Steppe Environment Research Articles

Carabus (Tomocarabus) bessarabicus Fischer von Waldheim, 1823 (Coleoptera: Carabidae)—New Steppe Element for the Bulgarian Fauna from the Karst Refugium of the Chepan Planina Mt.

During a study of the distribution and status of Carabus hungaricus Fabricius, 1792 (Coleoptera: Carabidae), with pitfall traps exposed between November 2021 and April 2022, immediately south of Petrovski Krast Peak (1206 m a.s.l.) in the Chepan Planina Mt., at 1188 m a.s.l., the rare and stenotopic steppe species Carabus bessarabicus Fischer von Waldheim, 1823, was found for the first time in Bulgaria and the European Union. In October 2022, elytra of both species were also found by handpicking in the same area. The coexistence of these two specific and rare steppe species has been recorded only in few localities in Ukraine and Russia and in no EU country. This finding is also very interesting given the high conservation status of Carabus bessarabicus, the significant remoteness of its newly established locality (more than 1200 km) from its previously known range, and its strong south-westward drift. The species is used as a bioindicator for the anthropogenically uninfluenced steppe environment, which can also probably be applied in Bulgaria. The establishment of this first record for the EU also implies an increase in the conservation status of the species through its inclusion in the Union-wide conservation documents and ecological networks.

The brain of the North American cheetah-like cat Miracinonyx trumani.

The cheetah Acinonyx jubatus, the fastest living land mammal, is an atypical member of the family Felidae. The extinct feline Miracinonyx trumani, known as the North American cheetah, is thought to have convergently evolved with Acinonyx to pursue fast and open-country prey across prairies and steppe environments of the North American Pleistocene. The brain of Acinonyx is unique among the living felids, but it is unknown whether the brain of the extinct M.trumani is convergent to that of Acinonyx. Here, we investigate the brain of M.trumani from a cranium endocast, using a comparative sample of other big cats. We demonstrate that the brain of M.trumani was different from that of the living A.jubatus. Indeed, its brain shows a unique combination of traits among living cats. This suggests that the case of extreme convergence between Miracinonyx and its living Old World vicar should be reconsidered.

Essential Role of Forest Fires in Humic Acids Structure and Composition Alteration

Pyrogenic components of soil organic matter are practically not taken into account when assessing the implications of global climate changes on the SOM sequestration rate and its stability. In this regard, both the amount and structural stability of SOM were investigated for postpyrogenic forest–steppe environments. Mature unaffected by fire Psamment Entisols were investigated in comparison with same soil strongly affected by surface and crown fires in 2010 in Tolyatti city. This article discusses postpyrogenic succession when comparing the results of field works in 2010 with 2020. The elemental composition of humic acids as well as 13C NMR spectra were investigated for the studied humic acids. Moreover, for the first time ever, integrated indicators of HAs’ molecular composition were presented for postpyrogenic soils. The data obtained showed that there are significant changes in the structural organization of organic matter as a result of forest fires. A simultaneous decrease in the H/C and O/C atomic ratios was identified as a result of fire, which indicates a slight loss of oxygen-containing functional groups, while the aromaticity degree of molecules increases. An increase in the content of oxygen-containing groups in the HA molecules was shown for 10 years after the fires, which was accompanied by the oxidation of the HA molecule with the same increase in the aromaticity degree of the HA molecule. The HA molecules of 2020 turned out to be more resistant to environmental factors compared to analogues in 2010. As a result of fires, the aromaticity degree of HAs molecules significantly increases.

Mongolian Marmot (<i>Marmota sibirica</i>) Ecosystem Engineering Effects on Herpetofauna

The Mongolian marmot (Marmota sibirica) is a relatively large-bodied, social rodent that lives in colonies across the Mongolian steppes and adjacent parts of China and Russia. Marmots serve as ecosystem engineers that display multiple functions on the steppe environments they inhabit. Mongolian marmots experienced a 75% decline across Mongolia in the 1990s that led to their listing as endangered globally. The decline of marmots likely affected other species given their importance to the ecosystems they inhabit. To examine the role of marmots on herpetofauna, we established drift fence arrays with associated pitfall and funnel traps on active marmot colonies, inactive colonies, and control sites in the forest-steppe and semi-desert zones of Mongolia. In total, we identified 555 individuals representing 5 species of reptiles in Ikh Nart Nature Reserve (semi-desert) from 2010 – 2011 and 22 individuals of 3 species of reptiles and one amphibian species in Hustai National Park (forest-steppe) in 2014 and 2016. We found significantly higher species abundance and some diversity indices on active and inactive colonies compared to control sites in Hustai. Vegetation height and cover significantly affected the abundance and species richness of reptiles in Ikh Nart. In Ikh Nart, we found that under conditions of higher vegetation cover and height, reptiles were distributed more widely across the landscape, but with lower vegetation cover and height, reptiles associated more strongly with marmot burrows. Burrows likely provide shelter from extreme climatic conditions and refugia from predation. Our research provides insights into how marmots create important habitats for associated fauna. This and similar experimental approaches will allow us to better understand the biodiversity patterns in and around marmot burrows.

