How are Interannual Variations of Land Surface Phenology in the Highland Pastures of Kyrgyzstan Modulated by Terrain, Snow Cover Seasonality, and Climate Oscillations? An Investigation Using Multi-Source Remote Sensing Data

In the semiarid, continental climates of montane Central Asia, with its constant moisture deficit and low relative humidity, agropastoralism constitutes the foundation of the rural economy. In Kyrgyzstan, an impoverished, landlocked republic in Central Asia, herders of the highlands practice vertical transhumance—the annual movement of livestock to higher elevation pastures to take advantage of seasonally available forage resources. Dependency on pasture resource availability during the short mountain growing season makes herds and herders susceptible to changing weather and climate patterns. This dissertation focuses on using remote sensing observations over the highland pastures in Kyrgyzstan to address five interrelated topics: (i) changes in snow cover and its seasonality from 2002 through 2016; (ii) pasture phenology from the perspective of land surface phenology using multi-scale data from 2001 through 2017; (iii) relationships between snow cover seasonality and subsequent land surface phenology; (iv) terrain effects on the snow-phenology interrelations; and (v) the influence of atmospheric teleconnections on modulating the relationships between snow cover seasonality, growing season duration, and pasture phenology. Results indicate that more territory has been experiencing earlier snow onset than earlier snowmelt, and around equivalent areas with longer and shorter duration of snow seasons. Significant shifts toward earlier snow onset (snowmelt) occurred in western and central (eastern) Kyrgyzstan, and significant duration of the snow season shortening (extension) across western and eastern (northern and southwestern) Kyrgyzstan. Below 3400 m, there was a general trend of significantly earlier snowmelt, and this area of earlier snowmelt was 15 times greater in eastern than western rayons. In terms of land surface phenology, there was a predominant and significant trend of increasing peak greenness, and a significant positive relationship between snow covered dates and modeled peak greenness. While there were more negative correlations between snow cover onset and peak greenness, there were more positive correlations between snowmelt timing and peak greenness, meaning that a longer snow cover season increased the amplitude of peak greenness. The amount of thermal time (measured in accumulated growing degree-days) to reach peak greenness was significantly negatively correlated both with the number of snow covered dates and the snowmelt date. Thus, more snow covered dates translated into fewer growing degree-days accumulated to reach peak greenness in the subsequent growing season. Terrain features influenced the timing of snowmelt more strongly than the number of snow covered dates. Slope was more important than aspect, but the strongest effect appeared from the interaction of aspect and the steepest slopes. The influence of atmospheric teleconnection arising from climate oscillation modes was marginal at the spatial resolutions of this study. Thermal time accumulation could be largely explained with Partial Least Squares (PLS) regression models by elevation and snow cover metrics. However, explanation of peak greenness was less susceptible to terrain and snow cover variables. This research study provides a comprehensive evaluation of the spatial variation of interannual phenology in the highland pastures that serve as the foundation of rural Kyrgyz economy. Finally, it contributes to a better understanding of recent environmental changes in remote highland Central Asia

Utilizing Satellite Fusion Methods to Assess Vegetation Phenology in a Semi-Arid Ecosystem

