Search

Quality irrigation water is precious in agriculture under arid conditions. The value addition in agricultural product makes a new commodity outside the traditional frame to achieve higher returns with improved shelf-life and minimizes post-harvest losses. The aim of this study is to evaluate and quantify the improvements possible in water productivity through value addition in date cultivated under arid conditions in Oman. The primary and secondary data were collected through questionnaire surveys from farmers, sellers, factories and ministry extensions. The comparisons were made between the marketing of raw product against those with value-added, which were produced using the same quantity of resources; particularly irrigation water. The productivity was estimated by the ratio of agricultural benefits in kg to the irrigation water use in m3. The net-profit based productivity ratio improvements in Khalas and Fardh dates were 540% and 360% respectively for value-added dates packed with nuts. The lowest productivity ratio was observed in Khalas dates with saffron and other flavors (111%), and Fardh date paste (129%). In Khalas, the best improvement by the value-addition in average water productivity from the base-values of 0.57 kg/m3, or 0.63 OMR/m3 of the raw date were 2.06 kg/m3 or 2.28 OMR/m3 in date with nuts respectively while in Fardh, the same were 1.55 kg/m3 or 1.71 OMR/m3 respectively. The observed potential improvements in equivalent water productivity indicates the benefit of value addition would be vital for achieving agricultural sustainability goals under arid agriculture.

There has been increased focus across the world on enhancing the efficiency of energy consumption in multiple sectors. The overall aim is to find solutions to eliminate problems caused by the expanding demand for energy while ensuring that natural resources are not depleted. This paper presents an optimisation of the parameters of the building envelope of a single-storey residential building in the semi-arid and warm Mediterranean climate zone of the city of Amman, Jordan. The objective was to achieve a reduction in cooling and heating loads while ensuring that the existing levels of thermal comfort can be sustained through the use of mechanical systems for cooling and heating. A typical Jordanian single-storey residential building with dimensions of 187 m2 was chosen to modify its design variables and examine their effect on the overall thermal performance. The process of optimisation was initiated by performing a simulation using DesignBuilder software, followed by a sensitivity analysis of 12 design variables to evaluate their importance for cooling and heating loads. An optimisation using the genetic algorithm was then implemented. The final results indicated that the total energy consumption could be reduced to 293.74 kWh/year (99.79 kWh/year in terms of the cooling and 193.95 kWh/year in terms of the heating), compared with 5225.97 kWh/year for the reference module (separated into 4075.41 kWh/year for the heating and 1150.56 kWh/year for the cooling).

Zinc (Zn) is an essential micronutrient required to enhance crop growth and yield. In the arid - semiarid region, Zn deficiency is expected due to alkaline calcareous soil. Contrarily, Zn toxicity is also becoming an environmental concern due to increasing anthropogenic activities (metal smelting, copper industry, etc.). Therefore, balanced Zn application is necessary to save resources and achieve optimum crop growth and yield. Most scientists suggest biological approaches to overcome the problem of Zn toxicity and deficiency. These biological approaches are mostly environment-friendly and cost-effective. In these biological approaches, the use of arbuscular mycorrhizae fungi (AMF) symbiosis is becoming popular. It can provide tolerance to the host plant against Zn-induced stress. Inoculation of AMF helps in balance uptake of Zn and enhances the growth and yield of crops. On the other hand, maize (Zea mays L.) is an important cereal crop due to its multifarious uses. As maize is an effective host for mycorrhizae symbiosis, that's why this review was written to elaborate on the beneficial role of arbuscular mycorrhizal fungi (AMF). The review aimed to glance at the recent advances in the use of AMF to enhance nutrient uptake, especially Zn. It was also aimed to discuss the mechanism of AMF to overcome the toxic effect of Zn. We have also discussed the detailed mechanism and physiological improvement in the maize plant. In conclusion, AMF can play an imperative role in improving maize growth, yield, and balance uptake of Zn by alleviating Zn stress and mitigating its toxicity.

The impacts of climate change and human activities on vegetation dynamics have attracted wide attention, especially in sensitive and vulnerable areas such as the Qingzang Plateau of China. In this region, a series of ecological restoration projects have been launched while the effectiveness of these projects requires evaluation and further improvements. Remote sensing with high temporal resolution and spatial coverage is an effective way for the vegetation dynamics research in this region. In this study, the spatial and temporal distribution of climate factors and vegetation coverage as well as the influencing factors such as air temperature, precipitation, land use, slope, slope direction, soil and altitude were analyzed. The geographical detector was used to analyze the influence of climate factors on vegetation coverage and the interaction among factors in different eco-geographical regions. The results showed that: 1) the average values from the 20 years of normalized difference vegetation index (NDVI) decreased gradually from southeast (> 0.61) to northwest (0.12). The overall average of NDVI increased 0.02 per year from 1998 to 2018 and the impact factors varied among different eco-geographical regions; 2) some controlling factors showed nonlinear enhancement such as altitude and slope; 3) land use was an important factor affecting the distribution of vegetation especially in humid, semi-arid and arid areas, but the impacts of elevation and temperature were stronger than land use types in semi-humid and humid areas. The design and construction of ecological protection and restoration projects on the Qingzang Plateau required scientific and detailed demonstration as well as monitoring and evaluation. In addition, new tools and theories were also needed in the selection of ecosystem restoration strategies. Based on the findings, this study also provides suggestions for the sustainable ecological restoration on the Qingzang Plateau.

Landfilling is viewed nowadays as a serious threat associated with various burdens and stressors on the urban environment. To date, there is little information available on actual value of landfilled waste namely plastic solid waste (PSW) resulting from mining operations. In this work, PSW reclaimed from an active unsanitary landfill site (MAB) has been studied with the aim of determining its thermal profile and degradation behaviour for future utilisation in thermo-chemical conversion (TCC) processes. The materials were characterised by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) in accordance with internationally approved test methods in a simulated pyrolytic environment. In addition, chemical analysis using Fourier Transform Infrared Spectroscopy (FTIR) was applied to study the nature of the materials reclaimed. The degradation kinetics of the reclaimed PSW were studied with the aim of determining the apparent activation energy (Ea) of the pyrolytic reactions. The Ea values determined ranged from 199 to 266 kJ mol−1 which is in-line with pyrolytic reactions applicable for future use in fuel recovery units. TGA showed a clear shift in thermograms indicating a clear change in the degradation mechanism. The physico-chemical studies conducted on the materials also favours TCC treatment over other conventional end of life options such as physical (mechanical) recycling or incineration. The degradation mechanism was also determined from the Criado method showing that Avarami-Erofeve was the model that best represents PSW degradation. Overall, this work points towards future intervention schemes for reclaimed municipal solid waste (MSW) and in particular PSW favouring TCC technologies.

