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Trends for increased vegetation greenness based on satellite-derived data have been repeatedly published for the temperate grassland biome (including forest steppes) of eastern Inner Asia since 1982. Although this greening trend has been attenuated or partially reversed by drought in the early twenty-first century, linear increases in the Normalized Difference Vegetation Index (NDVI) or other parameters of vegetation greenness are nevertheless evident when the period since 1982 is regarded. However, the question arises whether these trends are part of a long-term trend driven by climate change, as simultaneously forests in the region show widespread drought-induced growth reductions and mortality outbreaks. Therefore, we hypothesized that the post-1982 greening trend was neither part of a long-term trend nor unprecedented. To test this hypothesis, we analyzed monthly maximum NDVI data from AVHRR time series and correlated these data with standardized tree-ring data of Larix sibirica from two regions of western Mongolia. We used linear regression to model the NDVI from tree-ring anomalies and to reconstruct the NDVI since 1940. These reconstructions show that the availability of satellite-based NDVI data coincidentally began during a dry period of low vegetation greenness in the early 1980s and was followed by a wet phase in the 1990s, producing the linear greening trend. No positive long-term trend in the reconstructed NDVI was observed from 1940 to 2010. This result rules out a recent climate change-driven greening trend for the grasslands and forest steppes of western Mongolia and calls into question its existence for all of eastern Inner Asia. [ABSTRACT FROM AUTHOR]

Vegetation and climate reconstruction in the forest–steppe of Mongolia is still challenging regarding the pattern of forest and grassland distribution during the Holocene. Different sediments containing paleosols and humic layers provide geomorphological archives for landscape development in Mongolia. n -Alkane and macro-charcoal ratios represent specific indicators to distinguish the share between grasses and trees. In a preliminary study, we investigated the applicability of these two paleo-proxies from soils for vegetation reconstruction comparing different relief positions and site conditions in the northern Khangai Mountains of Mongolia. n -Alkanes that are deposited from leaf waxes in the soil have the potential to indicate vegetation composition on a local scale. Depending on site-specific environmental conditions, n -alkanes are subjected to different degrees of microbiological decomposition, which is more intensive in soils of dry steppe than of forests. Mongolian forests are often underlain by permafrost that may reduce microbiological activity. In steppe soils, the decomposition of n -alkanes increases the quantity of mid-chain n -alkanes that adulterate the biomarker proxy signal to indicate more forest share. Macro-charcoals in soils have a site-specific component, but additional eolian input of macro-charcoals from long-distance transport can provide a distinct proportion in sediments. Thus, eolian influx of wood-derived macro-charcoal can dominate the proxy signal at sites where trees were few or had never existed. Radiometric dating of several paleosols and humic layers has shown that both proxies coincide as evidence for high grassland-to-forest ratios during the Early Holocene. By contrast, the proxy signals diverge for the Late Holocene. For this period, n -alkanes generally indicate more grassland, whereas macro-charcoals show increased wood-derived proportions. We imply that this difference is caused by increased forest fires and simultaneously spreading steppe area. A main portion of leaf waxes and charcoal particles in soils directly derive from the covering and nearby vegetation, whereas large lakes and glacier may receive these biomarkers from a larger catchment area. Thus, we conclude that soil archives provide proxies on a more local and site-specific scale than other archives do. Although the temporal resolution of soil archives is lower than for the other ones, biomarker proxies for paleosols and humic layer can be related to periods of distinct geomorphological processes. Further investigations comparing the multi-proxy data of different geomorphological archives are necessary to improve the paleo-ecological reconstruction for landscape development in Mongolia. Kurzfassung: Die Rekonstruktion von Klima und Vegetation in der mongolischen Waldsteppe stellt nach wie vor eine große Herausforderung in Hinsicht auf die