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Many terrestrial endotherm food webs constitute three trophic level cascades. Others have two trophic level dynamics (food limited herbivores; plants adapted to tackle intense herbivory) or one trophic level dynamic (herbivorous endotherms absent, thus plants compete for the few places where they can survive and grow). According to the Exploitation Ecosystems Hypothesis (EEH), these contrasting dynamics are consequences of differences in primary productivity. The productivity thresholds for changing food web dynamics were assumed to be global constants. We challenged this assumption and found that several model parameters are sensitive to the contrast between persistently warm and seasonally cold climates. In persistently warm environments, three trophic level dynamics can be expected to prevail almost everywhere, save the most extreme deserts. We revised EEH accordingly and tested it by compiling direct evidence of three and two trophic level dynamics and by studying the global distribution of felids. In seasonally cold environments, we found evidence for three trophic level dynamics only in productive ecosystems, while evidence for two trophic level dynamics appeared in ecosystems with low primary productivity. In persistently warm environments, we found evidence for three trophic level dynamics in all types of ecosystems. The distribution of felids corroborated these results. The empirical evidence thus indicates that two trophic level dynamics, as defined by EEH, are restricted to seasonally cold biomes with low primary productivity, such as the artic–alpine tundra and the temperate steppe. [ABSTRACT FROM AUTHOR]

Context: The niche reduction hypothesis (NRH) predicts that the realised niche of declining species is reduced by threats that are mediated by environmental, biotic and evolutionary processes, explaining why species decline in some locations but not others. The critically endangered central rock-rat (CRR) survives only in rugged mountain range habitat in central Australia and is highly vulnerable to cat predation. We predicted that cat density and ranging behaviour, and, hence, predation risk, is mediated by habitat complexity, thus explaining the mechanism maintaining the CRR refuge. Aims: We sought to determine whether cat densities were lower in the rugged CRR refuge than in an adjacent valley dominated by less complex rocky habitats and no longer occupied by CRRs. Methods: We installed arrays of camera traps along two parallel mountain ranges in the refuge and in the intervening valley habitats. We identified uniquely patterned individual cats and compared spatially explicit capture–recapture (SECR) models to evaluate our hypothesis that cat density varies with topographic complexity. Key results: The dominant effect in all models was the significant negative relationship between cat detection probability and fine-scale topographic ruggedness. Two of the best three SECR models indicated lower cat densities and relative home-range sizes in the refuge than in the valley. In total, 17% of cats were detected in both habitat types. Conclusions: We found some evidence that cat density and home-range size were mediated by habitat complexity. Further, the negative relationship between cat detection probability and topographic complexity suggests that cats spend less time foraging in CRR refuge habitat. Implications: Cat management programs, aimed at reducing predation pressure on the CRR, must include the refuge and surrounding habitats to control cats that pose a threat to CRR subpopulations. We sought to determine whether cat detectability and density were lower in a rugged refuge for the central rock-rat, than in an adjacent valley with flatter terrain. Cat detection probability and possibly density were lower in the refuge, suggesting that terrain complexity mediates cat predation risk. In total, 17% of cats were detected in both habitat types. Cat management programs must include the refuge and surrounding habitats to control cats that pose a threat to central rock-rats. Photograph by Peter J. McDonald. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Streamflow in arid and semi-arid regions is predominantly temporary, an integral part of mountain block hydrology and of significant importance for groundwater recharge and biogeochemical processes. However, temporary streamflow regimes, especially ephemeral flow, remain poorly quantified. We use electrical resistance sensors and USGS stream gauge data in 15 southern Arizona streams spanning a climate gradient (mean annual precipitation from 160 to 750 mm) to quantify temporary streamflow as streamflow presence and water presence, which includes streamflow, ponding and soil moisture. We use stream channel sediment data to estimate saturated hydraulic conductivity and potential annual infiltration. Annual streamflow ranged 0.6–82.4% or 2–301 days; while water presence ranged from 2.6 to 82.4% or 10 to over 301 days, or 4–33 times longer than streamflow. We identified 5 statistically distinct flow regimes based on the annual percent streamflow and water presence: (1) dry-ephemeral, (2) wet-ephemeral, (3) dry-intermittent, (4) wet-intermittent, and (5) seasonally-intermittent. In contrast to our expectations, stream channel density was a better predictor of annual streamflow and water presence than annual rainfall alone. Whereas, the dry-ephemeral and wet-ephemeral flow regimes varied with seasonal precipitation, the dry-intermittent, wet intermittent and seasonally-intermittent flow regimes did not. These results coupled with the potential infiltration estimates indicate that streamflow at the driest sites occurs in response to rainfall and overland flow while groundwater discharge and vadose zone contributions enhance streamflow at the wetter sites. We suggest that on a short temporal scale, and with respect to water presence, wetter sites might be buffered better against shifts in the timing and distribution of precipitation in response to climate change. Flow regime classifications that include both stream flow and water presence, rather than on stream flow alone, may be important for predicting thresholds in ecological functions and refugia in these dryland systems.

