Recovery of lichen-dominated soil crusts in a hyper-arid desert

Soil crust lichens can be the dominant vegetation in desert regions that are unsuitable for higher plants, and are vital to soil stabilization and primary production. Biological soil crusts are vulnerable to disturbance and there is little evidence of the lichen components achieving full recovery following human disturbances in semi-arid to arid environments, and no records of recovery in hyper-arid deserts. Eight sites with varying anthropogenic, mechanical disturbance regimes were assessed in the hyper-arid Namib Desert for levels of recovery and successional convergence, based on a comparative analysis of overall lichen cover and community composition in disturbed and control locations. Recovery time estimations ranged from 5 to 530 years, with no detected linear relationship to impact gradient (low to high impact). Variables that were found to most strongly influence recovery rates were the overall cover of lichen growth and total number of lichen species in the bordering undisturbed areas, followed by the extent of soil compaction in the disturbed area, altered soil surface microrelief and vitality of subsurface soil crust components. An assessment of pioneering species demonstrated a link between increased soil depressions, i.e. track ruts, and the occurrence of fragmenting, wind-dispersing species. Track ruts in hype-arid deserts are not as vulnerable to the water erosion found in less arid deserts, and may be advancing recovery by trapping fragments. However, the lichen community structure was significantly different between all of the disturbed and control areas, regardless of the recovery phase, suggesting that while the lichen community composition may not. The ecological consequences of such disturbances may be far reaching in hyper-arid deserts where lichens are primary heterotrophs soil stabilizers. Given the economic development occurring within coastal hyper-acid deserts of the world, these impacts undoubtedly call for conservation attention.     

Habitat ecology of southern African quartz fields: studies on the thermal properties near the ground

Desert pavements of white quartz stones (quartz fields) represent azonal habitats in several arid regions of southern Africa. The vegetation of these quartz fields is characterised by dwarf and highly succulent growth forms which contrast strongly with the shrubby vegetation of the surroundings. Incoming and reflected global solar radiation, air temperature near the ground, soil-surface temperatures and leaf-surface temperatures of dwarf plants were determined under natural habitat conditions inside and outside of the quartz fields. Surface temperatures of quartz and shale stones were compared. The study was conducted in the Kners-vlakte and the Little Karoo (Succulent-Karoo Biome), South Africa. The daily maximum temperatures of the air near the ground of quartz fields was several degrees lower than the air near the ground of neighbouring soils without quartz cover. Maximum soil-surface temperatures of the quartz fields, however, were only lower in summer. Accordingly, the leave surfaces of dwarf plants (Aizoaceae) growing inside quartz fields were up to 3 K cooler than identical plants outside the quartz fields. The lower maximum temperatures is associated with an about 5% higher reflection of quartz fields compared to neighbouring soils without quartz cover. At night, the minimum temperatures of the air near the ground and the soil surface temperatures on quartz fields were above those of soils without quartz cover. The nocturnal surface temperatures of quartz stones did not differ considerably from that of shale and often ranged above the temperatures and dew-point of the ambient air. Consequently, the relatively cooler quartz fields seem to provide less adverse growing conditions for plants near the ground compared to surrounding soils without quartz cover. This revised version was published online in August 2006 with corrections to the Cover Date.     

An arsenic-tolerant new species of Eleocharis (Cyperaceae) from Chihuahua, Mexico

A new aquatic, arsenic-tolerant species ofEleocharis (Cyperaceae) endemic to Chihuahua, Mexico, is described and illustrated. It belongs toEleocharis sect.Eleogenus seriesMaculosae. A key for the species ofEleocharis sect.Eleogenus from Mexico is included.

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Resumen  Sc describe e ilustra una nueva especie deEleocharis (Cyperaceae) acuática, tolerante a altas concentraciones de arsénico, y endémica de Chihuahua, México. Forma parte de la secciónEleogenus serieMaculosae. Se incluye una clave para las especies deEleocharis sect.Eleogenus de México.

