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Cakile maritima ssp. aegyptiaca (Wild.) Nyman is growing with dimorphic leaf forms (entire or pinnatifid lamina) along the Mediterranean coast of Egypt. The cytotoxic activities of dried shoot systems of the two morphological forms were evaluated by testing and comparing the effects of ethanolic and aqueous extracts on the viability of five human cell lines. GC-MS analysis was performed to identify the bioactive and anticancer compounds present in the most active extracts. MTT assay indicated that both aqueous and ethanolic extracts have selective cytotoxic activities against cancer cell lines with no inhibitory activities against normal Wi38 or Vero cell lines. The underlying mechanism of cytotoxicity involved the induction of G2/M phase arrest in targeted cells MCF-7 and HCT-116 associated with inducing apoptosis in both cell lines, as indicated by Annexin-V assay. Apoptosis investigation in MCF-7 and HCT-116 cells treated with ethanolic extracts, was further investigated through RT-PCR, which exhibited elevation of proapoptotic genes of P53, BAX, Capase-3,6,7,8,9, and downregulation of antiapoptotic gene (BCL-2) upon treatment. The GC-MS analysis of ethanolic extracts of pinnatifid and entire forms revealed the existence of 18 and 13 compounds, respectively, with eleven compounds that were detected in pinnatifid form only and seven compounds were identified exclusively in the entire form. Molecular Docking study revealed that the identified compounds exhibited good binding affinity towards BCL-2 inhibition, and this agreed with the suggested apoptotic mechanism. To the best of authors' knowledge, this is the first scientific evidence underline the variability in the chemical composition associated with variable anticancer activities of dimorphic forms of C. maritima.Communicated by Ramaswamy H. Sarma.

We studied the diet and vegetation composition of Egyptian tortoise, Testudo kleinmanni, habitat in North Sinai, Egypt. Dietary data was recorded through direct observations and the vegetation composition was recorded through the use of quadrats and line transects in 66 sampling points (33 in tortoise areas and 33 in non-tortoise areas). Our results showed that vegetation of Egyptian tortoise habitat had high species richness, Simpson’s diversity index, and vegetation cover in contrast to areas without Egyptian tortoises. These tortoises ate thirty four species of plants, a majority of these being perennials, with most feeding observations occurring in spring and winter. The consumption of perennials may enable Egyptian tortoises to find and consume food in an arid environment with low, variable and unpredictable rainfall. The plants most consumed were rare in our vegetation survey, suggesting food preferences. Our study suggests that Egyptian tortoises, which rely on vegetation for food and refugia, may suffer if vegetation cover and richness decrease.

Mistletoes are epiphytic hemiparasitic plants that are known to negatively affect the growth of their hosts, increase tree mortality, and as a consequence change the community dynamics. Mistletoe alters the mineral nutrition of the host and the nutrient cycle in the soil. In the present study, the elemental nutrient status is described for Acacia asak, A. ehrenbergiana, A. gerrardii, and A. tortilis that were infected with the mistletoe Plicosepalus curviflorus, at three levels of infection (no infection, low and high infection). The nutrients of the mistletoe and the soil under the studied acacias were also determined. The elemental contents of the infected Acacia species were significantly reduced compared to non-infected trees, particularly for potassium and sodium. The reduction in the elemental composition was also species-specific and dependent on infection density. Elemental contents of the mistletoe were significantly higher than their Acacia hosts, particularly for nitrogen, phosphorus, and potassium, and the concentrations of minerals in mistletoe tissues were host- and density-dependent. This study revealed a significant increase in nutrients in the soil beneath the canopy of infected Acacia compared to the non-infected trees. Overall, it appears that mistletoe infection has a dual effect. It threatens the health of the Acacia, potentially killing its host tree due to absorption of host nutrients particularly when the infection intense. It also has a positive effect in that it improves the availability of the micro-habitat of nutrients under the canopy, which in turn may contribute to the maintenance of biodiversity.

ARTHROCNEMUM macrostachyum is a halophyte naturally growing on Manzala Lake shoreline of Egypt and able to tolerate and accumulate heavy metals. The use of metal-resistant rhizobacteria is an important technology to improve the tolerance capability of the halophytes in metal-polluted environments. A total of 33 bacterial isolates were obtained from the root system of A. macrostachyum and screened for resistance to 1.25 and 12.5mM of Cr(VI) in plant-based culture medium prepared from the halophyte shoot juice. The six most tolerant isolates were identified based on cell morphology and API microtube profiles. Those isolates were found closely related to Bacillus lentus, Burkholderia cepacia, Raoultella ornithinolytica and Providencia retgeri indicated on the online database. Among the strains tested for their ability to accumulate chromium, Bacillus lentus was the most effective with an average accumulation percentage of 17.8, Providencia retgeri ranked thereafter (15.1%). Bacillus circulance was the least with a negligible accumulation level of 0.5%. The biosorption rate of the heavy metal was contact time- and bacterial strain-dependent. Again, Bacillus lentus showed the highest uptake capacity of 32.8mg g-1, a parameter that positively correlated with contact time (r= 0.865), this was not the case with Burkholderia cepacia where the correlation was negative (r= – 0.811). When introduced into an aqueous solution of 25mg L-1 Cr(VI), Burkholderia cepacia was the superior in Cr(VI) reduction (86.7%), while Bacillus circulance failed to reduce the heavy metal. The pH 5.5 was the most favorable for bacterial Cr accumulation which proportionally decreased as the acidity of the solution increased. This study provides more understanding of the significant contribution of the heavy metal-tolerant microbiome to improve the metal remediation efficiency of halophytic plant covers of stressed environments.