Lamb survival till first 28 days of life is critical as it increases the chances of economic gain in flock. Objective of the current study was to assess the incidence of neonatal mortality in lambs born in arid region of India and genetic and non-genetic factors affecting it. The present study was conducted using the data on 4,137 Magra and 4,595 Marwari sheep over 17 years (1999 to 2016). Incidence of neonatal mortality was very low in Magra (1.04%) and Marwari (2.48%) sheep, respectively in semi-intensive management system. Year and seasonal variation was observed for neonatal losses. Males had lower odds of survival as compared to females. Odds of survival were low if the lambs were born to dams of low body weight and in their first parity. It was observed that the lamb survival can be improved if due care of the lambs born with low birth weight (

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.

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. [ABSTRACT FROM AUTHOR]

Biological soil crusts (biocrusts) and arbuscular mycorrhizal (AM) fungi are communities of soil organisms often targeted to assist in the achievement of multiple ecological restoration goals. In drylands, benefits conferred from biocrust and AM fungal inoculation, such as improved native plant establishment and soil stabilization, have primarily been studied separately. However, comparisons between these two types of soil inoculants and investigations into potential synergies between them, particularly at the plant community scale, are needed to inform on‐the‐ground management practices in drylands. We conducted two full‐factorial experiments—one in greenhouse mesocosms and one in field plots—to test the effects of AM fungal inoculation, biocrust inoculation, and their interaction on multiple measures of dryland restoration success. Biocrust inoculation promoted soil stabilization and plant drought tolerance, but had mixed effects on native plant diversity (positive in greenhouse, neutral in field) and productivity (negative in greenhouse, neutral in field). In greenhouse mesocosms, biocrust inoculation reduced plant biomass, which was antagonistic to % root length colonized by AM fungi. Inoculation with native or commercial AM fungi did not influence plant establishment, drought tolerance, or soil stabilization in either study, and few synergistic effects of simultaneous inoculation of AM fungi and biocrusts were observed. These results suggest that, depending on the condition of existing soil communities, inoculation with AM fungi may not be necessary to promote dryland restoration goals, while inoculation with salvaged biocrust inoculation may be beneficial in some contexts. [ABSTRACT FROM AUTHOR]

Aims: Soil respiration (Rs) is a major pathway for carbon release to the atmosphere. We explored variability in dryland Rs response to rainfall pulses at multiple levels of spatial heterogeneity: 1) along a hyper-arid to arid rainfall gradient, 2) across soil surfaces that differ in stability and composition, and 3) among different geomorphic and vegetation patch types. Methods: We measured in situ Rs responses for 48 h following simulated rainfall pulses in the Namib Desert. Working across the rainfall gradient, we compared Rs responses on two soil surfaces. Each soil surface had two vegetation/geomorphic patch types that differed in organic matter sources and transport processes, with one characterized by depositional inputs and one characterized by erosional losses. Results: Soil respiration was highly responsive to rainfall pulses, although soil surfaces and patch types often exerted more control on Rs than did rainfall pulses. Rainfall generally had proportionally greater influence on Rs with higher annual rainfall. Greater Rs occurred on stable than unstable soil surfaces and in depositional than erosional patch types. Conclusions: Large differences in Rs among rainfall zones, soil surfaces, and patch types point to the need to carefully consider multiple scales of spatial heterogeneity when interpreting dryland biogeochemical fluxes. [ABSTRACT FROM AUTHOR]

A population of the crest-tailed mulgara (Dasycercus cristicauda) was recently located in the southern Strzelecki Desert in 2015. We analysed the diet of this population from scats (n = 87) collected over two sampling periods in 2016. Beetles were the most favoured food item, followed by spiders, ants and the small mammal Notomys fuscus. Within the beetles, ground beetles (Carabidae) and darkling beetles (Tenebrionidae) were the most frequently consumed. Dasycercus cristicauda appeared to exhibit a seasonal shift in prey consumption, moving from vertebrates in July 2016 to invertebrates in November 2016, while also consuming a wide and varied range of prey, even including rabbits in their diet in July 2016. The flexible diet observed in Dasycercus cristicauda may be a response to the fluctuating availability of food found in desert environments. Here, we analyse the diet of the crest-tailed mulgara (Dasycercus cristicauda) in the Strzelecki Desert. Dasycercus cristicauda consumed a wide and varied range of prey, even including rabbits in their diet. Beetles were the most frequent food item, followed by spiders, ants and the rodent Notomys fuscus. Prey consumption shifted from predominantly vertebrates in July 2016 to invertebrates in November 2016. The flexible diet observed in D. cristicauda may be a response to fluctuating availability of food in desert environments [ABSTRACT FROM AUTHOR]