Liquid fresh water is scarce in arid and semi-arid regions. Some organisms in these stressful habitats are well adapted to the environmental conditions and obtain fresh water directly from the atmosphere. This ability of “moisture harvesting” relies on specific microstructural features organisms exhibit at their external surfaces. In this respect, the dew harvesting ability of the arid plant species Opuntia stricta (Cactaceae) has been investigated. Its tiny stem spines, known as glochids, have a unique microstructure, ordered in hierarchical manner with an anisotropic surface. The glochids are covered with cone-shaped barbs and have dense mats of hygroscopic trichomes at the base. Dew harvesting ability in O. stricta seems to be controlled by three driving forces, namely: Laplace pressure difference, Wenzel relation and differences in wettability. The formation of special external microstructural features supporting this ability represents an adaptive trait in O. stricta to dry arid environments. Studying such structures in detail will give insights on how biomimetic inspired devices may contribute to optimize moisture harvesting in dry regions.

The Bar-tailed Lark (Ammomanes cinctura) breeds in desert and semi-desert areas of the Saharo-Sindian region, from north-west Africa through the arid plains of the Arabian Peninsula to the Sind. Despite having a wide distribution, little information is available on the breeding ecology of this species. This study was conducted in a desert in the north of Saudi Arabia, where the daytime ambient temperature may exceed 40 °C. In contrast, the night ambient temperature may reach less than 10 °C in late spring and early summer. The objectives of this study were to collect some baseline data on some aspects of the breeding ecology of this species and to record the nest attendance behavior. The study found that Bar-tailed Larks preferred to nest under shrub trunks, which may camouflage both nests and incubating parents against predators and protect eggs, nestlings and incubating parents from hostile weather conditions. Moreover, nest attendance was high, as Bar-tailed Lark parents incubated their eggs 95.97 ± 2.62% over the entire day, and they seemed to maintain the eggs at temperatures around 23–33 °C. In addition, they incubated more at night than during the daytime. Temperatures under the shrubs at night fell below 21 °C, thus parents increased the nest attendance to warm the eggs and prevent the embryos from exposure to lethal temperatures.

Accurate and up to date land use and land cover (LU/LC) changes information is the main source to understanding and assessing the environmental outcomes of such changes and is important for development plans. Thus, this study quantified the outlines of land cover variation of 10-years in the northwestern costal land of the Red Sea, Saudi Arabia. Two different supervised classification algorithms are visualized and evaluated to preparing a policy recommendation for the proper improvements towards better determining the tendency and the proportion of the vegetation cover changes. Firstly, to determine present vegetation structure of study area, 78 stands with a size of 50 × 50 m were analysed. Secondly, to obtain the vegetation dynamics in this area, two satellite images of temporal data sets were used; therefore, SPOT-5 images were obtained in 2004 and 2013. For each data set, four SPOT-5 scenes were placed into approximately 250-km intervals to cover the northwestern coastal land of the Red Sea. Both supervised and non-supervised cataloguing methods were attained towards organise the study area in 4-major land cover classes through using 5 various organizations algorithms. Approximately 900 points were evenly distributed within each SPOT-5 image and used for assessment accuracy. The floristic composition exhibits high diversity with 142 species and seven vegetation types were identified after multivariate analysis (VG I: Acacia tortilis-Acacia ehrenbergiana, VG II: Acacia tortilis-Stipagrostis plumosa, VG III: Zygophyllum coccineum-Zygophyllum simplex, VG IV: Acacia raddiana-Lycium shawii-Anabasis setifera, VG V: Tamarix aucheriana-Juncus rigidus, VG VI: Capparis decidua-Zygophyllum simplex and VG VII: Avicennia marina-Aristida adscensionis) and ranged between halophytic vegetation on the coast to xerophytic vegetation with scattered Acacia trees inland. The dynamic results showed rapid, imbalanced variations arises between 3-land cover classes (areas as urban, vegetation and desert). However, these findings shall serve as the baseline data for the design of rehabilitation programs that conserve biodiversity in arid regions and form treasured resources for an urban planner and decision makers to device bearable usage of land and environmental planning.

The aim of this study was to generate land suitability maps for maize farming in calcareous and saline-sodic soils in the Marvdasht plain, Iran. An analytic hierarchy process (AHP) multi-criteria method integrated with GIS and geostatictic was employed to estimate weighting of soil properties, climate and topography data. The results indicated that soil texture showed the highest specific weight (0.20) for maize farming followed by electrical conductivity (0.121), slope (1 2 0) and pH (0.118). The land suitability map showed that 38.72% (76,646.7 ha) of the studied agricultural land were the best soils for the maize production i.e. high suitable class, 26.89% (53,216.0 ha) was for the moderately suitable class and 23.98% (47,473 ha) was for marginally suitable class. The 10.41% (20,586.4) of study region was classified as not-suitable for maize farming. It was concluded that soil property, climate and topography data combined with local expert opinion is a first step in site-specific crop farming.

Background: Malaria outbreaks due to Plasmodium falciparum have been reported from various parts of India. Rainfall is considered as one of the major determinants for malaria outbreaks, however, an estimate of rainfall threshold for malaria is not known. Owing to the vast geographic area, the present study was planned to determine the amount of rainfall required for malaria outbreaks and the lag period between outbreak and rainfall in different Indian climatic regions. Methods: Simple statistical methods of overall mean and moving mean (case/mean ratio, CMR) were used to identify the districts with P. falciparum malaria outbreak due to rainfall and the amount of rainfall required for outbreaks. Of 120 districts reporting P. falciparum malaria outbreaks, 99 districts having substantially low number of cases (70 to >600 mm in different districts. The month of outbreak varied with the climatic zones viz. arid, semi-arid, humid and per-humid districts. In humid and per-humid districts, outbreaks occurred during monsoon period whereas in arid and semi-arid regions outbreaks occurred during the post monsoon period. The lag period varied from 1-3 months; long lag period was observed in arid, semi-arid region, while short lag period in humid and per-humid regions. Conclusion: Malaria outbreaks can occur in post monsoon in arid and semi-arid region whereas in summer/monsoon in humid and per-humid regions. The lag period between rainfall and outbreak differs from one month with short lag (humid and per-humid) to long lag (arid and semi-arid). Based on the determined threshold of rainfall, the findings would be helpful in forewarning of imminent outbreak of malaria for the timely preparedness of malaria outbreaks not only in 21 studied districts, but also in several other districts of different climatic regions of India.

Summary: The aim of this study was to conduct the first comprehensive evaluation of carbon stock in the sediments of Avicennia marina (black mangrove) and Rhizophora mucronata (red mangrove) along the coastline of an arid region (Farasan Islands, Saudi Arabia). Such information is necessary for the development of any management plan for the mangrove ecosystems along the Saudi Red Sea islands and provide a rationale for the restoration of mangrove forests in Saudi Arabia. A. marina and R. mucronata locations showed significant (P < 0.001) differences in sediment bulk density (SBD) and sediment organic carbon (SOC) concentration with higher mean values for both in the sediments of A. marina. Considering the whole depth of sediment sampled (0–50 cm), the highest value of SOC stock (12.3 kg C m−2) was recorded at A. marina locations and the lowest (10.8 kg C m−2) at R. mucronata locations. Thus, the SOC stock of A. marina was greater than that of R. mucronata by 114.3%. Consequently, considering the rate of carbon sequestration and the area of mangrove forests (216.4 ha), the total carbon sequestration potential of mangroves in the Farasan Islands ranged between 10.3 Mg C yr−1 and 11.8 Mg C yr−1 for R. mucronata and A. marina locations, respectively. Thus, it is necessary to protect and restore these ecosystems for the sequestration of carbon and for their other valuable ecosystem services. Keywords: Blue carbon, Carbon sequestration, Carbon stocks, Climate change, Coastal ecosystems

