Arid Periods Research Articles

Isotopic evidence of diet breadth hunter-gatherers changes during the Holocene in the Central Pampean Dunefields (Argentina, South America).

Based on the analysis of stable carbon and nitrogen isotopes of bone collagen, stable carbon isotopes of bone apatite and an extensive AMS dating series (~10,000-299 years cal BP), the human paleodiets of 34 individuals from the Central Pampean Dunefields (Argentina, South America) are evaluated. These data are interpreted from the isotopic ecology of animals with archaeofaunal evidence of consumption and isotopic models of human diet. Multivariate carbon and nitrogen stable isotope model and Bayesian stable isotope ellipses were used to interpret human diets. Analysis of isotopic values indicates intake of enriched lipids and/or carbohydrates in relation to the proteins consumed throughout the Holocene. The isotopic values of Middle Holocene humans in relation to the values of exploited resources point out that individuals obtained protein mainly from guanaco. Subsequently, there was an increase in the human breadth diet during the Late Holocene, with a greater relevance of small prey of high trophic levels and vegetables. This contrasts with zooarchaeological information indicating generalist human diets during the Middle Holocene and specialized human diets in guanaco during the Late Holocene. It is proposed that during the Middle Holocene arid period, the combination of low human population density and high residential mobility in wide foraging ranges allowed the guanaco to be the main source of protein. During the Late Holocene humid period, there was an increase in human population density and a decrease in residential mobility, which caused greater pressure on foraging territories and increased dietary breadth.

Assessment of the Drought Risk in Constanta County, Romania

Drought poses a significant risk in many parts of the world, especially in regions reliant on agriculture. Evaluating this risk is an essential step in preventing and reducing its impact. In this context, we assess the drought intensity at six sites in Constanța County (Romania) using the de Martonne aridity index. The risk of aridity and vulnerability to drought were evaluated by the Drought Hazard Index (DHI) and Drought Risk Index (DRI), computed based on the Standardized Precipitation Index (SPI). The de Martonne index indicates a variation between the slightly arid and semi-arid climates for Adamclisi station, with periodic changes from semi-arid to arid. At Cernavodă station, we notice a passage from an arid period towards a moderately humid one (in 2005), followed by a movement in the opposite direction to the limit of the arid zone (in 2011), and a return inside the “limits” of the semi-arid to moderately arid climate. A similar variation for 2000–2018 is noticed at Medgidia, Hârșova, and Mangalia. DRI classifies two stations in the low risk to drought category and one in the moderate risk to drought class. The other two locations experience a high or very high risk of drought. The drought intensities varied in the intervals 0.503–1.109 at Constanța, 0.473–1.363 at Mangalia, 0.511–1.493 at Adamclisi, 0.438–1.602 at Hârșova, 0.307–1.687 at Medgidia, and 0.463–1.307 at Cernavodă, and the prolonged drought periods were over 99 months at all stations.

Paleoenvironmental characterization and historical trends of polycyclic aromatic hydrocarbons (PAHs) of Nutrias Lagoon, Uruguay

Concentrations of polycyclic aromatic hydrocarbons were assessed in a sediment core retrieved from Nutrias Lagoon, located within the Rocha Lagoon Protected Area along the SE Uruguayan coast. Using a 210Pb chronology, we reconstructed the historical accumulation of polycyclic aromatic hydrocarbons over the past 123 years (1895-2018). This study, the first of its kind in Uruguay, fills a research gap in understanding historical PAH accumulation and source changes. Our examination of dating, geochemical, and sedimentological data unveiled four main events, with minor instances in 1956±5 and 1964±4, and more significant occurrences in 1914±9 and 1997±2. Additionally, two prominent trend shifts were identified, one predating 1900 and the other in 1986±2. Before 1900, a dry spell was apparent, supported by all proxies, alongside a notable surge in heavy polycyclic aromatic hydrocarbons, likely attributed to fires during this arid period. Post-1986±2, a rise in sedimentation rates in the lagoon was observed, possibly due to increased rainfall. Also, the eutrophication of the lagoon over the years can be observed. Furthermore, a recent increase in polycyclic aromatic hydrocarbons influx at the core's surface was linked to the construction of a nearby lagoon bridge and associated roadwork. Our findings suggest that atmospheric deposition constitutes the primary source of polycyclic aromatic hydrocarbons in the lagoon, offering insights into its recent environmental history and basin dynamics. This study establishes a critical baseline for future research in the region and facilitates the development of effective and sustainable environmental management strategies.