With regard to the climatology included in the monography on Cabrera published in 1993, the subsequent operation of two new climatological stations in the main island (Cabrera), one with temperature data, in addition to those of rainfall, and the other with complete data, including wind and humidity, has allowed to complete the previous climatology with much more local information. From here the behaviour of Cabrera has been evaluated as a factor of its own climate, with the result that the effects associated with the presence of the island, on the wind, the temperature and the precipitation are not negligible, but they are much more moderate than those that generate larger islands, such as Menorca or Eivissa and, of course, Mallorca. Cabrera is situated, climatically speaking, halfway between what would be a costal islet and a larger island. About the climate of Cabrera, it can be added that it is quite windy and maritime, fully representative of the Mediterranean area where the archipelago is located, with strong seasonality, changing from a warm and dry summer to a period with temperate temperature and variable rainfall, with an also alternate wind regime, from predominance of eastern winds in summer to predominance of western winds in winter. The climate of Cabrera is not clearly arid, but it is not far from aridity. [ABSTRACT FROM AUTHOR]

For nearly three decades, the Whitfield (1992) characterisation scheme served as a reference framework to type South African estuaries. We outline a revised ecosystem classification scheme that incorporates biogeographical zonation and introduces new types. Coastal outlets were re-categorised as estuaries or micro-systems. For functional estuaries, the Estuarine Lakes, Estuarine Bays and Predominantly Open Estuary types were largely retained. New types are Estuarine Lagoons and Arid Predominantly Closed Estuaries. The numerically dominant, temporarily open/closed category was subdivided into Small and Large Temporarily Closed Estuaries, with a total habitat area of 15 ha, serving as threshold separating these two subdivisions. River mouths were renamed Fluvially Dominated Estuaries and divided into large and small size categories to reflect dissimilar catchment influences. Micro-systems were separated into micro-estuaries, micro-outlets, and waterfalls. South Africa's 290 estuaries were classified into 22 estuarine ecosystem categories arising from nine estuary types occurring across four biogeographical zones. In addition, 202 micro-systems were classified into nine ecosystem types, of which only the micro-estuaries (42) share possible functionality with estuaries. Estuaries subjected to functional shifts were also identified. The classification system provides a framework that integrates biogeography and the range of biophysical parameters evident in South Africa, and can be used for red listing of ecosystem types and determining estuarine sensitivity to pressures. [ABSTRACT FROM AUTHOR]