     

Molecular docking elucidates the plausible mechanisms underlying the anticancer properties of acetyldigitoxigenin from Adenium obesum

Adenium obesum (Forssk.) Roem. & Schult. is a promising medicinal plant belonging to the Apocynaceae family. It is a rich source of various phytochemicals such as cardiac glycosides, flavonoids, terpeniods, pregnanes etc. which have different pharmacological properties such as anticancer, antibacterial, acaricidal etc. While previous reports showed the anticancer activity of the aerial parts of the plant extract of A. obesum, the mechanisms of action of its chemical constituents are not known. The present study is aimed at elucidation of plausible mechanisms of anticancer activity of the plant by evaluating the binding interaction of its nine major selected compounds with macromolecular receptors implicated in the initiation and progression of cancer using various in silico approaches. Molecular docking results showed that the compound Δ¹⁶-3-Acetyldigitoxigenin (16-anhydro-3-acetylgitoxigenin) scored the best binding energy scores with the majority of the target proteins. The molecular binding of the compound was stabilized through hydrogen bonds as well as hydrophobic interactions, and also possesses favorable drug-like properties without significant toxicities.     

Basal rate of metabolism and temperature regulation of two desert herbivorous octodontid rodents: Octomys mimax and Tympanoctomys barrerae

Summary We studied the energetics of two herbivorous desert rodents from South America. The two species had slightly lower basal metabolic rates, lower thermal conductances, and higher temperature differentials than those expected from their body mass. Mass-independent basal rates of metabolism were higher than those reported for seed-eating desert rodents from North America. Our observations support the hypothesis that desert rodents that eat foods with high water content have higher mass-independent metabolic rates than seed-eating desert rodents.     

Allometric equations to predict the total aboveground biomass of tree species in a planted forest in Egypt

The aim of this study is to estimate the total above‐ground biomass (TAGB), stem height (H), diameter at breast height (dbh) and basal area of five tree species (ages 7‐8 years) irrigated by municipal sewage water in the Egyptian‐Chinese friendship forest, Sadat City, Egypt. From the biomass data that obtained through destructive sampling, models for predicting aboveground biomass were developed. The highest values for stem density and height were estimated for Eucalyptus citriodora, while the lowest value for density was obtained for Dalbergia sissoo and stem height for Khaya senegalensis. The highest values for basal area and dbh were obtained for Casuarina spp., while the lowest values were recorded for Dalbergia sissoo. Eucalyptus camaldulensis had the highest stand stem biomass and TAGB (55.5, 83.9 t DW ha^‐1, respectively). In addition, Casuarina spp. had the highest leafy branches biomass (32.5 t DW ha^‐1) while Dalbergia sissoo had the lowest values for all tree components. All the generated allometric equations had high correlation coefficients at high probability levels. Moreover, the results revealed that not only the dbh data can be used as independent variable for biomass determination, but also stem height and size index are recommended for biomass estimation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The ankylosaurid dinosaurs of the Upper Cretaceous Baruungoyot and Nemegt formations of Mongolia

The discovery of a new ankylosaurid skull with some unusual features from the Baruungoyot Formation of Mongolia prompted a systematic review of ankylosaurid specimens from the Baruungoyot and Nemegt formations. Dyoplosaurus giganteus was found to possess no diagnostic features and is regarded as a nomen dubium. The holotype of Tarchia kielanae (previously synonymized with Tarchia gigantea) has one autapomorphy, an accessory postorbital ossification with surrounding furrow, and Tar. kielanae is here considered a valid species, making the combination Tar. gigantea unnecessary. An accessory postorbital ossification is also found in the holotype of Minotaurasaurus ramachandrani, and this species is here considered a junior synonym of Tar. kielanae. The newly described skull from the Baruungoyot Formation forms the holotype of a new genus and species, Z araapelta nomadis gen. et sp. nov. , diagnosed by unusual bilayered ornamentation on the squamosal horn and extensive postocular ornamentation. Two distinct tail club handle morphotypes are present in the Nemegt Formation and probably represent two different species. However, it is impossible to assign either tail club morphotype to the single valid species from the formation, Saichania chulsanensis, because of a lack of overlapping material. A revised phylogenetic analysis including newly identified characters found Zaraapelta nomadis to be most closely related to Tar. kielanae. © 2014 The Linnean Society of London     