Aeolian sediments in western Mongolia: Distribution and (paleo)climatic implications

The largest dune fields in Mongolia are mainly restricted to the Basin of Great Lakes in western Mongolia. These dune fields extend from 800 m a.s.l. in the basins for 200 to 300 km into the mountains up to about 2100 m a.s.l. Analyses of these dune fields, using an integrative mapping approach, provide evidence for different wind regimes. The dune fields result from a long-term Quaternary sediment cycle. Rivers transported the sand into the basins from where the wind carried the sand eastwards along the dune fields with a concurrent loss of silt-sized particles. Different paleolake levels and sandy plains with mobilized sand at their western ends exist in the lake basins. The largest masses of dune sand are found in the central parts of the dune fields. Towards their eastern ends, lower and more vegetated dunes and sand sheets result from both the decrease in sediment supply and increased vegetation at higher elevations. Three climatic and paleoclimatic implications are derived from the mapping approach. A: Under the modern semi-arid to semi-humid climate, wind systems from north to the north-west prevail, whereas in the southern Mongolian Els also wind from the south-east occurs. B: The highest lake levels occurred during pluvial phases in the basins, caused by increased moisture supply, also due to water supply from glacier- and permafrost retreat. C: The fundamental west-east orientation of the dune fields is a result of westerly winds which were prevalent during arid periods.

When to generalise and when to specialise? Climate change and hominin biocultural adaptability in the African early and middle stone age

A growing number of authors have discussed the role of climate change in periods of important biological and cultural transition along the hominin lineage. This paper establishes a biocultural framework elucidating human behavioural adaptations during the African Early and Middle Stone Age, centred on three crucial dimensions of hunter-gatherer adaptation: mobility, social network dynamics, and technology. We contend that landscape properties, specifically resource diversity and seasonal to inter-annual resource variability, can be used to model the specific responses of hominin groups to climate change over time, based on their awareness of these properties. Specifically, we focus on hominin technological generalisation and specialisation, meaning the extent to which there is a high degree of specificity (or fit) between final tool form and the task(s) in which the tool is deployed.In this regard, we argue that the archaeological record reveals punctuated and discontinuous specialisation during certain phases of the Early Stone Age driven by landscape predictability. These periods encourage the expression of relevant innovations and stepwise increases in technological complexity. While some of them become lost to demographic or cultural stochasticity, others end up forming the basis for a standardisation of generalised forms within the context of unexpected climatic deterioration. This is highlighted by the late Acheulean: following a period of greater generalisation in the late Early Pleistocene correlating with repeated and severe orbitally-forced periods of aridity, smaller biface forms become more common (or absent) and regional experimentation with prepared-core technology in Eastern Africa takes place in the context of a return to more humid and stable climatic conditions. The onset of more arid and variable climates associated with the emergence of the Middle Stone Age led to the continental expansion of the prepared-core technological substrate underpinning generalised assemblages. The cycle continues in the Middle Stone Age with a return to climatic stability in the Late Pleistocene and subsequent regional diversification of this techno-complex, in which hominins responded with greater toolkit specialisation in a number of different ways. In this context, we support the existence of a cyclical and non-linear relationship between environmental adaptation and cognitive evolution, as part of a wider biocultural feedback loop, which contributes to explain the evolutionary roots of our “generalist specialist” niche.