The xeromorphic vegetation is a significant component of the Australian flora and phylogenetic and phylogeographic analysis of xeromorphic plants provides a basis for understanding the origins and evolutionary history of the Australian vegetation. Here we expand on previous reviews of the origins and maintenance of the Australian flora with an emphasis on the xeromorphic component. Phylogenetic evidence supports fossil evidence for evolution of sclerophyll and xeromorphic vegetation from the Eocene with lineages becoming more common in the Oligocene and Miocene, a time of major change in climate and vegetation in Australia. Phylogenetic evidence supports the mesic biome as ancestral to the arid zone biome in Australia in phylogenies of key groups. The diversification and radiation of Australian species shows single origins of xeromorphic group mainly at deeper levels in phylogenies as well as multiple origins of arid occurring species at shallower levels. Divergence across the Nullarbor is also evident and speciation rates in south-western Australia were higher than in the south-east in several plant families. Estimates of timing of diversification generally show either constant rates of diversification or increased diversification from the mid to late Miocene. Phylogeographic studies consistently demonstrate high localised genetic diversity and geographic structure in xeromorphic species occupying both mesic and arid biomes. Phylogenetic and phylogeographic analysis provides a basis for understanding the origins and evolutionary history of the xeromorphic component of the Australian vegetation. Phylogenetic evidence shows the history of the evolution of sclerophyll and xeromorphic vegetation types from rainforest ancestors, including single origin xeromorphic radiations as well as multiple origins. Phylogeographic evidence shows persistence of species through the Pleistocene with accumulation of genetic diversity and differentiation. This review highlights the complexities and nuances in different lineages and the multiple responses of the flora to aridification. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study was planned to conduct a cross-sectional prospective survey in cattle and buffalos of districts Khanewal (southern sandy zone), Faisalabad (central plain zone) and Chakwal (northern arid zone) to determine the epidemiology of bovine babesiosis. A total of 2176 cattle and buffalos randomly selected from each of the study districts were screened through conventional microscopy of Giemsa stained blood films. PCR was performed for 207, 201 and 210 collected blood samples from Khanewal, Faisalabad and Chakwal, respectively. The DNA was amplified using species-specific primers, then subjected to 1.5% agarose gel electrophoresis. Logistic regression and Odds ratio were applied to analyze the data statistically at 95% confidence interval. Babesiosis was found prevalent in the bovine populations of the study districts with lower cumulative distribution of 17.23% (1125/6528) through optical microscopy and higher (P<0.05) of 26.86% (166/618) through PCR. Prevalence was found highest (P<0.05) in district Khanewal (22.75-34.03%) followed in order by districts Faisalabad (18.47-29.85%) and Chakwal (10.48-16.67%). Animal species (cattle-20.19% vs buffalo-14.28%), buffalo breed (Kundi-23.25% vs Nili-Ravi-8.31%), cattle breed (exotic, cross bred and Sahiwal - 29.34%, 21.45% and 10.3%, respectively), sex (female-21.13% vs male-12.68%), age (young-23.17% vs adult-11.9%), animal keeping (tethered-23.48% vs open-11.10%), housing system (closed, semi-closed and open - 22.10%, 19.25% and 9.24%, respectively), hygienic system (very poor, poor and good - 21.04%, 19.78% and 7.07%, respectively), floor pattern (uncemented, partially cemented and cemented - 20.39%, 17.54% and 11.98%, respectively) and season (summer, autumn, spring and winter - 23.41%, 20.47%, 17.77% and 7.29%, respectively) were also found positively associated (P<0.05) with the dissemination of babesiosis in the bovine population of study districts. The study provided baseline data on the distribution of bovine babsesiosis in the selected three agro-geoclimatic zones of Punjab, Pakistan which can help in preventive management tools to reduce the risk of disease in the livestock population of Punjab, Pakistan. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing the risk of predation for small prey species. The postfire effect of predation has especially deleterious effects in Australian habitats owing to the presence of invasive mammalian predators, the red fox (Vulpes vulpes) and feral cat (Felis catus), that rapidly exploit burned habitats. Here, we investigated whether the provision of artificial shelter could alleviate the risk of predation perceived by two species of small marsupial, the dunnarts Sminthopsis hirtipes and S. youngsoni, in open postfire habitat in the sandridge system of the Simpson Desert, central Australia. We installed artificial shelters constructed from wire mesh that allowed passage of the dunnarts but not of their predators at one site, and measured and compared the perceived risk of predation by the dunnarts there with those on a control site using optimal patch-use theory (giving-up densities, GUDs). GUDs were lower near artificial shelters than away from them, and near dune crests where dunnarts typically forage, suggesting that the shelters acted as corridors for dunnarts to move up to the crests from burrows in the swales. Foraging was lower near the crest in the control plot. Two-day foraging bouts were observed in dunnart activity, with recruitment to GUD stations occurring a day earlier in the augmented shelter plot. Despite these results, the effects of the shelters were localized and not evident at the landscape scale, with GUDs reduced also in proximity to sparse natural cover in the form of regenerating spinifex grass hummocks. Mapping dunnart habitat use using the landscape of fear (LOF) framework confirmed that animals perceived safety near shelter and risk away from it. We concluded that the LOF framework can usefully assess real-time behavioral responses of animals to management interventions in situations where demographic responses take longer to occur. [ABSTRACT FROM AUTHOR]

Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing the risk of predation for small prey species. The postfire effect of predation has especially deleterious effects in Australian habitats owing to the presence of invasive mammalian predators, the red fox (Vulpes vulpes) and feral cat (Felis catus), that rapidly exploit burned habitats. Here, we investigated whether the provision of artificial shelter could alleviate the risk of predation perceived by two species of small marsupial, the dunnarts Sminthopsis hirtipes and S. youngsoni , in open postfire habitat in the sandridge system of the Simpson Desert, central Australia. We installed artificial shelters constructed from wire mesh that allowed passage of the dunnarts but not of their predators at one site, and measured and compared the perceived risk of predation by the dunnarts there with those on a control site using optimal patch-use theory (giving-up densities, GUDs). GUDs were lower near artificial shelters than away from them, and near dune crests where dunnarts typically forage, suggesting that the shelters acted as corridors for dunnarts to move up to the crests from burrows in the swales. Foraging was lower near the crest in the control plot. Two-day foraging bouts were observed in dunnart activity, with recruitment to GUD stations occurring a day earlier in the augmented shelter plot. Despite these results, the effects of the shelters were localized and not evident at the landscape scale, with GUDs reduced also in proximity to sparse natural cover in the form of regenerating spinifex grass hummocks. Mapping dunnart habitat use using the landscape of fear (LOF) framework confirmed that animals perceived safety near shelter and risk away from it. We concluded that the LOF framework can usefully assess real-time behavioral responses of animals to management interventions in situations where demographic responses take longer to occur. [ABSTRACT FROM AUTHOR]