Verbreitungsmuster von Wald- und Grasslandschaften im Laufe des Holozäns dar. Verschiedenartige Sedimente mit Paläoböden und organischen Schichten können dafür als hervorragende Archive für die Analyse der Landschaftsentwicklung in der Mongolei dienen. Die proportionalen Verhältnisse verschiedener n -Alkane und Typen von Holzkohlepartikeln lassen sich als Indikatoren zur Bestimmung der Grass und Baumanteile heranziehen. Im Rahmen einer Vorstudie haben wir die Anwendbarkeit dieser zwei Paläoproxies für die Vegetationsrekonstruktion aus Bodenarchiven untersucht. Dafür wurden Profile mit unterschiedlichen Reliefpositionen und Standortbedingungen aus einem Untersuchungsgebiet im Norden des Khangai-Gebirges in der Mongolei verglichen. n -Alkane von der Wachsschicht der Blätteroberflächen gelangen in den Boden und bieten die Möglichkeit die Zusammensetzung der Vegetation auf lokaler Ebene zu analysieren. Abhängig von den standortspezifischen Umweltbedingungen werden n -Alkane mikrobiell unterschiedlich stark abgebaut, wobei der Abbau in Böden der Trockensteppen intensiver ist als in den Wäldern. In den Wäldern der Mongolei ist häufig Permafrost im Boden vorhanden, der die mikrobiologische Aktivität verringert. In den Steppenböden erhöht sich durch die Zersetzung von n -Alkanen den Anteil an mittelkettigen n -Alkanen, was das Biomarker-Proxysignal in Richtung eines höheren Waldanteils verfälscht. Holzkohlepartikel in Böden haben eine standortspezifische Komponente. Allerdings kann ein zusätzlicher äolischer Eintrag von Holzkohlepartikeln aus dem Ferntransport einen deutlichen Anteil in den Sedimenten ausmachen. Durch den äolischen Anteil können holzspezifische Kohlepartikel in den Proxysignalen an Standorten dominieren, an denen es nur wenige oder niemals Bäume gab. Radiometrische Datierungen von Paläoböden und organischen Schichten zeigen, dass beide Proxys einen hohen Anteil von Grasland gegenüber Wald im frühen Holozän aufweisen. Im Gegensatz dazu divergieren die Proxysignale für das späte Holozän. Für diesen Zeitraum deuten n -Alkane allgemein auf mehr Grasland hin, während die Holzkohlepartikel einen höheren Waldanteil erkennen lassen. Wir vermuten, dass dieser Unterschied durch vermehrte Waldbrände und die gleichzeitige Ausbreitung von Steppenflächen verursacht wurde. Allgemein lässt sich folgern, dass Bodenarchive mehr lokale und ortsspezifische Proxies liefern als es bei Archiven aus Seen und Gletschereis zu erwarten ist. Diese Archive erhalten einen Materialeintrag aus wesentlich größeren Einzugsgebieten. Obwohl die zeitliche Auflösung von Bodenarchiven geringer ist als bei den anderen Archiven, können Biomarker aus Paläoböden und humosen Schichten mit Perioden spezifischer geomorphologischer Prozesse verknüpft werden. Weitere Detailuntersuchungen zum Vergleich von Multiproxy-Daten aus verschiedenen geomorphologischen Archiven sind notwendig, um die paläoökologischen Rekonstruktionen zur Landschaftsentwicklung in der Mongolei auf regionaler Ebene zu verbessern. [ABSTRACT FROM AUTHOR]

Background: Forest distribution in the forest-steppe of Mongolia depends on relief, permafrost, and climate, and is highly sensitive to climate change and anthropogenic disturbance. Forest fires and logging decreased the forest area in the forest-steppe of Mongolia. The intention of this study was to identify the geoecological parameters that control forest distribution and living-tree biomass in this semi-arid environment. Based on these parameters, we aimed to delineate the area that forest might potentially occupy and to analyse the spatial patterns of actual and potential tree biomass. Methods: We used a combination of various geographic methods in conjunction with statistical analyses to identify the key parameters controlling forest distribution. In several field campaigns, we mapped tree biomass and ecological parameters in a study area within the Tarvagatai Nuruu National Park (central Mongolia). Forest areas, topographic parameters and vegetation indices were obtained from remote sensing data. Significant correlations between forest distribution and living-tree biomass on one hand, and topographic parameters, climate data, and environmental conditions on the other hand, were used to delineate the area of potential forest distribution and to estimate total living-tree biomass for this area. Results: Presence of forest on slopes was controlled by the factors elevation, aspect, slope, mean annual precipitation, and mean growing-season temperature. Combining these factors allowed for estimation of potential forest area but was less suitable for tree-biomass delineation. No