Dryland ecosystems cover over 40% of the Earth’s surface, and are highly heterogeneous systems dependent upon rainfall and temperature. Climate change and anthropogenic activities have caused considerable shifts in vegetation and fire regimes, leading to desertification, habitat loss, and the spread of invasive species. Modern public satellite imagery is unable to detect fine temporal and spatial changes that occur in drylands. These ecosystems can have rapid phenological changes, and the heterogeneity of the ground cover is unable to be identified at course pixel sizes (e.g. 250 m). We develop a system that uses data from multiple satellites to model finer data to detect phenology in a semi-arid ecosystem, a dryland ecosystem type. The first study in this thesis uses recent developments in readily available satellite imagery, coupled with new systems for large-scale data analysis. Google Earth Engine is used with the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) to create high resolution imagery from Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS). The 250 m daily MODIS data are downscaled using the 16-day, 30 m Landsat imagery resulting in daily, 30 m data. The downscaled images are used to observe vegetation phenology over the semi-arid region of the Morley Nelson Snake River Birds of Prey National Conservation Area in Southwestern Idaho, USA. We found the fused satellite imagery has a high accuracy, with R2 ranging from 0.73 to 0.99, when comparing fusion products to the true Landsat imagery. From these data, we observed the phenology of native and invasive vegetation, which can help scientists develop models and classifications of this ecosystem. The second study in this thesis builds upon the fused satellite imagery to understand pre-and post-fire vegetation response in the same ecosystem. We investigate the phenology of five areas that burned in 2012 by using the fusion imagery (daily) to derive the normalized difference vegetation index (NDVI, a measure of vegetation greenness) in areas dominated by grass (n=4) and shrub (n=1). The five areas also had a range of historical burns before 2012, and overall we investigated the phenology of these areas over a decade. This proof of concept resulted in observations of the relationship between the timing of fire and the vegetation greenness recovery. For example, we found that early and late season fires take the longest amount of time for vegetation greenness to recover, and that the number of historical fires has little impact in the vegetation greenness response if it has already burned once, and is a grass-dominated region. The greenness dynamics of the shrub-dominated study site provides insight into the potential to monitor post-fire invasion by nonnative grasses. Ultimately the systems developed in this thesis can be used to monitor semi-arid ecosystems over long-time periods at high spatial and temporal resolution

Vegetation Dynamics Revealed by Remote Sensing and Its Feedback to Regional and Global Climate

This book focuses on some significant progress in vegetation dynamics and their response to climate change revealed by remote sensing data. The development of satellite remote sensing and its derived products offer fantastic opportunities to investigate vegetation changes and their feedback to regional and global climate systems. Special attention is given in the book to vegetation changes and their drivers, the effects of extreme climate events on vegetation, land surface albedo associated with vegetation changes, plant fingerprints, and vegetation dynamics in climate modeling

Land Degradation Assessment with Earth Observation

This Special Issue (SI) on “Land Degradation Assessment with Earth Observation” comprises 17 original research papers with a focus on land degradation in arid, semiarid and dry-subhumid areas (i.e., desertification) in addition to temperate rangelands, grasslands, woodlands and the humid tropics. The studies cover different spatial, spectral and temporal scales and employ a wealth of different optical and radar sensors. Some studies incorporate time-series analysis techniques that assess the general trend of vegetation or the timing and duration of the reduction in biological productivity caused by land degradation. As anticipated from the latest trend in Earth Observation (EO) literature, some studies utilize the cloud-computing infrastructure of Google Earth Engine to cope with the unprecedented volume of data involved in current methodological approaches. This SI clearly demonstrates the ever-increasing relevance of EO technologies when it comes to assessing and monitoring land degradation. With the recently published IPCC Reports informing us of the severe impacts and risks to terrestrial and freshwater ecosystems and the ecosystem services they provide, the EO scientific community has a clear obligation to increase its efforts to address any remaining gaps—some of which have been identified in this SI—and produce highly accurate and relevant land-degradation assessment and monitoring tools

Assessment of climate change effects on vegetation and river hydrology in a semi-arid river basin

Climate change plays a key role in changing vegetation productivity dynamics, which ultimately affect the hydrological cycle of a watershed through evapotranspiration (ET). Trends and correlation analysis were conducted to investigate vegetation responses across the whole Upper Jhelum River Basin (UJRB) in the northeast of Pakistan using the normalized difference vegetation index (NDVI), climate variables, and river flow data at inter-annual/monthly scales between 1982 and 2015. The spatial variability in trends calculated with the Mann-Kendall (MK) trend test on NDVI and climate data was assessed considering five dominant land use/cover types. The inter-annual NDVI in four out of five vegetation types showed a consistent increase over the 34-year study period; the exception was for herbaceous vegetation (HV), which increased until the end of the 1990s and then decreased slightly in subsequent years. In spring, significant (p<0.05) increasing trends were found in the NDVI of all vegetation types. Minimum temperature (Tmin) showed a significant increase during spring, while maximum temperature (Tmax) decreased significantly during summer. Average annual increase in Tmin (1.54°C) was much higher than Tmax (0.37°C) over 34 years in the UJRB. Hence, Tmin appears to have an enhancing effect on vegetation productivity over the UJRB. A significant increase in NDVI, Tmin and Tmax during spring may have contributed to reductions in spring river flow by enhancing evapotranspiration observed in the watershed of UJRB. These findings provide valuable information to improve our knowledge and understanding about the interlinkages between vegetation, climate and river flow at a watershed scale