The formation of subsurface freshwater lenses on top of brackish groundwater is a fascinating hydrologic phenomenon that creates groundwater supplies of great potential value in arid regions. Information on the recharge quantity and mechanism of these lenses is both scarce and uncertain. This study examines the formation and macroscale stability of the Rawdatain freshwater lens in Kuwait, for which significant pre‐development data are available. The Rawdatain is a large (150 million m3) subsurface freshwater lens overlying brackish groundwater compared to the other freshwater lenses in the Arabian Peninsula. In this study, a three‐dimensional (3D) density‐dependent groundwater flow model is tested against the following data targets to estimate long‐term diffuse and focused groundwater recharge: (i) groundwater head, (ii) total dissolved solids (TDS) groundwater concentration, (iii) volume and vertical thickness of stored groundwater of three different water quality TDS ranges (0–700, 700–1000 and 1000–2000 mg/L) and (iv) geometrical shape features of the lens along cross‐sections. To better represent the spatial variation in TDS, six different recharge zones were assigned to allocate diffuse and focused recharge conditions. Twelve recharge rate scenarios, encompassing a wide range of feasible long‐term average annual recharge values (200,000–5,000,000 m3/year), were tested against the multiple targets and compared with the groundwater age of the Rawdatain lens. Based on comparison with data targets, the long‐term average annual recharge is estimated to be 500,000 m3/year. Scenarios of reduced recharge, which may occur due to changes in land‐use or climate, demonstrate the extremely slow response of the lens, which is in agreement with the slow development and formation of the lens (>2,000 years). Within a 100‐year time frame, a 50% reduction in annual recharge reduces the lens volumes by 21, 17 and 9% for the three water quality categories, respectively. This study demonstrates the stability of freshwater lenses in arid regions and also provides methodology for similar focused rainfall recharge freshwater lenses. [ABSTRACT FROM AUTHOR]

Sunflower (Helianthus annuus L.) is an important oilseed plant with high adaptability to semi-arid conditions for reasonable vegetable oil production. The aim of this study was to determine the agronomic responses of Bosfora hybrid sunflower cultivar sown inter-row (50 and 70 cm) & intra-row (20, 25, 30, 35 and 40 cm) spacing in rainfed conditions. The field experiment was laid out on split plots in randomized blocks with three replications for two years (2016 and 2017). Inter row spacings were placed in the main plots and intra row spacings were placed in the subplots. Narrower inter-row (50 cm) and intra-row (20 and 25 cm) plant spacing caused taller plant development but decreased stem thickness, head diameter, thousand-seed weight, number of seeds in a head, dehulled seed ratio, seed weight of per plant, crude oil ratio, day to flowering and maturity. The highest yield (2759.9 kg ha-1) was obtained in 50×20 cm spacing while the lowest (1963.8 kg ha-1) yield was obtained in 70×20 cm spacing, more likely, due to the increase in the number of plants per unit area. The crude oil ratio was decreased by narrower spacing. However, oil yield was increased with seed yield (kg ha-1) and reached the highest amounts (1221.9 and 844.2 kg ha-1) in narrow row spacing, attributed to the plant population per unit area. To conclude that the highest seed yield was obtained from narrower (50×20 cm and 50×25 cm) seeding rates in rainy year (2016), while the highest yields were obtained from lowest plant population (70×20 and 70×25 cm) rates in dry year (2017). [ABSTRACT FROM AUTHOR]