significant differences in mean living-tree biomass existed between sites exposed to different local conditions with respect to forest fire, exploitation, and soil properties. Tree biomass was reduced at forest edges (defined as 30 m wide belt), in small fragmented and in large forest stands. Tree biomass in the study area was 20 × 109 g (1,086 km2 forest area), whereas the potential tree biomass would reach up to 65 × 109 g (> 3168 km2). Conclusions: The obtained projection suggests that the potential forest area and tree biomass under the present climatic and geoecological conditions is three times that of the present forest area and biomass. Forest fires, which mostly affected large forest stands in the upper mountains, destroyed 43% of the forest area and 45% of the living-tree biomass in the study area over the period 1986–2017. [ABSTRACT FROM AUTHOR]

The central Mongolian forest steppe forms a transition between different ecozones and is as such particularly sensitive to environmental changes. It is commonly affected by disturbances such as logging and forest fires. Intensified drought events aggravate stress on the trees that are anyway at their drier limit in the forest steppe. Climate change increases evapotranspiration and reduces the distribution of discontinuous permafrost, which leads to drier soil conditions. The motivation for this study came about through our previous observation that forest stands show great differences with respect to their recovery after disturbance by fire or logging. Sometimes, no regrowth of trees takes place at all. As water availability is the main limiting factor of forest growth in this region, we hypothesised that differences in soil hydrology control the forest recovery pattern. To test this hypothesis, we analysed soil properties under forests, predominantly consisting of Siberian larch (Larix sibirica Ledeb.), in the forest steppe of the northern Khangai Mountains, central Mongolia. We distinguished the following four vegetation categories: (1) near-natural forest (FOR), (2) steppe close to the forest (STE), (3) disturbed forest with regrowth of trees (DWIR), and (4) disturbed forest showing no regrowth of trees (DNOR). A total of 54 soil profiles were described in the field and sampled for soil chemical, physical, and hydrological analysis. We found a significant difference in soil texture between soils under DWIR and DNOR. Sand generally dominated the soil texture, but soils under DWIR had more silt and clay compared to soils under DNOR. Soil pF curves showed that soils under DWIR had higher plant-available field capacity in their uppermost parts than soils under DNOR. In addition, hydraulic conductivity tended to be higher in the uppermost horizons of soils under DWIR compared to their counterparts under DNOR. Chemical properties of the soils under DWIR and DNOR showed no significant differences. We conclude that the differences in post-disturbance tree regrowth are mainly caused by different soil hydrology. High plant-available field capacity is the key factor for forest recovery under semi-arid conditions. High hydraulic conductivity in the uppermost soil horizons can further support tree regrowth because it reduces the evaporation loss and the competition of larch saplings with grasses and herbs for water. Another important factor is human impact, particularly grazing livestock on cleared forest sites, which often keeps seedlings from growing and, thus, inhibits forest recovery. None of the disturbed sites (DWIR and DNOR) had permafrost. We, thus, conclude that permafrost is no major factor for the post-disturbance tree regrowth pattern, although it generally supports tree growth in the forest steppe by preventing meltwater from seasonal ice from seeping below the root zone, thus increasing the water supply in summer. [ABSTRACT FROM AUTHOR]

In semi‐arid central Asia, relief has a strong impact on the distribution of vegetation and discontinuous permafrost. Our aim was to analyse causal chains and inter‐relationships that control the spatial patterns of forest and permafrost in the forest‐steppe of the northern Khangai Mountains in Mongolia. For this purpose, we conducted soil‐profile descriptions, ground‐penetrating radar sounding, and vegetation mapping to gain information about forest and permafrost distribution. We integrated remote‐sensing analysis and field‐mapping data, including soil properties, vegetation cover, forest fires and anthropogenic forest use. We developed and applied a technique for spatial delineation of permafrost distribution, based on the parameters Topographic Wetness Index (TWI), incoming solar radiation and Normalized Difference Vegetation Index (NDVI). Key outcomes of this study are that the occurrence of discontinuous permafrost within 1 m depth is limited to forest stands larger than 100 ha on north‐facing slopes. Dense ground vegetation supports permafrost, whereas sandy soil texture leads to greater depth of the permafrost table. As the seasonal ice in the active layer progressively melts down during summer, meltwater interflow above the permafrost table provides additional soil moisture downslope. This process is reflected in enhanced vitality of the steppe vegetation on toe slopes below forests with permafrost. This effect can in turn be used to indirectly detect permafrost in forest stands by remote sensing. Permafrost mostly disappears after forest fires and other severe disturbances, but it may re‐establish during forest regrowth. However, climate warming is presently leading to a loss of permafrost regeneration potential after disturbance, and to a shift from climate‐induced and ecosystem‐driven permafrost to entirely ecosystem‐protected permafrost. These trends will result in a further decrease of permafrost area after forest disturbance. [ABSTRACT FROM AUTHOR]

Glacial and lacustrine sediments from the Mongolian Altai provide paleoclimatic information for the late Pleistocene in Mongolia, for which only a few sufficiently studied archives exist. Glacial stages referred to global cooling events are reported for the last glacial maximum (27–21 ka) and the late glacial period (18–16 ka). Sedimentary archives from the first part of the last glacial period are infrequent. We present proxy data for this period from two different archives (88–63 and 57–30 ka). Due to the limitation of effective moisture, an increase of precipitation is discussed as one trigger for glacier development in the cold-arid regions of central Asia. Our pollen analysis from periods of high paleolake levels in small catchments indicate that the vegetation was sparse and of dry desert type between 42–29 and 17–11 ka. This apparent contradiction between high lake levels and dry landscape conditions, the latter supported by intensified eolian processes, points to lower temperatures and cooler conditions causing reduced evaporation to be the main trigger for the high lake levels during glacier advances. Rising temperatures that cause melting of glacier and permafrost ice and geomorphological processes play a role in paleolake conditions. Interpreting lake-level changes as regional or global paleoclimate signals requires detailed investigation of geomorphological settings and mountain–basin relationships. [ABSTRACT FROM AUTHOR]

The Mongolian forest-steppe is highly sensitive to climate change and environmental impact. The intention of this study was to identify, which geoecological parameters control forest distribution and tree growth in this semi-arid environment, and to evaluate the actual and potential tree biomass. For this purpose, we applied a combination of tree biomass and soil mapping, remote sensing and climate data analysis to a study area in the northern Khangai Mountains, central Mongolia. Forests of different landscape units and site conditions generally showed minor differences in tree biomass. We found no significant correlation between tree biomass and NDVI (normalized differentiated vegetation index). Tree biomass was reduced at forest edges, in small fragmented forest stands of the steppe-dominated area, and in large forest stands, compared to all other forest units. The tree biomass of forests on slopes ranged between 25 and 380Mgha-1. The mean tree biomass in forests of 10-500ha was 199-220Mgha-1, whereby tree biomass at the forest edges was 50-63Mgha-1 less than in the interior parts of the forests. The mean tree biomass of forests >500ha was 182Mgha-1, whereas that of forests <10ha in the steppe-dominated area was only around 142Mgha-1. Forests in alluvial plains had maximum tree biomasses of 440-688Mgha-1. In contrast to tree biomass, the spatial extension of forests showed distinct relationships with topographic and climatic parameters. Presence of forest was controlled by elevation (<2600ma.s.l.), aspect (no southern slopes below 2100ma.s.l.), slope (<25°), mean annual precipitation (160-340mm) and mean growing season temperature (6.5-10.8°C). The actual forests of the study area covered 1,086km². In 1986, prior to extensive forest fires, it was 1,898km². The actual tree biomass of 20×109g represented 57% of that in 1986. Modelling of the potential forest area resulted in 3,552km², with 65×109g tree biomass (based on topographic parameters) and 3,113km² with 58×109g tree biomass (based on climatic parameters), respectively. The modelled potential forest area was thus about three times the actual forest area. [ABSTRACT FROM AUTHOR]