Samples from 12 drillhole-cores from the Urals-Emba region to the north-east of the Caspian Sea were analysed for pollen and spores. The records reveal vegetation and climate changes for the late Pliocene to early Pleistocene within the time interval from ca. 3.6 to ca. 1.65 Ma. According to the results of the pollen analysis, at the beginning of the Akchagylian stage (3.6–3.4 Ma) there was a cooling and change in structure of the dendroflora, and steppe-dominated landscapes were present. At the end of the early Akchagylian, and continuing into the middle Akchagylian, a maximum variety of pollen from tree species occurred. The presence of mesophilic and thermophilic elements signifies a moderately warm and humid climate occurred at around 3.2 Ma, probably related to the ‘Mid-Pliocene Warm Period’. A second major cooling occurred at around 2.5 Ma coinciding with the onset of northern hemisphere glaciations. During this time, coniferous forests dominated by Picea, Pinus and Abies with lesser numbers of broad-leaved trees were established. At the end of the Akchagylian, at around 1.8 Ma, the climate became more arid and steppe landscapes were re-established. During the Akchagylian, alternations between forest- and steppe-dominated landscapes occurred at least three times in the Urals-Emba region. Results are compared with pollen spectra in surface samples, and with ostracods and foraminiferal assemblages in cores from the study region.

Achieving sustainability by improving the urban microclimate is a key principle in mitigating the urban heat island (UHI) effect. This study focuses on the reduction of the urban heat island phenomena in a combination of historical compacted areas with multi-storey housing projects in Baghdad’s Al-Karkh district to identify better urban solutions by examining human thermal satisfaction levels via certain urban alterations. Changes were simulated using ENVI-Met and RayMan-pro modelling programmes. Findings suggest that the UHI effect can be reduced by urban interventions and greenery and high-albedo construction materials to influence the mean radiant temperature (Tmrt) factor while simultaneously respecting the height to width ratio of buildings. The urban geometry of a compacted traditional area is one solution to severe summers experienced in Baghdad. Despite the physiological equivalent temperature (PET) level declination reaching 32.2 °C at 3:00 pm, thermal stress levels in compact areas had halved, providing ideal comfort levels that remained constant most of the day. With the growing need for urban development, a concentration of modern high-rise structures can offer tolerable solutions by providing ample shade by casting shadows, in addition to considering wind speed and direction to enhance the urban microclimate and enabling human thermal comfort in arid areas. Keywords: Urban heat island, Sustainability, ENVI-met, Outdoor thermal comfort, Urban microclimate, Baghdad

Summary: In the present work, we assessed the carbon sequestration capacity of mangrove forests (Avicennia marina) in relation to nutrient availability and salinity gradients along the Red Sea coast of Saudi Arabia. This was achieved through estimating the sediment bulk density (SBD), sediment organic carbon (SOC) concentration, SOC density, SOC pool, carbon sequestration rate (CSR) and carbon sequestration potential (CSP). The present study was conducted at 3 locations (northern, middle and southern), using 7 sites and 21 stands of mangrove forests (A. marina) along ∼1134 km of the Red Sea coastline of Saudi Arabia (from Duba in the north to Jazan in the south), all of which are in an arid climate. The correlation coefficients between the water characteristics and the first two Canonical Correspondence Analysis (CCA) axes indicated that the separation of the sediment parameters along the first axis were positively influenced by TDS (total dissolved solids) and EC (electric conductivity) and were negatively influenced by total N and total P. On the other hand, the second axis was negatively correlated with total N, total P, EC and TDS. The SOC pools at the northern (10.5 kg C m−2) and southern locations (10.4 kg C m−2) were significantly higher than the SOC pool at the middle location (6.7 kg C m−2). In addition, the average CSR of the northern (5.9 g C m−2 yr−1) and southern locations (6.0 g C m−2 yr−1) were significantly higher than they were in the middle location (5.0 g C m−2 yr−1). Keywords: Carbon sequestration, Coastal wetlands, Mangroves, Red Sea, Saudi Arabia, Climate change

Geological records indicate that the hyper-aridity in the Atacama Desert has prevailed since at least the mid-Miocene, with shorter periods of increased humidity punctuating long-term aridity. The 7-m-high accumulation of colluvial sediments at the Salar Grande (21°S/70°W) studied here provides a key palaeoclimate record to understand hillslope dynamics and its relation to humid periods. While 10Be surface exposure ages point to long-term surface stability of the flat upslope surface, a combination of humidity-driven soil creep, overland flow and soil creep related to seismic shaking, caused denudation of the hillslope and accumulation of several metres of colluvium over much shorter timescales during the last 130 ka. A robust chronology for the hillslope sediments has been established by using Infrared Stimulated luminescence (pIR-IR225 protocol) on K-feldspar extracts from nine samples collected within the accumulation. A series of tests has been carried out to confirm the suitability of the method. The estimated ages indicate accelerated sedimentation at 35–80 ka, and 100–130 ka, which are interpreted as periods with more humid climate conditions than present. These findings agree with climate variations in the hyper-arid Atacama indicated by the activity of coastal alluvial fans and river catchments.

The quantitative description of valley profiles is useful for understanding their geomorphological and dynamic features. To this end, the cross-sections of 45 valleys in the Kahar, Taft, and Granite formations in the Yazd–Ardakan catchment were investigated. Fractal properties, mathematical functions, the ratio of valley floor width to valley height (Vf), and the ratio of valley depth to valley top width (Fr) were used to study the morphology of the valleys. The average Vf values calculated for the Kahar, Taft, and granite formations were 5.56, 3.52, and 1.38, respectively. The average Fr values for these three formations were 0.07, 0.12, and 0.17, indicating the heterogeneity of lithological composition and structural status of the valleys. The multifractal analysis of valley cross-sections showed the transition of valley sections from a monofractal to multifractal nature. Therefore, the multifractal analysis seems appropriate for evaluating complexities in the valley and geomorphological properties of the catchment under study.

In this chapter the general factors affecting the equilibrium and stability of arid regions are discussed, with particular focus given to rainfall, the primary factor influencing the continuity and development of these environments. Unfortunately, the scarcity or complete lack of rain gauges in such areas complicates the collection of sufficient rainfall data. Consequently, systematic steps are proposed toward the development of alternative analyses of the spatiotemporal distribution of rainfall in arid regions. The foremost approach is the incorporation of remote sensing data, along with the appropriate classifiers, into the indirect evaluation of rainfall. For the purpose of assessing the suitability of the proposed methods, a detailed study on rainfall in the eastern side of the Gulf of Suez in Egypt is presented.

