Hyper-arid Region Research Articles

Uneven Distribution of Halobacillus trueperi Species in Arid Natural Saline Systems of Southern Tunisian Sahara

The genetic diversity of a collection of 336 spore-forming isolates recovered from five salt-saturated brines and soils (Chott and Sebkhas) mainly located in the hyper-arid regions of the southern Tunisian Sahara has been assessed. Requirements and abilities for growth at a wide range of salinities\ showed that 44.3% of the isolates were extremely halotolerant, 23% were moderate halotolerant, and 32.7% were strict halophiles, indicating that they are adapted to thrive in these saline ecosystems. A wide genetic diversity was documented based on 16S-23S rRNA internal transcribed spacer fingerprinting profiles (ITS) and 16S rRNA gene sequences that clustered the strains into seven genera: Bacillus, Gracilibacillus, Halobacillus, Oceanobacillus, Paenibacillus, Pontibacillus, and Virgibacillus. Halobacillus trueperi was the most encountered species in all the sites and presented a large intraspecific diversity with a multiplicity of ITS types. The most frequent ITS type included 42 isolates that were chosen for assessing of the intraspecific diversity by BOX-PCR fingerprinting. A high intraspecific microdiversity was documented by 14 BOX-PCR genotypes whose distribution correlated with the strain geographic origin. Interestingly, H. trueperi isolates presented an uneven geographic distribution among sites with the highest frequency of isolation from the coastal sites, suggesting a marine rather than terrestrial origin of the strains. The high frequency and diversity of H. trueperi suggest that it is a major ecosystem-adapted microbial component of the Tunisian Sahara harsh saline systems of marine origin.

Mining Activities and Associated Environmental Impacts in Arid Climates: A Literature Review

Mining operations have released measurable levels of geogenic trace metals (e.g. Cd, Cr, Pb), metalloids (e.g. As, Se), and anthropogenic chemicals (e.g. CN - , Hg) into surrounding sediments. Abandoned mining sites in hyperarid climates has not been the focus of much research compared to wet and temperate areas. Research has focused on historical mining sites in semiarid and wetter regions in the United States, south pacific and Europe. Those areas have obvious risks associated with them including aqueous phase mobilization as a result of abundant precipitation. However, many mining areas in the American Southwest and aboard are located in hyperarid regions and viewed as not having a potential for mobilization of contaminants. Seasonal storm events can mobilize sediments containing contaminates beyond a small, localized area and into the wider environment. Literature indicates that arid and hyperarid mining regions have not been studied as extensively as those in wetter climates.

Sediment Contamination along Desert Wash Systems from Historic Mining Sites in a Hyperarid Region of Southern Nevada, USA

Abandoned mining sites in hyperarid environments are generally assumed to present an insignificant risk to water availability. This study investigated the impact abandoned mine sites in Southern Nevada can have on the wider environment. Southern Nevada is characterized with little precipitation and prolonged droughts. Precipitation in Southern Nevada is often in the form of short and intense events with the potential to mobilize and transport contaminated sediments down gradient. This work evaluated the movement of trace elements (Ag, As, Ba, Cd, Cr, Hg, Pb, and Se) and cyanide in surface sediments of three desert washes near the historic mining town of Nelson, a hyperarid region of Southern Nevada. Results indicate trace elements have been mobilized and transported down gradient from sources to areas not directly impacted by mining. Contaminants used in mining operations (Hg and CN−) as well as those of geogenic nature migrated as far as 6000 m, providing evidence of their transport in hyperarid environments, contrary to the generally held belief. Although contaminants in this study are below levels that are environmentally significant, the findings show that transport is possible. This study demonstrates that large amounts of contaminant-laden sediments might be a significant threat in hyperarid environment and to areas down gradient from source materials.

Elucidating the microbial resuscitation cascade in biological soil crusts following a simulated rain event

Biological soil crusts (biocrusts) are photosynthetic mats formed through an association of prokaryotic and eukaryotic microorganisms with soil particles. Biocrusts are found in virtually any terrestrial ecosystem where vascular plant coverage is abiotically limited, with drylands comprising the primary habitat for them. We studied the dynamics of the active bacterial community in two biocrusts from an arid and a hyperarid region in the Negev Desert, Israel, under light-oxic and dark-anoxic incubation conditions after simulated rainfall. We used H2(18)O for hydrating the crusts and analysed the bacterial community in the upper and lower parts of the biocrust using an RNA-stable isotope probing approach coupled with 454-pyrosequencing. In both biocrusts, two distinct bacterial communities developed under each incubation condition. The active anaerobic communities were initially dominated by members of the order Bacillales which were later replaced by Clostridiales. The aerobic communities on the other hand were dominated by Sphingobacteriales and several Alphaproteobacteria (Rhizobiales, Rhodobacterales, Rhodospirillales and Rubrobacteriales). Actinomycetales were the dominant bacterial order in the dry crusts but quickly collapsed and accounted for < 1% of the community by the end of the incubation. Our study shows that biocrusts host a diverse community whose members display complex interactions as they resuscitate from dormancy.

