to interstitial biotopes and larger ones typical of karstic aquifers. These species cohabit in ecotones between interstitial and karstic water systems. The putative presence of stenasellids in hypogean waters of Yemen and South Iran is suggested. The taxonomic status of the genus Stenasellus auct. needs to be reconsidered in the future. A scenario to explain the origin and the presence of thes…
Recent trends of temperature change under hot and cold desert climates: Comparing the Sahara (Libya) and Central Asia (Xinjiang, China)
2011
Abstract According to trend computations at three stations each in Sahara desert (Libya), characterized by a “hot” desert type (“BWh”, according to the Koeppen climate classification), and in Central Asia (Xinjiang, China) identified as a “cold” desert type (“BWk”, after Koeppen), increasing annual temperatures were detected over the period 1955–2005 corresponding with global temperature warming. From 1955–1978, negative (decreasing) temperature trends were, however, observed at all three hot desert stations and at two of the three cold desert stations. From 1979–2005, strikingly positive temperature trends were seen at all six stations. In seasonal respects, winter (December to February) a…
The potential of multilayer green roofs for stormwater management in urban area under semi-arid Mediterranean climate conditions
2022
Different low impact development measures have been proposed to make cities more flood-resilient, and recent literature is paying great attention to the evaluation of their direct benefits in terms of flood risk mitigation and the numerous co-benefits that they may offer. This study describes an experimental prototype of a technologically advanced multilayer green roof installed in a Mediterranean urban area (i.e., Palermo, Italy) and explores the results of an analysis of data collected over a one-year monitoring period by a complex sensors network. Multilayer green roofs, or "blue-green" roofs (BGRs), are characterized by a high water retention capacity compared to traditional green roofs…
Islands of biogeodiversity in arid lands on a polygons map study: Detecting scale invariance patterns from natural resources maps.
2016
Many maps (geology, hydrology, soil, vegetation, etc.) are created to inventory natural resources. Each of these resources is mapped using a unique set of criteria, including scales and taxonomies. Past research indicates that comparing results of related maps (e.g., soil and geology maps) may aid in identifying mapping deficiencies. Therefore, this study was undertaken in Almeria Province, Spain to (i) compare the underlying map structures of soil and vegetation maps and (ii) investigate if a vegetation map can provide useful soil information that was not shown on a soil map. Soil and vegetation maps were imported into ArcGIS 10.1 for spatial analysis, and results then exported to Microsof…
A late Eemian aridity pulse in central Europe during the last glacial inception
2005
How do ice ages begin? It's an obvious question to ask as we enjoy the relative luxury of an interglacial, but a hard one to answer. A look at past transitions may give some clues as to how this period will one day come to an end. A climate reconstruction based on sediments found beneath a lake in the Eifel mountains in Germany provides evidence of an extreme climate event lasting 468 years right at the end of the last interglacial. Dust storms, aridity, bushfires and the loss of trees associated with a warm climate coincided with a southward shift of the warm waters of the North Atlantic drift. In terms of insolation — the rate of delivery of the Sun's radiation to Earth — conditions then …
Chemical composition and biological activities of Artemisia judaica essential oil from southern desert of Jordan
2016
Abstract Ethnopharmacologic relevance Artemisia judaica L. (Arabic name: Beithran ), is a medicinal and aromatic plant growing in the valley bottoms of desert areas, particularly in the southern desert of Jordan nearest to the Jordan-Saudi Arabia borders and in Wadi Araba in the Southern Badia. In Jordan, A. judaica is widely used in traditional medicine being recommended by aboriginal Bedouins in the North Badia region of Jordan as calmative. Furthermore, it is used for the treatment of stomach ache, heart diseases, sexual weakness, diabetes, gastro-intestinal disorders and external wounding. Additionally, other folk medicines of the Arabic region commonly use this aromatic plant for the t…
Coping with arid environments: A critical threshold for human expansion in Europe at the Marine Isotope Stage 12/11 transition? The case of the Iberi…
2020
Abstract Archaeological remains have highlighted the fact that the interglacial Marine Isotope Stage (MIS) 11 was a threshold from the perspective of hominin evolution in Europe. After the MIS 12 glaciation, considered one of the major climate-driven crises experienced by hominins, the archaeological records show an increasing number of occupations, evidence of new subsistence behaviors, and significant technical innovations. Here, we used statistical and geographic techniques to analyze the amphibian- and reptile-based paleoclimate and habitat reconstructions generated from a large data set of the Iberian Peninsula to (1) investigate if temperature, precipitation, and/or forest cover may h…