Off-road vehicle driving is considered as main contributor to land degradation in arid regions. This study examined the impact of off-road vehicles (ORV) on soil and vegetation in a natural recreational desert meadow of Raudhat Khuraim, Saudi Arabia. Vegetation canopy cover and plant height away from road tracks were assessed. Also, species density and canopy cover, bare ground cover and soil attributes were assessed in four microhabitats; tracks, inter-tracks, verges, and away from vehicle tracks (undisturbed natural areas). Results show that the cover of forbs and grasses was negatively associated with distance from road verges. It was observed that the height of woody species responded negatively to distance away from tracks. Cover of native species decreased under verge, inter-track and track microhabitats giving more opportunity for weeds to flourish. Bare ground was highest (60.7%) in tracks. ORV impact on soil bulk density was clear with an increase of 38% under tracks compared to soils of undisturbed natural vegetation and a similar decrease in porosity was observed. On the other hand, soil electrical conductivity was significantly higher (5.45 mS cm−1) under disturbance compared to 1.32 mS cm−1 in undisturbed natural vegetation. Organic matter and nitrogen were not affected significantly by ORV disturbance. The results emphasize that managing off-road vehicle driving is essential for conserving native vegetation. Keywords: Off-road driving, Tyre tracks, Bulk density, Raudhat system, Plant diversity

In recent years, the phenomenon of abandonment of arable fields has increased in Saudi Arabia due to low soil fertility, drought, low rainfall, high levels of evapotranspiration, soil salinization, and low level of groundwater. We evaluated the effect of agricultural land abandonment on soil properties, perennial vegetation composition, and population structure in the Al-Kharj region, Saudi Arabia. A total of 11 perennial plant species belonging to 9 families and 11 genera were detected in the different abandoned fields of the study area. Four plant communities were identified after the application of the detrended correspondence analysis (DCA) ordination. The indicator species were (1) Seidlitzia rosmarinus&mdash, Zygophyllum hamiense, (2) Traganum nudatum&mdash, Seidlitzia rosmarinus, (3) Traganum nudatum&mdash, Prosopis farcta, and (4) Calligonum comosum&mdash, Pulicaria undulata. Results of the soil analysis showed significant differences in soil texture, pH, salinity, and nutrient content among the four recognized plant communities. Demographic analysis indicated that populations of Zygophyllum hamiense and Calligonum comosum tended to be either inverse J-shaped or positively skewed which may have indicated rapidly-growing populations with high reproductive capacity. Conversely, the size&ndash, frequency distribution of Traganum nudatum, S. Rosmarinus, and Prosopis farcta was approximately symmetrical (i.e., bell-shaped). The present study sheds light on the necessity of managing abandoned agricultural fields for restoring and improving rangelands with native species that are adapted to the local conditions such as low water demand.

Understanding the strategies and mechanisms of invasive species could guide their control and management especially in arid ecosystems. This study compares the vegetative and reproductive functional traits of the invasive Mexican poppy (Argemone ochroleuca), in seven habitat types, in southwestern Saudi Arabia. The results showed that the aboveground phenological attributes such as plant height, leaf area, and leaf dry mass attained the highest values in the wadi channels, whereas these attributes attained the lowest values in the mountain ranges. Maximum specific leaf area, root parameters, and all reproductive traits were recorded in the abandoned fields. In contrast to all other habitats, populations from abandoned fields had a greater investment of resources in belowground structures, while the population growing in the wadi channels and mountain ranges habitat allocated more energy to vegetative parts. The plasticity in vegetative and reproductive resource allocation in A. ochroleuca is an important mechanism in determining its colonizing ability in different habitat types and expanding the distribution range. The present data of the functional traits of A. ochroleuca agree with the resource fluctuation hypothesis, where the plant flourished in the abandoned fields that attained the highest values of organic matter and nutrients. Therefore, the restoration of these disturbed habitats could improve the resistance toward invasion by this noxious weed.

