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Speleothem deposits in nowadays arid environments are important climate archives, as they indicate phases of enhanced precipitation and can precisely be dated by uranium-series dating. So far only very few of such archives have been found in the today hyper-arid Saharo-Arabian Desert (SAD). Therefore, the study at hand fills a gap that exists for speleothem climate archives in Northeast Africa. A new record from Saqia Cave (Central Eastern Desert, Egypt) documents for the first-time speleothem growth in Egypt for all sub-stages of MIS 5 and singular phases during MIS 6. Most important growth phases occur during periods of strong increase and maximum orbitally-forced northern hemisphere insolation, but also during phases of low insolation, which are in general attributed to aridity in North Africa. Here, at least semi-arid climate conditions are proposed for periods of low insolation during stadials of MIS 5. This suggests an impact of different possible sources of precipitation, apart from large scale shifts of the African monsoon, such as Red Sea Troughs, tropical plums and a larger spatial extent of the Mediterranean winter-rainfall zone. Concerning the spatial rainfall pattern in Egypt, we propose a considerable east to west rainfall gradient in Egypt for the Last Interglacial and suggest a stronger impact of variable moisture sources in the Eastern Desert near the Mediterranean and Red Sea in comparison to the more continental Western Desert of Egypt. This reveals more favorable pre-conditions for an enhanced land use potential in the past. Therefore, the more sustaining wetter climate in the Eastern Desert point to a recurring feasible dispersal corridor for Homo sapiens from the tropical climate into the temperate climate regime throughout MIS 5. Such a more humid climate provided an ideal basis for long-term, favorable environmental conditions east of the Nile Valley, creating a kind of contiguous landscape corridor that may have been attractive to humans and wildlife alike, linking the East African tropical climate regime with that of the temperate zone in Northeast Africa and Eurasia.

Roselle (Hibiscus sabdariffa L.) is recognized as a valuable food crop due to its nutraceutical potential, rich pigment content, and medicinal properties. However, there is limited information on planting dates and suitable genotypes for roselle cultivation in arid and semi-arid regions. The objective of this field study was to investigate the influence of five planting dates (March, April, May, June, and July) on morphological and phytochemical characteristics of different roselle genotypes. Among genotypes, eight (Jiroft, Dalgan, Bampoor, Iranshahr, Nikshahr, Roodbar, Saravan, and Qaleganj) were Iranian landraces, and HA and HS-24 were originated from Ghana and Bangladesh, respectively. Planting date significantly influenced the number of branches, bolls and seeds per plant, sepal fresh weight, calyx and biomass yields, and harvest index in tested roselle landraces. The greatest morphological growth, fresh sepal weight (50.6 g plant−1) and calyx yield (1519 kg ha−1) were observed with the roselle planted in early May. Moreover, amounts of chlorophyll, flavonoids and antioxidant remained higher in roselle when planted between April–May. The number of branches/plant was found to be an important determinant of calyx yield (r = 0.707) in roselle. Dalgan resulted in the greatest growth and yields within a comparatively shorter period of time compared to other tested landraces. Both principal component analysis (PCA) and cluster analysis also indicated that Dalgan landrace possessed most suitable morphological and phytochemical traits among tested landraces, and therefore, it could be planted adopted for extensive cultivation settings in the arid and semi-arid regions.

The Azraq oasis in the Eastern Desert of Jordan has produced considerable stone artefacts attributed to the early Palaeolithic, yet relatively few data are available regarding the chronology and palaeoenvironmental contexts of the remains. In this study, we present stratigraphic, sedimentological, and micropalaeontological analyses of the Late Acheulean site SM1 located within the former Shishan Marsh, which we combine with geochronological and sedimentological data from 13 neighbouring geological exposures to reconstruct landscape evolution at the western margin of the Shishan Marsh. We then discuss the Late Quaternary palaeolandscapes of the Greater Azraq Oasis Area over the past c. 350 ka. Our work demonstrates that the central Azraq Basin experienced three local wetting-drying cycles since the late Middle Pleistocene that would have dramatically shifted the quantity and distribution of freshwater resources, ranging from expansive wetland landscapes to desert refugia characterised by isolated spring pools—changes that would have significantly impacted the mobility decisions and settlement patterns of Palaeolithic inhabitants. Our study highlights that developing long-term records of human-environment dynamics in arid environments requires a mosaic approach to palaeoenvironmental reconstruction that is nested within a well-developed understanding of landscape evolution.

Mycobionts make up most of the genetic diversity of underground life. Despite their abundance, their impact on terrestrial ecosystem processes is still poorly understood. Estimates suggest that 95% of plant species rely entirely on microbial symbiotes for growth and survival, underlining their importance in soil as a regulator of plant species richness and diversity. In this study, we explore an inventory of the fungal rhizobiome of two populations of Atlas pistachio in Laghouat (Algeria), a typical hot and arid region. Six healthy trees of different age classes were randomly sampled from each site during April 2016. In spite of the arid climate in our study area, microscopic identification revealed important fungal richness belonging to four phyla: Ascomycota, Glomeromycota and Basidiomycota with the exclusive presence of Mucoromycota in dayate Saadi. The fungal strains recorded indicate a high abundance of the Acaulospora sp. and Glomus sp. genera for the Glomeromycota phylum and Fusarium sp. genus for the other phyla. Shannon-Wiener diversity and evenness indices proved to be the highest at dayate Saadi. Dayate El Gouffa, however, is the least disturbed. Most of the strains recorded correspond to genera with a strong affinity for environments rich in organic matter, with high levels of total limestone, basic pH, and high levels of clay and fine silts as shown in the dayate Saadi soils. As for the dayate El Gouffa soils, they show a low organic matter content. They are less calcareous, with a very basic pH and predominance of coarse silts and coarse sands. The high rate of these granulometric fractions could explain the presence of Gigaspora sp. only in this daya. Our results indicated the strong impact of soils proprities on the rhizobiome community composition and might be explained by differences in the degree of fungi selectivity for each sampled site.

A Late Cretaceous fossil flora composed of five fossil seed genera and two charophyte genera was discovered and reported here from the siltstone and green marl band of the Lameta Formation at the Chui Hill section and the Chhota Simla Hill section in the Jabalpur area. On the basis of comparative studies, including thin-section and XRD analysis, the palaeoenvironment is deduced to be arid to semi-arid fluvial-lacustrine. The recovered flora suggests Laurasian palaeobiogeographic affinity and shows the dispersal route from Europe to India via Africa.

Relationships between genome size and environmental variables suggest that DNA content might be adaptive and of evolutionary importance in plants. The genus Larrea provides an interesting system to test this hypothesis, since it shows both intra- and interspecific variation in genome size. Larrea has an amphitropical distribution in North and South American deserts, where it is most speciose. Larrea tridentata in North America shows a gradient of increasing auto polyploidy; while three of the four studied South American species are diploids, L. divaricata, L. nitida, L. ameghinoi, and the fourth is an allopolyploid, L. cuneifolia. We downloaded available focal species’ georeferenced records from seven data reservoirs. We used these records to extract biologically relevant environmental variables from WorldClim at 30 arcseconds scale, to have a broad characterization of the variable climatic conditions of both regions, and a climatic envelope for each species. We estimated relative DNA content index and relative monoploid genome values, by flow cytometry, of four most abundant Larrea species throughout their respective ranges. Then we winnow the bioclimatic dataset down to uncorrelated variables and sampled locales, to analyse the degree of association between both intra- and interspecific relative DNA content and climatic variables that are functionally relevant in arid environments using Pearson correlations, general linear and mixed effects models. Within the genus Larrea, relative DNA content increases with rising temperature and decreases with rising precipitation. At the intraspecific level, all four species show relative DNA content variation across climatic conditions. Larrea is a genus that shows genome size variation correlated with climate. Our results are also consistent with the hypothesis that extreme environmental pressures may have facilitated repeated whole genome duplication events in North America, while in South America, reticulate evolution, as allopolyploidization, and speciation might have been climate-dependent since the Oligocene.