Slow growth improves compensation ability: examining growth rate and starvation endurance in pit-building antlions from semi-arid and hyper-arid regions

Different environments are expected to exert differential selective pressures, often generating distinct sets of traits in organisms inhabiting different geographic regions. Starvation endurance is an important trait for organisms in harsh (i.e., extreme climate and/or biotically poor) and unpredictable environments. This is especially true for sit-and-wait predators, such as antlions, which experience stronger fluctuations in prey arrivals than do actively searching predators. We conducted an experimental comparison of starvation endurance in pit-building antlions, originating from semi-arid and hyper-arid environments. We hypothesized that individuals from the climatically harsher and biotically poor environment (i.e., hyper-arid) should be better adapted to endure long starvation periods. Additionally, we posited that faster-growing individuals are expected to be more sensitive to starvation because of their need to sustain higher metabolic rates. We found that antlions originating from the semi-arid region maintained higher activity levels, which led to slightly higher mass loss rates during starvation, but enabled faster recovery when food supply was renewed. Conversely, antlions originating from the hyper-arid region had lower activity levels, consistent with their lower rate of mass loss during starvation, but this came at the expense of decreased response to prey and lower growth rate when food became available again. Each strategy holds its advantages for coping with long starvation periods, and we cannot say decisively which strategy is better. Results from both regions were consistent with the predictions of the growth compensation phenomenon: antlions that were fed less frequently pre-starvation grew at faster rates when food supply was renewed. Our study demonstrates that individuals originating from different environments adopt different strategies in order to endure starvation, exemplifying antlions’ ability to compensate for mass lost during starvation.

Microorganisms in desert rocks: the edge of life on Earth.

This article reviews current knowledge on microbial communities inhabiting endolithic habitats in the arid and hyper-arid regions of our planet. In these extremely dry environments, the most common survival strategy is to colonize the interiors of rocks. This habitat provides thermal buffering, physical stability, and protection against incident UV radiation, excessive photosynthetically active radiation, and freeze-thaw events. Above all, through water retention in the rocks' network of pores and fissures, moisture is made available. Some authors have argued that dry environments pose the most extreme set of conditions faced by microorganisms. Microbial cells need to withstand the biochemical stresses created by the lack of water, along with temperature fluctuations and/or high salinity. In this review, we also address the variety of ways in which microorganisms deal with the lack of moisture in hyper-arid environments and point out the diversity of microorganisms that are able to cope with only the scarcest presence of water. Finally, we discuss the important clues to the history of life on Earth, and perhaps other places in our solar system, that have emerged from the study of extreme microbial ecosystems.

Zebra stripes in the Atacama Desert: Fossil evidence of overland flow

Some hillslopes in the hyperarid region of the Atacama Desert in northern Chile have surface clasts organized into distinct, contour-parallel bands separated by bare soil. We call the bands “zebra stripes” due to the contrast between the darkly varnished clasts and the light-colored, salt-rich soil. Gravel that comprises the zebra stripes is sorted such that the coarsest clasts are at the downslope front and fine progressively upslope. How and when the zebra stripes formed are perplexing questions, particularly in a region experiencing prolonged hyperaridity. Using GoogleEarth, satellite imagery, and field observations, we report the first quantitative and qualitative observations of zebra stripes in order to test hypotheses of the mechanisms and timing of their formation. We consider soil shrink-swell, seismic shaking, and overland flow as possible formation mechanisms, and find that overland flow is the most likely. Based on cosmogenic 10Be concentrations in surface clasts, salt deposition rates from the atmosphere, and content in the soils, we propose that the salt-rich soils began accumulating ~106y ago and the zebra stripes formed 103–104y at the latest. The zebra stripe pattern has been preserved due to the self-stabilization of the clasts within the stripes and the continued absence of life (which would disturb the surface, as seen at a wetter site to the south). We conclude that the occurrence of zebra stripes is diagnostic of a set of distinct characteristics of local and/or regional precipitation, soil, hillslope form, and bedrock type.