Linkages between Atmospheric Circulation, Weather, Climate, Land Cover and Social Dynamics of the Tibetan Plateau

The Tibetan Plateau (TP) is an important landmass that plays a significant role in both regional and global climates. In recent decades, the TP has undergone significant changes due to climate and human activities. Since the 1980s anthropogenic activities, such as the stocking of livestock, land cover change, permafrost degradation, urbanization, highway construction, deforestation and desertification, and unsustainable land management practices, have greatly increased over the TP. As a result, grasslands have undergone rapid degradation and have altered the land surface which in turn has altered the exchange of heat and moisture properties between land and the atmosphere. But gaps still exist in our knowledge of land-atmosphere interactions in the TP and their impacts on weather and climate around the TP, making it difficult to understand the complete energy and water cycles over the region. Moreover, human, and ecological systems are interlinked, and the drivers of change include biophysical, economic, political, social, and cultural elements that operate at different temporal and spatial scales. Current studies do not holistically reflect the complex social-ecological dynamics of the Tibetan Plateau. To increase our understanding of this coupled human-natural system, there is a need for an integrated approach to rendering visible the deep interconnections between the biophysical and social systems of the TP. There is a need for an integrative framework to study the impacts of sedentary and individualized production systems on the health and livelihoods of local communities in the context of land degradation and climate change. To do so, there is a need to understand better the spatial variability and landscape patterns in grassland degradation across the TP. Therefore, the main goal of this dissertation is to contribute to our understanding of the changes over the land surface and how these changes impact the plateau\u27s weather, climate, and social dynamics. This dissertation is structured as three interrelated manuscripts, which each explore specific research questions relating to this larger goal. These manuscripts constitute the three primary papers of this dissertation. The first paper documents the significant association of surface energy flux with vegetation cover, as measured by satellite based AVHRR GIMMS3g normalized difference vegetation index (NDVI) data, during the early growing season of May in the western region of the Tibetan Plateau. In addition, a 1°K increase in the temperature at the 500 hPa level was observed. Based on the identified positive effects of vegetation on the temperature associated with decreased NDVI in the western region of the Tibetan Plateau, I propose a positive energy process for land-atmosphere associations. In the second paper, an increase in Landsat-derived NDVI, i.e., a greening, is identified within the TP, especially during 1990 to 2018 and 2000 to 2018 time periods. Larger median growing season NDVI change values were observed for the Southeast Tibet shrublands and meadows and Tibetan Plateau Alpine Shrublands and Meadows grassland regions, in comparison to the other three regions studied. Land degradation is prominent in the lower and intermediate hillslope positions in comparison to the higher relative topographic positions, and change is more pronounced in the eastern Southeast Tibet shrublands and meadows and Tibetan Plateau Alpine Shrublands and Meadows grasslands. Geomorphons were found to be an effective spatial unit for analysis of hillslope change patterns. Through the extensive literature review presented in third paper, this dissertation recommends using critical physical geography (CPG) to study environmental and social issues in the TP. The conceptual model proposed provides a framework for analysis of the dominant controls, feedback, and interactions between natural, human, socioeconomic, and governance activities, allowing researchers to untangle climate change, land degradation, and vulnerability in the Tibetan Plateau. CPG will further help improve our understanding of the exposure of local people to climate and socio-economic and political change and help policy makers devise appropriate strategies to combat future grassland degradation and to improve the lives and strengthen livelihoods of the inhabitants of the TP