Harvesting water from the atmosphere is an important process to solve the extreme lack of water resources in arid regions. Adsorption-based atmospheric water harvesting (AWH) takes advantage of solar thermal energy to harvest water from air. This technique is particularly suitable for arid regions characterized by low humidity and an abundance of sunshine. Nonetheless, under low humidity conditions, AWH is highly dependent on water-adsorbing materials exhibiting excellent performance. In this work, a metal–organic framework (MOF), namely [Zn2(bpy) (btec)(H2O)2]·2H2O, also denoted as MWH-1, was investigated for application in water harvesting under low humidity conditions ( 200 cm3∙cm−3; RH = 10%, uptake: >250 cm3∙cm−3). This ensured effective water harvesting at high temperatures during the day. In situ powder X-ray diffraction and Fourier-transform infrared analyses confirmed the sensitive water adsorption process of MWH-1a. The X-ray single-crystal study further demonstrated that single-crystal structures could be completely restored following water harvesting. MWH-1 showed good structural stability and enabled water harvesting under low humidity and high temperature conditions. Thus, it has the potential for application in round-the-clock water harvesting in extremely arid regions.

We present a multiproxy record of grain size and stable carbon isotope from the Lilaur lake, Ganga Basin, India to understand the history of lake formation linked to changes in Indian monsoon precipitation during ~13714 to 3073 calibrated year before Present (cal yr BP). A comparison is made between Lilaur lake proxy record with those from other parts of South Asia as well as North Atlantic to understand extent and causes of monsoon variability and its influence on the fauna and flora of the region. Chronology of lake core was constrained using AMS 14C and optically stimulated luminescence (OSL) dates. This study suggests a transition from river to lake during ~5800 to 5189 cal yr BP which is supported by reduced precipitation with weakening of the Indian summer monsoon (ISM). This river to lake transition culminated in a severe arid phase during 4250 to 4050 cal yr BP (4.2 ka event), corresponding to enhanced El Nino activity, southward shift of the Inter-Tropical Convergence Zone, and aridification of India when the ISM was weak.

Hydrologic response in a watershed is driven by precipitation. Multi-site rainfall generators can be used to model watersheds using spatially varied rainfall inputs to better analyze how the rainfall variability affects runoff generation. This study adopted both a single-site rainfall generator (CLIGEN) and a multi-site rainfall generator to generate two rainfall data sequences, which were then used to drive the Soil and Water Assessment Tool (SWAT) for runoff simulation. The 148-km2 Walnut Gulch Experimental Watershed and its two sub-watersheds were selected to evaluate the hydrologic response. Runoff calibration was done against measured runoff in the watershed. Statistics showed that the single-site and multi-site rainfall generators gave similar results regarding annual precipitation. However, the multi-site generator performed much better than the single-site generator in both mean summer flow and for the different return period flows. The runoff derived from the single-site generator was significantly over-estimated in all three watersheds. As for the multi-site generator, the derived runoff was satisfactorily predicted in the smaller watersheds but only overestimated in the largest watershed. This indicated that in small to medium sized watersheds, the spatial variability of rainfall could play an important role for hydrologic response because of the heterogeneity of convective rainfall in this semi-arid region, which makes the application of multi-site rainfall generator a better option than the single-site generator.

Fat-tailed Barbary sheep are well-adapted to Tunisian arid areas and extensive management. Multivariate morphometric characteristics of this important breed have not been investigated. Morphometric data, collected during February-April 2014, of 249 purebred redhead Barbary ewes, ranged into young (1–2 years) and adults (2–9 years), and reared in Sfax, southern Tunisia, were used to explore the breed morphostructural characteristics under harsh arid conditions (

Rates of soil development provide critical information about the types and rates of geomorphic and landscape evolutionary processes. Soil development in arid and semiarid regions of the southwestern United States is predominantly controlled by influx of eolian dust, yet our ability to quantify the rates of morphologic development and of dust and carbonate incorporation is limited by available age control. We describe 10 pedons in the Socorro area of central New Mexico and analyze their silt, clay, and carbonate contents. These soils have well-established direct or indirect age control that we used to estimate average rates of dust and carbonate accumulation over the past ~0.5–800 ka. We also computed the profile development index (PDI) for these soils using 10 common morphologic properties and compare our resulting PDI chronofunction to those from northern and southern New Mexico. We find that the net silt-and-clay content increases in progressively older soils at rates similar to the profile-mass carbonate contents, presumably sourced primarily from eolian dust. Our chronofunction comparison indicates that soil development occurs more rapidly in higher latitude regions of New Mexico than in the drier warmer climates of the Socorro area and southern New Mexico. We interpret the N–S regional trend of soil development considering a regional climate gradient. We conclude that greater mean annual precipitation and cooler mean annual temperatures and/or slower rates of eolian dust accumulation into the soil profile at higher latitude northern sites cause the observed differences in regional soil development. This would promote greater mobility of available silt and clay, and also increase rates of soil formation, as indicated by the presence of argillans in late-Pleistocene soils of northern New Mexico.

This paper presents the first insight into the interpretation of the wood charcoal from the Holocene layers of Wonderwerk Cave. Situated in the Northern Cape Province in the arid interior of South Africa, the site provides a unique and valuable chronological record of past environmental fluctuations and responding human behavioural adaptations spanning the last two million years. The Holocene strata have been dated to cover the last 12.5 ka cal BP years, but exclude the last 100 years because of contamination. A sizeable amount of charcoal was recovered from these strata and remnants have been identified, described and the species composition amongst the strata compared. Most identified species are those that tolerate hot, dry conditions, signalling an arid trend during the Holocene. Comparison with present day species distributions suggests an eastwards shift in modern vegetation. The charcoal data also indicate that during the mid Holocene there was a wetter period from 6.2 to 4.5 ka cal BP, coinciding with stratum 4a.

We have reassessed the palynological record of Equus Cave in the Savanna Biome of the southern Kalahari, one of the longest Late Quaternary pollen records for the semi-arid central interior of South Africa. We combined published pollen results from the cave, derived from hyena coprolites and the rubified deposits in which they occur, into a single sequence. By re-considering the chronology of this sequence, we critically evaluated the palaeoenvironmental record for the site. We compared the pollen evidence from Equus Cave to that from the longer Wonderwerk Cave records (stalagmite, sediments and dung), also located in the Savanna Biome. Then, we contrasted Equus and Wonderwerk records with other previously published pollen sequences derived from a range of sources from several sites in central South Africa. These sites follow a broad northwest to southeast transect of c. 500 km through the Grassland and Nama Karoo Biomes of the Free State and Eastern Cape. Applying Principal Components Analysis to the pollen data, we derived climatic signals at a regional scale to refine reconstructions of Late Quaternary changes for central South Africa., LS was supported by the National Research foundation (South Africa) (NRF Grant no. 85903). The Leakey Foundation (USA) and the National Science Foundation (USA) respectively supported CBB’s work at Baden-Baden and Blydefontein. LS appreciates Juan Ochando Tomas’ collaboration relating to hyena coprolites in Project CGL-PID2019-1049449GB-I00 (FEDER/Ministry of Science and Innovation, Spain).

The Yangtze River is a major component of the ‘Asian Water Tower’ and it provides freshwater resources for hundreds of millions of people in East Asia. Hence, climatic and environmental changes in the source region of the Yangtze River (SRYR) are of major significance for understanding changes in the status of its freshwater resources. However, due to the contradictory results shown by the available paleoclimatic records from the SRYR and neighboring regions, it remains unclear how the regional climate and hydrology have evolved since the middle Holocene. Here, we present records of hydrological variations based on multiple proxies (grain size, scanned micro-scale X-ray fluorescence (XRF) element composition, and loss on ignition (LOI)) of the sediments of alpine lake Saiyong Co, with the aim of reconstructing hydrological changes in the SRYR since 5.8 ka. The first principal component (PC1) of the XRF scanned element record is dominated by Ti, Fe and K, representing terrigenous inputs from the catchment. The LOI profile shows an inverse pattern of variation to that of PC1, suggesting that the sedimentary organic matter is primarily derived from aquatic plants. Since 5.8 ka the overall decrease in sample scores on PC1 and the increasing LOI, together with the grain-size based lake-level record, indicate an overall drying trend in SRYR. Furthermore, several major droughts are recorded, at ∼4.0 ka, ∼2.8 ka and ∼1.8 ka. The hydrological variations at Saiyong Co are supported by multiple records from the SRYR, suggesting that millennial-scale environmental variations were regionally synchronous and were influenced by Northern Hemisphere summer insolation and movement of the intertropical convergence zone.