Pedogenic response to Holocene landscape evolution in the forest-steppe zone of the Russian Plain

Soils buried under five defensive ramparts of the Early Iron and Middle Ages were studied in the forest-steppe zone of the Russian Plain (Lipetsk region, Russia). The time of the burial differs from each other for hundred years allowing studying variation of soil properties based on short-term chronosequences within these ranges and reconstructing the comparatively short climatic trends. Similar topographic positions, particle-size distribution, bulk elemental composition, and major morphological features were the base for comparing buried and surface soils, aiming to link the differences in the pedofeatures with climatic fluctuations. The studied soils display polygenetic features that were formed under forest (clay cutans) or steppe (carbonate neoformations, mollic horizons) environments. Generally, the Early Iron Age environment was similar to the modern one, which is confirmed by the similarity between the soil buried ∼ 2500 yrs BP and the surface soils (Greyzemic Luvic Phaeozems). The detailed chronosequence allows distinguishing alternating humid and arid phases during the studied time interval. Soil response to climatic phases is recorded by rather dynamic pedofeatures: carbonate, gypsum and greyzemic properties, and the properties of the mollic horizon. Following climatic fluctuations, these pedofeatures can appear and then be erased or transformed, evidenced by a multi-layered cutan complex with alternating clay and carbonate coatings. As a result, the surface soils of the study area are polygenetic and combine features formed under steppe and forest environments. The alternating phases of forest and steppe pedogenesis throughout the entire Holocene, especially in the Late Holocene, when ancient tribes influenced the studied areas, testifies against the decisive role of anthropogenic input in the formation of Chernozems.

Mapping potential desertification-prone areas in North-Eastern Algeria using logistic regression model, GIS, and remote sensing techniques.

Desertification is an environmental threat that affects many countries in the world, and it poses specially an ecological issue to Algeria. This study aimed to assess areas sensitive to desertification in North-Eastern Algeria (Tebessa province) using a logistic regression model (LRM), and geomatics-based approaches. Topsoil Grain Size Index (TGSI), Normalized Difference Vegetation Index (NDVI), Aridity index (AI), and Anthropic pressure on the steppe environment (APSE) were selected as desertification indicators for representing land surface conditions from soil, vegetation, climate, and anthropic disruptors. Results indicate that both AI and TGSI are the most crucial indices conditioning desertification risk. Other indices; NDVI and ASPE were appeared as secondary important indices. Herein, although vegetation generally is a key factor for reading desertification, this result shows that vegetation changes in this study are less important than other desertification conditioning parameters. Area under curve value equal 0.94 indicates a satisfactory accuracy for the proposed model. In total, desertification risk changes increasingly along a North-to-South gradient of the whole research area. Besides, slight, moderate, high, and very high classes occupied 0.87%, 21.08%, 19.33% and 58.72% of the total land area, respectively. LRM is recommended as an accurate and easily applied tool to monitor desertification, especially in scarce data environment in developing countries. Additionally, the results obtained in this paper represent a basic scientific tool for implementing current and future policies to control desertification at areas with high risk.

Palaeoecological significance of the “wolf event” as revealed by skull ecometrics of the canid guilds

Members of the mammalian order Carnivora are rarely considered as proxies for palaeoecological reconstructions due to their broad phenotypic plasticity and high climatic tolerance. However, palaeontologists have traditionally interpreted the appearance of some particular carnivoran species in relation to major climatic events. The ‘wolf event’ characterised the inset of climatic deterioration for continental Eurasian fauna, ca 2.0 million years ago. It was defined as the dispersal of cursorial wild canids from East Asia to Europe consequently to the spread of the steppe environment. Anecdotal interpretations were never supported by rigorous testing about the palaeoecological significance of these canid taxa. Here, we employ two dimensional geometric morphometrics of canid skulls to characterise and interpret the structure of extant guilds and its relationship with climate and provide inferences on the early Pleistocene Valdarno community. Averaged skull size and shape of canid guilds are currently associated with climatic parameters that reflect annual mean temperature, seasonality and precipitation. The canid guild from Valdarno showed a clustered phylogenetic structure and its average shape resembles those of communities characterised by relatively high seasonal environments. This study supports the use of canid community structure for palaeoclimatic reconstructions and validate the early Pleistocene as a period of climatic deterioration for Eurasian large mammal fauna.