The instability of soil aggregates is one of the most important land degradation processes in different parts of Iran, particularly in arid and semi-arid regions with loess-derived soils. In this study, we modeled soil stability (measured as soil bulk density (BD) of the topsoil layer) using two algorithms: random forest (RF) and support vector regression (SVR). In this study, we used nine environmental variables, driven by unmanned aerial vehicles (UAV) and soil samples collected from a depth of 0–20 cm to map BD. The RF algorithm was applied to prioritize the factors affecting the BD. The Results were assessed using RMSE, MSE, and R2. The results of the variable importance analysis showed that distance to a river, distance to road, and altitude are the most important factors affecting soil stability. The prediction model for mapping soil BD has reasonable accuracy, i.e., the RMSE values of the training set of RF and SVR models were 0.08 (R2 = 0.95) and 0.16 (R2 = 0.21), respectively. We recognized that the methodology of this study could easily produce a soil property probability map (BD in this study) in the topsoil layer.

The effect of external roof shading on the spatial distribution of air temperature and relative humidity in a greenhouse (Tin and RHin) was evaluated under the arid climatic conditions of Riyadh City, Saudi Arabia. Two identical, evaporatively-cooled, single-span greenhouses were used in the experiment. One greenhouse was externally shaded (Gs) using a movable black plastic net (30% transmissivity), and the other greenhouse was kept without shading (Gc). Strawberry plants were cultivated in both greenhouses. The results showed that the spatial distribution of the Tin and RHin was significantly affected by the outside solar radiation and evaporative cooling operation. The regression analysis showed that when the outside solar radiation intensity increased from 200 to 800 W m–2, the Tin increased by 4.5°C in the Gc and 2°C in the Gs, while the RHin decreased by 15% in the Gc and 5% in the Gs, respectively. Compared with those in the Gc, more uniformity in the spatial distribution of the Tin and RHin was observed in the Gs. The difference between the maximum and minimum Tin of 6.4°C and the RHin of 10% was lower in the Gs than those in the Gc during the early morning. Around 2°C difference in the Tin was shown between the area closed to the exhausted fans and the area closed to the cooling pad with the external shading. In an evaporatively-cooled greenhouse in arid regions, the variation of the Tin and RHin in the vertical direction and along the sidewalls was much higher than that in the horizontal direction. The average variation of the Tin and RHin in the vertical direction was 5.2°C and 10% in the Gc and 5.5°C and 13% in the Gs, respectively. The external shading improved the spatial distribution of the Tin and RHin and improved the cooling efficiency of the evaporative cooling system by 12%, since the transmitted solar radiation and accumulated thermal energy in the greenhouse were significantly reduced.

Surface temperature is one of the critical factors used to study microclimate conditions through Land surface Temperature (LST), a widely used data source. This paper tests a classification approach using moderate spatial satellite resolution images to extract surface properties of Local Climate Zones (LCZs) in a semi-arid region against measured LSTs. However, LST is used to study and explore the spatial relationship between temperature and urban morphology. Therefore, it is considered an alternative and reliable data source to complement in-situ measurement, especially in developing countries. The used methodology is based on two statistical approaches: 1) auto-spatial correlation using Getis Ord Gi* statistic, and 2) ANOVA test. Results showed an inversion effect of surface urban heat island - SUHI, where a strong correlation between specific LCZs and the surface temperature was found. The urban classes represented by open-low-rise, compact-low-rise have shown a significant decrease in surface temperature for almost two decades and in both summer and winter seasons compared to non-urban ones. Therefore, the outcomes of this study may have critical implications for urban planners who seek to mitigate SUHI effects in arid and semi-arid urban areas. Also, the approach used in this study can be helpful to follow the urban environment's spatial and temporal development as an application framework of sustainable development.

The Aspidosperma pyrifolium Mart. & Zucc. is one of the main species of Caatinga biome, a seasonally dry tropical forest in Brazilian Semi-arid, very prominsing for the restoration of degraded or desertified areas. The combined effects of salt and water stress on morphological dynamics, biomass accumulation and gas exchange in A. pyrifolium were investigated. The experiment was conducted in state of Pernambuco, Brazil. A completely randomised design was adopted, where the plants were submitted to four water regimes based on a percentage of the reference evapotranspiration (ET0): 25%, 50%, 75% and 100%.ET0, and four salinity levels, using NaCl: 0.2 (control), 1.8, 2.82 and 3.93 dS m−1. Biometric, biomass and gas exchange data were obtained, and water use efficiency, momentary and intrinsic water use efficiency were calculated. The water deficit affected stem diameter, and stem and root biomass. Gas exchange showed a reduction for an increase in salt and water stress. Momentary and intrinsic efficiency were maximized under a water regime of 65%.ET0 and an electrical conductivity of 1.51 dS m−1, and 67%.ET0 and 1.75 dS m−1, respectively. It is concluded that the species A. pyrifolium changes the biomass partitioning between the plant structures to compensate the salt and water stress.

Rainfall is a complex meteorological phenomenon with high spatio-temporal variability. These variations in hydrologic time series can be better analyzed using homogeneity and trend tests. In this paper, three homogeneity tests were applied to the annual rainfall series of 1980–2013 from 30 raingauge stations over the study area. The rainfall stations with homogeneous time series were subjected to cluster analysis (Agglomerative Hierarchical Clustering technique) and thereafter traditional trend tests (Mann-Kendall test and Spearman Rank-order Correlation test) and one emerging trend test (called ‘Innovative Trend test’) were applied to individual clusters. Based on the homogeneity test results, 27 rainfall stations with homogeneous time series were classified under six clusters. The results of the trend analysis revealed that a distinct pattern of increasing (decreasing) rainfall trend exists in the northern (southern) part of the study area. Although the traditional tests detected insignificant trends, the Innovative Trend (IT) test indicated the trends to be significant in all the clusters. However, the magnitude of trends detected by the traditional trend tests and non-traditional trend tests is similar for all the clusters. It is concluded that the emerging IT test is highly sensitive to the changes in the rainfall time series. The findings of this study suggest that the orography, population density, industrialization and agricultural intensity lead to a precipitation gradient in the study area.

11 Pags.- 7 Figs.- 4 Tabls., Salinity is one of the most widespread abiotic stresses affecting crop growth and productivity, particularly when soil and irrigation water are salty. Field experiments were performed in an arid Mediterranean climate to investigate agronomic responses of twenty-one diverse barley genotypes to naturally occurring salinity. Three saline fields (7.72 dS/m) were irrigated with well water of three incremental salinity levels, low (5.25 dS/m), intermediate (8.35 dS/m), and high (11.12 dS/m). The results revealed considerable genotypic variability at the three salinity levels and significant genotype by salinity interaction that could be traced to specific yield components. Increasing salinity level decreased performance of all agronomic traits, but with different patterns, with yield components determined earlier being more affected than traits determined later. Days to heading exhibited a strong and negative relationship with grain yield across all salinity levels, while 1000-grain weight demonstrated the highest association with grain yield, followed by number of grains per spike, plant height, and harvest index, consistently at the three salinity levels. The genotypes were classified based on their yield indices at the three salinity levels into six groups varying from highly salt-tolerant (group A) to highly salt-sensitive genotypes (group F). Genotype-by-salinity interaction was studied based on rankings of performance across salinity levels. Close examination of yield component trends across levels allowed the identification of genotypes with different behaviors, indicating the presence of variation in potentially different mechanisms of response to salinity. This diversity of responses could be used in breeding to improve tolerance over the whole crop cycle, from plant establishment and tillering to grain filling.

