A temporal analysis of the consequences of the drought regime on the water footprint of agriculture in the Guadalupe Valley, Mexico

Changes in water availability have a substantial impact on the sustainability and maintenance of agriculture, with water footprint (WF) being a robust methodology to assess these transformations. The Guadalupe Valley is one of the places with the highest agricultural production in Mexico. Despite its semi-arid climatic conditions, it provides high-quality crops that are well-positioned in the world. The historical trend of rainfall and temperatures between 1987 and 2017 was analyzed to identify climatic patterns in the territory. Through the calculations of the water footprint of Grapevine and Olive crops, the sensitivity of the crops to recurrent water deficit and their adaptation in their yields to drought episodes was identified. The reduction in precipitation and occurrence of extreme temperatures have contributed significantly towards augmenting crop evapotranspiration and, consequently, intensifying crop irrigation demands. As a result, there has been an apparent increase in the consumption of WFagricultural since 2007. Thus, the period of highest WFagricultural consumption was 2014 (Extremely dry), as opposed to 2011 (Very wet). In particular, the lowest WFgreen consumptions were observed in extremely dry years, that is, > 20% of the WFagricultural intensifying drought events. Therefore, these periods were compensated with higher uses of WFblue and WFgray, which are inversely correlated with precipitation, where vine crops consume 73% more WFagricultural compared to olive plantations, showing greater interannual variability. These results contribute to analyzing the temporal evolution of water consumption for agriculture, providing a basis for rational water use strategies.

Multi-temporal Landsat imagery and MSAVI index for monitoring rangeland degradation in arid ecosystem, case study of Biskra (southeast Algeria)

The Algerian Saharan rangelands are an arid ecosystem characterized by limited soil, water, and vegetation resources, which make it very susceptible to degradation. This research focuses on the diachronic assessment and multi-temporal mapping of the degradation of steppe vegetation in the south of Biskra during the period 1987-2019, using remote sensing data (MSAVI index), for extracting spatiotemporal data to monitor the rangeland vegetation dynamics. We examined demographic evolution, number of livestock, and land use from quantitative data. The results show that during this period, the landscape of the region changed considerably. The area of rangelands decreased from 19,939 ha (1987) to 3605 ha (2019), where 58% of the pre-existing vegetation was transformed into bare soil. This study confirmed that the rangeland vegetation health is closely related to climate, and its degradation is mainly due to the recurrence, duration, severity, and magnitude of drought events. Manmade activities were also a determinant factor of long-term degradation of the rangeland, such as the expansion of new land development areas that increased from 3754 ha (1987) to 24,410 ha (2019). This trend was found throughout the region, including predominantly pastoral regions such as Oumache and El Haouch, leading to overgrazing with a loss of about 2% of vegetation cover. All these factors have led to a severe and continuous degradation of pastoral resources in a vulnerable environment. The preservation of these limited resources requires appropriate management of the ecosystem and a rational exploitation of its vegetation, soil, and water resources.

Investigation of the relationship of groundwater quality and irrigation: the case of Mardin Kiziltepe Plain (Mesopotamia) in Turkey

Underground water resources are one of the most valuable vital resources for mankind. Groundwater is used as drinking water and for agricultural irrigation. However, in recent years, it has been exposed to dangerous pollution, mainly due to man-made reasons. The study area is located in the Upper Mesopotamian region, where dry agriculture has been practiced since ancient times, which has semi-arid characteristics and where important civilizations lived. In this direction, the changes in groundwater quality were investigated with seasonal, annual samples taken from selected wells in Mardin Kiziltepe Plain in Upper Mesopotamia region and representing the plain in general and were subjected to water quality classifications. Statistical analyses were carried out on EC and NO3- parameters, which are important in determining the quality of groundwater. The results obtained were interpreted, evaluated in terms of drinking and agricultural uses, and it was observed that there were no non-standard values. In addition, the study area will be opened for irrigation in the near future within the framework of GAP, the largest integrated irrigation project in Turkey. This study, which is the first scientific research to be carried out before intensive irrigation, will be the first memory that will provide a very important data set for the region and will be recorded. In addition, the results of the study will be the basis for the comparison of the research to be carried out after the transition to irrigated agriculture depending on the GAP and the pre-irrigation data.

Water footprint of small-scale dairy farms in the central coast of Peru

Worldwide, dairy sector consumes 19% of the water in the livestock sector. However, in Latin America, the amount of water used in this sector is unknown, especially in arid zones. On the other hand, water footprint (WF) is a methodology to estimate the use of water to produce a product. The aim of this work was to estimate the WF of dairy production in the arid zone of the Peruvian central coast. Data from five dairy farms were used. The WF was calculated in its three dimensions: green water, blue water and grey water. In addition, the WF was measured for categories: feed, drinking and service. To measure the WF of feed production, the CROPWAT software was used, whilst the NRC (2001) equations were used to estimate the drinking water. The reference unit was cubic metres per kilogram of fat and protein corrected milk (FPCM). In average, 99% of the WF comes from feed production, followed by drinking water (0.4%). From the three dimensions of the WF, green water is responsible of 60% of the WF, followed by the blue water (30%). Imported water represented 63% of the WF. In general, WF of dairy production in these systems was 0.66 m³/kg FPCM. In conclusion, feed production, as the main source of WF from which most is imported, shows the possibility of reducing the WF of these systems by prioritizing and optimizing water consumption by crops using local resources with lower water requirements.