Lake ecosystems in arid Central Asia are in crisis due to water abstraction and eutrophication, and it is important to understand their response to combined climate and human impacts. In this study, based on the relationship between modern chironomids and salinity, we studied subfossil chironomid remains in a ~4550-year sedimentary record from Lake Ulungur in northwest China, with the aim of reconstructing past ecosystem dynamics, especially in response to climate change and human impacts. The results show that from 4550–580 cal yr BP the hydrological status of Lake Ulungur was transformed from close to open and the salinity decreased causing an increase in freshwater chironomid species. Comparison with regional paleoclimatic records makes us to infer that the lake ecosystem evolution has been primarily controlled by changes in the westerly driven by the Northern Hemisphere insolation. Since 580 cal yr BP, the lake returned to be closed and the structure of the aquatic community reorganized. In recent centuries, human activities have made a more significant effect on lake ecosystems in northwest China than natural climate changes, which largely was induced by a surge in the human population related to national policies. Furthermore, due to the combined effects of global warming and intensifying human activities, lake ecosystems in Central Asia are subject to unprecedented anthropogenic pressures and urgent action is needed to protect them.

In this study we investigate the timing and nature of moisture availability in the Late Holocene by examining a multiproxy paleoenvironmental record from Kathu Pan at the southern edge of the Kalahari. In a region where organic proxy records are scarce, Kathu Pan provides a unique record of changes in past environmental conditions. Pollen, spore, charcoal, and stable isotope records were obtained from organic deposits at Kathu Pan and examined within a radiocarbon-constrained chronological framework. The Kathu Pan record registers a relatively moist phase occurring between 4.8 ka and 2.5 ka cal BP. Local environmental conditions at Kathu Pan shift gradually beginning around the terminal Northgrippian ~4.8 ka cal BP. Kathu Pan reaches maximum moisture availability with marsh-like conditions signaled by increased organic content, dominance of Cyperaceae pollen, presence of freshwater fungi, and δ13C values consistent with local C3 vegetation, around the inception of the Meghalayan Stage, although due to uncertainties in the age-depth model these changes may have taken place 1–2 centuries on either side of the formal date for the onset of the Meghalayan at 4.2 ka cal BP. This interval also corresponds with the highest charcoal concentrations, indicating the importance of adequate moisture conditions to support the growth of biomass which eventually becomes a fuel source. The moist phase lasts ca. 2000 years until a hypothesized shift to arid conditions occurs c. 2.5 ka cal BP leading to a change in local hydroclimate that may have terminated the accumulation of organic-bearing sediments.

This work analyze the technological management of raw materials and the mobility strategy of the human groups that occupied during the mid-Holocene (ca. 8000-3000 BP) the eastern Tandilia mountain range, and discuss them inside of settlement systems context for the southeastern Pampean region. The lithic study results of 13 occupations excavated in caves and rockshelters shows that mobility strategies in Tandilia mountain ranges were closer to collector models, where logistical groups moved into mountain range valleys in search of natural resources. We can recognize different strategies for raw material procurement: the immediately available rocks were obtained through direct access on daily foraging trips; the regional rocks were obtained through logistical displacements, residential movements and embedded strategies; and the access to the long distance rocks was through exchange between neighboring populations. Besides, during ca. 7000 to 5000 cal BP an increased use of immediately available raw materials and a high archaeological signal was detected. This scenario can be linked with an increased environmental aridity episode where human groups occupied with most intensity the Tandilia mountain valleys due to the greater availability of the water resources. Finally, this work provides new data suggesting that during this period in the southeastern Pampean region context, the hunter-gatherer groups combined forager and collector strategies to take advantage of the natural resources of the landscape with diverse environments (coastline, grassland plains, dunes field and mountain ranges).

This study presents a paleolimnological and paleoclimatological reconstruction based on diatoms and phytoliths of four Pampean shallow lakes (from south to north, La Salada, Sauce Grande, Los Chilenos, and Puan) strategically located along a climatic gradient from arid (south) to semiarid conditions (north). This research aims to identify the main drivers and mechanisms of long-term ecological change, and the main climatic mechanisms behind the regional hydroclimatic variability. It was found that these lakes were initially temporary, with clear waters, and eventually, became permanent with turbid waters. We propose that this change is due to an increase in precipitation in the last ca 1000 years, which resulted in higher lake levels and an increase in surface area, leading to an increased fetch and subsequent resuspension of sediment. This climatic amelioration occurred after ∼910 cal yr BP, first in what is today the arid Pampean region, then in the semiarid region, and finally in the modern humid region at ∼ -9 cal yr BP (1959 CE). Variations in lake's water level were the main driver of ecological change, followed by salinity (in Puan and La Salada) and nutrient load (in Los Chilenos and Sauce Grande). In general, those lakes on the southwest, located closer to the limit of moisture influence originating in the Pacific and Atlantic oceans (Arid Diagonal) were more sensitive to hydroclimatic changes than those located in the central Pampean region.

As a common measure for grassland restoration, the fence for prohibition of grazing is usually applied to the steppe in northern China. A study in Hulunbuir grassland showed the average litter mass in the steppes that enclosed for ten years can reach 70-550g/m2. The excessive accumulation of litter caused by long-term grazing prohibition can intercept more precipitation, which will reduce the water available to grassland plants and hinder the further recovery of plant communities. Therefore, the establishment of a reasonable litter interception model can help estimating the interception of steppes with different litter accumulation and provide some theoretical support for the formulation of fencing policies. Based on the model of litter interception rate change, we established a dynamic interception model of litter: I = I m ( 1 − e − k t ) ( t : time; I : dynamic interception; I m : maximum interception; k : exponential coefficient of litter interception). After testing by an indoor simulated rainfall experiment, we found that this model has high accuracy ( R 2 : 0.908 – 0.992). The litter mass (LM) determines the maximum interception, and the rainfall intensity (RI) determines the speed of interception which reaches its maximum value. After the conversion of coefficients, we established a prediction model of litter interception based on LM and RI: I = ( 0.003 L M + 0.44 ) [ 1 − e − ( 0.33 R I + 3.76 ) t ] , R 2 = 0.86 , P 0.001 . The easily obtainable characteristics of LM and RI data make this model easy to apply.

Urban parks play an essential role in urban settings; significantly contribute to the health of every age group person. Parks provide opportunities for families to connect with nature and breathe in the fresh air. Due to global climate change and increased urbanisation in the past few decades, extreme heat can be experienced in urban areas. Mental and physical health issues arise primarily due to a sedentary lifestyle in cities. Staying at parks for a longer duration could promote stress reduction and perceived physical health. The present study aims to assess the thermal comfort conditions at an urban park in the hot semi-arid climate(BSh) of Haryana, India. The present study investigated the outdoor thermal comfort range and thermal sensations of visitors at a park during the summer season using the onsite monitoring of the microclimate parameters and questionnaire survey in the hot-semi arid region of India. Thermal comfort indices, Physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI) and Wet bulb globe temperature(WBGT) have been applied to investigate the outdoor thermal comfort conditions. The seven-point sensation scale has been used to record the visitors' thermal sensations. The results indicated that:1) WBGT was found to be the most suitable index to investigate the OTC conditions. The neutral UTCI, PET, and WBGT ranged within 28.03 °C to 35.6 °C, 24.04 °C to 37.5 °C, and 23.5 °C to 26.1 °C, respectively. 2) The neutral PET ,UTCI, and WBGT were found to be 30.8 °C, 31.8 °C, and 24.8 °C, respectively.3) Dry bulb temperature is the most significant thermal comfort parameter affecting visitors' thermal sensations, followed by mean radiant temperature.4) Thermal comfort indices were found to be most significantly affected by globe temperature. The study's outcome could provide theoretical design reference to urban designers to develop new parks and existing parks, ultimately promoting public health.