Lake level or water depth are key physical variables known to respond dramatically to climate change, especially in arid regions, and their fluctuations exert substantial influences on lake biodiversity and ecosystem functioning. However, it is unclear how multiple ecosystem functions (i.e., ecosystem multifunctionality, EMF) respond to changes in water depth and how aquatic community attributes, such as species richness, evenness and community compositions, are linked to EMF along water depth gradients. Lake Hulun, a representative of semiarid-region lake in China, has experienced serious lake area shrinkage over the past 20 years. Here, we explored the water-depth patterns of three microbial taxonomic groups of bacteria, archaea and fungi and nine ecosystem functions related to nutrient cycling in Lake Hulun. We further examined the relative importance of different community attributes on EMF variations. We found that the community compositions of bacteria, archaea and fungi showed consistent water-depth decay patterns, and EMF and most individual ecosystem functions involved in C, N, P and S cycling increased with water depth. Further, EMF was predominantly mediated by microbial evenness and community composition, but not species richness, as predicted by the traditional theory of biodiversity-ecosystem functioning relationships. In addition, water depth indirectly affected the relationships between the microbial community and EMF via sediment nutrient contents. These findings indicate that the water depth changes under climate change could substantially alter ecosystem structure and functioning in arid regions. We further emphasize the necessity of including multiple community attributes in biodiversity-EMF relationship research to clarify the biotic and abiotic forces underlying EMF variations.

Climate change resulted in farmers shifting from drought intolerant to drought tolerant crops in dry regions of the world. The study assessed the influence of precipitation and soil-type distribution on uptake of small grains in Mberengwa and Zvishavane districts in Zimbabwe. A mixed methods research design was adopted in this study and both qualitative and quantitative research approaches were employed to probe data. Questionnaires, interviews, focus group discussions and observations were used to collect data in this study. Microsoft excel 2013 and Geographic Information System (GIS) were adopted for data analysis in this study. Findings showed that soil type and precipitation distribution have significant influence on uptake of small grains in Mberengwa and Zvishavane Districts. Research findings indicated that perceptions of farmers towards small grain production are determined by precipitation received in the area and the type of soil available. Areas with high precipitation and soils of higher water retention capacity had low uptake of small grains compared to areas with lower precipitation and soils of poor water retention capacity. The study concludes that declining precipitation in arid and semi-arid regions requires adoption of small grains which thrives under dry conditions despite some areas receiving enough precipitation for maize production. The study recommends that organizations or projects that wish to support small grain production in areas of heterogeneous soil type and precipitation distribution focus more on areas of little precipitation and soils of poor moisture retention capacity which do not support large grains to guard against compromising small grain uptake.

This study investigated the impact of COVID-19 lockdown on particulate matter concentrations, specifically PM2.5 and PM10, in Kuwait. We studied the variations in PM2.5 and PM10 between the lockdown in 2020 with the corresponding periods of the years 2017–2019, and also investigated the differences in PM variations between the ‘curfew’ and ‘non curfew’ hours. We applied mixed-effect regression to investigate the factors that dictate PM variability (i.e., dust and meteorological covariates), and also processed satellite-based aerosol optical depths (AOD) to determine the spatial variability in aerosol loads. The results showed low PM2.5 concentration during the lockdown (33 μg/m3) compared to the corresponding previous three years (2017–2019); however, the PM10 concentration (122.5 μg/m3) increased relative to 2017 (116.6 μg/m3), and 2019 (92.8 μg/m3). After removing the ‘dust effects’, both PM2.5 and PM10 levels dropped by 18% and 31%, respectively. The mixed-effect regression model showed that high temperature and high wind speed were the main contributors to high PM2.5 and PM10, respectively, in addition to the dust haze and blowing dust. This study highlights that the reductions of anthropogenic source emissions are overwhelmed by dust events and adverse meteorology in arid regions, and that the lockdown did not reduce the high concentrations of PM in Kuwait.

Increased aridity, associated with climate change, is predicted worldwide in the coming decades. Species persistence in the face of climate change is thought to be influenced by plasticity, potential for adaptation, and dependence on non-climatic factors, but their relative importance has rarely been quantified. We investigated 13 populations of Eschscholzia californica (California poppy) distributed across a fourfold gradient in annual precipitation. In a greenhouse, plants received precipitation treatments approximating the wettest and driest sites, crossed with the presence and absence of soil inoculum from their collection location. We documented clinal variation across populations; plants from southern populations (arid sites) emerged later, flowered earlier, had shorter growing seasons, higher mean fitness, higher reproductive effort, and were more drought tolerant than plants from northern populations (mesic sites). A second experiment demonstrated clinal variation in biomass allocation, with higher root allocation in northern populations. We found no evidence of adaptive phenological plasticity to drought; instead, the drought treatment decreased fitness and growing season length (maladaptive phenological plasticity) more for plants from mesic than arid sites. Individuals grown with home soil inoculation produced 10% more biomass than when grown in common garden soil; however, the influence of soil was small relative to the 13-fold variation across populations in fitness responses to drought. Our results suggest that restoration efforts involving California poppy may benefit from assisted gene flow; sourcing seeds from arid parts of the species range may improve individual fitness and population persistence of this iconic species in the face of future climate change.

Drylands cover about 41% of the Earth's land surface and are inhabited by more than two billion people, who rely on the diversified ecosystem services provided by drylands for their livelihoods. Achieving sustainable livelihoods (SLs) is a key component of achieving the sustainable development goals set by the agenda in 2030. Although it has aroused extensive interest, research on SLs in drylands at a regional scale is still limited. This paper aims to address this research gap by evaluating SLs through a geographic gradient of aridity in Inner Mongolia. A sustainable livelihood index (SLI) was developed using a wide range of indicators in a sustainable livelihood framework (SLF). The weight of the indicators was determined by the entropy weight method, and the characteristics of the spatial distribution of the SLI were analyzed. The results showed that the SLI varies greatly across aridity zones. In terms of livelihood assets, the SLI in the dry sub-humid zone was 15% higher than in the arid zones, while, surprisingly, semi-arid zones were found to have the most vulnerable livelihoods (rather than the arid zones). The reason for this is that land management and planning approaches are necessary in drylands. In further detail, Moran's I index illustrated that the overall performance of the SLI of each league or city has a positive spatial correlation, while through local spatial correlation it was found that Hinggan and Chifeng are hot spot areas and Hohhot is a cold spot area. The lack of physical and social capital is an important obstacle for SLs. Based on the analysis of SLs in Inner Mongolia, the characteristics of the sustainable development of local residents were revealed. In this paper, we call for an integrated (i.e., focusing on natural and human capital) land management and planning approach for drylands to reflect the nature of the tightly coupled socio-ecological systems.