The nuanced nature of mesic refugia in arid landscapes: a tale of two peas

BACKGROUND AND AIMS

Understanding how genetic diversity is distributed and maintained within species is a central tenet of evolutionary and conservation biology, yet is understudied in arid regions of the globe. In temperate, glaciated environments, high genetic diversity in plant species is frequently found in refugial areas, which are often associated with southern non-glaciated landscapes. In arid, unglaciated environments, landscape features providing mesic conditions are likely to be refugia, although our understanding needs more refinement in these biomes. We test whether refugia and nuclear diversity hotspots occur in high-elevation, topographically complex areas for co-distributed shrubs (Petalostylis labicheoides and Indigofera monophylla; Fabaceae) in the ancient, arid Pilbara bioregion of north-western Australia.

METHODS

We conducted extensive sampling of the Pilbara (>1400 individuals from 62 widespread populations) to detect patterns in nuclear diversity and structure based on 13-16 microsatellite loci. Evidence of historical refugia was investigated based on patterns of diversity in three non-coding chloroplast (cp) sequence regions for approx. 240 individuals per species. Haplotype relationships were defined with median-joining networks and maximum likelihood phylogenetic trees.

KEY RESULTS

We found cpDNA evidence for a high-elevation refugium in P. labicheoides but not for I. monophylla that instead exhibited extraordinary haplotype diversity and evidence for persistence across a widespread area. Nuclear diversity hotspots occurred in, but were not exclusive to, high-elevation locations and extended to adjacent, low-elevation riparian areas in both species.

CONCLUSIONS

Phylogeographic refugia in arid environments may occur in high-elevation areas for some species but not all, and may be influenced by species-specific traits: a mesic montane refugium in P. labicheoides could be related to its preference for growth in water-gaining areas, while a lack of such evidence in I. monophylla could be related to maintenance of cpDNA diversity in a large soil seed bank and dynamic evolutionary history. Mesic environments created by the intersection of topographically complex landscapes with riparian zones can be contemporary reservoirs of genetic diversity in arid landscapes.

Patterns of organic matter accumulation in dryland river corridors of the southwestern United States

We use Google Earth imagery, drone imagery, and ground-based field measurements to assess the abundance, spatial distribution, and size of accumulations of organic matter in perennial, intermittent, and ephemeral channels in drylands of the southwestern United States. We refer to these accumulations as organic matter jams (OMJs). We examine correlations between OMJ characteristics and indicators of spatial heterogeneity within river corridors. We hypothesize that OMJs occur primarily in association with obstacles such as living woody vegetation and that spatially heterogeneous river corridors have greater numbers of OMJs per surface area of river corridor. Using data from 19 river reaches across four areas in Arizona and Utah, we find that OMJs are preferentially associated with bars in the active channel and with living woody vegetation in the channel and floodplain. We also find that whether greater spatial heterogeneity corresponds to greater spatial density of OMJs can be influenced by downstream distance from major sources of large wood and organic matter and whether the river corridor is supply- or transport-limited with respect to organic matter. Consequently, the strongest influence on OMJ location and abundance can vary between individual reaches of a river corridor and between watersheds. The abundance and size of OMJs in river corridors of sparsely vegetated drylands fall within the ranges of values published for perennial river corridors in wetter climates. We suggest that management of dryland river corridors explicitly include protecting and restoring organic matter accumulations in these environments.

Transport and migration of plutonium in different soil types and rainfall regimes

Leaching and transport of contaminants is a complex interacting system affected by a suite of environmental factors. This study demonstrates the potential significance of weather events and moisture movement when interpreting plutonium (Pu) migration and advective transport in the soil matrix. Using a column transport experiment, two soil types, a sandy soil and clay-rich soil, were spiked with ²³⁸Pu as a tracer to observe the effect of simulated tropical and arid rainfall events on Pu mobility. Partition coefficients (Kd) were determined over a period of weeks and under varying rainfall rates to establish the impact of changing weather events on Pu mobility. The variability of these temporal Kds covers six orders of magnitude over a relatively brief time period. This demonstrates the necessity for non-static Kds to accurately describe Pu transport in these systems. The Pu Kds determined by these column transport experiments fall within the bounds of anticipated values (approximately 80-300,000 mL g^-1) from immobile (magnitude 10⁶ mL g^-1) to moderately mobile (magnitude 10¹ mL g^-1). The overall transport rate, shown by a decrease in calculated Kd, increases in environments where rainfall is more episodic, such as in arid regions as opposed to the consistently abundant rainfall in tropical regions. In contrast to the ²³⁸Pu spike, ^239+240Pu resulting from contamination from nuclear tests in the sandy soil (aged for >30 years) showed higher mobility; we hypothesise that the ageing of the contamination, in particular Pu-bearing particles, accounts for this significant increase in Pu mobility. Low intensity, high frequency events in tropical sandy soil systems containing Pu particle contamination have the potential to mobilise Pu (>10⁵ decrease in calculated Kd) over shorter periods of weeks, and not years as previously assumed. This increased mobility, when applied to radioecological models using Kd as a site-specific parameter, shows that there is likely to be a continued impact (risk quotient >1) on non-human biota in tropical sandy soil ecosystems.