Agricultural Drought-Triggering for Anticipatory Action in Papua New Guinea

Throughout its history, Papua New Guinea (PNG) has faced recurrent agricultural droughts, imposing considerable strain on both livelihoods and the economy. Particularly severe droughts have been associated with El Niño climate patterns. During these episodes, PNG becomes especially vulnerable to extended periods of aridity and diminished precipitation. Historically, humanitarian assistance for these events has primarily focused on responding to emergencies after an agricultural drought has been declared and communities have already been impacted. Here, we developed a proactive agricultural drought-triggering method for anticipatory action (AA) in PNG to offer a more sustainable and cost-effective approach to address this hazard. Our AA uses weather forecasts and risk data to identify and implement mitigative actions before a disaster occurs. The research details a step-by-step guide from early warning to action implemented by the Food and Agricultural Organization of the United Nations and the Government of Papua New Guinea. This preemptive disaster risk management initiative integrates a combined drought index (CDI) with specific thresholds and tailored anticipatory actions based on crop calendars. Moreover, the developed CDI provides a 3-month lead time for implementing AA to reduce the impact of the agricultural drought. During the El Niño-induced drought event that began in 2023, the CDI was tested and the AA was piloted for the first time.

Pre-hispanic wetland irrigation and metallurgy in the South Andean Altiplano (Intersalar Region, Bolivia, XIVth and XVth century CE)

The high-altitude Andean Altiplano has been subject to abrupt climate changes during the Holocene. The resulting impact on the hydrological cycle has obliged ancient societies to adapt and develop strategies to face droughts and sustain agropastoral activities. Here, we present the results of archaeological prospections together with the biogeochemical characterization of a well-dated core collected at Saitoco wetland in the arid southern Altiplano (Intersalar Region, Bolivia). Archaeological survey allowed the mapping of a network of channels collecting water from the surrounding mountains to the wetland, and the presence of small copper mines and metallurgical installations. Traces and major element concentrations and accumulation rates, together with elemental and isotopic characterization of organic matter (OM) (i.e., Corg and δ13Corg) in the wetland core have been used to document the evolution of the landscape in relation to climatic and anthropogenic pressure. While OM, bromine (Br), selenium (Se) and mercury (Hg) data were used to assess the variability of precipitations during the Late Holocene (4.2 ka BP to the present), local and regional mining activities have been reconstructed through the variations of lead (Pb), copper (Cu), and antimony (Sb). Our results show an abrupt change in OM composition during the 14th and 15th century CE, characterized by an abrupt shift in δ13Corg synchronous with a rise in Br, Se and Hg, testifying for the waterlogging of the wetland during a known arid period in the region. This change is attributed to anthropogenic transformation of the landscape through the irrigation of the wetland by channeling streams from the surrounding mountains. At the same time, a mining pollution signal was recorded supporting local Cu mining and metallurgy. The mining signal then reached its maximum values during the Inca and Colonial periods, which matches with reported enhanced mining activities in the region. From the colonial era onward, the wetland progressively dried up, likely resulting from the abandonment of the site. Through the combination of a biogeochemical record and archaeological prospections, this study provides evidences that societies of the arid Intersalar region have transformed their landscape and developed wetland irrigation and mining during the arid 14th and 15th century CE Period.

Palaeoenvironmental changes since the last deglaciation recorded at Moon Lake on the Bashang Plateau, northern China: implications for the future sustainability of regional forests

Warming-induced ecological degradation and the continuous shrinking of lakes have been observed in the Bashang Plateau, northern China, leading to the recent demise of cultivated forests. The objective of this paper is to investigate the long-term palaeoenvironmental context of these recent changes through a multi-proxy sediment core analysis at Moon Lake to better understand forest sustainability in the future. The core chronology was determined based on seven accelerator mass spectrometry (AMS) 14C dates and covers the period from 14,000 yr BP to the present. The Moon Lake record reveals four climate stages: (1) a warm and humid period followed by a cold and arid phase corresponding to the Allerod warm period and the Younger Dryas stadial (14,000 to 11,700 yr BP), (2) a relatively warm and humid period (11,700 to 7400 yr BP), (3) a period of fluctuating dry-wet-dry changes (7400 to 4000 yr BP), and (4) a relatively arid period (4000 yr BP to present). Since 1800 yr BP, drought conditions have intensified, and significant warming and drying trends have been observed over the past 500 yr BP. This consistent warming and drying trend over the past few centuries indicate that large-scale afforestation is no longer sustainable in the Bashang region. Coupled with instrumental records of soil drying and water scarcity, our Holocene records of climate change are useful for ecological resource management and sustainable forestry planning in the region.