Rapid global warming during the Paleocene-Eocene Thermal Maximum (PETM) profoundly affected the marine and terrestrial environments. However, details of the climate and vegetation of subtropical and arid regions of central China during the hyperthermal event are poorly understood. Here, we report a palynological record from the black shale of the lowermost Yangxi Formation exposed in Songzi city, western Jianghan Basin, central China. Biostratigraphy, magnetostratigraphy and isotope stratigraphy indicate a PETM age for the sedimentary succession. The palynological assemblage was characterized by high abundances of diverse tropical and subtropical broadleaved tree pollen, providing strong evidence of a dense south subtropical forest ecosystem that once existed in the arid belt of central China during the PETM. The reconstructed climatic parameters indicate an extremely warm and humid south subtropical climate, with mean annual temperatures (MAT) ranging from 21 to 24 °C and mean annual precipitation (MAP) ranging from 1396 to 1997 mm. The reconstructed precipitation was surprisingly high for such an arid setting that widespread arid climate prevailed in central China at that time. These findings demonstrate that rapid global warming during the PETM significantly increased precipitation, leading to the growth of dense forest ecosystems as well as increasing lake eutrophication in central China. The changes to precipitation and terrestrial ecosystems during this warming event are considerably more significant than previously reported in other mid-latitude regions, and highlighting the need to consider regional geographic characteristics to fully understand how the environment responds to rapid global warming.

Little attention has been paid to climate change in the marginal regions of the Asian summer monsoon (ASM) domain since Marine Isotope Stage (MIS) 3 (60-27 cal kyr BP). Here, based on the mineralogy and grain size of a 24-m-long sediment core retrieved from Jilantai Salt Lake, we provide a paleolake evolution record from a marginal region of the ASM domain over the past 47 kyr. Our results indicate that the lake was a brackish or saline lake and that the region was relatively humid during 47–43 cal kyr BP. From 43 to 27.5 cal kyr BP, the lake salinity increased and the climate began to deteriorate. From 27.5 to 11.8 cal kyr BP, aeolian activity intensified and the climate was arid. From 11.8 to 5.6 cal kyr BP, the lake salinity continuously increased, and the climate was persistently arid. After 5.6 cal kyr BP, the lake salinity dramatically increased, the lake became a salt lake, and the climate was extremely arid. In general, the climate was semihumid in mid-late MIS 3, arid in MIS 2 (27–11.7 cal kyr BP), and hyperarid in the Holocene. This climate change pattern is apparently different from that in the regions influenced by the Asian monsoon and westerlies, indicating that the enhanced Asian monsoon or westerlies were not the main forcing mechanism driving climate change in the marginal regions of the ASM domain. Enhanced ice-albedo feedback caused by the expanded Northern Hemisphere ice volume during MIS 3 would have resulted in less net incoming solar radiation and relatively low temperatures in the mid-high-latitudes. The relatively low temperatures might have weakened the evaporation capacity of Jilantai Basin and increased south-north temperature gradients, resulting in an increase in local precipitation. Therefore, the climate was semihumid in mid-late MIS 3. The lowest Northern Hemisphere summer insolation (NHSI) combined with significantly increased ice-albedo feedback associated with the largest Northern Hemisphere ice volume would have led to a remarkable reduction in temperature, resulting in the reorganization of major atmospheric and hydrological systems in the Northern Hemisphere and an arid climate in MIS 2. Subsequently, the Northern Hemisphere ice volume nearly vanished, and the rising NHSI enhanced evaporation, thereby generating a hyperarid climate in the Holocene.

The absence of large archaeological settlements in the Eastern Arabian Peninsula suggests that most of the recent wet periods occurring during climate oscillations in these areas were short-lived. However, a ∼ 2-by-3-km buried rectangular feature was discovered opportunistically in the southeast of the Qatar Peninsula while performing radar subsurface mapping of structural conduits for groundwater characterization. The feature is characterized by its unique contrasting patterns of surface and subsurface roughness as well as its organic-rich mixture of soils, as assessed from high-resolution radar and multispectral observations, respectively, and validated with GPR and EM subsurface probing. The above characteristics could be the only remaining evidence for a large primitive settlement due to the harsh erosive setting. To explore the natural or anthropogenic origin of this anomalous feature, we compare its dimensions, structural setting, roughness, and composition to similar formations in the Qatar Peninsula and other arid karst environments. Findings suggest that the feature is texturally and compositionally unique within the Qatar Peninsula, and is not reproduced in other arid karst terrains nor reproduced by the fracture patterns associated with the Qatar-South Fars Arch. We hypothesize that the feature is a karst depression modified by semi-stationary primitive human settlements ∼ 3640 BP or earlier based on radiocarbon dating of in-situ charcoal samples. Moreover, the organic-rich mixture of soil and the occurrence of several symmetrical features observed inside the perimeter suggest that landscaping, farming and irrigation activities could have occurred within the site, further suggesting that long-lasting wet conditions—with sufficient fresh water resources or reliance on karst aquifers—were able to sustain a relatively large primitive settlement not previously witnessed in the region’s archaeological record. Future improvements in the resolution and coverage of orbital L-band radar observations, as used above, can provide new insights into understanding prehistoric human occupation under fluctuating climatic conditions and groundwater dynamics in these hyper-arid regions.

Soil salinization caused by natural and anthropogenic factors is an important environmental hazard especially in arid and semi-arid regions of the world. Accumulation of salts in the soil is a major threat to crop production and global agriculture; therefore, rapid and precise detection of salt-affected lands is highly critical for preserving soil sustainability and supporting food production. Advancement in remote sensing techniques and machine-learning algorithms has started to contribute to fast and large-scale monitoring and mapping of soil salinization throughout the world. This paper aims to analyze the performance of three different machine-learning algorithms to map soil salinity using Landsat-8 OLI, Sentinel-2A satellite images, and ground-based electrical conductivity (EC) measurements with the aid of Google Earth Engine (GEE) platform. Classification and regression trees (CART), random forest (RF), and support vector regression (SVR) methods are implemented to create a correlation between ground measurements and satellite-derived environmental variables or spectral indices. After selecting the optimum five variables including wetness band, three soil salinity indices, and one vegetation index, soil salinity maps are generated in three machine-learning algorithms. The output soil salinity map in RF algorithm demonstrated the most reliable spatial distribution of various soil salinity classes in the selected study area. Despite CART provided slightly better prediction of soil salinity with R-squared (R2) of 0.98 for Sentinel-2A data, and 0.96 for Landsat-8 OLI data in comparison with accuracy results of RF technique with R2 of 0.96 for Sentinel-2A data and 0.94 for Landsat-8 OLI data, the output map of RF model estimated more reliable salinity levels in salt crusts, agricultural lands, drainage areas, and swamps. The corresponding result highly matched with visual interpretation. Soil salinity maps derived from SVR algorithms by using various combinations of input variables displayed relatively poor estimation of soil EC values compared to the other two methods.

An unprecedented demand for Food, Energy, and Water (FEW) resources over coming decades and the rising climate concerns require integrated FEW innovations with least environmental footprint. Collocating photovoltaic (PV) technology with agriculture is a promising approach towards dual land productivity that could locally fulfill growing food and energy demands particularly in rural areas. This ‘agrivoltaic’ (AV) solution can be highly suitable for hot and arid climates where an optimized solar panel coverage could prevent excessive thermal stress during harsh weather thereby increasing the crop yield and lowering the water budget. One of the concerns with using standard fixed tilt solar array structure that faces North/South ( N / S ) direction for AV farming is the spatial heterogeneity in the daily sunlight distribution for crops and soil water contents, both of which could affect crop yield. Dynamic tilt control through a tracking system can eliminate this problem but could increase the system cost and complexity. Here we present the investigation of vertically tilted bifacial AV farms which can be especially attractive for climates where PV losses due to dust are high. The relative food-energy performance for the vertical East/West faced bifacial panel ( bi- E / W ) scheme is compared with the standard monofacial tilted panels facing North/South ( mono- N / S ) through integrated models for energy conversion, spatial/temporal shade patterns, and the crop yield that is benchmarked against the reported field experiments for lettuce. We show that both schemes have similar food-energy yields for shade-sensitive crops which require a relatively low array density (i.e. ⩽ 1 / 2 of that for the standard ground mounted PV systems). On the other hand, the two PV schemes have remarkably different food-energy yields for denser PV array configuration for which bi- E / W provides higher crop yield and mono- N / S exhibits higher energy yield. To preserve ⩾ 80% of lettuce yield, the maximum array density is limited from half to twice of the standard PV systems corresponding to the varying shade response for the crop. Similarly, to preserve 80% of the energy yield, the lettuce yield is predicted to vary from 65% (shade-sensitive) to 100% (shade-tolerant). The vertical bi- E / W scheme is although not superior in terms of the combined food-energy performance, it could be attractive for its distinct advantages such as spatial homogeneity for shades and rainfall under panels, convenient architecture for farm machinery mobility, and an inherent resilience to soiling.