Climate variability is among the main threats to rain-dependent smallholder farming in most sub-Saharan Africa countries. Hence, farmers should make efforts at the local level to utilize indigenous knowledge (IK) combined with conventional knowledge to adapt to climate variability impacts. We assessed; IK used by farmers in climate forecasting, their perceptions of climate variability and adaptation strategies, and their correlation with conventional approaches. We conducted the study in Tharaka South and Kitui Central sub-counties of Kenya. We used the triangulation approach to obtain the quantitative and qualitative data. To select respondents, we used purposive and random sampling strategies combined with the snowballing technique. Observed rainfall and temperature data from 1998 to 2018 were obtained from the Kenya Meteorological Department (KMD). Results showed that there were significant (p

It is commonly believed that climate plays an important role in shaping the patterns of plant species richness. However, it remains unclear how climate may affect plant richness across large spatial scales and also over long-terms, for example across massive arid regions during the Quaternary and into the future. To fill this knowledge gap, we examined the long-term trends in plant species richness across vast drylands in China based on our newly developed climate-species richness models. We first generated optimal random forest models based on the relationships between the current (CUR, 1970–2000) annual, perennial, woody and total species richness and climatic variables. We subsequently hindcasted and forecasted plant species richness in five other periods: last interglacial (LIG, 120,000–140,000 years BP), last glacial maximum (LGM, about 22,000 years BP), mid-Holocene (MH, about 6000 years BP), 2041–2060 (2050), and 2061–2080 (2070). Our results showed that total and herbaceous species richness exhibited similar patterns that were driven by temperature and precipitation. Both groups of species formed a transition zone between arid and semi-arid regions in all periods except LIG. In contrast, woody species richness did not form any transition zone because it was regulated mainly by temperature. Furthermore, the mean richness of herbaceous, woody and all species exhibited gradually increasing trends from LIG to 2070 across drylands in China. On the one hand, herbaceous species were much more sensitive to climate change than woody species. On the other hand, plant species richness in mountain-basin systems and Taklamakan Desert regions were more sensitive to climate change than in meadows and steppes. These results shed new insights into the past and future changes in plant species richness over vast drylands and provide valuable information for future conservation efforts under global warming.

Dust pollution is one of the major environmental crises in the arid regions of Iran and there is a need to predict dust pollution and identify its controlling factors to help reduce its adverse effects on the livelihood of residents of these areas. Although deep neural networks (DNN) are powerful tools in the modelling of environmental phenomena, they are recognized as being challenging to interpret due to their black-box nature. To address this issue and understand the importance of each environmental control on dust pollution, game theory (i.e., Shapley values) was used to better understand the performance and interpretability of DNN models. Here, monthly mean values of precipitation, air temperature, surface wind speed, potential evapotranspiration, normalized difference vegetation index, normalized difference salinity index, Palmer drought severity index, soil heat flux, and surface pressure were selected as explanatory variables. The dust storm index (DSI), an indicator of dust pollution, was the predicted response variable for the cold and warm months. The results showed that the accuracies of the DNN model in predicting cold months DSI (CMDSI) and warm months DSI (WMDSI) were higher compared to other traditional machine learning algorithms. DNN model increased the R2 by 13% and 15% for predicting CMDSI and WMDSI, respectively, compared to the Random Forest model, which was the second most effective approach. According to the Shapley values, the most important controls on the occurrence of dust storms during the cold months of the study period (2000–2018) were wind speed, soil heat flux, and precipitation. During the warm months, wind speed was the most important controlling factor and was followed by precipitation, soil heat flux, and potential evapotranspiration. Overall, the results demonstrate the effectiveness of the DNN model and game theory in identifying the factors affecting dust pollution, which may help mitigate its impacts on the residents of western Iran.

In arid and semi-arid regions, groundwater plays an important role in both local economic and population development. Therefore, the cost effective and rapid assessment of locations that are suitable for well drilling is crucial. In this study, the improved entropy method and the improved catastrophe method, coupled with geographic information system -based multi-criteria decision analysis, were adopted as a potential method for groundwater exploration. Eight criteria were selected, namely, soil type, land use/land cover, elevation, slope, groundwater level, average rainfall, cumulative sand thickness, and distance to surface water bodies. The improved entropy method and improved catastrophe method were used to assign criteria weights, and the map of the groundwater potential zones was then generated using geographic information system -based multi-criteria decision analysis. Finally, 63 actual potentialities corresponding to the drilled boreholes scattered in the study area and the receiver operating characteristics curve were used to validate the accuracy of the generated the groundwater potential zones. The results showed accuracies of 0.808 and 0.811 for the improved entropy method and improved catastrophe method, respectively. Therefore, these methods are suitable for the evaluation of groundwater potential. Additionally, the adoption of criteria removal and single criterion sensitivity analysis showed that cumulative sand thickness, groundwater level, and average rainfall are the most influential parameters in the evaluation model. Therefore, to solve the local groundwater crisis, an increase in rainfall collection and a decrease in groundwater extraction is recommended.

Legume plants are pioneer species in desert ecosystem that can be used to reestablish degraded ecosystem functions and soil properties, and reshape underground microbial communities. However, the distribution in soil nutrients and bacterial communities after introducing leguminous shrubs have not been well described. Here, we quantified the variations in soil nutrients and bacterial communities in soil profiles (0–100 cm) across stand ages (5-year, 8-year, 15-year) and severe desertification (SD), and further investigated the bacterial contributions to soil nutrients during stand development. The total phosphorus (TP), total nitrogen (TN) and organic carbon (OC) contents significantly increased, whereas the available nitrogen (AN) and available phosphorus (AP) contents showed a downward trend across stand ages. Bacterial diversity increased after introducing leguminous shrubs. Vertical spatial variation of bacterial communities attenuated during stand development. Bacterial beta-diversity, specific microbial phyla (i.e., Proteobacteria and Firmicutes) and nitrification process were strongly associated with vertical spatial variation in soil nutrients. Combined analyses revealed that leguminous shrubs can ameliorate soil OC, TN and TP with increasing legumes growth time, but could still exhibit no facilitating effect on the improvement of soil available N and P even for legumes aged 15 years. Improving the bioavailability of nutrient elements and microbial function diversity could be targeted for further studies in arid barren sandy.

Rainfall patterns in arid and semi-arid regions are characterized by a reduction in rainfall frequency. However, under this novel climatic condition, potential changes in soil nematode community among different degraded grasslands remain unclear. We conducted a mesocosm experiment to test the effects of lower precipitation frequency (decreased by 50% from the long-term mean) on nematodes in the lightly degraded (LDG), moderately degraded (MDG) and severely degraded grasslands (SDG). The decreased precipitation frequency treatment significantly reduced the total abundance of nematodes by reducing soil moisture and enhancing moisture variability. Compared with other trophic groups of nematode, bacterivores were more sensitive to the altered precipitation and were significantly suppressed by higher soil moisture variation caused by lower precipitation frequency in the degraded grasslands. The decreased precipitation frequency treatment promoted plant belowground biomass through increasing soil moisture variation, which promoted plant parasites in LDG. However, in MDG and SDG, plant parasites were mainly suppressed by higher soil moisture variation under the altered precipitation frequency treatment, and were less impacted by the aforementioned stimulation in plant belowground biomass. The nematode community structure was not affected by the altered precipitation frequency treatment. This study provides experimental data for predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands.