Evaluation of the Compound Effects of the 2022 Drought and Heatwave on Selected Forest Monitoring Sites in Hungary in Relation to Its Multi-Year Drought Legacy

The effects of the changing frequency and severity of drought events in Central Europe may become a growing concern for its forests. In this study, we looked into how Hungary’s forests have been affected by the 2022 compound heatwave and drought, following an arid period from 2018 to 2021. We used our active intensive monitoring plots of the Forest Protection Measuring and Monitoring System (Level II in the ICP Forests) across the country between 2017 and 2022. We analyzed satellite images to support a survey of the large-scale drought utilizing moderate and high-resolution data. The health state of the forest calculated and mapped on the NDVI, ZNDVI, and NDWI indices showed damage and regeneration throughout the period studied. Overall, the forest stands observed tolerated the negative impacts of the drought (126–204 mm water deficit in 2022) based on our biomass data (the summer leaf loss was 14% in each monitoring plot). However, the classified Z-NDVI values of the Sentinel-2 satellite imagery for the period 2017–2022 showed a severe drought in 2022, which was followed by some improvement in 2023.

Adaptive foraging behaviours in the Horn of Africa during Toba supereruption.

Although modern humans left Africa multiple times over 100,000 years ago, those broadly ancestral to non-Africans dispersed less than 100,000 years ago1. Most models hold that these events occurred through green corridors created during humid periods because arid intervals constrained population movements2. Here we report an archaeological site-Shinfa-Metema 1, in the lowlands of northwest Ethiopia, with Youngest Toba Tuff cryptotephra dated to around 74,000 years ago-that provides early and rare evidence of intensive riverine-based foraging aided by the likely adoption of the bow and arrow. The diet included a wide range of terrestrial and aquatic animals. Stable oxygen isotopes from fossil mammal teeth and ostrich eggshell show that the site was occupied during a period of high seasonal aridity. The unusual abundance of fish suggests that capture occurred in the ever smaller and shallower waterholes of a seasonal river during a long dry season, revealing flexible adaptations to challenging climatic conditions during the Middle Stone Age. Adaptive foraging along dry-season waterholes would have transformed seasonal rivers into 'blue highway' corridors, potentially facilitating an out-of-Africa dispersal and suggesting that the event was not restricted to times of humid climates. The behavioural flexibility required to survive seasonally arid conditions in general, and the apparent short-term effects of the Toba supereruption in particular were probably key to the most recent dispersal and subsequent worldwide expansion of modern humans.

Sedimentological evolution of the Quibas site: High-resolution glacial/interglacial dynamics in a terrestrial pre-Jaramillo to post-Jaramillo sequence from southern Iberian Peninsula

The sedimentary infill of the Quibas karstic site (Early Pleistocene, southern Spain) represents the only continuous succession with remains of continental vertebrates in Europe from pre-Jaramillo to post-Jaramillo age. The Quibas site, with a significant paleontological record, is dated between 1.1 and 0.9 Ma and offers a unique opportunity to carry out a paleoclimatic reconstruction of the time period immediately after the arrival of the first humans to western Europe. For this reason, defining the dominant sedimentary processes in the different stratigraphic units and the associated paleoenvironment is essential. The Quibas site is made up of two karstic features with two stratigraphic sequences: Quibas-Cueva, containing six lithostratigraphic units, and Quibas-Sima, which contains seven lithostratigraphic units. The detailed description and analyses of the stratigraphic sections have allowed the characterization of various autochthonous and allochthonous facies of cave deposits. Paleoclimatic proxies, inferred from sedimentological analyses, reveal a record of several alternating humid and arid phases resulting from the Early Pleistocene glacial-interglacial cycles, allowing correlation to the marine oxygen isotope record. The lowermost units (pre-Jaramillo) were deposited during a long-lasting interglacial, correlated to MIS 33–31. It was followed by an increase in aridity in the intermediate units of Quibas-Sima and uppermost unit of Quibas-Cueva (Jaramillo), revealing the beginning of a glacial period at the start of the Jaramillo subchron (1 Ma), which can be correlated to MIS 30. The upper Jaramillo and post-Jaramillo units suggest these were deposited in alternating periods of aridity and humid conditions, although less humid than the pre-Jaramillo period, probably representing the MIS 29 interglacial, the MIS 28 glacial and the MIS 27 interglacial.