Soil inorganic carbon (SIC) is an important reservoir of carbon (C) in arid, semi-arid, and semi-humid regions. However, knowledge is incomplete on the dynamics of SIC and its relationship with soil organic C (SOC) under different land use types in the semi-humid region, particularly in coastal zones impacted by soil salinization. We collected 170 soil samples from 34 profiles across various land use types (maize-wheat, cotton, paddy, and reed) in the middle-lower Yellow River Delta (YRD), China. We measured soil pH, electrical conductivity (EC), water-soluble salts, and SOC and SIC contents. Our results showed significant differences in both SOC and SIC among land use types. The dry cropland (maize-wheat and cotton) soils had significantly higher SOC and SIC densities (4.71 and 15.46 kg C m–2, respectively) than the paddy soils (3.28 and 14.09 kg C m–2, respectively) in the 0–100 cm layer. Compared with paddy soils, reed soils contained significantly higher SOC (4.68 kg C m–2) and similar SIC (15.02 kg C m–2) densities. There was a significant positive correlation between SOC and SIC densities over a 0–100 cm soil depth in dry cropland soils, but a negative relationship in the paddy soils. On average, SOC and SIC densities under maize-wheat cropping were 15% and 4% lower, respectively, in the salt-affected soils in the middle-lower YRD than the upper YRD. This study indicated that land use types had great influences on both SOC and SIC and their relationship, and salinization had adverse effect on soil C storage in the YRD.

Water crises in arid and semi-arid regions, particularly in desert areas, are considered a challenge owing to the fact that no functioning solutions have been introduced throughout history to change the whole map from yellow to green. Current desert regions are still deserts from millions of years ago, and all scenarios that have been introduced to occupy desert regions accounts for 1%–2% of the total area. Middle East and North Africa (MENA) countries that are located in such arid and semi-arid zones are disadvantaged by limited water supply because of high temperature, low precipitation, and limited water resources. We have found that, there is no consortium between different fields of interest in the hopes of eventually overcoming the global water crisis. This is practically the case when it comes to using desalination and wastewater treatment technologies and their application for agriculture. Water crises should not only be solved using desalination and wastewater treatment, but other items should be also taken into consideration such as soil, plant, and organic matter use, among others. In the present perspective, we are developing novel solutions to overcome the global water crisis via nonconventional water reuse with minimum constrains to ecosystems using the principles of the Sophisticated Desert Development Project (SDDP) or “Electro-agric technology”. Electro-agric is technique that uses electrical fields throughout agricultural practices. Electro-agric technology comprises five main sections, including water, soil, organic matter, and plants, among others, that may be achieved via the establishment of a consortium between different major establishments like the Faculties of Engineering, Agriculture, and Science. Traditional approaches for cultivating land in arid and semi-arid regions are inappropriate and electro-agric technologies may be considered as the only alternative solution for regions that are located between the latitudes 35°N to 35°S in which the arid and semi-arid weather prevails and in which in seven of the world's major deserts are located. We believe that the map of MENA countries produced will transform from yellow to green, indicating reclamation of this resource; however this can only be accomplished if we comply with electro-agric technologies. Moreover, national incomes will be increased, and new communities will be stabilized.

The degradation and desertification of grasslands pose a daunting challenge to China's arid and semiarid areas owing to the increasing demand for them in light of the rise of animal husbandry. Monitoring grasslands by using big data has emerged as a popular area of research in recent years. As grassland degradation is a slow and gradual process, the accurate identification of grassland cover is key to monitoring it. Vegetation coverage is currently monitored mainly by combining inversion-based methods with field surveys, which requires significant human effort and other resources and is thus unsuitable for use at a large scale. We proposed to use time series from the enhanced vegetation index (EVI) in capsule network-based methods to identify grasslands. The process classified grassland coverage into four levels, high, medium, low, and other, based on Landsat images from 2019. The accuracy in classifying the grasslands at each level was higher than 90%, with an overall accuracy of 96.32% and a kappa coefficient of 0.9508. The proposed method outperformed the SVM, RF, and LSTM algorithms in terms of classification accuracy.

The eco-environment of semi-arid regions is extremely sensitive and vulnerable to climate change and human activities. The realization of sustainability of eco-environments has long been a key issue. Consequently, we analysed the Chinese Loess Plateau (CLP) to identify solutions to the sustainable development of such regions. We first reviewed the eco-environmental changes in the CLP and discussed the impacts of human activities over the past 3000 years, and then summarized previous experiences on the protection and restoration of degraded eco-environments. Our study indicates that the increasing demand for cultivated land has led to the destruction of vegetation and subsequent worsening of soil erosion on the CLP, which in turn, has led to an increase in floods in the Yellow River basin. However, many positive measures, such as slope cropland abandonment and afforestation have been demonstrated to be effective in improving the eco-environment via reducing soil erosion, and decreasing sediment input and flood disasters in the Yellow River in recent decades. Nonetheless, emerging problems such as water shortage, food insecurity, rapid urban development, and over-exploitation of energy resources hinder the sustainable development of the eco-environment in the CLP. Given the historical and present eco-environmental situations of the CLP, we provide suggestions for the sustainable development of both the eco-environment and social economy, which could serve as guidelines for eco-environmental design and government policy-making in semi-arid regions globally.

Interpreting the similarities and dissimilarities in spatiotemporal variations and various controls between surface and canopy urban heat islands (UHIs) is critical for a better understanding of their vertical structure. Preceding comparisons of the surface UHI (SUHI) and canopy UHI (CUHI), however, remain mostly restricted either in a single city or over a few cities within limited background climates; therefore, the associated similarities and dissimilarities between the SUHI and CUHI under different climates, especially at a global scale, remain largely unknown. Based on both satellite and in situ data, we simultaneously investigated the spatiotemporal patterns of the SUHI intensity (SUHII) and CUHI intensity (SUHII) of 366 global cities within various background climates. We further investigated the different impacts of several controls (e.g., vegetation coverage, population size, precipitation) on SUHII and CUHII. Our results indicate the following: (1) For the selected 366 cities, the annual mean SUHII is higher than CUHII by 1.1 ± 1.9 °C (mean ± Std) during the day and 0.3 ± 1.5 °C (mean ± Std) at night. The SUHII and CUHII in the equatorial, warm temperate, and snow climates are generally consistent with the above characteristics (i.e., SUHII > CUHII), however, in arid regions SUHII is lower than CUHII by 0.8 °C during the day. (2) The annual mean day–night difference in SUHII is positive (i.e., 0.6 ± 1.8 °C (mean ± Std)), while the difference in CUHII becomes negative (i.e., −0.2 ± 1.6 °C (mean ± Std)), indicating that urbanization increases the diurnal temperature range (DTR) based on land surface temperature, but it decreases the DTR based on surface air temperature. (3) Despite the high correlation between vegetation coverage and impervious surface percentage (ISP), their impacts on SUHII and CUHII were not consistent. The urban–rural difference in ISP exerts an insignificant impact on both SUHII and CUHII during the day and a greater impact on CUHII than on SUHII at night, whereas the urban–rural difference in vegetation coverage has a greater impact on SUHII than on CUHII during the day, while the opposite occurs at night. The impacts of population size on SUHII and CUHII are much greater during the night than on the day in which their impacts can be minimal. The relationship between annual mean precipitation and SUHII is positive during the day but negative at night, while for CUHII, their relationship is insignificantly negative both during the day and at night. These results can improve our understanding of the spatiotemporal patterns and controls of these two types of UHIs under various climates.