A comparative analysis of gaseous phase hydration properties of two lichenized fungi: Niebla tigrina (Follman) Rundel & Bowler from Atacama Desert and Umbilicaria antarctica Frey & I. M. Lamb from Robert Island, Southern Shetlands Archipelago, maritime Antarctica

Gaseous phase hydration properties for thalli of Niebla tigrina from Atacama Desert, and for Umbilicaria antarctica from Isla Robert, maritime Antarctica, were analyzed using ¹H-NMR relaxometry, spectroscopy, and sorption isotherm analysis. The molecular dynamics of residual water was monitored to distinguish the sequential binding very tightly, tightly, and loosely bound water fractions. These two species differ in hydration kinetics faster for Desert N. tigrina [A₁ = 0.51(4); t₁ = 0.51(5) h, t₂ = 15.0(1.9) h; total 0.7 for p/p₀ = 100%], compared to Antarctic U. antarctica [A₁ = 0.082(6), t₁ = 2.4(2) h, t₂ = [26.9(2.7)] h, total 0.6 for p/p₀ = 100%] from humid polar area. The ¹H-NMR measurements distinguish signal from tightly bound water, and two signals from loosely bound water, with different chemical shifts higher for U. antarctica than for N. tigrina. Both lichen species contain different amounts of water-soluble solid fraction. For U. antarctica, the saturation concentration of water soluble solid fraction, c_s = 0.55(9), and the dissolution effect is detected at least up to Δm/m₀ = 0.7, whereas for N. tigrina with the similar saturation concentration, c_s = 053(4), this fraction is detected up to the threshold hydration level equal to ΔM/m₀ = 0.3 only.

Estimating potential evapotranspiration based on self-optimizing nearest neighbor algorithms: a case study in arid-semiarid environments, Northwest of China

Changes in potential evapotranspiration will affect the surface ecology and environment of the land. Accurate and quick estimation of potential evapotranspiration will help to analyze environmental change. In this study, in combination with the canonical correlation analysis (CCA) and k-nearest neighbor algorithm (k-NN), a new method for calculating potential evapotranspiration (CCA-k-NN) based on self-optimizing nearest neighbor algorithm was proposed, in which less meteorological data were used for estimation. By analyzing the basic principles of CCA and k-NN and according to the requirement of estimating ET₀, the CCA-k-NN method was constructed, and its basic principles and key steps were described. In this method, CCA algorithm was used to find the most relevant meteorological data for potential evapotranspiration, and the dimensionality of meteorological data for subsequent estimation of ET₀ was reduced. Then, k-NN algorithm was used to estimate ET₀. The Northwest of China was chosen as the research area to evaluate the applicability of this method. The 148 data stations in the region were divided into training datasets, testing datasets, and validation datasets. ET₀ was estimated on three datasets using the proposed method, and the estimation accuracy of the CCA-k-NN method was evaluated with FAO-56 Penman-Monteith as a reference. The results show that the CCA-k-NN method maintains a high correlation with FAO-56 Penman-Monteith (correlation coefficient is greater than 0.9) and has a good estimation accuracy. RMSE and MAE are both less than 1 mm day^-1, and the overall performance of NSCE is greater than 0.5, all of which reach the level of "applicable" and above. At the same time, the CCA-k-NN method has low time complexity O(n). Comparison of the results of the CCA-k-NN method with those of other empirical models showed that the CCA-k-NN method is more accurate and can be employed successfully in estimating ET₀.

First data of statistic and ecological behavior of orthoptera insects in arid region (Southern West of Algeria)

The activity developed in vast areas of northwest africa causes serious invasions of different species of orthoptera insect which poses a great danger to agriculture and thus to nutrition of peoples and animals in general. In (Algeria), FAO considers the regions of naama, tindouf, adrar and bechar in Algeria as the theater of signaling of swarms and intervention. In this article, we want to shed light on the peculiarities of this insect (orthoptera), its statistics, its species and the families it belongs to in the arid region called naama (southwestern Algeria). The study of orthoptera in the arid region of naama (southern west of Algeria) conducted at three stations (Mecheria, Ben ammar) and the wetland of (Ain ben khelil) during the period from august 2015 until august 2017 allowed to identify nineteen (19) species divided into two sub-orders ensifera and caelifera. They are divided into five families (Tettigonidae, Gryllidae Pamphagidae, Acrididae, and Pyrgomorphidae). Acrididae family is the largest with five species. Oedipodinae subfamily is the most numerous genera and species it includes four (4) different types genders and seven species (7). The highest diversity index of the shannon-weaver is obtained at the wetland ain ben khelil is 2.12 bits, followed by the station of ben ammar with 2.06 bits and station of mecheria remains in third with 1.89 bit values of fairness are close to one corresponding to populations in balance entered them. The determination of species, genders and families of this population is based on several morphological criteria such as the shape of the pronotum, and the color of membranous wings and the shape of the hind legs.

Natural fluorapatite dissolution kinetics and Mn2+ and Cr3+ metal removal from sulfate fluids at 35 °C

In light of the consequences of global warming and population growth, access to safe drinking water becomes an ever greater challenge, in particular in low to middle income countries in arid regions. Moreover, mining which may cause acid mine drainage and heavy metal contamination puts further pressure on management of limited water resources. Hence, the development of cost effective water treatment methods is critical. Here, using batch reactor experiments we investigate the kinetics and mechanisms behind divalent Mn and trivalent Cr removal from sulfate fluids using natural fluorapatite at 35 °C. The results show that the fluorapatite dissolution rate depends on fluid pH, and that dissolution is the dominant mechanism in fluids with pH below 4. Apatite can thus serve as remediation to neutralize acidic fluids. Fluid pH of 4-6 triggers a dissolution-precipitation mechanism, in some cases following upon a dissolution-only period, with the formation of a metal phosphate. In these experiments, Cr removal is two to ten times faster than Mn removal given similar solution pH. The results demonstrate that natural apatite represents a promising, cost effective material for use in passive remediation of mining-induced contamination of soils and groundwater in arid regions.