New Complex Investigations of the Novhorod-Siverskyi Upper Palaeolithic Site

In the article the materials of the Novhorod-Siverskyi site research both in the 1930's, and relatively recently, are analyzed. First of all, attention is paid to the faunal collection. The faunal associations from old excavations are coherent, typical of a cold steppe environment from the glacial period, near a riparian forest. However, it seems to result to a mix between natural taphonomic complexes and animal remains associated with human activity. Judging by the flint collection from the old excavations, the site was inhabited by representatives of the Pushkari type. New research yielded two archaeological layers that are very poor in flint artefacts. Concerning fauna, the faunal spectrum is restricted in both layers, with the woolly mammoth, the woolly rhinoceros, the horse and the reindeer in the lower and upper layers. In the upper layer there are also the bison, the fox and the hare. According to taphonomic observations, the bones had remained for a long time at an open air before being buried, in subsurface in a wet environment but few submitted to precipitations in link with permafrost activities. Particularly in the lower layer (2) some remains appear to be in place, while others seem to have been imported by hydraulic phenomena, either from the top of the promontory or from the Desna River. In the upper layer (1), some bones show possible anthropogenic impacts of breakage, linked to marrow recovery. In both layers we have some cranial and postcranial elements, mainly from adults sensu lato which could correspond to human predation. They could correspond to temporary camps of quite small human groups, potentially occupied at the end of the cold season/beginning of the warm season.

Holocene Environmental Changes Inferred From an Aeolian-Palaeosol-Lacustrine Profile in the Mu Us Desert, Northern China

An excavated profile of aeolian-palaeosol-lacustrine sediments (the Wapianliang profile), located at the southeastern part of the Mu Us Desert, Northern China, was studied to reconstruct regional Holocene environmental changes. A chronology was established based on three AMS 14C and two OSL dates, and variations in the lithology and grain size, magnetic susceptibility, soil micromorphology, and chemical elements were used to explore the regional depositional environments during the Holocene. The results showed that since around 14 ka BP, this region had experienced seven alternations of wetting and drying. A shallow lake, which was identified by celadon lacustrine sediments with sporadic freshwater gastropod fossils, occurred in this area from around 13.0 ka BP to 9.9 ka BP. There existed two obvious intervals of soil formation, inferred from the environmental proxies of the palaeosol/sandy palaeosol layers, with relatively fine average grain-size, high magnetic susceptibility value, remarkable pedogenesis features, and strong chemical weathering, in particular, a well-developed palaeosol layer dating from the middle Holocene (8.6 ka BP to 4.2 ka BP). A weakly-developed palaeosol layer (from around 1.2 ka BP) at the upper part of the profile is possibly an indication of the Medieval Warm Period. This implies a forest steppe environment at both of these sedimentary stages. After 0.9 ka BP, a desert environment returned, analogous to before around 13.0 ± 1.4 ka BP, between 9.9 ± 1.1 ka BP to 8.6 ka BP, and between 4.2 ka BP to 1.6 ka BP, indicating the aggravation of aeolian activity and the expansion of mobile sand dunes. The variations in sedimentary environments were mainly triggered by changes in the East Asian Summer Monsoon (EASM).

Experience in using phyto-structures for tertiary treatment of urban wastewater

This paper considers the experimental biocenosis development for tertiary wastewater treatment with respect to the climate features of South of Russia. The plant species with advantaged biotechnical characteristics that acceptable for steppe environment are described. The growing season productivity of the highest aquatic vegetation for the phyto-structures first year exploitation is determined. The quantitative statistics for indicative microorganism populations is calculated. The data obtained allows to measure the ecological effectiveness of wastewater treating phyto-system and to develop a cheap and recyclable biocenosis for the inhabited localities with temperate continental climate.