Water loss due to increasing planted vegetation over the Badain Jaran Desert, China

© 2018 by the authors. Water resources play a vital role in ecosystem stability, human survival, and social development in drylands. Human activities, such as afforestation and irrigation, have had a large impact on the water cycle and vegetation in drylands over recent years. The Badain Jaran Desert (BJD) is one of the driest regions in China with increasing human activities, yet the connection between human management and the ecohydrology of this area remains largely unclear. In this study, we firstly investigated the ecohydrological dynamics and their relationship across different spatial scales over the BJD, using multi-source observational data from 2001 to 2014, including: total water storage anomaly (TWSA) from Gravity Recovery and Climate Experiment (GRACE), normalized difference vegetation index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS), lake extent from Landsat, and precipitation from in situ meteorological stations. We further studied the response of the local hydrological conditions to large scale vegetation and climatic dynamics, also conducting a change analysis of water levels over four selected lakes within the BJD region from 2011. To normalize the effect of inter-annual variations of precipitation on vegetation, we also employed a relationship between annual average NDVI and annual precipitation, or modified rain-use efficiency, termed the RUEmo. A focus of this study is to understand the impact of the increasing planted vegetation on local ecohydrological systems over the BJD region. Results showed that vegetation increases were largely found to be confined to the areas intensely influenced by human activities, such as croplands and urban areas. With precipitation patterns remaining stable during the study period, there was a significant increasing trend in vegetation greenness per unit of rainfall, or RUEmo over the BJD, while at the same time, total water storage as measured by satellites has been continually decreasing since 2003. This suggested that the increased trend in vegetation and apparent increase in RUEmo can be attributed to the extraction of ground water for human-planted irrigated vegetation. In the hinterland of the BJD, we identified human-planted vegetation around the lakes using MODIS observations and field investigations. Four lake basins were chosen to validate the relationship between lake levels and planted vegetation. Our results indicated that increasing human-planted vegetation significantly increased the water loss over the BJD region. This study highlights the value of combining observational data from space-borne sensors and ground instruments to monitor the ecohydrological dynamics and the impact of human activities on water resources and ecosystems over the drylands

Climate Sensitivity of the Arid Scrublands on the Tibetan Plateau Mediated by Plant Nutrient Traits and Soil Nutrient Availability

Climate models predict the further intensification of global warming in the future. Drylands, as one of the most fragile ecosystems, are vulnerable to changes in temperature, precipitation, and drought extremes. However, it is still unclear how plant traits interact with soil properties to regulate drylands’ responses to seasonal and interannual climate change. The vegetation sensitivity index (VSI) of desert scrubs in the Qaidam Basin (NE Tibetan Plateau) was assessed by summarizing the relative contributions of temperature (SGST), precipitation (SGSP), and drought (temperature vegetation dryness index, STVDI) to the dynamics of the normalized difference vegetation index (NDVI) during plant growing months yearly from 2000 to 2015. Nutrient contents, including carbon, nitrogen, phosphorus, and potassium in topsoils and leaves of plants, were measured for seven types of desert scrub communities at 22 sites in the summer of 2016. Multiple linear and structural equation models were used to reveal how leaf and soil nutrient regimes affect desert scrubs’ sensitivity to climate variability. The results showed that total soil nitrogen (STN) and leaf carbon content (LC), respectively, explained 25.9% and 17.0% of the VSI variance across different scrub communities. Structural equation modeling (SEM) revealed that STN and total soil potassium (STK) mediated desert scrub’s VSI indirectly via SGST (with standardized path strength of −0.35 and +0.32, respectively) while LC indirectly via SGST and SGSP (with standardized path strength of −0.31 and −0.19, respectively). Neither soil nor leave nutrient contents alone could explain the VSI variance across different sites, except for the indirect influences of STN and STK via STVDI (−0.18 and 0.16, respectively). Overall, this study disentangled the relative importance of plant nutrient traits and soil nutrient availability in mediating the climatic sensitivity of desert scrubs in the Tibetan Plateau. Integrating soil nutrient availability with plant functional traits together is recommended to better understand the mechanisms behind dryland dynamics under global climate change