Predictive modelling of the distribution of Clematis sect. Fruticella s. str. under climate change reveals a range expansion during the Last Glacial Maximum

Background

The knowledge of distributional dynamics of living organisms is a prerequisite for protecting biodiversity and for the sustainable use of biotic resources. Clematis sect. Fruticella s. str. is a small group of shrubby, yellow-flowered species distributed mainly in arid and semi-arid areas of China. Plants in this section are both horticulturally and ecologically important.

Methods

Using past, present, and future environmental variables and data with Maximum Entropy (Maxent) modeling, we evaluated the importance of the environmental variables on the section's estimated distributions, thus simulating its distributional dynamics over time. The contractions and expansions of suitable habitat between the past and future scenarios and the present were then compared.

Results and Discussion

The models revealed that the areas with high and moderate suitability currently encompass about 725,110 km². The distribution centroid location varies between points in Ningxia and Inner Mongolia during the different scenarios. Elevation, Mean UV-B of Lowest Month, Precipitation of Coldest Quarter, and Mean Temperature of Driest Quarter were major factors determining the section's distribution. Our modeling indicated that Clematis sect. Fruticella underwent a significant range contraction during the last interglacial period, and then expanded during the last glacial maximum (LGM) to amounts like those of the present. Cold, dry, and relatively stable climate, as well as steppe or desert steppe environments may have facilitated range expansion of this cold-adapted, drought-resistant plant taxon during the LGM. Predicted future scenarios show little change in the amounts of suitable habitat for Clematis sect. Fruticella. This study aids understanding of the distributional dynamics of Clematis sect. Fruticella, and the results will help the conservation and sustainable use of these important woody plants in Chinese arid and semiarid areas.

Under the weather: Corticosterone levels in wild nestlings are associated with ambient temperature and wind

Animals time reproductive events to overlap with periods of favorable environmental conditions. However, weather conditions can be unpredictable. Young animals may be particularly susceptible to extreme weather during sensitive developmental periods. Here, we investigated the effects of adverse weather conditions on corticosterone levels (a hormone linked to the avian stress response) and body condition of wild nestling zebra finches (Taeniopygia guttata). We sought to tease apart the direct versus indirect (i.e. parental) effects of weather on nestling physiology and condition by increasing parental work load with a clutch manipulation experiment. We found that high temperatures were associated with lower levels of restraint-induced corticosterone and high wind speeds were associated with higher levels of baseline corticosterone. We found no associations between weather and nestling body condition. However, clutch manipulation did affect body condition, with nestlings from experimentally enlarged clutches in worse condition compared to nestlings from experimentally reduced clutches. Our findings suggest that weather can directly affect wild nestlings via changes in corticosterone levels. Further research is needed to understand how changes in corticosterone levels affect phenotype and survival in wild nestlings. Understanding how developing animals respond to changes in environmental predictability and extreme weather is vital for understanding the potential for rapid adaptation in the face of changing climatic conditions.

Genomes and secretomes of Ascomycota fungi reveal diverse functions in plant biomass decomposition and pathogenesis

BACKGROUND

The dominant fungi in arid grasslands and shrublands are members of the Ascomycota phylum. Ascomycota fungi are important drivers in carbon and nitrogen cycling in arid ecosystems. These fungi play roles in soil stability, plant biomass decomposition, and endophytic interactions with plants. They may also form symbiotic associations with biocrust components or be latent saprotrophs or pathogens that live on plant tissues. However, their functional potential in arid soils, where organic matter, nutrients and water are very low or only periodically available, is poorly characterized.

RESULTS

Five Ascomycota fungi were isolated from different soil crust microhabitats and rhizosphere soils around the native bunchgrass Pleuraphis jamesii in an arid grassland near Moab, UT, USA. Putative genera were Coniochaeta, isolated from lichen biocrust, Embellisia from cyanobacteria biocrust, Chaetomium from below lichen biocrust, Phoma from a moss microhabitat, and Aspergillus from the soil. The fungi were grown in replicate cultures on different carbon sources (chitin, native bunchgrass or pine wood) relevant to plant biomass and soil carbon sources. Secretomes produced by the fungi on each substrate were characterized. Results demonstrate that these fungi likely interact with primary producers (biocrust or plants) by secreting a wide range of proteins that facilitate symbiotic associations. Each of the fungal isolates secreted enzymes that degrade plant biomass, small secreted effector proteins, and proteins involved in either beneficial plant interactions or virulence. Aspergillus and Phoma expressed more plant biomass degrading enzymes when grown in grass- and pine-containing cultures than in chitin. Coniochaeta and Embellisia expressed similar numbers of these enzymes under all conditions, while Chaetomium secreted more of these enzymes in grass-containing cultures.

CONCLUSIONS

This study of Ascomycota genomes and secretomes provides important insights about the lifestyles and the roles that Ascomycota fungi likely play in arid grassland, ecosystems. However, the exact nature of those interactions, whether any or all of the isolates are true endophytes, latent saprotrophs or opportunistic phytopathogens, will be the topic of future studies.