No significant change noted in annual nitrous oxide flux under precipitation changes in a temperate desert steppe

AbstractAs the third most important greenhouse gas, nitrous oxide (N2O) poses a significant threat to global warming and the ozone layer. However, the effects of precipitation changes on N2O emissions in arid areas remain unclear, particularly in desert steppe environments. Therefore, an in situ control experiment was conducted from July 2018 to July 2020 to examine the N2O emissions with changes in precipitation in the Urat Desert Steppe, northwestern China. The results showed that the N2O emission rate was relatively low in this desert steppe, at −0.04 to +15.0 μg N m−2 hr−1 with an annual flux of 0.20 ± 0.03 kg N ha−1. An increasing trend of N2O emission was observed in the early growing season (February to June 2019) when the precipitation was increased by 40% and 60% of its natural level. In contrast, no significant change in N2O emissions was observed when the precipitation was decreased during the same period. During the middle and late growing season and in the nongrowing season, precipitation changes did not significantly affect N2O emissions. In particular, no significant change in the annual N2O flux was observed during the entire observation period whether the precipitation was increased or decreased. Furthermore, the results of a structural equation model showed that the most important controlling factor for N2O emission is an abundance of key functional ammonia monooxygenase genes of ammonia‐oxidizing archaea, which are restricted by the soil NH4+‐N content, followed by abundances of key functional NO2− reductase (nirK) and N2O reductase (nosZ) genes. In contrast, the indirect effect of soil moisture on the abundance of nosZ compensated for the direct effect of soil moisture on N2O emissions. These results show that the primary and secondary origins of N2O emissions are soil ammonia oxidation and soil denitrification processes, respectively. In these two processes, N2O emissions are influenced more by the abundance of key functional microorganisms than by soil moisture, which might be limited mainly by the available soil nitrogen. Overall, the N2O emissions in the desert steppe environment were not sensitive to precipitation changes and were regulated mainly by nitrogen‐related key functional microorganisms.

Stratigraphy And Paleolithic Landscapes of the Beganchik Site at the Kama-Volga Confluence

The Beganchik locality is a stratigraphic sequence of loessic deposits, pedogenic horizons and Paleolithic occupations located at the Kama-Volga confluence. The sequence is exposed on a bluff formed on the west side of an erosional remnant between the Kuybyshev Reservoir and the former channel of the Aktay River. Although the site is known for its Terminal Paleolithic-Mesolithic occupations of the Pleistocene-Holocene transition, evidence of older occupations and remains of fauna has been identified. Our research team identified evidence of human presence associated with a pedogenic horizon of MIS 3 age. Two AMS radiocarbon ages from a hearth produced ages around 47 000 years BP. Pollen and phytoliths from two soils horizons, including the one associated with the hearths indicate a steppe environment coincident with the formation of correlative soils elsewhere in the Russian Plain.

Effect of gender on hematological parameters in growing Ouled Djellal sheep of semi arid zones of Northeastern Algeria

Ouled Djellal sheep is the most dominant breed in Algeria due to its adapta-tion to harsh steppe environment. Hematological parameters are good indi-cators of animal health, but their values are breed-specific, and they are affected by age and gender. Therefore, this study aimed to determine the hematological profile of healthy Ouled Djellal lambs and ewe lambs reared traditionally under semi-arid zones of Algeria during the growing peri-od. Blood samples were taken from twenty-four Ouled Djellal lambs (12 males, 12 females) at 42, 63, 84 and 105 days of age to evaluate the count of White Blood Cells, Lymphocyte, Monocyte, Granulocyte, Red Blood Cell and total Platelet, the percentage of Lymphocyte, Monocyte and Granulocyte, Hemoglobin concentration, Hematocrit, Mean Corpuscular Volume, Mean Corpuscular Hemoglobin and Mean Corpuscular Hemoglobin Concentration by usual known methods. Both male and female lambs did not show signifi-cant variations in mean values of White Blood Cells, Lymphocyte count, Red Blood Cells, Hemoglobin, Mean Corpuscular Hemoglobin concentration, per-centage of Monocyte, Monocyte count, Gran percentage and Granulocyte count from 42ͭ ͪ day to 105ͭ ͪ days. Mean values of percentage of Lymphocyte, Hematocrite in lambs, Mean Corpuscular Hemoglobin in ewe lambs, and Mean Corpuscular Volume, Platelets levels in both lambs and ewe lambs indicated also variations during this period of growth. Significant Pearson's correlations were found between some hematological parameters in Ouled Djellal lambs and/or ewe lambs. Therefore, these findings provide usual val-ues, which can be considered for assessing the physiological, nutritional and health status of these animals.