Hydraulic project alerts hydrological cycle and changes biochemistry of water as a result. In this paper, we investigated the change in groundwater chemistry in Qinwangchuan basin as affected by the Yindaruqin irrigation project. Groundwater samples were taken from the basin and were chemically analyzed before and after the irrigation project was in operation. The change in groundwater chemistry was analyzed using methods including statistics, Gibbs graphs and ions ratios. The results showed that the coefficient of variation (CV) of all main ions was larger than 10%, with their CV in the plain area being higher than that in the loess hill area. The total dissolved solids in the groundwater were currently high, with Na+ being the dominant cation and Cl- and SO4 2- the dominant anions. Salty and brackish water was found in most parts of the basin, and fresh water with total dissolved solids less than 1.0 g/L existed only in the middle of the basin. The total dissolved solids in the groundwater decreased from the loess hills at the edge of the basin towards the central plain area, and the associated hydro-chemical type of the groundwater changed gradually from Cl·SO4- Na type to HCO3·SO4- Na type. Before the irrigation project was constructed, the main geochemical type of the groundwater was Cl·SO4- Na, Cl·SO4- Na·Mg and SO4·Cl – Na. At earlier operating stage of the project, leaching of soluble salts from the topsoil led to an increase in total dissolved solids and hardness in the groundwater. With the decrease in soluble salts in the topsoil due to leaching, however, the total dissolved solids in the groundwater have been in decline since 2009, especially in the center of the plain where the total dissolved solids in the groundwater in some areas had reduced to < 1.0 g/L from > 3.0 g/L and the groundwater type changed from Cl·SO4-Na to HCO3·SO4- Na, HCO3·SO4- Na·Ca·Mg, and Cl·SO4·HCO3- Na, respectively. In contrast, the groundwater chemistry in the loess hills at the edge of the basin did not show significant change due to limited irrigation, and its chemical type is still Cl·SO4-Na·Mg despite a slight increase in total dissolved solids and total hardness. The groundwater type at Dangpu area in the southern basin changed from Cl·SO4-Na to Cl·SO4-Na·Mg, with a light decrease in total dissolved solids and total hardness. The change in groundwater chemistry in the Qinwangchuan basin is affected by both natural and anthropogenic factors. The infiltration and salt leaching due to irrigation increased the total dissolved solids in the groundwater initially followed by a dilution. Rock weathering and dissolution of minerals increased the total dissolved solids, and groundwater evaporation also increased the total dissolved solids in areas where the groundwater table was shallow. The ions in the groundwater originated from silicate weathering and dissolution of halite, along with the evaporation-induced condensation. Industry did not affect groundwater chemistry but the application of chemical fertilizer led to an increase in NO3- in the groundwater. These results provide a useful dataset for sustainable management of the groundwater resources in proximal areas of the Qinwangchuan irrigation project. [ABSTRACT FROM AUTHOR]

Drylands cover 41% of the Earth's terrestrial surface, play a critical role in global ecosystem function, and are home to over two billion people. Like other biomes, drylands face increasing pressure from global change, but many of these ecosystems are close to tipping points, which, if crossed, can lead to abrupt transitions and persistent degraded states. Their limited but variable precipitation, low soil fertility, and low productivity have given rise to a perception that drylands are wastelands, needing societal intervention to bring value to them. Negative perceptions of drylands synergistically combine with conflicting sociocultural values regarding what constitutes a threat to these ecosystems. In the present article, we propose a framework for assessing threats to dryland ecosystems and suggest we must also combat the negative perceptions of drylands in order to preserve the ecosystem services that they offer. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]

Rainwater harvesting and associated storage is essential for cattle ranching in the drylands of Argentina and elsewhere. This is the first study to attempt to quantify the hydrological inflows and losses from rainwater harvesting impoundments. To address the direct effect of cattle within impoundments, a typical cattle-affected impoundment was instrumented and compared with that of a similar impoundment but without cattle access. Analysis of the storage dynamics with reference to the controlling variables demonstrated the highly episodic nature of the generation of infiltration-excess overland flow that recharged the impoundments. The impoundments experienced 43 and 35% of storage loss to open-water-evaporation for the cattle-affected and control impoundments, respectively. Critically, the cattle-effected impoundment lost only 15% of storage to leakage (after cattle consumption was taken into account), while the control lost 65% of its water to basal leakage. Indeed systems modelling of the rainfall-storage dynamics showed that the cattle-affected impoundment, despite consumption by 300 cows, maintained water in the impoundment (per a unit input of rainfall) for longer than the control (a 65- versus 25-day residence time). These results highlight the unintended beneficial effect of cattle trampling on the floor of the impoundment reducing leakage losses. [ABSTRACT FROM AUTHOR]