Drought is the most widespread event under climate change and is projected to lead to high uncertainties in quantifying the terrestrial carbon exchange. However, considering the complexity of drought quantification and the differences in the physiological responses to drought among different vegetation types, the potential mechanisms of vegetation in response to drought across different climate regions and their responses to drought at varying time scales remain unclear globally. Here, we analyzed the response of vegetation activity to drought at different time scales and determined the time scale dominating the drought-induced vegetation variations, then explored its potential driving factors (temperature, precipitation, potential evapotranspiration, and water balance) under different climatic conditions and vegetation types from 2000 to 2015 using the Standardized Precipitation Evapotranspiration Index (SPEI) and Net Primary Productivity (NPP). Our results indicated that the NPP-SPEI correlation was stronger under arid and semi-arid conditions compared to that in humid and sub-humid zones globally. Vegetation mainly responded to the drought from short to medium time scales and the shortest response time scale was observed for deciduous needle-leaf forests and closed shrublands, which mainly located in semi-arid regions of southeastern Australia, central Africa, and southern Russia. Moreover, grassland and cropland ecosystems were found to be also highly vulnerable to drought across the globe. Analysis of the effects of various meteorological factors on NPP-SPEI correlation and drought timescales showed that water balance was the most predominant factor affecting the response of vegetation to drought. In particular, the increase in water balance significantly reduced the response intensity of vegetation to drought and prolonged the response timescales. Analysis of the effects of various meteorological factors on NPP-SPEI correlation and drought time-scales showed that water balance was the most predominant factor affecting the response of vegetation to drought. In particular, the increase in water balance significantly reduces the response intensity of vegetation to drought and prolongs the response time-scales. Therefore, the identification of the dominant timescales at which drought mostly impact land biomes is projected to assist assessing the stability of terrestrial ecosystem and thus support drought mitigation to reduce land degradation.

Globally, extreme droughts are likely to become more frequent, more intense, and longer in duration with climate change. Understanding the impacts of drought on ecosystem function (i.e., resistance) and its recovery after drought (i.e., resilience) is critical for long-term sustainability of ecosystem services under climate change. We tested the effects of drought duration on ecosystem resistance by imposing four years of extreme drought (

The Belt and Road Initiative (BRI) will play an essential role in boosting the world’s economy. However, the main portion of the Belt and Road (B&R) is in arid, semi-arid, or sub-humid fragile ecological regions, which with global climate change and the intensification of human activities will face many pressing environmental challenges in the future. Despite this, in the existing research on the B&R, papers in the field of natural sciences are less than 1.2–4.3% of the total number of papers on the main databases, which is far lower than the coverage in humanities and social sciences. And those focused on the ecological and environmental issues along the B&R are even fewer, so necessary understanding of both the risks and adequate mitigation measures remains unclear. This paper systematically reviews the relevant research on the eco-environments along the B&R, and summarizes it in terms including of spatial patterns and cognition, cost efficiency and evaluation, ecological security and evaluation, ecological footprint and carrying capacity. It further suggests that a better understanding of environmental changes and their effects on the B&R is needed. Additionally, it is essential that the potential positive socio-economic impacts for the future under the BRI are sustainable. Finally, future research directions are proposed to improve for the better eco-environments in B&R regions with consideration of global changes.

Exploring the composition of soil organic carbon (SOC) and aggregate stability over a range of elevations is essential to evaluate the stability of SOC and the conversion of carbon source or sink of mountain ecosystems. However, information of those changes in mountain ecosystems in arid and semi-arid regions is still scarce to date. In this study, we estimated the response of SOC stability along elevation gradient (1,380–2,438 m) by combining physical protection of aggregates with chemical protection of SOC using a redundancy analysis method in the Helan Mountains, northwest China. Results showed that the dominated aggregates of Helan Mountains changed from microaggregates to macroaggregates with increasing elevation, and the mean weight diameter (MWD) in mid and high elevations (2,139–2,248 m) was significantly higher than that in low elevations (1,380–1,650 m). Solid-state 13C NMR spectra showed that O-alkyl C was the main chemical composition of SOC in the different elevations. Regression analysis indicated that with the increase of elevation, the proportion of aromatic C and aromaticity gradually increased, peaked at the mid elevation and subsequently decreased. These findings indicated that the soil structure and chemical composition of SOC are more stable in the mid elevation. Macroaggregates were positively correlated with O-alkyl C and aromatic C, while silt and clay were positively correlated with alkyl C, indicative of a lower decomposition rate of macroaggregates. The RDA analysis confirmed that aggregate stability were significant associated with SOC content and chemical composition such as O-alkyl C, indicating that the soil labile carbon pool was most related to affect aggregate stability. Our findings suggest that the Helan Mountains had a better soil structure and a more stable SOC chemical composition at mid elevation ranges. The soil structure at low elevations is sensitive to environment change; therefore, a reduction in anthropogenic disturbance is suggested for improved sustainability of the ecosystem.

Drought disasters restrict economic and social development. Understanding the evolution of the spatiotemporal characteristics of drought plays a vital role in basin risk response and management. Complex empirical orthogonal function analysis is widely used in meteorological research and is an important tool for studying the spatial-temporal distribution structure of arid fields. This research aims to take the Yellow River Basin (YRB) as an example, separate the temporal and spatial distribution structure of drought based on the CEOF method, and explore the abrupt changes, trends, and periodic characteristics of different temporal and spatial distribution patterns. In addition, the cross-wavelet analysis reveals the lagging correlation relationship between the distribution pattern of the arid field in the basin and the Southern Oscillation factor. Results indicated that: (1) there are three typical spatial and temporal distribution patterns (full basin type, southeast-northwest reversed type and east-west reversed type) of the interannual scale drought in the YRB; (2) interannual drought evolution have obvious spatial propagation characteristics. (3) There are correlations between the three types and the Southern Oscillation on the temporal-frequency scale, and there is a time lag of 1-2a with the Southern Oscillation factor.

Currently, studies analysing the relationship between climatic factors and vegetation may present some problems, including considering insufficient spatiotemporal characteristics, contradictory results and deficiencies in reflecting vegetation changes in the future. To address this, we first analysed the spatiotemporal characteristics of the impact of climatic factors on the normalized difference vegetation index (NDVI) using a multiple regression model constructed from the perspective of water deficit. Second, the two carbon emission scenarios provided by Coupled Model Inter-comparison Project phase 5 (CMIP5) were combined to predict the future vegetation conditions in China. Finally, trend analysis, Sen's slope and cycle analysis methods were employed to explore the trend of the NDVI and its spatiotemporal characteristics in the arid and semiarid regions of China. The results show that the impact of climate change on vegetation possesses distinct spatiotemporal characteristics, and the influences are different depending on the month and location. Vegetation has greened in most arid and semiarid areas of China during historical periods. In the future, NDVI variation will show a fluctuating tendency, and increasing and declining trends for the NDVI will alternately occur monthly. Although both precipitation and temperature will increase in the future, spring vegetation will be threatened by stress in some areas due to severe drought caused by the increase in evaporation, which is caused by increasing temperature. The impact of climatic factors on the amplitude and cycle of vegetation type zones varies monthly. The impact of carbon concentration on the NDVI in vegetation type zones was not significant but was relatively large in some areas. The influence of the carbon concentration on the NDVI cycle is different each month. Carbon concentration basically has no effect on amplitude.