The cryogenic structure and texture of seasonally freezing soil in the steppe zone of the Trans-Volga-Urals region

The formation of ice lenses and associated frost heave were found in soils the steppe environment with positive mean annual air temperature. The ice lenses due to soil freezing occur in soils with expressed microrelief when they have additional ground moistening. In soils formed on quaternary loam with shallow groundwater the formation of ice was not differentiated across the microrelief; the morphology of the microrelief is similar to thufur. Soils formed on fine-dispersed limestone (chalky polygons) and on the material of ancient weathering crust (frost mounds) do not have clear evidence of subsoil extramoisterning exhibit the differentiated formation of cryotexture according to microrelief. The ice lenses were found in soils of microhights. The formation of cryogenic lenticular and platy structures occur after to the melting of ice lenses in soils. Local frost heave in steppe soils determines the small-scale differentiation of soil processes and the formation of the complex soil cover.

The impact of shifting Köppen-Geiger climate zones on soil organic carbon concentrations in Australian grasslands

The factors determining the spatial distribution of soil organic carbon (SOC) at large-scales closely align with bioclimate regions; reflecting climate, ecosystem and soil properties. Recent studies of the Köppen-Geiger climate zones of Australia have highlighted an extension of the hot, arid, steppe environment from central Australia into the southeast (SE) under future climate change scenarios (2071–2100 under RCP 8.5). As SOC concentrations are highest in Australia's SE, it is important the effect of this shift is quantified. This study assesses this and how changes in the factors that control SOC formation may alter SOC concentrations. Field measured SOC concentrations were compared to current climate, soil, topography, vegetation, and soil erosion variables for 12 grassland sites from SE to NW Australia. SOC concentrations ranged from 0.39% in northwest (NW) and Central Australia to as high as 6.88% in the SE. Using regression analyses; temperature, elevation and Normalised Difference Vegetation Index were found to be the only significant drivers (α = 0.95) of SOC across the sites. Partial correlation analyses then identified temperature, elevation and clay content as imparting a significant effect on the relationships between SOC and water availability variables. This indicates that an extension of the arid environment into SE Australia may lead to a decrease in SOC (up to 1.12%), as mean annual temperature exceeds threshold values that limit SOC concentration. This is significant as the majority of Australia's SOC is stored in this area and these environments exert a strong influence on global carbon cycling.

Palaeoecological background of the Upper Palaeolithic site of Ságvár, Hungary: radiocarbon‐dated malacological and sedimentological studies on the Late Pleistocene environment

ABSTRACTIn this paper, the authors present new palaeoecological and sedimentological results from the Upper Palaeolithic site of Ságvár, Hungary. Simple (abundance and dominance) and advanced (cluster analysis, principal component analysis, correspondence) statistical analyses of malacological results were carried out, determining eight malacological zones (MZs) and the key species of the fauna evolution in the sequence. Furthermore, an age–depth model was calculated via Bayesian modelling using new radiocarbon age data. The accumulation rate (AR) was calculated by deriving data from the age–depth model. The palaeoecological reconstruction indicated a cool/cold climate and chiefly steppe environment, with low loess ARs. Not only the vegetation cover but also the geographical setting of the sequence could have led to the low AR values. However, in the uppermost part of the sequence, during the GS 3 and GS 2.1c stadials, the reconstructed palaeoclimate indicated a warming period. Nevertheless, this contradiction is not unique in the Carpathian Basin. The settled Upper Palaeolithic hunters around 22 300 cal a bp lived in a progressively warming wooded steppe environment, hunting mainly for reindeer. Climate change might have forced them to migrate away, following the reindeer.

Development and resilience of deciduous Nothofagus forests since the Last Glacial Termination and deglaciation of the central Patagonian Andes

Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years.