Patterns of plant biomass partitioning are fundamental to estimates of primary productivity and ecosystem process rates. Allometric relationships between above‐ground plant biomass and non‐destructive measures of plant size, such as cover, volume or stem density are widely used in plant ecology. Such size‐biomass allometry is often assumed to be invariant for a given plant species, plant functional group or ecosystem type.Allometric adjustment may be an important component of the short‐ or long‐term response of plants to abiotic conditions. We used 18 years of size‐biomass data describing of 85 plant species to investigate the sensitivity of allometry to precipitation, temperature or drought across two seasons and four ecosystems in central New Mexico, USA.Size‐biomass allometry varied with climate in 65%–70% of plant species. Closely related plant species had similar sensitivities of allometry to natural spatiotemporal variation in precipitation, temperature or drought. Annuals were less sensitive than perennials, and forbs were less sensitive than grasses or shrubs. However, the differences associated with plant life history or functional group were not independent of plant evolutionary history, as supported by the application of phylogenetically independent contrasts.Our results demonstrate that many plant species adjust patterns in the partitioning of above‐ground biomass under different climates and highlight the importance of long‐term data for understanding functional differences among plant species. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Serum progesterone, estradiol 17-β and energetic metabolites profiles were investigated during the spring breeding season in non-pregnant and pregnant "Ouled Djellal" ewes bearing singleton or twin fetuses in arid and semi-arid climates of Algeria. Twenty and thirty ewes aged 1 to 4 years from semi-arid and arid zones, respectively, were used. In semi-arid zone, 15 ewes were pregnant (eight carrying one fetus and seven carrying twins). In arid zone, from 24 pregnant ewes, 14 carried singleton and 10 carried twins. Blood sampling were collected before mating, in the first and the last month of pregnancy and after lambing. Significant effect (p < 0.05) of litter size was found during early gestation on progesteronemia in arid region and on estradiolemia (p < 0.05) in both regions. During late pregnancy significant effect of fetal number was observed in semi-arid (p < 0.05) and arid (p < 0.001) area for progesterone and only in arid zone (p < 0.05) for estradiol. In the present study, no significant effect of litter size was found on serum glucose, cholesterol and triglycerides in both regions. Reproductive hormones profiles and energetic metabolism in pregnant ewes raised in arid zone are more altered than those in semi-arid zone. [ABSTRACT FROM AUTHOR]

A lack of water quality monitoring stations in arid regions makes it difficult to estimate the exact level of water pollution. Satellite technology is crucial for monitoring the water quality of salt lakes, but due to the diversity of terrestrial water bodies, it is challenging to establish relationships between lake water color parameters and remote sensing reflectance. This study aims to evaluate the reliability of the colored Quasi-Analytical Algorithm Dissolved Organic Matter (QAA-CDOM) model over Ebinur Lake. The absorption coefficient measured on May 19, 2021 was used to analyze the optical properties of Ebinur Lake. The findings show that the QAA-CDOM model performed well in estimating the absorption coefficient of CDOM at 443 nm, with the r2 and RMSE values of 0.69 and 0.12 m−1, respectively. The Landsat 8 OLI data and QAA-CDOM model were then used to derive the spatial-temporal characteristics of the CDOM concentration over Ebinur Lake from 2014 to 2021. The concentration of CDOM changes significantly across time and space, ranging from 0 to 2.5 m−1, with the lowest concentration in May and the highest in August. The central region of the lake has a lower concentration of CDOM than the other regions due to the reflectance of the shallow parts of the lake. This study clarified the inherent optical characteristics of saline lakes and proved the applicability of using the QAA-CDOM model to monitor surface water quality in arid regions of China. This research may be useful for future analyses of the carbon cycle calculations in salt lakes in arid regions. • Explore the optical characteristics of Lake. • Validate model's applicability. • Analyze CDOM change. [ABSTRACT FROM AUTHOR]

Rising crop risk for farmers and greater subsidy costs for governments are both associated with changing climatic conditions, including increased water scarcity. The resilience of Agave spp. in both hot and dry conditions, combined with their wide range of uses, position these plants as novel high-yielding crops suitable for both (i) a warming climate and (ii) agricultural regions with finite water resources. A simple model of the physiological response of Agave americana to variations in solar radiation, temperature, and precipitation was used to predict A. americana yields globally at a 4 km spatial resolution for both contemporary climate and high-end warming scenarios. The potential growing region for A. americana expanded by 3–5% (up to 3 million ha) and potential biomass production increased by 4–5% (up to 4 Gt of additional biomass) with climate warming scenarios. There were some declines in biomass with the climate warming projected in smaller dispersed locations of tropical South America, Africa, and Australia. The amount of water required for optimal A. americana yield is less than half of the current water required for other crops grown in semi-arid agricultural regions of the southwestern US, and a similar low water demand can be expected in other semi-arid regions of the world. Rock mulching can further reduce the need for irrigation and increase suitable cropland area for A. americana by 26–30%. We show that >10 Mg ha−1 y−1 of A. americana biomass could be produced on 27 million ha of cropland without requiring irrigation. Our results suggest that cultivation of A. americana can support resilient agriculture in a future with rising temperatures and water scarcity.