This study aims to evaluate the potential of Bayesian additive regression trees (BART) for predicting global and diffuse solar radiation. Long-term daily weather data were collected at four stations in arid and humid areas. Models with different input combinations were created. The default parameters within R language package of BART were used. Model accuracy was assessed with Pearson correlation coefficient (R), root mean square error (RMSE), mean absolute error (MAE), relative root mean square error (RRMSE), and Nash-Sutcliffe efficiency coefficient (NSE). Taylor diagram was applied to illustrate model performance. On average, the model with sunshine duration, theoretical sunshine duration, mean temperature, maximum temperature, minimum temperature, relative humidity, and rainfall performed best for predicting global solar radiation, with mean R of 0.973, RMSE of 1.685 MJ/m2d, NSE of 0.944, RRMSE of 0.124, and MAE of 1.265 MJ/m2d. The model with sunshine duration, theoretical sunshine duration, global solar radiation, extraterrestrial solar radiation, and day of year outperformed others for predicting diffuse solar radiation, with mean R of 0.912, RMSE of 1.291 MJ/m2d, NSE of 0.827, RRMSE of 0.214, and MAE of 0.933 MJ/m2d. The results showed that BART was a suitable method for predicting global and diffuse solar radiation using climatic variables.

Made available in DSpace on 2022-04-29T08:31:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Savanna tree communities occurring in confluence zones with other biomes likely experience different environmental pressures, resulting in shifts in the selection of individual traits, the combinations of such traits, and species composition. In seasonally dry fire-prone environments, plant survival is presumably associated with adaptive changes in bark properties related to fire protection and water storage. Here, we integrated the multiple functions of the bark to investigate whether different selective pressures could influence patterns of variation in bark structure and allocation across species in a broad geographical range. We measured thickness, density, and water content of the inner and outer bark in branches and the main stem of the 51 most abundant species in three savanna communities differing in climatic aridity, one located at the core region of Cerrado in Central Brazil and the other two at its periphery, in the transition zones with Amazonia and Atlantic forest biomes. We found no difference in outer bark thickness but markedly difference in inner bark thickness between the three plant communities. In the central region, where dry season is long and fire is frequent, branches and main stem showed thicker inner bark. Contrastingly, in the south periphery region, where dry season is short, species showed thinner inner bark in both branches and main stem. Species from the north periphery region, where mean annual precipitation is higher, but fire is frequent and the dry season is also long, showed similar main stem inner bark thickness, but thinner branch inner bark compared to core region species. Our findings support the idea that investing in inner bark thickness and bark moisture may be the most advantageous strategy in plant communities that suffer from high evaporative demand during a long period and are at a high risk of fire. Programa de Pós-Graduação em Ecologia e Conservação Universidade Federal do Paraná Departamento de Biologia Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista Environmental Change Institute School of Geography and the Environment University of Oxford Departamento de Botânica Universidade Federal de São Carlos Department of Biological Sciences Macquarie University Departamento de Zoologia Universidade Federal do Paraná Laboratório de Ecologia Funcional de Comunidades (LABEF) Departamento de Botânica Universidade Federal do Paraná Department of Plant & Microbial Biology North Carolina State University Programa de Pós-graduação em Ecologia e Conservação Universidade do Estado de Mato Grosso – UNEMAT Laboratório de Ecofisiologia Vegetal Departamento de Botânica Instituto de Ciências Biológicas Universidade de Brasília Select Carbon Pty Ltd Departamento de Biologia Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista

The purpose of this research is to determine the optimum location to construct gas power plants (GPPs) in semi-arid regions. A combination of ordered weight averaging (OWA) and analytic hierarchy process (AHP) method named OWA-AHP is utilized to prepare land suitability maps with different risk scenarios when fuzzy method is to homogenize inputs. In the proposed method, AHP is to weigh each different parameter while OWA considers risk levels. In order to validate the accuracy of the proposed method, the receiver operating characteristics (ROC) curve is investigated. Besides, the self-organizing map (SOM) algorithm and Pearson correlation are used to determine the most important parameters for constructing GPP. According to obtained results, the areas located in the north and parts of the east and south of the selected case study (about 15%) at all risk levels are the optimum areas to be hosted for GPPs. Furthermore, ROC curve shows that the Area Under the Curve (AUC) values are high for both AHP and OWA-AHP methods (AUC Fuzzy-AHP = 94.0%, AUC OWA = 89.0%). The results of the SOM algorithm and Pearson correlation with high accuracy (R Model1 : 0.853 and R Model2 : 0.940) also depict that distance to the pipeline and road are the most important parameters to identify suitable locations for GPP.

Ground source heat pumps (GSHPs) are considered to provide very efficient air conditioning systems, and this assists in achieving sustainability goals as well as reducing electricity consumption and carbon emissions. The design of such systems, however, depends on the climatic conditions and the geological characteristics of the site; in practice, the optimum design of the system also depends on the characteristics of the surrounding soil. The majority of the research into GSHPs has been focused on cold regions, thus this work is a very useful reference and important in GSHPs’ design in Saudi Arabia and therefore in other hot and arid regions. For the first time in such a hot/dry climate, a rigorous sensitivity analysis method applying the Ground Loop Design software has been employed to analyse 12 parameters that most affect the behaviour of the system. It is concluded that the most important four design parameters are the: thermal conductivity, soil temperature, building load, and fluid flowrate. On increasing these values they have opposing effects on arid environmental conditions, such as those found in the city of Riyadh in Saudi Arabia. In addition, the near-optimum design of a GSHP system in the city of Riyadh in Saudi Arabia has been investigated. The temperature of the water entering the heat pump is an adjustable factor that determines the performance of a GSHP unit. Because of the coefficient of performance of the heat pump, it can also be measured by the value of the entering water temperature. Thus, the entering water temperature (EWT) was selected to be the performance measure of the system, as all the heat transfer processed between the ground heat exchanger components and the surrounding soil is manifested in the entering water temperature. The value of the EWT was fixed both at the baseline and in the proposed design systems, and these were tested over the lifespan of 20 years. The results showed that the length of the ground heat exchanger and power consumption in the proposed design could be reduced by 15% and 1.12% respectively, compared to the baseline system. These results can be used to simplify the design of buildings in similar arid regions worldwide.

The Kettara abandoned mine, Morocco, is a highly acid drainage-generating site with negative impacts. In order to impede the water–oxygen migration within tailings of Kettara mine, a store-and-release (SR) cover made with phosphate mine wastes (PMW) layers was implemented on the tailings of Kettara mine in five experimental cells. The characterization of vegetation is an important aspect of the monitoring strategy for the SR cover. In this optic, the objective of this study was to follow the local flora dynamic on the SR cover. Furthermore, this research highlighted the potential of this flora for the development of other appropriate phytomanagement plans of mining wastes. The monitoring surveys were carried out over five years (March 2015–April 2019). Six permanent transects were placed on five-constructed cells. The method of Line Intercept Transect was used to evaluate the vegetation cover and to determinate the floristic composition and relative frequency of the species. Plant diversity was quantified by Shannon diversity (H′) and Pielou evenness (J') indices. Four functional groups of plants were identified; therophytes and chamaephytes were the most abundant. Among 19 recorded families on SR cover, the most widely represented were Compositae (26.83%), Leguminosae and Poaceae with 9.76%, Apiaceae and Brassicaceae with 7.32% of the total taxa for each one of them. Of the 39 identified vascular species on SR cover, the most abundant were Anacyclus valentinus L., Calendula arvensis M.Bieb., Emex spinosa (L.) Campd., Hirschfeldia incana (L.) Lagr.-Foss., Spergularia rubra (L.) J.Presl & C.Presl, Stipa capensisthunb, and Herniaria cinerea L. Significant differences in Shannon diversity index (H′) were observed between the sampling areas (p > 0.05), it ranged from 0.739 to 3.857 bits/ind. on SR cover. The Pielou evenness index was not significantly different through transects; it varied from 0.578 to 0.978. These values indicated an equitable distribution of individuals within species on the investigated transects. The study revealed 29 vascular plant species that represent a great potential to be promoted for the phytomanagement of mine wastes in the context of arid and semi-arid environments.