Quercus robur survival at the rear edge in steppe: Dendrochronological evidence

Climate change is altering forest ecosystems worldwide, particularly in steppe landscapes, where the rare tree communities are challenged with steadily increasing droughts. In the steppe of Eastern Europe, amid dry conditions, Quercus robur occupies mostly riverine habitats and ravines. Here we study the climate sensitivity and drought vulnerability of a Q. robur population located at the rear edge of the species range, in the steppe of Ukraine. The population occupies two adjacent but clearly contrasting in their microclimatic conditions sites: a river floodplain and a steep-sloping river bank. We develop tree earlywood, latewood, and total ring width site-level chronologies and evaluate their relationship with regional climate variables and the local river's water level using response function analysis. We find that trees growing in the floodplain and at the steep river bank have exhibited slightly different growth patterns. The trees at the flooded site have benefited from water proximity, which facilitated their earlywood growth. These trees have responded positively to the current May and previous September precipitation and previous and current May temperatures. At the non-flooded site, the trees have experienced warm temperatures and the lack of precipitation in June. The extreme drought episodes have triggered a decrease in the latewood and total ring width in trees from both sites. We established that oak growth in the floodplain had been depressed by an unknown stressor around 1900, therefore limiting our ability to identify the more beneficial steppe habitat for Q. robur conclusively. Nevertheless, our results provide a dendrochronological evidence of Q. robur survival in a dry steppe environment and lend new insights into local microclimatic factors contributing to it.

Palaeoenvironmental changes in Eocene Tibetan lake systems traced by geochemistry, sedimentology and palynofacies

• Late Eocene continental climate in Central Asia remains poorly understood. • Tibetan lake deposits preserve records of Eocene palaeoenvironmental changes. • Saline lakes in east-central Tibet existed in a cool and semi-arid desert-steppe. • Late Eocene aridification caused a palaeoenvironmental shift in Central Asia. • Tibetan palaeoclimate was primarily influenced by regional to global drivers. Ancient lake deposits preserve detailed records of Cenozoic environmental changes, providing information on past climate, vegetation, precipitation and lake chemistry. This study focuses on palaeoenvironmental changes recorded in Eocene limnic environments across what is today the modern Tibetan Plateau. We describe a section dated as late Eocene (~38–37 Ma) and integrate these findings within a regional context of similarly-aged Tibetan lake deposits across the plateau. These sedimentary archives of environmental change indicate a period of late Eocene aridification and cooling in the lead-up to the greenhouse-icehouse transition, which remains poorly understood in Central Asia. We show, based on geochemical, sedimentological, and palynofacies analyses, that a large saline lake existed within a semi-arid to arid steppe environment in the Nangqian Basin, east-central Tibet. The saline lake experienced cyclic drying intervals with shifts to a playa lake / mudflat system. Evidence of increased aridity is recorded in the upper part of the section, including a thinning of gypsum beds, decrease in palynomorph abundance, and concurrent increase in wood debris and amorphous organic matter. This is consistent with late Eocene aridity in Asia, drying of the playa lake, and an impoverished desert-steppe vegetation. Grain size data and geochemistry indicate a stable provenance of sedimentary material, suggesting that tectonic activity did not dominate sedimentation in east-central Tibet during deposition of these successions. Rather, palaeoenvironmental changes across the Tibetan region were most probably controlled by global climate oscillations and retreat of the proto-Paratethys Sea during the late Eocene: knowledge that is relevant for ecological interpretations through the Cenozoic, Quaternary and to the present.

Seasonal variation in soil temperature and moisture of a desert steppe environment: a case study from Xilamuren, Inner Mongolia

Soil temperature and moisture are important factors affecting vegetation growth and drought in desert steppe environments. These factors also strongly influence grassland ecosystems. This study interpreted long-term (2009–2019) ground observation data on soil temperature, soil moisture, and meteorological factors from a study area in Inner Mongolia. The monitoring station collected soil moisture, soil temperature, and precipitation data. Covarying relationships indicated how soil properties influence each other throughout the year. Soil temperature was clearly affected by atmospheric changes, solar radiation, and freeze/thaw processes. The surface soil layers showed the greatest degree of variation, while middle and lower layers showed less seasonal variation and smaller differences between daily highs and lows. Surface soil moisture correlates strongly with the vertical temperature decline in soil. Time series revealed major variation in soil moisture throughout the year with lower soil layers showing obvious hysteresis effects. Multi-year soil moisture data allowed for subdivision of the year into seven intervals based maximum and minimum values. Soil temperature showed unique patterns of covariation with soil moisture during different time periods. Differences in soil moisture cause more rapid changes in temperature during soil thawing relative the moisture-induced temperature changes observed 1 month after soil freezing. When soil temperature was greater than 0 °C (32 ℉), soil temperature and soil moisture showed inverse correlation. A dependency of evapotranspiration on soil temperature can explain its effect on soil moisture. When soil temperature fell below 0 °C(32 ℉), soil temperature and soil moisture showed a positive correlation. During an interval defined as the summer fluctuation (SF), precipitation and soil moisture showed a significant positive correlation. During other periods, soil moisture did not clearly covary with precipitation.