The Miniaturized Raman System and Detection of Traces of Life in Halite from the Atacama Desert: Some Considerations for the Search for Life Signatures on Mars

Raman spectroscopy is being adopted as a nondestructive instrumentation for the robotic exploration of Mars to search for traces of life in the geological record. Here, miniaturized Raman spectrometers of two different types equipped with 532 and 785 nm lasers for excitation, respectively, were compared for the detection of microbial biomarkers in natural halite from the hyperarid region of the Atacama Desert. Measurements were performed directly on the rock as well as on the homogenized, powdered samples prepared from this material-the effects of this sample preparation and the excitation wavelength employed in the analysis are compared and discussed. From these results, 532 nm excitation was found to be superior for the analysis of powdered specimens due to its high sensitivity toward carotenoids and hence a higher capability for their detection at relatively low concentration in bulk powdered specimens. For the same reason, this wavelength was a better choice for the detection of carotenoids in direct measurements made on the rock samples. The 785 nm excitation wavelength, in contrast, proved to be more sensitive toward the detection of scytonemin.

Modern pollen-vegetation-climate data set based on surface and rodent midden samples from the Atacama Desert (Chile) and its potential application to Late Quaternary reconstructions

Although the Atacama is the oldest and most continuous dry desert on Earth, organic matter (OM) is ubiquitous in its surface sediments. Today, vegetation growth is restricted to the Coastal Cordillera and the Andean foothills, which are predominantly supplied by fog or rainfall. The sources of OM in topsoils of hyperarid regions and deep sediments remain an open question; therefore, we hypothesized that desert plants exhibit specific n-alkane compositions that can be traced in adjacent topsoils and assessed possible OM sources and formation processes in hyperarid regions and soil depths of desert. We determined the n-alkane signatures of plants (n = 28), of soil OM in their vicinity, of hyperarid surface sediments (n = 82), and of four depth profiles (up to 200 cm).We found that n-alkane distributions in fog-fed plants were dominated in order by nC31, nC29, nC33, and nC27 alkanes, while rain-fed plants were dominated by nC29 and nC31 alkanes. When the ratio of nC27+nC33/nC29+nC31 was applied as a “fog-to-rain n-alkane ratio”, the data in surface soils and sediments below 1200 m a.s.l. (in the west of the desert) indicated fog-influenced formation of organics, while all soils and sediments formed higher than 1200 m a.s.l. (in the center and east of the desert) archived n-alkanes from plants fed by rain. Surprisingly, 75–98% of the desert’s OM was found in deep sediments, even under recent vegetation cover. Hence, our findings indicate that currently vegetation-free hyperarid regions of the Atacama Desert once varied in size depending on climate change.

Validation of six satellite-retrieved land surface emissivity products over two land cover types in a hyper-arid region

This study compares six satellite-retrieved land surface emissivity (LSE) products over gravel plains and sand dunes of the hyper-arid Namib desert in Namibia and validates them with in-situ measurements performed with the ‘emissivity box method’. The following products are compared: LSE derived by the Land Surface Analysis — Satellite Application Facility (LSA-SAF) for the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard Meteosat Second Generation (MSG), LSE products MOD11A2.C5, MOD11B1.C4.1, and MOD11B1.C5 derived for the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard EOS-Terra, LSE derived with the Temperature Emissivity Separation (TES) algorithm for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard EOS-Terra, and LSE derived with the TES algorithm for EOS-Terra/MODIS data. The LSA-SAF, MOD11A2.C5, and MOD11B1.C5 algorithms directly or indirectly utilize land cover classification and vegetation cover fraction data with the result that for arid regions their LSE are practically identical to the bare ground emissivities assigned to those classes. Over the gravel plains, mean LSA-SAF, ASTER-TES, and MODTES LSE are about 0.950 in the 11μm range, whereas mean MOD11A2.C5 and MOD11B1.C5 are about 1.5% (~1K) higher. The LSA-SAF algorithm misclassifies the sand dunes as ‘open & closed shrubland’, which results in an overestimated mean LSE (0.969). Since MOD11A2.C5 and MOD11B1.C5 utilize a similar classification and similar emissivity library data, their LSE estimates for the sand dunes are also too high (mean of 0.972 and 0.980, respectively). In contrast, the physics-based ASTER-TES and MODTES algorithms estimate mean sand dune LSE as 0.952 and 0.948, respectively. The physics-based MOD11B1.C4.1 algorithm produced noisy LSE estimates with frequent outliers at 5km resolution: spatial averaging yielded mean LSE of 0.950 and 0.954 for the gravel plains and the sand dunes, respectively. Based on a combined analysis of in-situ LSE and TES retrieved LSE, and also accounting for uncertainty in the fraction of dry grass (only gravel plains), for future work it is recommended to use SEVIRI ch10.8 emissivities of 0.941±0.004 for the sand dunes and 0.944±0.015 for the gravel plains, respectively. The results suggest that split window algorithms would benefit significantly from using physically based MODTES LSE.