Onopordum alexandrinum is a near-endemic to Egypt and neighboring countries. Its habitats are designated as priority sites for conservation in the south and east Mediterranean regions. We hypothesize that variation in morphological, reproductive, and molecular traits could provide a survival strategy that allows the species to occupy landscapes including anthropogenic habitats (barley and abandoned fields) and natural habitats (sand dunes and desert plateau) with different soil resources along the western Mediterranean coast of Egypt. The results indicated that plant functional traits associated with high rates of resource acquisition and growth (e.g., high values of vegetative height and specific leaf area, and low values of leaf dry matter content) occurred in populations located in abandoned fields with high soil resources. The genetic diversity analyses indicated similarity in genetic diversity of the present populations of O. alexandrinum in barley and abandoned fields with those of sand dunes. However, the genetic structures of these populations were different from those of natural desert plateau, which suggests reduced rates of gene flow. In this framework, it is essential to monitor and reduce the anthropogenic activity which will not only support the conservation of genetic diversity within populations but will also help ensure the resilience of O. alexandrinum in the face of environmental and climatic changes.

The genetic diversity of 177 accessions of Panicum turgidum Forssk, representing ten populations collected from four geographical regions in Saudi Arabia, was analyzed using amplified fragment length polymorphism (AFLP) markers. A set of four primer-pairs with two/three selective nucleotides scored 836 AFLP amplified fragments (putative loci/genome landmarks), all of which were polymorphic. Populations collected from the southern region of the country showed the highest genetic diversity parameters, whereas those collected from the central regions showed the lowest values. Analysis of molecular variance (AMOVA) revealed that 78% of the genetic variability was attributable to differences within populations. Pairwise values for population differentiation and genetic structure were statistically significant for all variances. The UPGMA dendrogram, validated by principal coordinate analysis-grouped accessions, corresponded to the geographical origin of the accessions. Mantel’s test showed that there was a significant correlation between the genetic and geographical distances (r = 0.35, P

P HYTOGENIC mounds (nebkhas) formed by halophytes are widely distributed in coastal and desert environments. Such nebkhas provide loci for geochemical and biological activities that influence ecosystem processes and function. Seasonal variation in soil and bacterial properties were investigated within the nebkhas under the canopy of Halocnemum strobilaceum and in the surrounding unvegetated sites at salt marshes of Lake Manzala. The parameters measured include soil moisture, organic matter, total nitrogen and phosphorus, pH, electrical conductivity (EC), and bacterial community and enzyme characteristics. Enrichment ratios for soil salinity and nutrients were evaluated to indicate the salinity and fertility islands within nebkhas. Soil moisture content showed significant differences between the different seasons with the highest value in winter (16.55%) at unvegetated control site.Soil electrical conductivity, total nitrogen and phosphorus had their significantly higher values in nebkhas during autumn. The enrichment values for the measured soil parameters ranged from 0.31 to 4.09 in the four seasons which indicates a clear accumulation effect for soil nutrients and salts within the nebkhas under the canopy of H. strobilaceum. Bacterial abundance was consistently higher in nebkhas through all seasons. Eleven genera of bacteria belong to Firmicutes, Actinobacteria and proteobacteria phyla were recorded in nebkha and unvegetated sites. These genera varied in their occurrence between the two locations and the four seasons. It can be concluded that the formation of nebkhas by halophytic vegetation have noticeable effects on accumulation of soil salinity and fertility during different seasons that affect bacterial abundance and activity in coastal environment.

Nurse plant facilitation in stressful environments can produce an environment with relatively low stress under its canopy. These nurse plants may produce the conditions promoting intense competition between coexisting species under the canopy, and canopies may establish stress gradients, where stress increases toward the edge of the canopy. Competition and facilitation on these stress gradients may control species distributions in the communities under canopies. We tested the following predictions: (1) interactions between understory species shift from competition to facilitation in habitats experiencing increasing stress from the center to the edge of canopy of a nurse plant, and (2) species distributions in understory communities are controlled by competitive interactions at the center of canopy, and facilitation at the edge of the canopy. We tested these predictions using a neighbor removal experiment under nurse trees growing in arid environments. Established individuals of each of four of the most common herbaceous species in the understory were used in the experiment. Two species were more frequent in the center of the canopy, and two species were more frequent at the edge of the canopy. Established individuals of each species were subjected to neighbor removal or control treatments in both canopy center and edge habitats. We found a shift from competitive to facilitative interactions from the center to the edge of the canopy. The shift in the effect of neighbors on the target species can help to explain species distributions in these canopies. Canopy‐dominant species only perform well in the presence of neighbors in the edge microhabitat. Competition from canopy‐dominant species can also limit the performance of edge‐dominant species in the canopy microhabitat. The shift from competition to facilitation under nurse plant canopies can structure the understory communities in extremely stressful environments.