Biogenic carbonates (queras) in loess-palaeosol sequences of the Ebro Basin and their potential use as a palaeoenvironmental proxy

Secondary carbonate accumulations are very common in arid and semi-arid soils but are often poorly described and classified. This is the case for queras that are observed in several loess-palaeosol sequences of the Ebro Basin. Micromorphologically, queras are complex pedogenic features basically consisting of infillings of calcified root cells in channels, surrounded by decarbonated hypocoatings. They apparently result from biologically mediated calcification/decalcification processes at a microscale. The aim of this study is to systematically characterize biocalcifications found in dated loess-palaeosol sequences, to determine the main factors of formation, and to discuss their possible use as a palaeoenvironmental proxy. Different queras show a similar number of biosparite layers (four to five) around a central channel, and a decarbonated hypocoating around the queras. This supports the hypothesis that queras originate from the calcification of root tips and are related to the acidification of surrounding soil for nutrient absorption. Under cathodoluminescence microscopy, biosparite has a different behaviour than non-biological calcite crystals: the latter appears reddish while biosparite remains black. The queras, with ages corresponding to Marine Isotope Stages 1–3, are younger than that of the loess where they are found in. The stable isotope values likely correspond to C3 plants, and the estimated temperatures of formation reflect a Mediterranean temperate climate. This suggests that the biocalcifications developed during short moist seasons amidst arid periods of the Quaternary.

The Geochemical Characteristics and Environmental Implications of the Paleocene–Eocene in the Jiangling Depression, Southwestern Jianghan Basin

Various isotopic and palynological indicators have shown interspersed periods of aridity and humidity for the late Paleocene to early Eocene in central China, so the paleoclimate conditions remain unclear. This research investigates the environmental characteristics of a saline lake in the Jiangling depression, southwestern Jianghan Basin, from the Paleocene to the Eocene, using bulk-rock geochemistry in a 1280 m sediment core. The ratios of FeO/MnO, Al2O3/MgO, and C-value indicate a semi-humid to semi-arid climate in the early–middle Paleocene. There was a rapid shift to a humid climate during the late Paleocene to early Eocene, following a short time of intense dryness. The Eocene climate was arid, but experienced intermittent humidity. The variation trend of the CIA, CIW and PIA was similar to that of FeO/MnO, Al2O3/MgO, and the C-value, so chemical weathering of the surrounding rocks was controlled by climate change. The lake redox conditions in the Jiangling depression from the Paleocene to the Eocene were reconstructed using the ratios of U/Th, Ni/Co, and V/Cr. During humidity and alternations of aridity and humidity, the lake water received external water input, resulting in weak stratification, so the sediments were in oxidizing conditions. During aridity, lakes become endorheic, leading to sediments forming in reduced conditions. The salinity of the lake in the Jiangling depression from the Paleocene to the Eocene was determined through analysis of sedimentary sequences and the trend of the Sr/Ba ratio. In the early–middle Paleocene, lake salinity varied greatly. From the late Paleocene to the early Eocene, lake salinity decreased. In the Eocene, lake salinity increased and halite precipitated, but lake salinity finally decreased due to a humid climate. During the late Paleocene–early Eocene, the occurrence of multiple humid climates in the Jiangling depression were not merely regional effects. The most significant humidity was caused by a global hyperthermal (PETM), which caused a huge increase in precipitation in the whole of East Asia and even in low latitudes around the world.

The mineralogy and geochemistry of the Pirashkaft bauxite, Zagros belt, Iran: New inferences on the paleo-climate at the time of formation and on the nature of the parent rock