Groundwater prospect map of Egypt's Qena Valley using data fusion

Groundwater is a precious resource of limited extent in arid and hyper-arid regions. Over the last few years, the demand for water supply has increased because of increasing population, urbanisation and agricultural activities. This is particularly true in developing countries like Egypt. In this article, an integrated approach of remote sensing (RS) and geographic information systems (GIS) methodologies was used to delineate groundwater potential zones. The selected location is Qena Valley (Wadi Qena) in the Eastern Desert of Egypt. Landsat enhanced thematic mapper and Shuttle Radar Topography Mission data were employed to prepare a groundwater prospection map. This was done by integrating slope, drainage, geology–geomorphology and lineament density maps through GIS techniques. These thematic maps were integrated after assigning weight factors to identify features in each case depending on infiltration properties. This resulted in classifying the region into six categories of groundwater potentiality from excellent to very low. The alluvial and flood plains consisting of thick sand and gravel strata were proven to be the most favourable zones for groundwater exploration. Field information and existing geophysical data were employed to validate the groundwater potential map. The overall results demonstrate that RS and GIS techniques provide powerful tools for better assessing, planning and monitoring of water resources in arid regions.

Vegetation analysis of Wadi Al-Jufair, a hyper-arid region in Najd, Saudi Arabia

Wadi Al-Jufair, a tributary of Wadi Nisah, is one of the important wadis of Najd region (Saudi Arabia) sheltering a rich diversity of higher plants. The study area is extended into approximately 15km2 encompassing the commonest geomorphological features encountered in desert wadis. The wadi supports several rare plants, including Maerua crassifolia Forssk., a regionally endangered tree, and Acacia oerfota (Forssk.) Schweinf., a rare shrub with restricted distribution. The present study aims to analyze the vegetation of wadi Al-Jufair and propose its designation as an important plant reserve. The vegetation type is fundamentally of chamaephytic nature with some phanerophytes, and distinguished into associations where the dominant perennial species give the permanent character of plant cover in each habitat. Four vegetation groups were identified with the application of TWINSPAN, DCA and CCA programs and named after the characteristic species as follows: Lycium shawii; A. oerfota; Acacia raddiana–Rhazya stricta and Artemisia monosperma. These plant associations demonstrate significant variation in soil texture, moisture, organic matter, pH, EC, and minerals of Wadi Al-Jufair.

Simulation and Evaluation of Ecohydrological Effect of Water Transfers at Alagan in Lower Tarim River

The riparian vegetation is highly dependent on the groundwater which is recharged by the river in arid regions. Water is the most important limiting factor for riparian vegetation in arid regions. From 1970s to 2000, the lower Tarim River almost dried up and the groundwater table fell down obviously. The riparian vegetation degraded seriously due to the low groundwater table. From 2000 to 2006, water transfers were implemented in the lower Tarim River to restore the ecological environment. Although the observation of groundwater and vegetation was carried out along lower Tarim River, the dynamics of the groundwater and vegetation along the cross section of the river were unknown. Ecohydrological evolution model on Riparian Vegetation in hyper-arid regions (ERV model) is a distributed ecohydrological model and has been validated at Yingsu in lower Tarim River. In this paper, the ERV model is applied to analyze the ecohydrological effect of water transfers at Alagan in lower Tarim River. At the same time, the ERV model is further validated. The simulation result is validated by observed groundwater table and vegetation coverage computed from remote sensing data. The result shows that the average groundwater table at Alagan increased by 4.74m from 2000 to 2006 and the average groundwater depth reached 6.36m. The average vegetation coverage increased from 0.130 to 0.194. In order to recover the green corridor, the further water transfers are required. The results are helpful for the ecohydrological research and water resources management in lower Tarim River.