Abstract The effective humidity, resulting from the balance between evapotranspiration and precipitation, largely controls the environmental conditions under the highly continental, semi-humid to arid climate of Mongolia. Minor variations of temperature and precipitation have resulted in considerable environmental changes over the Holocene, affecting vegetation composition and density, soil formation, geomorphological activity, desertification processes, lake level and glacier distribution. Thus, various paleoclimatic archives have been investigated in several studies over the last decades. Here, we present an overview of the existing reconstructions of climatic changes over the Late Glacial and Holocene. The aim of this work is to obtain a spatially differentiated synthesis of the currently available paleoenvironmental information, and to point to existing contradictions and knowledge gaps. Our results suggest that during the Late Glacial, dry and cold conditions dominated, whereas the early Holocene was warm, and characterized by increasing humidity. 6000 years ago, the temperature began to decrease. Enhanced aridity occurred in the rain shadow east of the Altai and Khangai Mountains, pointing to increasing influence of the westerlies. In the Valley of Great Lakes, east of the Altai Mountains, the Late Glacial was characterized by high lake levels that steadily decreased over the Holocene. In the Valley of Gobi Lakes, south of the Khangai Mountains, high lake levels persisted from the early Holocene until the beginning of the mid-Holocene. In contrast, the lake level of Telmen Nuur, north of the Khangai Mountains, remained low until the end of the mid-Holocene. Periods of enhanced eolian transport and deposition occurred from the Late Glacial until the early Holocene, and again during the late Holocene. In between, during the mid-Holocene, no soil erosion by eolian and fluvial processes took place over large areas. The present state of research shows that the limited number of investigated archives and the unbalanced spatial distribution of the studied sites hamper an integrative reconstruction with appropriate spatial and temporal resolution. Paleoclimate interpretations by different authors, which were derived from the same archives or from neighboring archives in the same region diverge in paleotemperature and -humidity. Thus, paleoclimate at a regional scale of up to 100 km, as well as the timing of climate changes at a temporal scale of several centuries is still ambiguous in Mongolia. Further challenges include the multiple possible causes of lake level changes and the difficulty to distinguish (i) between climatic and anthropogenic impacts on vegetation and landscape, and (ii) between local, regional and global signals in the proxy data. In addition, there are ambiguities with respect to the ages of various materials that are obtained by radiocarbon and luminescence dating. Highlights • The proxy data for paleoclimatic reconstructions in Mongolia derived from different archives is partly inconsistent. • Unbalanced spatial distribution of the studied siteshampers an integrative reconstruction with appropriate resolution. • There are difficulties to distinguish between climatic and anthropogenic impacts on vegetation and landscape. • Local, regional and global signals superimpose in the proxy data. • Multiple causes control lake level changes in Mongolia. [ABSTRACT FROM AUTHOR]

In the semi-arid to semi-humid regions of western Mongolia four different geomorphological aeolian and fluvial archives were investigated in order to gain environmental information of landscape evolution during the late glacial and the Holocene. These archives, which contain aeolian deposits, fluvial sediments, and paleosols, are situated upon glacial moraines, fluvial terraces, floodplains, or mountain slopes. While radiometric dating provides information about the age of the sediment and paleosols, grain size and element distribution provide information about the sediment source and soil development. Extensive aeolian sediment transport occurred from 17 to 10 ka during the late glacial when climate was cold and dry. Since that period the developing steppe and alpine meadow vegetation served as a dust trap. During the warm and wet early to mid-Holocene sediment transport was reduced under a dense vegetation cover. All paleosols of the investigated archives show late Holocene