Biodiesel is an eco-friendly renewable fuel that can be derived from microalgae. Maximization of biomass and lipid productivities are considered the main challenges for algal biodiesel production. Since conventional batch cultures are time-, space-, and reagent-consuming with many restrictions to apply many replicates, microfluidic technology has recently emerged as an alternative low-cost and efficient technology with high throughput repeatability and reproducibility. Different applications of microfluidic devices in algal biotechnology have been reported, including cell identification, sorting, trapping, and metabolic screening. In this work, Chlorella vulgaris was investigated by encapsulating in a simple droplet-based micro-array device at different light intensities of 20, 80, and 200 &micro, mol/m2/s combined with different nitrate concentrations of 17.6, 8.8, and 4.4 mM. The growth results for C. vulgaris within microfluidic device were compared to the conventional batch culture method. In addition, the effect of combined stress of deficiencies in irradiance and nitrogen availability were studied to illustrate their impact on the metabolic profiling of microalgae. The results showed that the most optimum favorable culturing conditions for Chlorella vulgaris growth within the microfluidic channels were 17.6 mM and 80 &micro, mol/m2/s.

Algae are potential sources for different industrial products. However, biofuel production from algae still needs to reach valuable economical approaches. Select algae and optimize culture conditions considered main challenges for biofuel production. Traditional batch cultures' techniques are time and labor consuming. PDMS-based Microfluidics is time-and labor-saving technique with high throughput single cell analysis. We present gradient-based microfluidics as tools for studying algal growth under different cultivation conditions. Applying our device provides the opportunity to generate droplets with different concentrations of medium nutrients' in 200 s which keeps reagent and time for preparing such solutions using conventional techniques. Chlorella vulgaris was encapsulated inside uniformly droplets with different NO3−-N concentrations of 2.46, 6.69, 10.91, and 15.14 mΜ/L. separated devices were exposed to different temperatures of 20, 27, and 37 °C. The photosynthetic energy conversion for each cell per droplet was calculated. It was observed that the higher the NO3− concentration, the higher the growth kinetics. According to the presented results, the optimum nitrate and temperature conditions were 15.14 mΜ/L and 37 °C. Our device is considered the third effort for applying a gradient chip in algal biotechnology field. It is unique and simple in use with high competence results.

We studied how emergence, survival, and growth of nebkha recruits are spatially affected by prevailing biotic and abiotic ecological drivers in a landscape with vegetation-induced dunes (nebkhas) in Saudi Arabia. Hereto Monte Carlo-based spatiotemporal analyses were performed on four remotely sensed study site maps, including adult nebkhas, recruits and elevation data, acquired over a three-year period. The emergence of new nebkha recruits was found substantially higher in topographic depressions and around adults, which we interpret as being a result of runoff water convergence to depressions and distance-limited seed dispersal from adults. The survival of recruits was also higher nearby nebkhas. However, the growth of already present recruits was suppressed near adult vegetation indicating competition, but unexpectedly increased far away from nebkhas which could be induced by augmented sand burial in these open areas, stimulating the nebkha development and its host plant. Combining the three demographic processes emergence, survival, and growth revealed systematically greater encroachment from nebkha recruits in zones with low vegetation cover, which creates a buffer against local disturbances in nebkha fields.

Five lakes (Mariut, Edku, Burullus, Manzala, and Bardawil) of global importance for migratory birds extend along the Egyptian Mediterranean coast. Burullus and parts of Lakes Manzala (i.e., Ashtum El-Gamil) and Bardawil (i.e., Zaranik) are managed protected areas. In addition, Burullus and Bardawil are Ramsar sites for the conservation of migratory birds. These lakes are evaluated for their plant diversity and ecosystem services. About 402 plant species, categorized into 45 plant communities, were identified in these lakes. Five of these species are endemics, while three are near endemics. Although the areas of these lakes (2,449 km2) contribute

Phytogenic mounds or nebkhas are formed by spatially isolated burial-Tolerant plants, which have been trapping windborne sediment within their canopies. They occur in drylands all over the world, and nebkha landscapes are considered intermediate between stable grasslands and unstable deserts with mobile dunes. Depending on the previous state of the landscape, they can thus be viewed both as indicators of desertification and as signs of stabilization. While individual nebkha mounds have been studied extensively, little is known about the organization of nebkha landscapes. In this study, we collected spatiotemporal data of vegetation and topography from four self-made remotely sensed maps, created over a three-year period from a study site in central Saudi Arabia dominated by the nebkha-forming shrub Rhazya stricta Decne. Using logistic regressions and t tests, we found that the nebkha shrubs grow in topographic depressions, while they shrink on topographic highs and in locations with high nebkha densities. We propose that this spatial variation in nebkha growth is driven by water availability, as the few extreme rain events that typically make up the bulk of precipitation in deserts would spatially redistribute to topographic lows, and as nebkha density would positively correlate with competition for water. Our data suggest a novel mechanism of biogeomorphological self-organization in deserts. The observed nebkha growth in depressions would lead to increased sedimentation on and in between the nebkhas owing to reduced wind speed, which after a time lag might transform depressions into topographic highs on which nebkhas tend to shrink because of water shortage. Shrinking nebkhas, in turn, could provoke soil erosion, on as well as in between the nebkha mounds, which may ultimately transform topographic highs into depressions, thereby closing the cycle of self-organization. ispartof: Ecosphere vol:7 issue:11 status: published