Ecological characteristics of Alhagi sparsifolia Shap. seedling roots under different irrigation treatments

An trench profile method was used to study seasonal variation of root ecological characteristics of Alhagi sparsifolia Shap. seedlings under different irrigation treatments. The results indicated the following: (1) Root morphology: under excellent soil moisture conditions, A. sparsifolia seedlings developed many horizontal roots and root sprouts to compete for light; but under poor soil moisture, the vertical root system expanded its resource space into deeper soil. Plasticity of root morphology is an important strategy to capture water and adapt to the hyperarid environment. (2) Root/shoot ratio: root/shoot ratio increased with declining soil moisture, and this trend was more obvious later in the growing season. Increase of root/shoot ratio is a strategy for adapting to drought. (3) Growth of root system: The seedlings prefer to develop roots in shallower surface layers with less water availability. The growth depth and vertical growth rate of roots increased with decreased soil moisture. (4) Accumulation of root biomass: biomass and surface area of the root system decreased with increased soil depth, with the roots distributed in an ‘inverted pyramid’ in vertical section view. The formation of root biomass conformed to a logistic ‘slow-quick-slow’ growth curve, and total biomass decreased with intensity of soil drought. The findings will provide data useful for effective restoration of A. sparsifolia and better utilization of water resources in hyperarid regions.

Spatial distribution of Tephrocactus aoracanthus (Lem.) Lem. in relation to shrubs in the hyperarid regions of west‐central Argentina

AbstractThe spatial intraspecific and interspecific distribution of Tephrocactus aoracanthus (Lem.) Lem. was studied using univariate and bivariate point pattern analysis, at landscape scale in four different physiographic units and at microscale in terms of the shrubs found in those units. The influence of shrubs on photosynthetically active radiation and on soil temperature under their canopies was analysed. Results show a high environmental variability in light and temperature under shrubs that generally has no influence on the distribution of T. aoracanthus. Apparently, this cactus has great ability to adapt to different conditions of both photosynthetically active radiation and temperature. However, intraspecific distribution was highly clustered in all physiographic units, independently of bushes. Possibly, the mode of seed dispersal and the rooting of cladodes at small scale are the main processes that determine the strong intraspecific clustering of T. aoracanthus.

The autecological characteristics of Desmostachya bipinnata in hyper-arid regions

This study aimed to investigate the main autecological characteristics of Desmostachya bipinnata L. (Poaceae) in a hyper-arid region. The study was carried out on Sistan plain, south-eastern Iran. The habitats of D. bipinnata were identified and then the climatic and edaphic characteristics of habitats were determined. Phenological stages, reproduction, root system, and nutritive and preference values of D. bipinnata were also studied. One single habitat of D. bipinnata was identified on Sistan plain. Average annual rainfall and temperature of the habitat were 60 mm and 21.8 °C, respectively. Loamy and loamy sand soils of the habitat had EC and pH values of 10-60 DS/m and 8.03-8.31, respectively. Secondary roots of D. bipinnata penetrated up to 2 m depth in soil. Mean canopy cover was 21.3% in the habitat. Vegetative growth started in the middle of February followed by flowering in May and seed ripening in July. Crude protein content of leaves and stems was 7.56% and 6.71% during vegetative growth, respectively. For both sheep and goats, D. bipinnata had a similar preference value of 25%. This species, with high resistance to unfavourable conditions, can be used for rehabilitation of desertified rangeland in hyper-arid regions.

Prediction of drought in dry lands through feedforward artificial neural network abilities

Drought is one of the most important natural hazards in Iran. It is especially more prevalent in arid and hyper arid regions where there are serious limitations in regard to providing sufficient water resources. On the other hand, drought modeling and particularly its prediction can play important role in water resources management under conditions of lack of sufficient water resources. Therefore, in this study, drought prediction in a hyper arid location of Iran (Ardakan region) has been surveyed based on the abilities of artificial neural. Standardized Precipitation Index (SPI) in different time scales (3, 6, 9, 12, and 24 monthly time series) computed based on the data gathered from four rain gauge stations. After evaluation and testing of different artificial neural networks (ANN) structures, gradient descent back propagation (traingd) network showed higher abilities than others. Then, the predictions of SPI time series with different monthly lag times (1:12 months) were tested. Generally, drought prediction by ANNs in the Ardakan region has shown considerable results with the correlation coefficient (R) more than 0.79 and in the most cases and it rises more than 0.90, which indicates the ANN’s ability of drought prediction.