The Pirashkaft karst type bauxite is located in north of the Paskuhak anticline, Pirashkaft region, in the Fars province (Iran). The deposit is composed of six bauxite horizons, occurring between upper Cretaceous Sarvak and Gurpy Formations, and formed in the late Turonian. Mineralogical composition includes boehmite, hematite, diaspore, kaolinite, goethite, anatase and minor minerals like, gibbsite, spinel, rutile, and kaolinite. The major oxides in the bauxite horizons mainly comprise Al2O3 (46.93–61.34 wt%), SiO2 (5.78–14.60 wt%), Fe2O3 (11.22–28.00 wt%), and TiO2 (1.66–3.03 wt%). The bauxite has a pisolitic–oolitic texture. Pisoids are mainly composed of large Al-bearing hematite cores, surrounded by layers of gibbsite or boehmite. This structure suggests that bauxite formed under a humid climatic regime, punctuated by periodic arid periods. In the Pirashkaft deposit, LREEs vary between 136.49 ppm and 928.56 ppm, whilst HREEs range from 16.48 ppm to 59.5 ppm. Positive anomalies of Ce (Ce/Ce* between 1.08 and 2.36) indicate dominant oxidizing conditions during the bauxitization process. The Eu/Eu* anomalies of the bauxite samples vary between 0.44 and 0.92, this suggesting that parent material likely derived from two geochemically distinct source rocks. Stratigraphical, mineralogical, and geochemical evidences, such as the REE distribution between the bauxitic horizons and the Sarvak marly limestone, suggest that the underlying marly carbonates were one of the sources of the Pirashkaft bauxite.

Upper Miocene aragonite sediments of the Eastern Paratethys (Zheleznyi Rog section): Whiting events or not?

The upper Sarmatian and lower Maeotian unlithified aragonite sediments of the Zheleznyi Rog section (Taman Peninsula, Eastern Paratethys, Russia) were investigated by field observations and laboratory methods, including scanning electron microscopy, X?ray diffraction and isotope analyses. Aragonite sediments occur at separate intervals of the studied section, forming thin (millimeter?sized) interlayers with clays. These carbonate sediments consist almost entirely of crystals (individuals and twins) and aggregates of aragonite, ranging in size from 5 to 23 ?m. It is assumed that the isotopic composition (?13C = 5.7 and 5.3?, ?18O = ?2.4 and ?2.8? for upper Sarmatian and lower Maeotian aragonites, respectively) reflects the sedimentation conditions, chara cterized by reduced basin salinity, increased surface water bioproductivity, and periods of aridization. Abiotic precipitation of these aragonites most likely occurred due to the action of triggering mechanisms, which could include planktonic algae blooms (e.g. diatoms). The obtained results do not contradict the hypothesis that the studied aragonites may be considered as sediments of whiting phenomenon.

First genetic evaluation of a wild population of Crocodylus intermedius: New insights for the recovery of a Critically Endangered species.

During the second third of last century, the Orinoco Crocodile (Crocodylus intermedius) underwent a hunting process driven by the demand from the North American, European, and Japanese leather industry, resulting in a sharp decline of its populations. Currently, only two known remaining populations of this Critically Endangered species persist in the Colombian Orinoquía: in the Guayabero-Duda-Lozada and the Cravo Norte-Ele-Lipa River Systems. The latter has been the only population subject of study, including recent surveys and local conservation initiatives such as egg and hatchling ranching. Despite suggestions for population recovery based on the observed increase in clutches in the area, information regarding its genetic status has been pending assessment. This research aims to provide a genetic characterization of this remaining population and to evaluate the diversity recovered during a period of the egg ranching initiative. For this purpose, we utilized variable molecular markers, specifically 17 microsatellite loci, nuclear DNA. Despite revealing intermediate levels of genetic diversity, we identified an effective population size of 11.5-17, well below the minimum values proposed for short-term subsistence. While no evidence of inbreeding was found, it is acknowledged as a potential risk based on the population's history. Additionally, we detected a historical bottleneck possibly influenced by arid periods affecting the region since the Pleistocene. While the evaluated population presents a unique opportunity for C. intermedius conservation, it also exposes a high risk of entering the extinction vortex. The primary action to be taken is to support the egg and hatchling ranching program, which successfully recovered most of the genetic diversity present in the population.