Spatiotemporal characteristics of future changes in precipitation and temperature in Central Asia

The arid and semi-arid areas in Central Asia have scarce water resources and fragile ecosystems that are especially sensitive and vulnerable to climate change. Reliable information regarding future projections of change in climate is crucial for long-term planning of water resources management and structural adjustment of agriculture in this region. However, the low-density meteorological observation network brings great challenges for investigating the effects of climate variations. In this study, variations of precipitation and temperature in Central Asia were examined by a combination of gridded climate dataset of the Climate Research Unit and the latest general circulation models (GCMs) under a representative concentration pathway 4.5. Three downscaling methods, Delta, Advanced Delta, and Bayesian model averaging (BMA) methods, translate the coarse GCMs to local climatic variations for the period 2021-2060 relative to 1965-2004. Major results suggested that the Advanced Delta and BMA methods outperformed the Delta method in precipitation downscaling. Projected precipitation exhibited a general increasing trend at a rate of 4.63 mm/decade for entire Central Asia with strong spatiotemporal heterogeneity. While a declining trend was observed in the southwestern and central parts of Central Asia in summer. The projected temperature was revealed an obvious ascending at 0.37 degrees C/decade, while the warming rate accelerated in higher latitude and mountainous areas. [Correction added on 03 December 2018, after first online publication: The preceding statement has been corrected in this version.] The surface land coverage had significant effects on the variations of precipitation and temperature, respectively. The driven factors of local climate were suggested by analysing the relationships between climate variations and large-scale atmospheric circulation fields anomalies. The findings of this study aims to provide useful information to improve our understanding for future climate change and benefit local decision makers

Geoecological analysis of forest distribution and post-disturbance tree regrowth in the forest-steppe of central Mongolia