ages which point to an environmental turning point around 3 ka. Since then, the Neoglacial period started with cooler climate conditions and periglacial processes intensified again. Recognizable glacier advances occurred during the Little Ice Age several centuries ago. Since then, global climate change leads to warmer and more arid conditions. During the late Holocene, a new period of strong geomorphological activity started and huge quantities of aeolian, colluvial and fluvial sediment accumulated. These intensified soil relocation processes cannot be explained exclusively by climate change because there are no explicit indications found in the palynological and lacustrine records of Mongolia. This discrepancy suggests that the additional factor of human impact has to be considered, which amplified the climate signal on the landscape. Simultaneously, when the enhanced geomorphological processes occurred, the prehistoric people changed from hunting and gathering to livestock husbandry. A first extensive population growth of the Scythian nomadic tribes is documented for the beginning of the Bronze Age in Central Asia. This temporal concurrence supports the finding of a first extensive human impact on landscape development. [ABSTRACT FROM AUTHOR]

Despite being a key location for paleoglaciological research in north-central Asia, with the largest number of modern and Pleistocene glaciers, and in the transition zone between the humid Russian Altai and dry Gobi Altai, little is known about the precise extent and timing of Holocene and late Pleistocene glaciations in western Mongolia. Here we present detailed information on the distribution of modern and late Holocene glaciers, and new results addressing the geomorphological differentiation and numerical dating (by optically stimulated luminescence, OSL) of Pleistocene glacial sequences in these areas. For the Mongolian Altai, geochronological results suggest large ice advances correlative to marine isotope stages (MIS) 4 and 2. This is in contrast to results from the Khangai mountains, central Mongolia, showing that significant ice advances additionally occurred during MIS3. During the Pleistocene, glacial equilibrium-line altitudes (ELAs) were ~500 to >1000m lower in the more humid portion of the Russian and western Mongolian Altai, compared to 300-600 m in the drier ranges of the eastern Mongolian Altai. Pleistocene ELAs in the Khangai mountains were depressed by 700-1000 m, suggesting more humid conditions at times of major glaciation than in the eastern Mongolian Altai. This paleo-ELA pattern reveals that the precipitation gradient from the drier to the more humid regions was more pronounced during glacial times than at present. [ABSTRACT FROM PUBLISHER]

In semi-arid central Mongolia, geomorphological dynamics and forest distribution are commonly regarded as a result of the climatic development over the Holocene. The aim of this study was to detect variations in geomorphological activity and related eolian, periglacial, colluvial and fluvial processes since the Late Glacial, triggered by climate changes and other factors such as regional lake-level changes, fire events, and human impact. For this purpose, we investigated sediment archives in various relief positions (slope, pediment, valley bottom, dune and lake shore) in a forest-steppe region at the northern edge of the Khangai Mountains. We used a combination of geomorphological mapping and sampling of sediments, soils, paleosols, and organic layers. The samples were subjected to sedimentological analysis, luminescence and radiocarbon dating. The ages obtained for the eolian sediments showed that intense eolian activity and periglacial processes occurred during the Last Glacial Period and mitigated after 11 ka. After the Younger Dryas, geomorphological processes decreased and intensified soil formation indicated a stabilization of the soil surface simultaneously when spreading of forests around 9.5 ka was previously shown in the Khangai Mountains. The early and mid-Holocene were characterized by minor geomorphological activity and low fire frequency, as documented by sparseness of charcoal fragments and paleosols in the sediments. Only between 8 ka and 7 ka, reactivation of eolian sand transport was recorded during a drier period. Widespread distribution of late Holocene colluvial, alluvial and eolian sediments containing abundant charcoal, and periglacial features point to a distinct turning point in the Holocene landscape development around 4.5 ka, when substantially enhanced geomorphological activity started. This enhanced geomorphic activity corresponds