Geomorphic evolution of the craton-derived Sone megafan in the southern Ganga plain, India: A tectono-climatic interplay

The Ganga plain neotectonics has been studied from surface and sub-surface faults, frequent geomorphic readjustment, changing sedimentation pattern, piedmont progradation, pedological variation, and frequent earthquake occurrences. However, being neotectonically stable, the peninsular region’s geomorphic changes are governed by climatic fluctuations, contributing to the Ganga plain’s sedimentation. Therefore, peripheral craton sourced marginal alluvial deposits in the Ganga basin are appropriate features to study the control of both the Himalayan tectonics and climate of core peninsular region away from their respective source areas. This study uses a process-response approach model to describe the geomorphic development of the Sone megafan, located at the marginal part of the Ganga plain to the south of the Ganga River, bordering the Indian craton.Geomorphological mapping, field investigation of the depositional features, soil profiles, and Optical Stimulated Luminescence (OSL) chronology suggest four phases of geomorphic evolution, i.e., in 22–8 Ka, 8.0 Ka–7.3 Ka, 7.3 Ka–2.4 Ka, and 2.4 Ka–0.5 Ka on the Sone megafan. The different evolutionary phases are marked by channel and floodplain abandonment and soil profile development. The megafan surface is divided into four distinct geomorphic units (OdSP – Oldest Sone Plain, OSP – Old Sone Plain, YSP – Young Sone Plain, and AFP – Active Floodplain) based on OSL ages and soil properties. Geomorphology and soil suggest a mixed climate in the source and sink area. The arid climate in the catchment contributed to the sediment production, and the humid climate promoted its transport, which resulted in the largest depositional unit of the megafan, even during the arid period in the Ganga basin. Contrast to the north of the Ganga River, no surface faults are found on the Sone megafan. However, the tectonic activity of the bounded basement faults, i.e., the East and the West Patna faults, are well pronounced in the sediment distribution and fluvial response. Tilting and twisting the fault-bounded block controls the sediment remobilization in space and time. Thus, the climatic fluctuation in the source, the sink, and the activity of the basement faults, propelled by the Himalayan tectonics, contributed to the Sone megafan’s geomorphic evolution. Two events of the Ganga River’s encroachment at the distal part of the Sone megafan were recorded (2.4 ± 0.14 and 1.3 ± 0.16 ka). The correlation between OSL ages of megafan units, climatic fluctuations in the Sone River’s catchment, and established time windows of tectonic episodes in the Ganga basin has also been investigated. As the Sone and the Gandak megafans rest on the same tectonic blocks, their tectono-geomorphic responses to the Himalayan neotectonics are similar.

Insights into the organic matter composition of soda lakes in the Pantanal, Brazil, through fatty acids analysis in sediments.

We conducted a geochemical analysis on three sediment cores collected from soda and freshwater lakes in the Pantanal region, in Brazil. Our objective was to identify the primary sources of organic matter associated with the Pleistocene-Holocene transition, as previously documented in that area. The Nhecolandia region, located in the Pantanal, encompasses over 10,000 lakes, with approximately 10% of them exhibiting alkaline characteristics. Soda lakes became highly saline and alkaline after ~ 910calyr BP, which influences biogeochemistry and aquatic ecology. They have high electrical conductivity and pH can reach 10.5. In contrast to freshwater, soda lakes are absent of surrounding vegetation. Literature suggests a strong influence by the Last Glacial Maximum on the region. We hypothesized that periods of aridity and increased precipitation influenced the composition of organic matter present in sediments and preserved within these cores. Our analysis focused on examining the presence and distribution of fatty acids, organic carbon content, and total nitrogen. In general, the cores exhibited two distinct parts in terms of organic matter sources: the upper sections of the cores were primarily composed by terrestrial sources, identified by the presence of long-chain fatty acids, while the deeper sections were dominated by aquatic sources, therefore short-chain fatty acids. We did not find significant difference among fatty acid profile that could distinguish freshwater from soda lakes, the only remarkable difference was the occurrence of saturated fatty acids, which is lower in freshwater lake. These findings suggest the occurrence of humid and arid periods in the region. The C/N ratio displayed a similar trend to the fatty acid's profiles, exhibiting an abrupt change that was likely induced by climate variations. Although diagenesis can alter the composition of organic matter and, subsequently, the C/N values, it is noteworthy that the abrupt change observed in the Salina da Ponta (soda lake) core corresponds to 3,200years BP. This coincides with documented climate changes that occurred during the Holocene. Our study revealed the influence of past climatic conditions on the sources and variations of organic matter in sediment cores from the Pantanal's soda and freshwater lakes. Consideration of diagenesis and climate variations is crucial for interpreting sedimentary records.