Die mongolische Waldsteppe bildet den Übergangsbereich zwischen der sibirischen Taiga im Norden und der Wüste Gobi im Süden. Die Baumvegetation in diesem Ökoton ist, aufgrund es hochkontinentalen, semiariden Klimas, in besonderem Maße von Wasserverfügbarkeit abhängig. Waldflächen sind aufgrund des niedrigeren Evapotranspiration auf Nordhängen anzutreffen, während die Mehrheit der Flächen mit Grasvegetation bedeckt ist. Innerhalb der letzten Jahrzehnte haben Dürren zu vermehrter Wachstumsverminderung und erhöhter Baumsterblichkeit in der Waldsteppe geführt. Zudem haben Waldbrände und Waldnutzung, vor allem Abholzung und Waldweide, die Waldverbreitung deutlich reduziert und die Bestandsstruktur beeinflusst. Geländebefunde verdeutlichten, dass sich stark gestörte Waldflächen, verursacht durch Feuer und Kahlschlag, nicht gleichmäßig unter augenscheinlich gleichwertigen Bedingungen erholen. Hierbei wurden Unterschiede von rascher Baumsukzession bis hin zum kompletten Ausbleiben der Baumsukzession dokumentiert. Um diese Vegetationsmuster und die Entwicklung der Waldvegetation in der mongolischen Waldsteppe zu verstehen, ist eine Untersuchung der geoökologischen Steuerungsfaktoren dieses Umweltsystems zwingend erforderlich. Aus diesem Grund hat diese Arbeit folgende Ziele: (1) die Waldverbreitung und die Voraussetzungen für Waldwachstum im nördlichen Khangai Gebirge, welches ein Teil der Mongolischen Waldsteppe bildet, zu bestimmen (2) die entscheidenden Unterschiede in den Standortbedingungen, insbesondere der Bodeneigenschaften und der Permafrostverbreitung, von gesunden Waldstandorten sowie von gestörten Standorten mit und ohne Baumsukzession zu identifizieren. Eine Vielzahl von Methoden auf verschiedenen räumlichen Skalen wurde genutzt um dieses Umweltsystem weitreichend zu analysieren. Landsat, TanDEM-X und Sentinel Satellitenaufnahmen sowie Klimadaten wurden mit Hilfe von Anwendungen im Bereich der Fernerkundung und der Geoinformationssysteme genutzt, um die aktuelle und potentielle Waldverbreitung zu ermitteln. Des Weiteren wurden diese Anwendungen genutzt, um die Darstellung und Interpretation der gemessenen Daten zu unterstützen. Eine umfassende Recherche deutscher, englischer und russischer Literatur wurde durchgeführt, um die Anforderungen für das Wachstum der sibirischen Lärche, welche die vorherrschende Baumart in der mongolischen Waldsteppe ist, zu charakterisieren. Während der Geländeaufenthalte 2017 und 2018 wurden 54 Bodenprofilen analysiert, beprobt und hydrologische Bodenparameter gemessen. Zudem wurde die Permafrosttiefe mittels Sondierungen, Bodenprofilen, Temperaturmessungen und dem Einsatz eines Georadars bestimmt. Im Labor wurden die Bodenproben anschließend auf deren chemische, physikalische und hydrologische Eigenschaften untersucht. Die Ergebnisse weisen darauf hin, dass die potenzielle Waldfläche im nördlichen Khangai Gebirge erheblich größer ist als die aktuelle Waldverbreitung. Mehrere Brände haben die Waldfläche im Vergleich zum Jahr 1986 um 40 % reduziert. Zudem verringern Abholzung und Waldweide vor allem die untere Grenze der Waldverbreitung und öffnen die Waldstruktur. Basierend auf vorhandener Literatur ist Feuer keine grundsätzliche Bedrohung für die sibirische Lärche, da sie sich auf Brandflächen schnell reetablieren kann. Im Gegensatz dazu gefährden intensive Dürreperioden und der Einfluss des Menschen die Waldverbreitung in der mongolischen Waldsteppe zunehmend, was sich in einer erhöhten Baumsterblichkeit und einem eingeschränktem Baumnachwuchs wiederspiegelt. Die Untersuchungen der Böden der gestörten Waldflächen haben gezeigt, dass die Flächen mit Baumsukzession signifikant höhere Schluffgehalte im Vergleich zu den Flächen ohne Baumsukzession aufweisen. Messungen der pflanzenverfügbaren Feldkapazität bestätigen diesen Unterschied mit vergleichsweise höheren Werten in Böden unter Baumsukzessionxiii vergleichen zu Boden, auf denen keine Baumsukzession festgestellt wurde. Bei den bodenchemischen Eigenschaften, wie zum Beispiel Kohlenstoff- und Stickstoffvorräte, effektive Kationenaustauschkapazität und austauschbare Kationen, konnte kein signifikanter Unterschied zwischen den beiden Gruppen ausgemacht werden. Aus diesem Grund wird geschlussfolgert, dass bodenhydrologische Eigenschaften, welche die Wasserverfügbarkeit für Baumvegetation erhöhen, entscheidend für das Aufkommen von Bäumen auf gestörten Waldflächen sind. Die Permafrostverbreitung ist abhängig von der Beschattung durch eine geschlossene Vegetation, von der thermalen Isolation durch eine organische Auflage und von der Verfügbarkeit von Wasser. Im Untersuchungsgebiet wurde Permafrost unter dichten Waldbeständen in einer Tiefe von 50 bis 200 cm aufgefunden. Im Gegensatz dazu war Permafrost auf den gestörten Waldflächen nicht mehr nachweisbar. Daher hat die diskontinuierliche Permafrostverbreitung keinen Einfluss auf das Wiederaufkommen von Bäumen nach schweren Störungen. Basierend auf den Erkenntnissen ist zu schlussfolgern, dass die Verfügbarkeit von Wasser der entscheidende Faktor für das Wiederaufkommen von Baumvegetation auf gestörten Waldflächen