Study region Little Kinyasungwe Catchment within the River Wami Basin of central, semi-arid Tanzania. Study focus Groundwater and its replenishment via recharge are critical to sustaining livelihoods and poverty alleviation in tropical drylands yet the processes by which groundwater is replenished remain inadequately observed and resolved. Detailed observations are examined from central Tanzania, where the Makutapora Wellfield supplies freshwater to the rapidly growing, capital city of Dodoma. New hydrological insights for the region The prominence of focused recharge from ephemeral stream discharges is shown from: (1) groundwater recharge correlates more strongly with the seasonal duration of ephemeral stream stage exceeding a threshold than seasonal rainfall; (2) hourly monitoring of groundwater-levels and stream stage shows that sustained groundwater-level rises, indicative of groundwater recharge, correspond better to observed pulses of stream discharge from intensive rainfall observed upstream of the wellfield than rainfall recorded proximate to piezometers; and (3) stable isotope ratios of O and H indicate similar compositions of groundwater and ephemeral streamflow; both have undergone evaporative enrichment and are linked to intensive (90th percentile) daily rainfall. This characterisation of focused groundwater recharge from intensive rainfall in this tropical dryland highlights the potential resilience of groundwater resources to climate change amplifying precipitation extremes and informs strategies to augment replenishment of groundwater supplying the city of Dodoma.

Study region The Shule River Basin (SRB) in northwestern China is a representative area of global glacier-covered arid areas. Study focus Water resources have greatly influenced sustainable development in global arid regions where glacier runoff is an important component of water resource supply. This study focused on the assessment of the water resources–carrying capacity in the SRB based on the United Nations Sustainable Development Goals (SDGs) indicator 6.4.2, level of water stress (LWS). New hydrological insights for the region During the period between 2000 and 2030, the runoff of the SRB was predicted to follow an overall increasing trend. From 2000 to 2020, the annual average runoff in the upper reaches of the SRB was 10.9 × 108 m3, and then from 2021 to 2030, it increased by 22.8 %. According this trend, the average contribution of glacier meltwater to the total basin runoff is expected to decrease from the current 23 % to 15 % by 2030 (Representative Concentration Pathway 2.6, RCP 2.6). The supply of fresh-water resources has been close to the level of demand since 2015 and the LWS may increase between 2021 and 2030. The existence of glacial meltwater is expected to result in the continued reduction of basin water stress in the SRB by an average of 0.71 during the period between 2000 and 2030. Therefore, it is necessary to control water consumption of the socioeconomic system and adjust the industrial structure to face or adapt to the crisis of water shortage in global glacier-covered arid areas.

Although the concept of ecological drought was first defined by the Science for Nature and People Partnership (SNAPP) in 2016, there remains no widely accepted ecological drought monitoring index. Therefore, this study constructed a new ecological drought index, the standardized ecological water deficit index (SEWDI). The SEWDI is based on the difference between ecological water requirement and consumption, referred to as the standardized precipitation index (SPI) method, which was used to monitor ecological drought in Northwestern China (NWRC). The performance of the SEWDI was compared with that of other widely–used drought indices, including standardized root soil moisture index (SSI), self–calibrated Palmer drought index (scPDSI), standardized precipitation–evaporation drought index (SPEI), and SPI, using the Pearson correlations between these indices and standardized normalized difference vegetation index (SNDVI) under different time scales, wetness and water use efficiencies (WUE) of vegetation. The SEWDI at a 12–month scale was decomposed in NWRC during 1982–2015 using the rotational empirical orthogonal function (REOF) in order to demarcate five ecological drought regions, including southeastern sub–region (SE), southwestern sub–region (SW), northwestern sub–region (NW), northeastern sub–region (NE), and central sub–region (CT). The characteristics of ecological drought in NWRC, such as intensity, duration, and frequency, were extracted using the run theory. The return periods of five types of drought were calculated using wavelet analysis. Results showed that the performance of SEWDI in monitoring ecological drought was the best among the drought indices under different time scales, and the 12–month–scale was largely unaffected by wetness and WUE. Results of monitoring indicated that serious ecological droughts in the NWRC mainly occurred in 1982–1986, 1990–1996, and 2005–2010, primarily in SE, SW, and CT, SW and NE, and NW, NE, and CT, respectively. Furthermore, SEWDI in the arid SW, NW and CT showed a longer return period compared to that in the humid NE and SE, and the evolution of ecological drought in arid regions was mainly influenced by meteorological drought and the scarcity of root soil moisture. This study provides ant approach for quantifying ecological drought severity across natural vegetation areas which can be employed by decision makers

Groundwater potentiality mapping is currently receiving more attention, particularly in arid regions, where natural freshwater resources are limited and scarce and instead costly unconventional methods such as seawater desalination are widely used to satisfy water demands. Water demand in Makkah city is considered a vital task, which receives millions of visitors every year for religious purposes. The present study evaluates the potential zones of groundwater in the southwest Makkah city applying hydrogeophysical modeling approach that integrates geoelectrical resistivity in form of vertical electrical sounding (VES), ground-penetrating radar (GPR), and topographic analyses. VES results indicate five main geoelectric layers: (1) dry wadi-fill deposits with a true resistivity varying from 73 to 650 Ohm.m and average thickness of 3.14 m, (2) partially saturated sands with a resistivity range between 19 and 43 Ohm.m and average thickness of 13 m, (3) water-bearing layer of saturated sands with a resistivity range between 55 and 110 Ohm.m, and average thickness of 52 m, (4) highly fractured diorite rocks with resistivity values ranging from 750 to 1450 Ohm.m and average thickness of 1.5 m, and (5) fresh diorite basement rocks with a resistivity of more than 4000 Ohm.m. Results of GPR profiles support the gained results of the VES technique, and together they are confirmed by the wells data. The integrated results suggest a structural control on the groundwater accumulation and call for a detailed mapping of alluvium-covered faults to provide a high-resolution mapping of groundwater occurrences and ensure environmental sustainability in southwest Makkah city.

This paper addresses the dynamics of space occupation of villages in the west of the Argentine Republic from the analysis of radiocarbon dates of La Rioja province over the last 2000 years. A bimodal curve of greater intensity was observed in the construction of social landscapes with peaks between 400 and 1000 CE and 1300–1600 CE, approximately. Processes of occupation and spatial reorganization of the east–west vector were identified associated with the use of more stable water basins in Andean environments with a predominance of arid conditions. Remarkably sustained growth was observed in general terms in Sierra de Velasco and Famatina during the period 400–900 CE. Finally, the Bermejo River Basin became the scene for the settlement of La Rioja between 800 and 1500 CE., The authors would like to thank Conicet (PUE 0125-CRILAR and PIP 11220150100307), ANPCyT (PICT 2018-02138), the National University of Cuyo (SIIP UNCuyo 06/G787), and the National University of La Rioja (UNLaR 00-07644/2018) for funding our projects.