The Atacama Desert (Chile) is one of driest places on Earth, with a hyper-arid climate and less than 2 mm yr−1 precipitation; nevertheless, it has experienced rare periods of sporadic rainfall. These periods shortly enhanced vegetation growth and microbial activity, which must have utilized major nutrients such as phosphorus (P). However, any biological cycling of P involves an oxygen exchange with water, which should now reside in the hyperarid soils as tracer of life. In order to identify such evidences, we performed sequential P fractionation and analyzed the oxygen isotope composition of HCl-extractable phosphate (δ18OHCl–P) in the surface soil (0–15 cm) of a climatic gradient along the rising alluvial fans of the Central Depression to the Precordillera, Chile. At the driest sites, the δ18OHCl-P values were constant with depth and deviated from biologically-driven isotopic equilibrium. In contrast, we observed a considerable increase of δ18OHCl-P values below the soil surface at less arid sites, where some isotope values were even within the range of full isotopic equilibrium with biologically cycled phosphate. For the latter sites, this points to most efficient biological P cycling right below the uppermost surface of the desert. Critically, the absolute concentrations of this biologically cycled P exceeded those of P potentially stored in living microbial cells by at least two orders of magnitude. Therefore, our data provides evidence that δ18OHCl-P values trace not recent but past biological activity, making it a powerful tool for assessing the existence, pathways and evolution of life in such arid ecosystems on Earth and, thus, potentially on other planets such as Mars.

Excess calcium (Ca) in soils of semi-arid and arid regions has negative effects on soil structure and chemical properties, which limits the crop root growth as well as the availability of soil water and nutrients. Quantifying the spatial variability of soil Ca contents may reveal factors influencing soil erosion and provide a basis for site-specific soil and crop management in semi-arid regions. This study sought to assess the spatial variability of soil Ca in relation to topography, hydraulic attributes, and soil types for precision soil and crop management in a 194-ha production field in the Southern High Plains of Texas, USA. Soils at four depth increments (0–2, 0–15, 15–30, and 30–60 cm) were sampled at 232 points in the spring of 2017. The Ca content of each sample was determined with a DP-6000 Delta Premium portable X-ray fluorescence (PXRF) spectrometer. Elevation data was obtained using a real-time kinematic GPS receiver with centimeter-level accuracy. A digital elevation model (DEM) was derived from the elevation data, and topographic and hydraulic attributes were generated from this DEM. A generalized least-squares model was then developed to assess the relationship between soil Ca contents of the four layers and the topographic and hydraulic attributes. Results showed that topographic attributes, especially slope and elevation, had a significant effect on soil Ca content at different depths (P

Fire is considered a critical process for limiting shrub encroachment and maintaining grassland structure and functions. Fire can be detrimental to grasses in upland settings of arid desert grasslands, but no studies have been performed in more productive swale grasslands. Monitoring of a prescribed fire treatment in a swale grassland in southern New Mexico indicated that perennial grasses had not recovered after 5 years, even with above-average rainfall. Furthermore, indicators of erosion susceptibility increased, and shrubs resprouted rapidly.

The Ladakh Range in the Trans Himalaya houses sub-routes of the Silk route through its passes (La in local language) which may have been the main commercial and cultural passage to connect the central Asia and Tibetan region with the rest of India. A ca 6400-220 cal yr B.P. hydroclimatic record of two lakes viz Tsoltak lake and Yaya Tso near the Chang La and Hor La passes of Ladakh Range is presented here. The overall record (mineral magnetic analysis and microbiota) from the Ladakh range shows wetter conditions ca 6400 cal yr BP consistently declining till ~5000 cal yr BP and moderately wet and stable till ~4300 cal yr BP, followed by an arid cold phase (~4300-4000 cal yr BP). This precedes two moderately wet phases (ca 4300-3500 cal yr BP and ca 1260-220 cal yr BP) and the peak arid conditions between 3500 and 2860 cal yr B P and 2230-855 cal yr BP, which may have affected the trade activities and had an adverse affect of cultural transitions during these periods across the Ladakh Range on the to and fro movements from this northern sub-route branch. The biotic assemblage is rich in Non Pollen Palynomorphs (76%) with minor amounts of pollens (24%). An improvement in the conditions since 855 cal yr BP and thereafter from 340 to 220 cal yr BP records the onset of the cold arid conditions again in the Ladakh Range. Presently due to contemporary deglaciation the Ladakh Range is becoming ice free and a number of lakes surrounded by herbaceous meadows are seen in the area due to glacial melt, likely to encourage the human settlements to soon occupy the higher reaches that will negatively affect the natural lake productivity.

Biological soil crusts (BSCs), or biocrusts, are composed of fungi, bacteria, algae, and bryophytes (mosses, etc.) that occupy bare soil, entwining soil particles with filaments or rootlike structures and/or gluing them together with polysaccharide exudates to form a consolidated surface crust that stabilizes the soil against erosion. BSCs are common in arid and semiarid regions where vascular plant cover is naturally sparse, maximizing the exposure of surface-dwelling organisms to direct sunlight. Although less prominent and less studied there, BSC organisms are also present in more mesic areas such as the Great Plains where they can be found in shortgrass and mixed-grass prairie, in the badlands of several states, where burrowing animals have created patches of bare soil, on damaged road-cuts, strip-mines, gas and oil drill pads, military training areas, heavily grazed areas, and burn scars. Even where BSCs are not readily visible to the naked eye, many of the organisms are still present. BSC organisms are passively dispersed to the Great Plains as airborne organismal fragments, asexual diaspores, or sexual spores that accompany wind-blown dust from as far away as northern China and Mongolia. BSCs can best be studied and managed by 1) acknowledging their presence; 2) documenting their diversity, abundance, and functional roles; and 3) minimizing unnecessary disturbance, particularly when the soils are dry. This paper describes the current knowledge of Great Plains BSCs in an effort to heighten awareness of these cryptic but crucial ecosystem components and to encourage new research initiatives to better understand and manage them in this biome. Some specific actions may include refined taxonomic and ecologic studies of BSC organisms in underexplored areas, particularly those previously less or not recognized as BSC habitat, and incorporation of techniques to sample airborne organisms.

Long-term carbon cycle models are critical for understanding the levels and underlying controls of atmospheric CO2 over geological time-scales. We have refined the implementation of two important boundary conditions in carbon cycle models, namely consumption by silicate weathering and carbon degassing. Through the construction of continental flooding maps for the past 520 million years (Myrs), we have estimated exposed land area relative to the present-day (fA), and the fraction of exposed land area undergoing silicate weathering (fAW-fA). The latter is based on the amount of exposed land within the tropics (±10°) plus the northern/southern wet belts (±40-50°) relative to today, which are the prime regions for silicate weathering. We also evaluated climate gradients and potential weatherability by examining the distribution of climate-sensitive indicators. This is particularly important during and after Pangea formation, when we reduce fAW-fA during times when arid equatorial regions were present. We also estimated carbon degassing for the past 410 Myrs using the subduction flux from full-plate models as a proxy. We further used the subduction flux to scale and normalize the arc-related zircon age distribution (arc-activity), allowing us to estimate carbon degassing in much deeper time. The effect of these refined modelling parameters for weathering and degassing was then tested in the GEOCARBSULFvolc model, and the results are compared to other carbon cycle models and CO2 proxies. The use of arc-activity as a proxy for carbon degassing brings Mesozoic model estimates closer to CO2 proxy values but our models are highly sensitive to the definition of fAW-fA. Considering only variations in the land availability to weathering that occur in tropical latitudes (corrected for arid regions) and the use of our new degassing estimates leads to notably higher CO2 levels in the Mesozoic, and a better fit with the CO2 proxies.