The structure and distribution of vegetation are critical components in the function of watersheds that provide many important ecosystem services in the arid regions of the World. Although the majority of these watersheds are highly disturbed by livestock grazing, few studies have examined the interactive effects of such disturbance with morphometry and soil on plant community structure and diversity. In this study, 54 vegetation stands were surveyed along 23 transects placed at set distances, ranging from 300 m to 25 km, from human settlement in Altwiqi watershed, central Saudi Arabia. For each stand, we measured morphometric and soil factors as well as grazing intensity indicators. Vegetation stands were classified into five plant communities based on relative abundances of different growth forms as well as palatable and unpalatable species. Non-metric Multidimensional Scaling (NMDS) ordination and Canonical Correspondence Analysis (CCA) revealed that community structure may be influenced primarily by a combination of morphometric and soil variables of the watershed, and grazing pressure. This combination may determine the distribution and abundance of moisture and nutrients, and perhaps promote habitat specialization and/or competitive exclusion. Those communities occurring on distant sites, with higher elevation, stream order, and fine textured soil close to the ephemeral water channels were more diverse in both species richness and growth forms. However, under heavy grazing near the village, in sites with lower elevation and stream order, the vegetation is dominated by a few unpalatable species on sandy textured soil. The findings of the study have implications for the design of rehabilitation programs through incorporating biotic and abiotic variables that optimize productivity and conserve biodiversity of ephemeral streams in arid regions.

Urban expansion and the associated increase in anthropogenic pressures have led to a great loss of the Red Sea's biodiversity. Floristic composition, diversity, and environmental controls were investigated for 210 releves on twenty coral islands of Farasan in the Red Sea, Saudi Arabia. Multivariate statistical analyses for classification (Cluster Analysis), ordination (Detrended Correspondence Analysis (DCA), and Redundancy Analysis (RDA) were employed to identify vegetation types and their relevance to the underlying environmental gradients. A total of 191 flowering plants belonging to 53 families and 129 genera were recorded. Geophytes and chamaephytes were the main life forms in the saline habitats, whereas therophytes and hemicryptophytes dominated the sandy formations and coral rocks. The cluster analysis and DCA ordination identified twelve vegetation groups that linked to five main habitats with definite floristic composition and environmental characteristics. The constrained RDA with Monte Carlo p...

Fat sand rats (Psammomys obesus) are strictly herbivorous and live in densely complex burrows in the desert of North Africa and the Middle East. Little is known however about the effect of their foraging and burrowing activities on surface morphology and plant community attributes. This study evaluated such effects by comparing burrow and mound surface morphology, canopy of the main host chenopod shrub Anabasis articulata, vegetation cover, and plant abundance and species richness on and off both active and abandoned colonies in the semi-stabilized sand dunes of the Northern Sinai. In general, active burrow systems were characterized by reduced A. articulata canopy area, and more soil disturbance, with higher and larger burrow mounds dominated by bare ground, dung, and dead and fresh litter. The abandonment of mounds for five years has resulted in significant increases of plant cover, canopy height, abundance and species richness. Vegetation structure and plant species assemblages differed between mound and non-mound patches of both active and abandoned sites. The results suggest that fat sand rats can have significant direct and indirect, short-term and long-term effects on vegetation dynamics and structure through their mound building and foraging.

Island biogeography theory and nestedness are two relevant and important concepts in biogeography and conservation. However, their integration and application has not been examined for maintaining or maximizing species diversity, especially in arid regions. The aim of this study is to investigate the ecological mechanisms related to the observed pattern of floristic diversity and nestedness in the Lake Bardawil islets on the Mediterranean coast of Sinai Peninsula before the execution of the North Sinai Agricultural Development Project (NSADP) that will threaten the ecosystem of the lake. Plant species on 15 islets were identified and categorized into ecological groups related to their life-form, salt tolerance and succulence. Richness of total plant species and their ecological groups were positively correlated with islet area, number of habitats and elevation, and negatively with disturbance index. The temperature calculator detected highly significant nestedness for the entire flora and all ecological groups. Distance from the mainland had no effect on either species richness or nested pattern of total plant species and their ecological groups. Both the analyses of species richness and nested distribution yielded evidence for a positive species-area relationship. Although nestedness was detected for the entire plant species and their ecological groups, many species and islets exhibited idiosyncratic distribution. Idiosyncrasies could be mainly attributed to demographic stochasticity which is an important character for species interaction and diversity maintenance in arid regions. Therefore, in developing conservation strategies for the Lake Bardawil islets, it is important to incorporate spatial and temporal stability of populations.