Ecohydrological evolution model on riparian vegetation in hyperarid regions and its validation in the lower reach of Tarim River

AbstractThe evolution of the ecohydrological system driven by external climatic forcing and internal feedbacks between vegetation and hydrology, which is more remarkable in arid and semiarid regions, has attracted substantial research attention in recent years. To examine critically the state‐of‐the‐art assumptions and dynamic equations used in the evolution study of an ecohydrological system, the rule of proceeding from simplicity to complexity should be followed. The riparian vegetation ecohydrological system in hyperarid regions (e.g. the lower Tarim River) can serve as a starting point given its simplicity, which has been seldom examined before in terms of system evolution. Further, the water transfer practice from 2000 to 2006 in the lower Tarim River serves as a valuable prototype experiment for model validation. This is because the remarkable changes in groundwater and vegetation in the area have taken place within a shorter period and thus can be easily observed. In the present study, the ecohydrological evolution model on riparian vegetation (ERV model) in hyperarid regions was proposed by coupling groundwater movement and vegetation dynamics. In the ERV model, the groundwater table serves as a critical feedback variable that determines the vegetation dynamics (colonization and mortality) and is determined by vegetation transpiration other than groundwater movement. The monitored groundwater table by wells and satellite‐observed vegetation coverage from the Moderate Resolution Imaging Spectroradiometer are used for model validation. The simulation results show the good performance of the ERV model with uncalibrated parameters. It was also calibrated manually using a multiobjective method, and the fine‐tuned parameters are close to the uncalibrated ones, indicating the robustness of the model. The analysis shows further that the increased evapotranspiration is substantially due to the water transfer and thus the vegetation growth, which implies the importance of ecohydrological coupling for long‐term hydrological modelling. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Climatological characteristics in the extreme hyper-arid region of Pampas de La Joya, Peru. Astrobiological approach in four years of observation: 2004–2008

AbstractThis study reports the environmental conditions of temperature, moisture and radiation for four years (May 2004 to July 2008) in the area known as Pampas de La Joya in southern Peru, which recently has been considered as a new Mars analogue. The period of evaluation includes the El Niño Southern Oscillation (ENSO) during the months of September 2006 to March 2007, which, despite not having catastrophic effects like its predecessor on 1997–1998, showed an interesting increase in humidity. Our data describe the extreme conditions present in the region and their relationship with the presence of potential habitats that could allow for the survival of micro-organisms. The average environmental temperature was 18.9°C, with a maximum of 35.9°C and a minimum of −4.5°C. The annual average incident solar radiation was 508 W m−2, with high near 1060 W m−2 at noon during the driest period between September and March. The average relative humidity (RH) was 29.5, 20.1 and 20.4% for air, soil and rock, respectively. The RH had higher values at night due to fog during the months of June and August, and during the early morning between December and March. During the months of ENSO event there were four episodes of precipitation (1.1, 1.5, 2.0 and 0.9 mm), of which three increased soil and rock moisture on an average more than 45% and persisted for over 15 days after precipitation, while the atmospheric environment had no significant variations. Finally, quartz rocks and evaporite minerals colonized with micro-organisms were found as the only micro-habitats, in this region, capable of supporting life in this extreme environment.

Vegetation analysis of Wadi Al-Jufair, a hyper-arid region in Najd, Saudi Arabia

Wadi Al-Jufair, a tributary of Wadi Nisah, is one of the important wadis of Najd region (Saudi Arabia) sheltering a rich diversity of higher plants. The study area is extended into approximately 15 km 2 encompassing the commonest geomorphological features encountered in desert wadis. The wadi supports several rare plants, including Maerua crassifolia Forssk., a regionally endangered tree, and Acacia oerfota (Forssk.) Schweinf., a rare shrub with restricted distribution. The present study aims to analyze the vegetation of wadi Al-Jufair and to propose its designation as an important plant reserve. The vegetation type is fundamentally of chamaephytic nature with some phanerophytes, and distinguished into associations where the dominant perennial species give the permanent character of plant cover in each habitat. Four vegetation groups were identified after the application of TWINSPAN, DCA and CCA programs and named after the characteristic species as follows: Lycium shawii; Acacia oerfota; Acacia raddiana – Rhazya stricta and Artemisia monosperma. These plant associations and speciation of Wadi Jufair demonstrate significant variation in soil texture, moisture, organic matter, pH, EC, and minerals.