Contributions of climate change to the terrestrial carbon stock of the arid region of China: A multi-dataset analysis

Dryland ecosystems have been threatened in recent decades by rapid climate change. However, the effects of climate change and rising CO₂ levels on the terrestrial carbon stock of the arid region of China remain unclear. In this study, we used three climate reanalysis datasets to drive an arid ecosystem model (AEM), which we used to assess uncertainties in spatial climate datasets. All simulations suggest that the arid region of China acted as a carbon sink (0.20-0.34 Pg C) from 1980 to 2014. However, we found large uncertainties in the spatial pattern of carbon stocks during this period, especially in northern Xinjiang and western Inner Mongolia. These uncertainties are related to changes in precipitation. To reduce the uncertainty of carbon stock assessment results in the arid region of China, efforts should be implemented to improve the reliability of climate data in northern Xinjiang and western Inner Mongolia. Specifically, China's policy makers should pay close attention to climate change and ecosystem health in southwestern Xinjiang. According to our study, this area experienced significant decreases in precipitation and increases in temperature from 1980 to 2014. The severe ecosystem degradation that occurred will very likely continue into the future. In addition, the Climate Forecast System Reanalysis (CFSR) dataset may overestimate ecosystem carbon sinks as this dataset overestimates the increase in precipitation in the arid region of China. Therefore, it is advisable to be cautious when using the CFSR dataset in ecological studies in northern Eurasian dryland areas.

Revision of the ant-eating spider genus Mallinus Simon, 1893 (Araneae, Zodariidae)

The zodariine spider genus Mallinus Simon, 1893 is redescribed and diagnosed. The type species, M.nitidiventris Simon, 1893 from South Africa, was originally described from subadult specimens. Adults of both sexes of M.nitidiventris are described for the first time, based on recently collected material, and the genus is rediagnosed, redescribed, and its relationships discussed. A single aberrant male specimen from Namibia is here described as a morphospecies, as it is presumed to only be superficially related. A second species, M.defectus Strand, 1906 from Tunisia, is considered a ‘species inquirenda’, as the type specimens could not be traced, but this species is in any case unlikely to be congeneric. The genus is one of 10 cases of a monotypic genus in the Zodariidae. Notes are provided on the biology of M.nitidiventris.

Evaluating the use of fire to control shrub encroachment in global drylands: A synthesis based on ecosystem service perspective

With the proliferation of woody plant species in much of the world's grasslands, human has manipulated landscape fire to return their forage provisioning service. Yet other ecosystem services (e.g., carbon sequestration, biodiversity conservation, erosion control) in the post-managed areas compared to those previously available in the shrub-encroached area are largely unknown, including trade-offs between ecosystem services. Using data from previous publications, we quantitatively synthesized the sustainability of fire as shrub management practice, expressed as its efficacy to control shrubs and its capacity to maintain different ecosystem services. A simple indicator (δ), defined as the ratio of an observed ecological attribute between area experiencing shrub management and untreated control, was used to quantify the changes. Our results showed that fire could be an effective strategy to control shrubs and to increase forage provisioning service (δ_{herbaceous biomass} = 1.39). However, there are possible trade-offs with other ecosystem services (e.g., erosion control, nutrient cycling) when a 54% increase in bare soil cover (δ_{bare soil} = 1.54) and ~74% loss of biological soil crusts cover (δ_{biological crust} = 0.26) were found. Because increasing forage provisioning at the cost of other ecosystem services might not be sustainable, management should focus on strategies to minimize such trade-offs, which may include but not limited to rotational grazing, adjustment in stocking rate, or supplementary external inputs (e.g., fertilizer). Unless those measures are employed, there is possible emergence of a novel crash (i.e., vegetation- and resource-poor scabland) resulting from a combination of soil erosion and high vulnerability of burnt landscape to exotic species invasion.

Sorption of benzene and naphthalene on (semi)-arid coastal soil as a function of salinity and temperature

Considerable activities from the oil and natural gas sector have risen some concerns about the pollution of soil and groundwater by petroleum hydrocarbons (PHCs) in (semi)-arid coastal regions. The understanding of the fate and transport of PHCs in these regions is therefore necessary to develop strategies for remediation. To quantify the sorption rates of PHCs in (semi)-arid coastal soil environments, we conducted a series of controlled-laboratory batch experiments under variable temperature and salinity conditions. The soil samples were collected from the eastern coast of Qatar which is near the two largest off-shore oil and natural gas fields of the country (North Gas and Al-Shaheen Oil Fields), and the volatile benzene and naphthalene were used as PHCs. The characterization of soil samples showed sand classification with the texture class of sabkha and saline beach sandy soils with calcite as potential dominant mineral. The concentrations of dissolved chloride and sodium were found to be high (> 400 mg L^-1) with a chloride-to‑sodium ratio of about 1.7. The results of sorption experiments showed that the rates of naphthalene sorption were more than for benzene, where the initial aqueous concentrations of benzene and naphthalene were reduced at equilibrium due to sorption by about 14-25% and 65-79%, respectively. This difference was attributed mainly to the organic carbon-water partitioning coefficient which is higher for naphthalene. The sorption rate experiments showed that sorption was stronger for benzene under higher salinity and lower temperature conditions. The sorption of naphthalene was not affected by the change in salinity but increased by 18% when the temperature decreased from 35 to 5 °C. A sorption kinetic model was also applied to define the sorption behavior of benzene and naphthalene for the coastal soil collected in Qatar and the best fits were achieved with the Langmuir sorption isotherm.