with a period previously shown to be more humid but also more unstable, and during which forests became more susceptible to severe fire events. After a forest fire, lack of vegetation cover favored intensive erosion. Enhanced geomorphological activity points to a trend towards desertification, which was increasingly aggravated by human impact, since pastoralism emerged latest in the early Bronze Age. Increased production of steppe biomass during humid periods led to growth of population and livestock. This growth in turn resulted in overgrazing in drier years. This mechanism probably amplified the aridity signals that were detected in proxies of various paleoenvironmental archives. • Low geomorphological activity during the mid-Holocene • Intensification of geomorphological processes at the beginning of late Holocene • Forest developed since 9.5 ka but charcoal was rare until 4.5 ka. • Human impact superimposed or amplified climate control geomorphology. [ABSTRACT FROM AUTHOR]

The landform ensemble of the Tsetseg Nuur Basin in Western Mongolia provides an archive for periods of different geomorphologic processes induced by changing climate conditions during the Holocene and late Pleistocene times. The geomorphologic map of Tsetseg Nuur basin in the Mongolian Altai illustrates the spatial relation and interaction between different types of sedimentation in semi-arid regions of Central Asia. The map is an instrument to visualize the geomorphologic settings, providing valuable information to distinguish periods of geomorphologic processes and to analyze the landscape evolution. This enables the creation of a relative morphostratigraphy of periods with different hydrological environments, mainly marked by the stages of lake level evolution in an interior drainage basin. The relative chronology calculated from the map receives an absolute chronostratigraphy through radiometric dating from selected sections investigated during field-work. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Largest dune fields in Mongolia derived from Pleistocene westerly wind systems • Dune fields are related to endorheic lake dynamics. • Damming of lakes by dune sand barriers • Quaternary sediment cycle from mountains and rivers towards lakes and finally dune fields [ABSTRACT FROM AUTHOR]

The Tarvagatai Nuruu National Park, situated in the northern Khangai Mountains in central Mongolia, is dominated by a forest-steppe ecosystem. An extreme continental and semi-arid climate is characteristic for forest-steppe ecosystems in Central Asia and their vegetation is very sensitive to climatic changes and human impacts by pastoralism and tree-logging. In the selected study area, nowadays human impact is exceptionally low, and it has potentially also been in the past. The focus of this paper was to reconstruct vegetation variability, climate dynamics, intensity of human impact and fire dynamics by applying a broad multi-proxy approach on a lacustrine sediment core from a small closed lake in the study area. The analyses include reconstructions of pollen, spores, non-pollen palynomorphs, and charcoal distribution as well as XRF-scanning. Overall, the radiocarbon-dated lacustrine sediment core reveals stable, long-term environmental conditions since the early Holocene (9570 cal yr BP). Palynological results indicate that vegetation varies on a comparably low level. We assume that nomadic pastoralism played a tangential role on the vegetation changes in the study area. Higher values of coprophilous fungi between 9570 and 8350 cal yr BP suggest the highest wildlife activity during the early Holocene. Hence, our multi-proxy data reveal a surprisingly stable vegetation composition and only slight climatic changes in north-central Mongolia for the entire Holocene. An initial moist and warm period from 9570 to 4180 cal yr BP was followed by a period of slightly drier and potentially cooler conditions from 4180 until 430 cal yr BP. The latest period from 430 cal yr BP to present was moist and warm. Fires were in general relatively rare except from a strong phase of fire activity between 3550 and 2960 cal yr BP. • A new multi-proxy record (pollen, NPPs, macro charcoal, XRF-data) from north-central Mongolia. • Detailed high-resolution Holocene palaeoecological record covering the last 9600 cal yr BP. • Reconstructed stable vegetation reflects limited human impact on the vegetation dynamics since the Early Holocene. • Values of coprophilous fungal spores during the early Holocene provide a baseline of wildlife activities. • Extensive fire episode from 3550 to 2960 cal yr BP. [ABSTRACT FROM AUTHOR]