Obtaining information about the spatial distribution of desert plants is considered as a seri- ous challenge for ecologists and environmental modeling due to the required intensive field work and infrastructures in harsh and remote arid environ- ments. A new method was applied for assessing the spatial distribution of the halophytic species (HS) in an arid coastal environment. This method was based on the object-based image analysis for a high- resolution Google Earth satellite image. The integra- tion of the image processing techniques and field work provided accurate information about the spatial distribution of HS. The extracted objects were based on assumptions that explained the plant-pixel rela- tionship. Three different types of digital image pro- cessing techniques were implemented and validated to obtain an accurate HS spatial distribution. A total of 2703 individuals of the HS community were found in the case study, and approximately 82 % were located above an elevation of 2 m. The micro- topography exhibited a significant negative relation- ship with pH and EC (r=−0.79 and −0.81, respec- tively, p

Livestock grazing is one of the main causes of rangeland degradation in Saudi Arabia. Fencing to exclude grazers is one of the main management practices used to restore vegetation and conserve biodiversity. The main objectives of this study were to investigate the changes in plant diversity and abundance, floristic composition and plant groups of the major life forms in response to thirty-five years of grazing exclosure in western Saudi Arabia. These vegetation attributes and palatability were compared in 30 sampling stands located in the excluded and grazed sites. Our results showed that livestock exclusion significantly increased covers, density and species richness of annuals, grasses, perennial forbs, shrubs and trees. Exclosure enhanced the abundance and richness of palatable species and depressed the development of weedy species. About 66.7% of the recorded species at the excluded site were highly palatable compared to 34.5% at the grazed site. In contrary, about 55.2% unpalatable species were found in the grazed site compared to 25.8% in the protected site. Jaccard’s similarity index between the excluded and grazed sites showed lower values of 0.39%, 0.40% and 0.31% at levels of families, genus and species, respectively. The results suggest that establishing livestock exclusion may be a useful sustainable management tool for vegetation restoration and conservation of plant diversity in degraded rangelands of arid regions.

The nebkhas of woody plants represent distinct habitats in arid and semiarid ecosystems. Nebkhas are mounds composed of wind-borne sediment within or around shrub canopies. We studied the effects of widely spaced nebkhas of Retama raetam shrub on their microenvironment and associated herbaceous vegetation in the Mediterranean coast of Sinai Peninsula. Our measurements included nebkha size (height and width) and shrub size (canopy height and diameter). We identified four distinct microsites at each nebkha: crest, mid-slope, edge, and internebkha space. We measured soil temperature and moisture, photosynthetically active radiation (PAR), and soil properties. The plant species grown at each microsite were identified and their densities were measured. Average soil temperature and PAR were highest at internebkha space and lowest at nebkha crest. The maximum diurnal temperature and PAR of internebkhas exceeded that of nebkhas. Soil moisture and nutrient concentrations showed a gradient of spatial heterogeneity and were highest at the nebkha edge. Regression analysis indicated that total herbaceous plant density was significantly related to nebkha size, and to shrub canopy diameter and area. Detrended correspondence analysis indicated that patterns of species composition were correlated with the spatial variability in soil moisture and nutrient content along the gradient of increasing distance from the nebkha crest. It is assumed that shrub canopy and its nebkha interact in governing ecosystem functioning in this environment.

Lake Bardawil is the only oligotrophic hypersaline lagoon along theMediterranean coast of Egypt. Its ecological significance is increasing due tothe progressive degradation of comparable wetlands in the region. The aim ofthis study is to analyse the structure and life forms of the vegetation alongthe lake before the execution of the North Sinai Agricultural DevelopmentProject (NSADP) which will threaten the ecosystem of the lake. A data set of150 stands was analysed using multivariate procedures(TWINSPAN, DCA and CCA), to classify the lake's vegetation, and to determinetherelationship between the plant community structure and the environmentalfactors. The classification and ordination resulted in a clear demonstration ofnine vegetation groups associated with four habitat types: submerged seagrasses, salt marshes and sabkhahs, eastern and middle calcareous dunes, andwestern non-calcareous dunes. The first axis of the CCA-ordination separatesthe salt marshes andsabkhahs species from those of the sand dunes along the soil salinity, watertable depth, cations, and pH gradients. CaCO3 and soil textureshowedhighly significant correlation with the second axis of CCA which was animportant predictor for the psammophytic species distribution. The life formsranged from hydrophytes (sea grasses) to phanerophyteswith the dominance of therophytes and chamaephytes. Geophytes and chamaephytesdominate the saline habitats, while therophytes and hemicryptophytes dominatedthe sandy dunes. Eventhough the eastern section of the lake (Lake Zaraniq) wasdeclared as a RAMSAR site, Lake Bardawil needs urgent management to prevent itspollution by the new land use system.