Chronic nitrogen addition induces a cascade of plant community responses with both seasonal and progressive dynamics

Short-lived herbaceous plants provide a useful model to rapidly reveal how multiple generations of plants in natural plant communities of sensitive desert ecosystems will be affected by N deposition. We monitored dynamic responses of community structure, richness, evenness, density and biomass of herbaceous plants to experimental N addition (2:1 NH₄⁺:NO₃^- added at 0, 0.5, 1, 3, 6 and 24gNm^-2a^-1) in three seasons in each of three years in the Gurbantunggut desert, a typical temperate desert of central Asia. We found clear rate-dependent and season-dependent effects of N deposition on each of these variables, in most cases becoming more obvious through time. N addition reduced plant richness, leading to a loss of about half of the species after three generations in the highest N application level. Evenness and density were relatively insensitive to all but the greatest levels of N addition for two generations, but negative effects emerged in the third generation. Biomass, both above and below ground, was non-linearly affected by N deposition. Low and intermediate levels of N deposition often increased biomass, whereas the highest level suppressed biomass. Stimulatory effects of intermediate N addition disappeared in the third generation. All of these responses are strongly interrelated in a cascade of changes. Notably, changes in biomass due to N deposition were mediated by declines in richness and evenness, and other changes in community structure, rather than solely being the direct outcome of release from limitation. The interrelationships between N deposition and the different plant community attributes change not only seasonally, but also progressively change through time. These temporal changes appear to be largely independent of interannual or seasonal climatic conditions.

Urbanization alters small rodent community composition but not abundance

Desert ecosystems are one of the fastest urbanizing areas on the planet. This rapid shift has the potential to alter the abundances and species richness of herbivore and plant communities. Herbivores, for example, are expected to be more abundant within urban desert remnant parks located within cities due to anthropogenic activities that concentrate food resources and reduce native predator populations. Despite this assumption, previous research conducted around Phoenix, AZ, USA has shown that top-down herbivory led to equally reduced plant biomass in both urban and outlying locations. It is unclear if this insignificant difference in herbivory at urban and outlying sites is due to unaltered desert herbivore populations or altered activity levels that counteract abundance differences. Small rodent herbivore/granivore populations were surveyed at four sites inside and four sites outside of the core of Phoenix during fall 2014 and spring 2015 in order to determine whether abundances and richness differ significantly between urban and rural sites. In order to survey species composition and abundance at these sites, 100 Sherman traps and eight larger wire traps that are designed to attract and capture small vertebrates such as mice, rats, and squirrels were set at each site for two consecutive trap nights. Results suggest that the commonly assumed effect of urbanization on herbivore abundances does not apply to small rodent populations in a desert city, as overall small rodent abundances were statistically similar regardless of location. Though a significant difference was not found for species richness, a significant difference between small rodent genus richness at these sites was observed, with altered community composition. The compositional differences likely reflect the altered vegetative community and may impact ecological interactions at these sites.

Dynamics of soil carbon and nitrogen stocks after afforestation in arid and semi-arid regions: A meta-analysis

Arid and semi-arid regions store approximately 27% of global soil organic carbon (SOC), thus playing an important role in the global carbon cycle. Although afforestation is widely used to achieve the goals of landscape protection and ecological restoration in these regions, its effects on the dynamics of SOC and total nitrogen (TN) stocks as well as the related controlling factors are still poorly understood. In this study, a meta-analysis was conducted by compiling results from published studies to evaluate the influences of afforestation on dynamics of SOC and TN stocks in mineral soils (0-30cm) in arid and semi-arid regions, and to examine whether the changes in SOC and TN stocks were influenced by prior land-use, planted tree species and plantation age. The results showed that overall, afforestation significantly increased SOC stock by 131% and TN stock by 88%. Prior land-use was found to be the most important factor that influenced the dynamics of SOC and TN stocks following afforestation. Significantly larger increases in SOC and TN stocks were observed after barren land afforestation in comparison to cropland and grassland afforestation. The accumulations in SOC and TN stocks after afforestation decreased in the following order: broadleaf deciduous forests>coniferous forests>broadleaf evergreen forests. However, significant differences in SOC and TN accumulations were only detected between broadleaf deciduous forests and broadleaf evergreen forests. Plantation age did not affect the dynamics of SOC and TN stocks after afforestation, mainly due to the rapid accumulations in SOC and TN after barren land afforestation. The results indicate that afforestation, especially on barren land with broadleaf deciduous species, provides substantial opportunities for SOC and TN sequestrations in arid and semi-arid regions.

Three-dimensional hydrodynamic modelling study of reverse estuarine circulation: Kuwait Bay

Hydrodynamics and associated environmental processes have always been of major concern to coastal-dependent countries, such as Kuwait. This is due to the environmental impact that accompanies the economic and commercial activities along the coastal areas. In the current study, a three-dimensional numerical model is utilized to unveil the main dynamic and physical properties of Kuwait Bay during the critical season. The model performance over the summer months (June, July and August 2012) is assessed against comprehensive field measurements of water levels, velocity, temperature and salinity data before using the model to describe the circulation as driven by tides, gravitational convection and winds. The results showed that the baroclinic conditions in the Bay are mainly determined by the horizontal salinity gradient and to much less extent temperature gradient. The gradients stretched over the southern coast of the Bay where dense water is found at the inner and enclosed areas, while relatively lighter waters are found near the mouth of the Bay. This gradient imposed a reversed estuarine circulation at the main axis of the Bay, particularly during neap tides when landward flow near the surface and seaward flow near the bed are most evident. The results also revealed that the shallow areas, including Sulaibikhat and Jahra Bays, are well mixed and generally flow in the counter-clockwise direction. Clockwise circulations dominated the northern portion of the Bay, forming a sort of large eddy, while turbulent fields associated with tidal currents were localized near the headlands.