in der mongolischen Waldsteppe ist. Jedoch unterliegt die Etablierung der Waldvegetation weiterer Einflüsse, insbesondere der klimatischen Bedingungen und des Einflusses des Menschen. Daher ist eine regulierende Forstwirtschaft zwingend nötig, um einen dramatischen Rückgang der Waldflächen in Zukunft zu verhindern.The Mongolian forest-steppe is an ecotone at the transition between the Siberian Taiga in the north and the Gobi Desert in the south. The highly continental, semiarid climate magnifies the importance of water availability for tree vegetation. Forests exclusively appear on northern slopes, due to less evapotranspiration, while the majority of surfaces in the area is covered by grass vegetation. Drought-induced growth reduction and increased tree mortality, intensified by climate change, was frequently observed in the forest-steppe during the last decades. Furthermore, forest fires and forest use, in particular logging and forest grazing, considerably reduced the forest distribution and affected the forest structure. Field investigations showed that severely disturbed forest stands, e.g. by fire or clear-cutting, do not recover equally under apparently similar conditions, ranging from quick tree regrowth to no regrowth of trees at all. It is obligatory to investigate the geoecological factors to understand the recovery pattern and the current development of the forest vegetation in the Mongolian forest-steppe. Therefore, two objectives were aimed in this research as follows: (1) to evaluate the forest vitality, and to determine the forest distribution and the specific requirements for tree growth in the northern Khangai Mountains, situated in the forest-steppe of central Mongolia, (2) to identify the difference in the site-specific conditions, including soil- and permafrost analyses, of healthy forest stands and disturbed forests with and without tree regrowth. A set of methods on different spatial scales was used to investigate this environment comprehensively. Remote sensing and GIS techniques were applied on Landsat, TanDEM-X and Sentinel satellite images as well as on climate data to characterise the present and potential forest distribution. Those techniques supported the illustration and interpretation of the conducted measurements. A literature review on English, German and Russian literature was carried out to identify the plant-specific needs of Siberian larch, the predominant tree species of the Mongolian forest-steppe. During two field campaigns, 2017 and 2018, 54 soil profiles were analysed, sampled, and hydraulic soil parameters were measured. Moreover, the permafrost depth was analysed using soil profiles, drillings, temperature measurements and ground-penetrating radar. Soil samples were investigated for their physical, chemical and hydrological properties in the laboratory. Statistical procedures were applied to the measured data. The results indicated that the potential forest area in the northern Khangai Mountains is substantially larger than the present forests. Several fires diminished the forested area by more than 40 % compared to the distribution in 1986. Moreover, logging and grazing livestock opened the forest structure and notably reduced the forest stands at their lower boundary. Based on the findings of the review, fire can be considered as a minor issue for Siberian larch forests due to their quick recovery on burned sites. In contrast, intensified drought events and human impact severely threaten the tree vegetation of the Mongolian forest-steppe by increased tree mortality and hampered tree regrowth. The soil investigations of the disturbed sites in the study area showed that silt contents of sites with regrowth of trees are significantly higher compared to those without regrowth of trees. Measurements on plant-available field capacity proved this difference by higher capacity in soils of areas with regrowth. Chemical soil properties, such as carbon and nitrogen stocks, effective cation exchange capacity and exchangeable cations, could not prove any significant differences between post-disturbance regrowth and no regrowth. Therefore, soil hydrological properties, which increase the water availability for tree vegetation, are decisive for the tree regrowth on disturbed sites. The permafrost distribution strongly depends on the shadowing of closed vegetation, the thermal isolation by a thick organic layer and the water availability. Dense forest stands contained permafrost within a depth of 50 to 200 cm. On disturbed sites,xi permafrost was not encountered anymore. Thus, the discontinuous permafrost distribution is vanished after severe disturbance and does not influence the tree regrowth pattern. Based on the findings, it is concluded that water availability is the crucial factor for the tree regrowth pattern after disturbances in the Mongolian forest-steppe. However, the reestablishment of forest vegetation underlies other influences, in particular climate conditions and human impact. Regulating forest management is therefore needed to prevent a dramatic decline of forested areas in future.2021-09-1