Estimation of the productivity of rice samples under severe field drought

Drought is one of the most important factors hindering the cultivation of rice, resulting in large yield losses, and limiting productivity growth. The purpose of the current study was to determine the drought resistance of rice varieties and samples of various origins under conditions of periodic irrigation with periods of prolonged soil aridity and high air temperature, to identify drought-resistant plants for the selection of upland varieties. There have been studied 68 varieties and samples of upland rice when grown on irrigated and flooded areas (Proletarsk, Rostov region). There has been established that varieties and samples under drought conditions and sufficient water supply formed different grain productivity, which in 2020–2021 with a lack of water amounted to 63.7 % of the norm, and in 2022 to 30.1 %. There has been found that the correlation of rice productivity under dry conditions with that under full moisture supply was weak negative (r = –0.22±0.12), and with the drought resistance index (DRI) it was high positive (r = 0.95±0.04). The values of quantitative traits under drought conditions have changed significantly in comparison with the control. Such traits as plant height (95.7 %), panicle length (73.1%), panicle density (58.7 %), number of harvested plants per 1 m2 (87.3 %), plant weight (42.3 %), panicle weight (25.1 %), total number of spikelets (54.5 %) and grains per panicle (32.4 %), 1000-grain weight (70.4 %) have decreased. Such traits as number of productive stems per 1 m2 (115.2 %), tilling capacity (126.1 %), the number of empty spikelets per panicle (205.1 %) and the percentage of empty grains (339.1 %) have increased. There have been identified such 9 varieties and samples with DRI from 51.1 to 93.7 % as ‘Kontro’, ‘An-Yun-Ho’, ‘Chan-Chun-Man’, ‘Hong-Mo’, ‘8323’, ‘8338’, ‘8337’, ‘ZULK 8’, ‘ZULK 9’, which formed maximum productivity in dry conditions (3.95–5.51 t/ha).

Paleofire dynamics in response to climate change during late Miocene derived from microcharcoal records in the Weihe Basin

The Weihe Basin, situated in the central part of Shaanxi Province between the Qinling and Weibei Mountains, falls under the influence of the Asian monsoon system. The basin's thick and continuous Cenozoic sedimentary layers offer a valuable repository for investigating environmental changes within a typical monsoon climate. Based on previous chronological research, our study delved into the microcharcoal concentration (MCC) of the samples extracted from Bahe Formation. This analysis aimed to reconstruct the paleo-fire and drought history during the late Miocene, shedding light on the region's evolutionary trajectory. Our findings unveil five distinct peaks in the microcharcoal record, occurring at approximately 9.9–9.7 million years ago (Ma), ∼9.5 Ma, ∼8.1 Ma, ∼7.6 Ma, and 7.4–7.2 Ma. These peaks signify high-frequency fire events, primarily taking place during periods of aridity. The combustion of broadleaved and coniferous trees was the predominant source of fuel for fires during 9.9–9.7 Ma, ∼9.5 Ma and ∼8.1 Ma, with elevated temperatures acting as the principal ignition catalyst. In contrast, the subsequent two fire events (∼7.6 Ma, and 7.4–7.2 Ma) coincided with drier climatic conditions, featuring xerophytic herbs s as the primary biomass. Drought emerged as the pivotal driving force behind these fire occurrences in this phase. The microcharcoal records of the Bahe Formation reveal a noteworthy pattern: the MCC during the latter two periods surpassed that of the initial three, indicating an escalated frequency of fires during dry intervals. This trend signifies a transition towards a dry and cold climate post ∼8.0 Ma. The expansion of grasslands and the occurrence of drought events since the late Miocene (∼8.0 Ma) can be attributed to the weakening of the Asian Monsoon. In summary, our investigation of microcharcoal concentration in the Bahe Formation provides valuable insights into the late Miocene paleo-fire and drought dynamics. By deciphering the interplay between vegetation, climate, and fire occurrences, our study contributes to a more comprehensive understanding of the environmental evolution within the Weihe Basin under the influence of the Asian monsoon system.