Developing reference criteria for the ecological status of West African rivers

Awareness of sustainable management of water and its biological resources is rising in West Africa, but application of effective tools for biomonitoring and detecting habitats at risk in aquatic ecosystems is limited. In this study, we provide key environmental descriptors to characterize reference sites by applying the following "a priori criteria" (physical and chemical, hydro-morphological, and land use parameters) by exploring their potential to determine suitable reference sites. Using data collected from 44 sites, we identified 37 criteria that reliably identify reference conditions in semi-arid rivers by reflecting the impacts of multiple pressures ranging from low to very high intensity of human uses and impairments. We integrated all these impacts in an overall pressures index, which showed that protected areas can reasonably be considered as credible reference sites as far as they show low overall impact levels from cumulative pressures. We recommend that development of bio-indicator standards should be based on the collection and integration of all the available information, especially quantitative, spatially-explicit data, from benthic macroinvertebrates and fish. Rigorous standardization of bio-indicator protocols will make them more easily applicable for management and conservation of aquatic ecosystem resources in semi-arid zones of Africa.

Facultative CAM photosynthesis (crassulacean acid metabolism) in four species of Calandrinia, ephemeral succulents of arid Australia

Crassulacean acid metabolism (CAM) was demonstrated in four small endemic Australian terrestrial succulents from the genus Calandrinia (Montiaceae) viz. C. creethiae, C. pentavalvis, C. quadrivalvis and C. reticulata. CAM was substantiated by measurements of CO₂ gas-exchange and nocturnal acidification. In all species, the expression of CAM was overwhelmingly facultative in that nocturnal H⁺ accumulation was greatest in droughted plants and zero, or close to zero, in plants that were well-watered, including plants that had been droughted and were subsequently rewatered, i.e. the inducible component was proven to be reversible. Gas-exchange measurements complemented the determinations of acidity. In all species, net CO₂ uptake was restricted to the light in well-watered plants, and cessation of watering was followed by a progressive reduction of CO₂ uptake in the light and a reduction in nocturnal CO₂ efflux. In C. creethiae, C. pentavalvis and C. reticulata net CO₂ assimilation was eventually observed in the dark, whereas in C. quadrivalvis nocturnal CO₂ exchange approached the compensation point but did not transition to net CO₂ gain. Following rewatering, all species returned to their original well-watered CO₂ exchange pattern of net CO₂ uptake restricted solely to the light. In addition to facultative CAM, C. quadrivalvis and C. reticulata exhibited an extremely small constitutive CAM component as demonstrated by the nocturnal accumulation in well-watered plants of small amounts of acidity and by the curved pattern of the nocturnal course of CO₂ efflux. It is suggested that low-level CAM and facultative CAM are more common within the Australian succulent flora, and perhaps the world succulent flora, than has been previously assumed.

Assessment of adaptability of zebu cattle (Bos indicus) breeds in two different climatic conditions: using cytogenetic techniques on genome integrity

The aim of this study was to evaluate the genome integrity so as to assess the adaptability of three breeds of indigenous cattle reared under arid and semi-arid regions of Rajasthan (Bikaner) and Haryana (Karnal) India. The cattle were of homogenous group (same age and sex) of indigenous breeds viz. Sahiwal, Tharparkar and Kankrej. A total of 100 animals were selected for this study from both climatic conditions. The sister chromatid exchanges (SCE's), chromosomal gaps and chromatid breaks were observed in metaphase plates of chromosome preparations obtained from in vitro culture of peripheral blood lymphocytes. The mean number of breaks and gaps in Sahiwal and Tharparkar of semi-arid zone were 8.56 ± 3.16, 6.4 ± 3.39 and 8.72 ± 2.04, 3.52 ± 6.29, respectively. Similarly, the mean number of breaks and gaps in Tharparkar and Kankrej cattle of arid zone were 5.26 ± 1.76, 2.74 ± 1.76 and 5.24 ± 1.84, 2.5 ± 1.26, respectively. The frequency of SCEs in chromosomes was found significantly higher (P < 0.05) in Tharparkar of semi-arid region (4.72 ± 1.55) compared to arid region (2.83 ± 1.01). Similarly, the frequency of SCEs was found to be 4.0 ± 1.41 in the Sahiwal of semi-arid region and 2.69 ± 1.12 in Kankrej of arid zone. Statistical analysis revealed significant differences (P < 0.05) amongst the different zones, i.e. arid and semi-arid, whereas no significant difference (P > 0.05) was observed in the same zone. The analysis of frequency of CAs and SCEs revealed significant effects of environmental conditions on the genome integrity of animals, thereby indicating an association with their adaptability.

Swimming through sand: connectivity of aquatic fauna in deserts

Freshwater ecosystems in arid regions range from highly fragmented to highly connected, and connectivity has been assumed to be a major factor in the persistence of aquatic biota in arid environments. This review sought to synthesize existing research on genetic estimation of population connectivity in desert freshwaters, identify knowledge gaps, and set priorities for future studies of connectivity in these environments. From an extensive literature search, we synthesized the approaches applied, systems studied, and conclusions about connectivity reached in population genetic research concerning desert freshwater connectivity globally. We restrict our scope to obligate aquatic fauna that disperse largely via freshwaters and exclude those with active aerial dispersal abilities. We examined 92 papers, comprising 133 studies, published from 1987 to 2014. Most described studies of fishes and invertebrates in the deserts of Australia and North America. Connectivity declined with increasing scale, but did not differ significantly among arid regions or taxonomic classes. There were significant differences in connectivity patterns between species with different dispersal abilities, and between spring and riverine habitats at local scales. Population connectivity in desert freshwaters is typically most influenced by the ecology of the species concerned and hydrological connectivity. Most studies did not assess predefined models of connectivity, but described gene flow and/or genetic structure. Climate change and anthropogenic impacts worldwide are likely to increase the incidence and impact of habitat fragmentation in already threatened desert freshwaters. To reduce this risk, biodiversity conservation and environmental management must address connectivity, but often the required information does not exist. Researchers can provide this by explicitly considering the effects of hydrology and species' ecology on connectivity, and incorporating these into connectivity models, which are vital for understanding connectivity in desert freshwaters.