Accurate determination of annual leaf litter amount constitutes the basis of scientific leaf litter nutrient release assessment. In this study, we tried to establish an equation between leaf litter amount and relevant tree characteristics of Populus euphratica (P. euphratica) tree on an individual scale, and to find the leaf litter nutrient content variation within 760 d incubation experiment in the main channel of the Tarim River, China. Results showed that there was no proper equation between leaf litter amount and tree height or diameter at breast height. There was great difference in leaf litter amount on an individual scale. The mean annual leaf litter amount per tree was 10.2, 14.83 kg/y obtained by field survey and the equation between annual leaf litter amount and canopy area on an individual scale, respectively. Leaf litter mass changed over incubation time and exhibited three main phases: an initial slow decomposition phase (0–173 d) with mass loss; a rapid mass loss phase (173–290 d); and a second rapid mass loss phase (470–560 d). Overall, carbon (C) and potassium (K) content decreased, and nitrogen (N) and phosphorus (P) content increased in a fluctuating manner over time in the P. euphratica leaf litter.

At gauged watersheds, the time of concentration can be estimated using rainfall-runoff data; however, at ungauged watersheds, empirical methods are used instead. Large errors in the application of empirical methods may cause inaccurate modeling of floods and unreliable structure design. In this paper, methods for calculating the time of concentration (Tc) were compared to identify the best equation for estimating Tc in ungauged watersheds of an arid region. The graphical method, based on measured data, was compared to 15 empirical methods to determine which empirical method returned the best results. The graphical method was applied to 33 rainfall-runoff events in four rural sub-watersheds located in the central parts of Hormozgan province, Iran. A ranking-based procedure was used to select the best performing empirical methods. To minimize bias and improve accuracy, the best performing empirical methods were modified by adjusting their formulas. According to the study, three empirical methods: (1) Williams, (2) Pilgrim and Mac Dermott, and (3) Arizona DOT, performed the best in the study areas. The results also showed that the modified Williams and Arizona DOT’s formulas were able to estimate the time of concentration in ungauged watersheds with an error lower than 1%.

The species Astragalus podolobus is one of the endemic species of winter pastures that grows in arid and semi-arid areas in the north of Gonbad-e Kavous. To investigate effective methods of breaking seed dormancy of Astr-agalus podolobus, an experiment was carried out in the framework of a completely randomized design with 15 treatm-ents and 3 replications. Treatments included controls, 98% sulfuric acid, dry chilling for 10 and 15 days, wet chilling for 10 and 15 days, and boiling water 1, 3, 5, 10 and 15 minute, respectively. Analysis of variance showed that the perc-entage and speed of germination were significant in different groups while the average time of germination in different treatments was not significant. The results of comparing mean values showed that the percentage and the speed of germination in boiling water treatments were best in comparison with other treatments with significant differences. The results of this experiment also showed that reducing the exposure time of seeds to boiling water increases the germination percentage and speed, consequently, the highest percentage and speed of germination was observed in boil-ing water 1 minute. Boiling water 1 minute treatment can increase the germination percentage up to 47% and the seed germination speed from 0.43 to 3.09 seeds per day

Southern Iran hosts abundant salt karst phenomena in numerous salt diapirs. This paper provides a new insight into the relationships among climate, cap soil and salt karst hydrogeology. Cave systems were documented and mapped. Soil, drip, stream, and flood waters from different environments were studied at several diapirs. It was revealed that the soil water chemistry depends on both the climate and cap soil thickness. In semi-arid climates, a thick cap soil forms (>3 m) and water has very low TDS values (0.15 g/l). In arid climates, a shallow cap soil forms, and soil water is gypsum-saturated with low dissolved halite contents. In both environments, drip waters from salt caves and springs displayed high TDS values (255 to 347 g/l). This is explained by the dissolution of halite and minor anhydrite/gypsum, a K-Mg sulfate and sylvite. Spring water plots on a local meteoric water line, whereas drips in caves have an evaporative signature. The flash flood runoff is dominated by event rain water based on isotopic data, while springs are dominantly supplied by a base flow component. The mean residence time of water on the diapirs is controlled by the cap soil thickness. Water residence times may reach several hundreds of years on a thick cap soil based on an exponential model butsoil.