Water scarcity is a real challenge in the Mediterranean countries such as Tunisia. Currently, in Tunisia, about 80% of the resources are allocated to the agricultural sector. The irrigated areas are estimated at 420000 ha, consist of 220000 ha of public perimeters and 200000 ha of private perimeters. In arid and semi-arid regions of central and southern Tunisia, the cultivation of the olive tree (Olea europaea L.) is an important widespread activity, mainly due to its great adaptability to the conditions of water deficit and its nutritional value. Olive oil is a susceptible product, its quality and organoleptic characteristics can be influenced by several factors from harvest to storage, such as irrigation. The results obtained in the present study allowed classifying the monovarietal oils samples in the extra virgin category. In general, the impact of irrigation is very remarkable, mainly in the reduction of the pigments, alpha tocopherols, oleic acid, and total phenol compound contents. This decrease recorded in these various parameters is found in olive oil produced from trees grown under daily irrigation in Ksar Ouled Debbab. The data registered in this present work revealed that oil composition and quality could be directly affected by irrigation. Our results can give useful indications for explaining more the relation between irrigation strategies and olive oil quality: Qualitative and quantitative compositional analysis showed that several oil parameters significantly decreased in the freshwater irrigated plot more than the rainfall plot.

Luís, A. D. A., & Cabral, P. (2021). Small dams/reservoirs site location analysis in a semi-arid region of Mozambique. International Soil and Water Conservation Research, 9(3), 381-393. https://doi.org/10.1016/j.iswcr.2021.02.002 The water crisis is one of the biggest human problems in developing countries, especially in semi-arid regions where it can form an obstacle to irrigation and cultivation, cattle raising and people's survival. The construction of small dams/reservoirs are a possible solution to remediate this problem. These infrastructures must be located in suitable areas to be successful. This study aimed to find the most suitable locations for small dams/reservoirs in the Tete province region, Mozambique, which has a pronounced water deficit. A Geographical Information System (GIS) based approach was used to implement a multi-criteria evaluation (MCE) analysis through an Analytic Hierarchical Process (AHP), which included local experts’ consultation. Three main categories of suitability were identified: “Not suitable” (15% of total area), “Modestly suitable” (78%), and “Suitable” (7%). We found that 35 of the 38 (92%) abandoned small dams/reservoirs were in areas classified as “Modestly suitable” confirming the robustness of our model. We also found that most of the dams/reservoirs currently operating (78%) and planned (73%) are in modestly suitable areas. This finding suggests that the decision to construct dams/reservoirs may not have considered the most critical suitability factors identified in this study. More data and/or additional criteria are required for the full understanding of finding out why so many dams/reservoirs failed before building new ones to address the population's water needs in the region. publishersversion published

Ground-mounted photovoltaic (PV) arrays of an agrivoltaic system (AVS) creates shade in the interspace areas as well as below PV areas of the AVS. Therefore, availability of photosynthetic photon flux density (PPFD) and daily light integral (DLI) in the AVS is negatively affected, which restricts optimum crop growth and yield. Therefore, in this study, spatial and temporal variation of PPFD and DLI in the AVS (105 kWp) developed at Jodhpur, India were quantified. Among three designs of PV arrays in the AVS, the proportion of shaded area in interspace was found highest in single row design and lowest in triple row design. The amount of PPFD varied widely in the AVS and even within the shaded area. Following semivariogram and kriging approach, spatial variation of PPFD and DLI was quantified within the AVS. Highest amount of PPFD was observed near noon in unshaded areas (1295 μmol m−2 s−1) whereas lowest amount was observed during morning at below PV array (24 μmol m−2 s−1). Based on the maps of PPFD and DLI, three distinct zones in the AVS were identified: (i) below PV array (DLI = 0–5 mol m−2 d−1), (ii) interspace area with partial shade (DLI = 5–20 mol m−2 d−1) and (iii) interspace areas with no shade (DLI = 20–30 mol m−2 d−1). Knowledge of spatial and temporal variation of PPFD and DLI may help in selection of suitable crops for the AVS.

Numerous paleoclimatic records from lake sediment cores in arid central Asia (ACA) suggest a more humid climate in the Little Ice Age (LIA) cold period than that of the contemporary warm period (the last century). Our high-resolution study of a sediment core from Yileimu Lake presents end members (EMs) of grain-size distributions (~5-year resolution), and major and trace elements (~10-year resolution), including the Chemical Index of Alteration (CIA) and Rb/Sr ratio. In contrast to records from these other lakes in ACA, our study indicates a warming and wetting trend in the southern Altay regional climate over the last five centuries. We suggest that continuously increasing snow/ice meltwater from the surrounding high mountains related to an increasing trend in atmospheric temperature, and increasing winter snowfall triggered by a decreasing trend in winter North Atlantic Oscillation (NAO) index, have dominated the regional climate in the southern Altay Mountains during 1620–1835 AD. We also suggest that temperature dependent evaporative losses greatly exceeding the water input to the lake, and reduced summer precipitation, caused the drought events during 1586–1620 and 1835–1870 AD. Heavy summer precipitation associated with significant increases in the local moisture supply induced by intense evaporation of snow/ice meltwater in the alpine and gorge terrain of the Altay Mountains played a critical role in the summer floods around the 1900s AD.

Nowadays, one of the most important challenges in developing greenhouses is meeting their energy demand. The other challenge is the high water consumption of evaporative-cooling systems in arid and semi-arid regions. In this study, a integrated dynamic model is developed to determine the greenhouse relative humidity, carbon dioxide, and temperature, considering transpiration. The model is applied to a greenhouse utilizing a ground to air heat transfer system, located in the Alborz province of Iran and the results are validated with experimental data. Energy and water performance of the greenhouse are evaluated for the case study greenhouse. Then, the model is applied to a greenhouse (similar to the case study) in different climate zones of Iran to study the impact of climatic conditions on greenhouse performance. The results are presented for both cases of presence and absence of plant in greenhouses. Transpiration causes the heating/cooling demand of the greenhouse to increases/decreases by 17–40%/63–71% from climate 1 (cold and dry-humid climatic conditions) to climate 4 (mild and hot-humid climate regions). The water consumption of the evaporative-cooling system decreases by 17–49% from climate 1 to 4 when transpiration is taken into consideration.

This paper focuses on the effects of chemical precipitation on the permeability of geotextile envelopes for a subsurface drainage system in arid areas by conducting precipitation experiments of the geotextile in static or flowing solution. The results show that the precipitation process is not significantly promoted or inhibited by the network structure of geotextile. The precipitates in the form of rhombus wrap around the fiber surface. The number of geotextile pores with the smaller diameters decreases significantly after precipitation experiments. As the increase of the area density of precipitates (ΔR), the variation of the pore area (ΔS) and the variation of permeability coefficient (ΔK) of the geotextile decrease rapidly at first and then slowly. The ΔK and ΔS VS ΔR data were best fitted with logarithmic trend line. This study provides a preliminary reference for quantifying the chemical clogging process of geotextile envelopes in arid areas.

Salinity is a major environmental restraint in arid and semi-arid regions. Excessive amounts of salt in natural soils and in saline irrigation reduce seed germination and plant growth of most plants in the agricultural lands of these regions. The purpose of this research was to investigate the effect of salinity on seed germination, growth performance, and physiological processes; such as chlorophyll content, chlorophyll fluorescence (Fv/Fm), and gas exchange of two Moringa species, Moringa oleifera and Moringa peregrina. Salinity treatments comprised 5 NaCl concentrations; (0, 50, 100, 150 and 200 mM). The germination test took place in petri dishes, while plants were grown in pots under controlled environments inside plant growth chambers. Results showed that seed germination was significantly affected by salinity. The effect of salinity on germination performance differed between the two species. For example, none of the two Moringa seeds germinated at the high level of salinity (200 mM), while M. oleifera seeds germinated at 150 mM and those of M. peregrina showed no signs of germination. Results demonstrated that salinity significantly reduced all growth parameters of the two Moringa species. However, low salinity (50 mM) enhanced all growth parameters and the photosynthetic performance of the two Moringa species compared to the control plants. The chlorophyll content was not affected by salinity for both species, but the saturation rate of photosynthesis was inhibited, and in particular under high NaCl concentration. The effect of salinity on quantum yield followed the same effect pattern as for the saturation rate of photosynthesis, while the (Fv/Fm) was not significantly affected. The two species of Moringa, M. oleifera and M. peregrina differed in the mechanisms of salt tolerance; for example, M. oleifera expressed high salt tolerance at germination phase, whereas M. peregrina demonstrated high photosynthesis rates at low and medium levels of salinity. The physiological responses of M. peregrina to withstand medium levels of salinity makes it a more successful species in harsh environments such as that of Saudi Arabia.