Combined effects of climatic gradient and domestic livestock grazing on reptile community structure in a heterogeneous agroecosystem

Grazing plays an important role in shaping ecological communities in human-related ecosystems. Although myriad studies have explored the joint effect of grazing and climate on plant communities, this interactive effect has rarely been studied in animals. We hypothesized that the effect of grazing on the reptile community varies along a climatic gradient in relation to the effect of grazing on habitat characteristics, and that grazing differentially affects reptiles of different biogeographic regions. We tested our hypotheses by collecting data on environmental characteristics and by trapping reptiles in four heterogeneous landscapes experiencing differing grazing intensities and distributed along a sharp climatic gradient. We found that while reptile diversity increased with grazing intensity at the mesic end of the gradient, it decreased with grazing intensity at the arid end. Moreover, the proportion of reptile species of differing biogeographic origins varied with the interactive effect of climate and grazing. The representation of species originating in arid biogeographic zones was highest at the arid end of the climatic gradient, and representation increased with grazing intensity within this area. Regardless of the climatic context, increased grazing pressure results in a reduction in vegetation cover and thus in changes in habitat characteristics. By reducing vegetation cover, grazing increased habitat heterogeneity in the dense mesic sites and decreased habitat heterogeneity in the arid sites. Thus, our results suggest that the same direction of habitat alteration caused by grazing may have opposite effects on biodiversity and community composition in different climatic contexts.

Crucial and novel cancer drivers in a mouse model of triple-negative breast cancer

BACKGROUND

We previously developed a mouse model of breast cancer that mimics human triple-negative breast cancer (TNBC) by inactivating the Retinoblastoma (Rb), Transformation related protein 53 (p53), and Breast cancer 1 (Brca1) pathways in the mammary gland. Despite inactivation of all three tumor suppressors throughout the epithelium, low tumor multiplicity indicated that malignant carcinoma progression requires additional oncogenic stimuli.

MATERIALS AND METHODS

In order to identify collaborating genetic events, we performed integrated analysis of 18 tumors (eight tumors with inactivation of pRbf/Brca1/p53 and ten tumors with inactivation of pRbf/p53) using comparative genomic hybridization and global gene expression. We then conducted flow cytometric analysis, immunostaining, tumorsphere, and cell viability assays.

RESULTS

Copy number aberrations were correlated with the transcript levels of 7.55% of genes spanned by the altered genomic regions. Recurrent genomic losses spanning large regions of chromosomes 4 and 10 included several cell death genes. Among the amplified genes were well-known drivers of tumorigenesis including Wingless-related MMTV integration site 2 (Wnt2), as well as potentially novel driver mutations including the Late cornified envelope (LCE) gene family. These tumors have a stem/luminal progenitor phenotype and active β-catenin signaling. Tumorsphere formation and cell survival are suppressed by Wnt pathway inhibitors.

CONCLUSION

Our novel mouse model mimics human TNBC and provides a platform to triage the pathways that underlie malignant tumor progression.

Microorganisms associated particulate matter: a preliminary study

This study aims to determine the microbiological quality of particulate matter (PM) in an urban area in Jeddah, Saudi Arabia, during December 2012 to April 2013. This was achieved by the determination of airborne bacteria, fungi, and actinobacteria associated PM10 and PM2.5, as well as their relationships with gaseous pollutants, O3, SO2 and NO2, and meteorological factors (T°C, RH% and Ws). High volume samplers with PM10 and PM2.5 selective sizes, and glass fiber filters were used to collect PM10 and PM2.5, respectively. The filters were suspended in buffer phosphate and aliquots were spread plated onto the surfaces of trypticase soy agar, malt extract agar, and starch casein agar media for counting of bacteria, fungi and actinobacteria-associated PM, respectively. PM10 and PM2.5 concentrations averaged 159.9 μg/m(3) and 60 μg/m(3), respectively, with the ratio of PM2.5/PM10 averaged ~0.4. The concentrations of O3, SO2 and NO2 averaged 35.73 μg/m(3), 38.1μg/m(3) and 52.5 μg/m(3), respectively. Fungi and actinobacteria associated PM were found in lower concentrations than bacteria. The sum of microbial loads was higher in PM10 than PM2.5, however a significant correlation (r=0.57, P ≤ 0.05) was found between the sum of microbial loads associated PM10 and PM2.5. Aspergillus fumigatus and Aspergillus niger were the common fungal types associated PM. Temperature significantly correlated with both PM10 (r=0.44), and PM2.5 (r=0.5). Significant negative correlations were found between O3 and PM2.5 (r=-0.47), and between SO2 with PM10 (r=-0.48). Wind speed positively correlated with airborne microorganisms associated PM. The regression model showed that the inverse PM2.5 concentration (1/PM2.5) was a significant determinant of fungal count associated PM. Chemical processes and environmental factors could affect properties of PM and in turn its biological quality.