Mounds originating from wind-blown sediment accumulation beneath vegetation (nebkhas) often indicate land degradation in dry areas. Thus far, most nebkha research has focused on individual plants. Here, we aimed to explore population-scale processes (up to scales of about 100 m) that might explain an observed nebkha landscape pattern. We mapped the Rhazya stricta Decne. population in a 3 ha study site in a hyper-arid region of Saudi Arabia. We compared the spatial patterns of five different cohorts (age classes) of observed nebkha host plants to those expected under several hypothesized drivers of recruitment and intraspecific interaction. We found that all R. stricta cohorts had a limited fractional vegetation cover and established in large-scale clusters. This clustering weakened with cohort age, possibly indicating merging of neighboring vegetation patches. Different cohort clusters did not spatially overlap in most cases, indicating that recruitment patterns changed position over time. Strong indications were found that the main drivers underlying R. stricta spatial configurations were allogenic (i.e. not driven by vegetation) and dynamic. Most likely these drivers were aeolian-driven sand movement or human disturbance which forced offspring recruitment in spatially dynamic clusters. Competition and facilitation were likely active on the field site too, but apparently had a limited effect on the overall landscape structure. ispartof: PLoS One vol:9 issue:3 ispartof: location:United States status: published

Habitat destruction is a key determinant of species extinction. Its principle components, habitat fragmentation and habitat loss, affect species persistence in landscapes, but few models have investigated how dispersal type and intraspecific competition (crowding effect) modulate this. If dispersal type or crowding changes extinction thresholds, then fragmentation and habitat loss might act differently on different species. Here we generate fragmented landscapes by varying the orthogonal neighbouring correlation between suitable and unsuitable habitat. We show that local dispersers undergo a strong negative impact of habitat fragmentation (lower occupancy of suitable sites), but only under severe habitat loss. In contrast, global dispersal eliminated fragmentation effects through random establishment. Both fragmentation and crowding effects enhanced the extinction risk of species that spread their seeds at close range, while long-range dispersers were not influenced. However, fragmentation improved the persistence of global dispersers that are highly sensitive to crowding, probably through reduced intraspecific competition. With respect to species conservation, our results suggest that random habitat destruction is a more serious threat to species persistence than clustered habitat destruction. Moreover, as species responses to habitat fragmentation depend on dispersal type and sensitivity to crowding, fragmented landscapes with different properties may accommodate different species.

Phytogenic mounds (nebkhas) often are symptoms of desertification in arid regions. Interactions among nebkhas and between nebkhas and their environment are however poorly examined. To this end, three main hypotheses of nebkha pattern formation were evaluated in this study. These state that nebkha patterns are either shaped by: (i) biologically induced recruitment inhibiting zones, (ii) biologically induced recruitment encouraging zones, or (iii) by the spatial distribution of abiotic factors which are not biologically driven. Contrasting nebkha landscapes were examined: a highly dense New Mexican mesquite (Prosopis glandulosa) and snakeweed (Gutierrezia sarothrae and Gutierrezia microcephala) ecosystem, and a low-density mixed Tamarix aphylla and Calligonum comosum field in central Libya. Spatial second-order statistics of strategically chosen nebkha subpatterns were compared with those of null models in which observed patches were spatially randomized without overlap. Null model deviations were assessed with goodness-of-fit tests, and interpreted in terms of hypothesized mechanisms of nebkha pattern formation. Our results suggest that biologically induced recruitment inhibiting zones surround adult mesquite nebkhas. The configuration of Calligonum and Tamarix nebkhas may be driven by spatial dynamics of abiotic microsites which are not caused by nebkha interactions. Hence we conclude that both biotic and abiotic drivers can shape nebkha spatial patterns.

Khalid Al Mutairi1, Mashhor Mansor1, Magdy El-Bana2,3,*, Saud L. Al-Rowaily2 and Asyraf Mansor1 1School of Biological Sciences, Universiti Sains Malaysia, Penang, 2Department of Plant Production, College of Agricultural & Food Sciences, King Saud University, Riyadh, 3Department of Biological Sciences, Faculty of Education at El-Arish, Suez Canal University, El-Arish, 1Malaysia 2Saudi Arabia 3Egypt