Modelling avian biodiversity using raw,unclassified satellite imagery

Applications of remote sensing for biodiversity conservation typically rely on image classifications that do not capture variability within coarse land cover classes. Here, we compare two measures derived from unclassified remotely sensed data, a measure of habitat heterogeneity and a measure of habitat composition, for explaining bird species richness and the spatial distribution of 10 species in a semi-arid landscape of New Mexico. We surveyed bird abundance from 1996 to 1998 at 42 plots located in the McGregor Range of Fort Bliss Army Reserve. Normalized Difference Vegetation Index values of two May 1997 Landsat scenes were the basis for among-pixel habitat heterogeneity (image texture), and we used the raw imagery to decompose each pixel into different habitat components (spectral mixture analysis). We used model averaging to relate measures of avian biodiversity to measures of image texture and spectral mixture analysis fractions. Measures of habitat heterogeneity, particularly angular second moment and standard deviation, provide higher explanatory power for bird species richness and the abundance of most species than measures of habitat composition. Using image texture, alone or in combination with other classified imagery-based approaches, for monitoring statuses and trends in biological diversity can greatly improve conservation efforts and habitat management.     

沙漠干热环境下中暑大鼠的心肌酶及心肌组织形态学改变

目的 探讨沙漠干热环境下中暑对大鼠心肌损伤的影响.方法 48只雄性SD大鼠随机平均分成6组：沙漠干热环境轻度中暑组及其常温对照组,中度中暑组及其常温对照组,重度中暑组及其常温对照组,然后将3个实验组大鼠分别置于干热环境（温度：41℃,湿度：10%）,3个对照组大鼠置于常温环境（温度：25℃,湿度35%）中,在建立沙漠干热环境中暑大鼠后,干热环境组及其对照组分别在实验开始70 min （轻度中暑）、110 min （中度中暑）、145 min （重度中暑）被处死并取材.用全自动生化检测仪检测大鼠血清心肌酶CK（磷酸肌酸激酶）、CK-MB（肌酸激酶同工酶）、LDH（乳酸脱氢酶）的变化,用HE染色观察心肌病理学变化,用电子显微镜观察心肌超微结构变化.结果 干热中暑各组大鼠血清心肌酶CK、CK-MB、LDH较常温对照各组显著升高（P〈0.05）,干热组CK、CK-MB、LDH均随中暑程度加重而升高,其中CK和LDH的轻度中暑组与中度中暑或重度中暑组比较差异具有显著性（P〈0.05）,但中度中暑组与重中暑度组比较差异无显著性（P＆gt;0.05）;干热中暑组CK-MB各个组间比较差异均有显著性（P〈0.05）;HE染色结果提示：干热中暑组心肌组织早期即心肌间血管明显出现扩张充血、出血,随热暴露时间延长充血、出血现象逐渐加重,常温对照组未见异常.电子显微镜结果显示：干热环境组心肌细胞部分肌丝紊乱断裂、溶解,Z线模糊消失,线粒体肿胀,线粒体基膜不清晰,见空泡形成,部分毛细血管内皮细胞增生,并随热暴露时间延长,心肌细胞损伤逐渐加重.结论 沙漠干热环境可造成大鼠心肌损伤,并随热暴露时间的延长及中暑程度的加重而损伤逐渐加重.提示沙漠干热环境下中暑的治疗应注意加强心肌损伤的保护.     

Near Eastern Neolithic genetic input in a small oasis of the Egyptian Western Desert

The Egyptian Western Desert lies on an important geographic intersection between Africa and Asia. Genetic diversity of this region has been shaped, in part, by climatic changes in the Late Pleistocene and Holocene epochs marked by oscillating humid and arid periods. We present here a whole genome analysis of mitochondrial DNA (mtDNA) and high‐resolution molecular analysis of nonrecombining Y‐chromosomal (NRY) gene pools of a demographically small but autochthonous population from the Egyptian Western Desert oasis el‐Hayez. Notwithstanding signs of expected genetic drift, we still found clear genetic evidence of a strong Near Eastern input that can be dated into the Neolithic. This is revealed by high frequencies and high internal variability of several mtDNA lineages from haplogroup T. The whole genome sequencing strategy and molecular dating allowed us to detect the accumulation of local mtDNA diversity to 5,138 ± 3,633 YBP. Similarly, theY‐chromosome gene pool reveals high frequencies of the Near Eastern J1 and the North African E1b1b1b lineages, both generally known to have expanded within North Africa during the Neolithic. These results provide another piece of evidence of the relatively young population history of North Africa. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.