Juniperus phoenicea L. is listed as threatened tree by IUCN Red List. In Egypt, J. phoenicea L. is the only conifer tree that is restricted to the three mountains of northern Sinai: Gabal El-Halal, Gabal El-Maghara and Gabal Yelleq. As a Mediterranean relict it has been included in a national list as target for conservation and management. To provide baseline information for the development of a conservation strategy, the present study aims at comparing the isolated populations of J. phoenicea and their associated plant composition and diversity at the three mountains. The application of TWINSPAN and DCA analysis techniques has resulted in identifying of four vegetation types associated with juniper, and each could be related to a specific geomorphologic habitat on a topographic gradient. Chiliadenus montanus and Zygophyllum dumosum characterized the slopes of smooth-faced rock outcrops in Wadi Abu Seyal (at 350–470 m altitude of Gabal El-Halal), Deverra tortuosa, Ephedra aphylla and Gymnocarpos decander inhabited together with the target species the soil pockets of north-facing slope in Neqeb Abu Hamam (at 600–700 m altitude of Gabal El-Halal), Stachys aegyptiaca and Moricandia nitens characterized the juniper occurrences in the runnels of Wadi Arar (at 450–560 m altitude of Gabal El-Maghara), and Artemisia herba-alba, Atriplex halimus and Reaumuria hirtella represent the stands on slope runnels (at 900–960 m) of Gabal Yelleq. The two vegetation types recognized at Gabal El-Halal had, on average, the highest species diversity, juniper density and cover. Juniper shows generally poor conditions of vitality at higher elevation (600–960 m) with a higher proportions of old and recent dead trees, and with the predominance of male individuals, as compared with the populations of Gabal El-Maghara and Gabal Yelleq. In contrast, the juniper populations at lower elevation (350–470 m) of Gabal El-Halal proved to be in best condition with mostly living foliage and reproductive branches. The differences in rock types and elevation among the three mountains reflect serious limitation on recruitment of J. phoenicea due to moisture availability. The results of this study showed that J. phoenicea is an endangered species and its conservation in northern Sinai mountains is a priority. For a successful conservation of this community it is highly recommended to preserve in particular the suitable habitats at Gabal El-Halal, but also the other stands merit conservation measures.

The Mediterranean sabkhat of Sinai are of importance for the conservation of migratory birds due to their unique geographical position. Field observations were used to document the floristic composition of these sabkhat before the execution of the North Sinai Agricultural Development Project (NSAD), which will have an impact on the sabkha ecosystems. A total of 43 halophytic species in 32 genera and 13 families were recorded. The sabkha flora includes endangered and endemic species of Sinai such as Zygophyllum propinquum, Z. aegyptium and Salsola tetrandra. The ecological consequences of the anthropogenic activities and management of sabkhat are discussed.

Natural accumulation of wind-borne sediments within or around the canopies of plants plays an important role in the ecological and evolutionary dynamics of many coastal and desert ecosystems. The formation of such phytogenic mounds (nebkhas) creates patches that can strongly influence the spatial distribution of plant and soil resources. In land restoration of arid and semiarid environments it is important to study the potential role of such biological patchiness that may provide sites for coexistence of species with different life and growth forms. Our main objective was to test whether the nebkhas of a leguminous shrub, Retama raetam (white broom), promote restoration of herbaceous vegetation and soil in the degraded rangelands of northern Sinai. Vegetation and microclimatic and edaphic characteristics within the nebkhas, as well as within internebkha spaces, were compared for ungrazed and grazed sites. Abundance and richness of herbaceous plants were positively related to nebkha area, which explained more of the variance of abundance and richness in the grazed site than in the ungrazed one. Protection from grazing, especially on nebkhas, was associated with an increase in abundance and richness of herbaceous plants, improved soil microclimate, and increased soil fine particles and nutrient concentrations. The results suggest that management (in casu protection from grazing) of nebkhas of woody perennial shrubs changes rangeland conditions and improves the resource regulatory processes. Furthermore, nebkhas of unpalatable plants have the potential to preserve plant diversity in overgrazed plant communities, because they are effective in capturing and retaining water, soil materials, and propagules within and from nearby areas, resources that would otherwise be lost.

Questions: The formerly overgrazed Inner Mongolia steppe was subject to retrogressive succession. Today, Artemisia frigida and Potentilla acaulis are two dominant species in different phases of successive degradation. To investigate the impact of grazing intensity on spatial community structure, we investigated the small-scale spatial association between A. frigida and P. acaulis at zero, light, medium and heavy sheep grazing, and proposed factors involved in the spatial associations between these two species along a grazing intensity gradient. Location: The Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences. Methods: Four grazing intensities were selected: zero, light (1.33 sheep/ha), medium (4.0 sheep/ha) and heavy (6.7 sheep/ha). After 13 years of grazing three 2 m × 2 m quadrats with 100 × 100 cells of size 2 cm × 2 cm were randomly selected in each treatment in July and August 2002. The presence of A. frigida and P. acaulis in each cell was recorded and th...