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Permafrost-Forest Dynamics
Abstract
Eastern Siberia is located at the centre of a continuous permafrost zone. The most prominent feature of this zone is its vast cover by deciduous coniferous boreal (taiga) forest. Underlying the boreal ecosystem is an extensive and massive ice layer within the permafrost (Yedoma), which was crucial for the development of large ground subsidence during the Holocene, which is closely related to ice volume loss. Therefore, scattered large grassland depressions (alas) and transitional topography under permafrost degradation (thermokarst) are also observed throughout central Yakutia. Extensive thermokarst evolution in this region has resulted in the development of successive thermokarst landforms. Thermokarst processes are enhanced by soil warming, indicating that both atmospheric warming and precipitation changes in summer and winter have had a marked effect on hydrothermal conditions within the active layer and upper part of the permafrost during recent decades. An increase in the mean active-layer depth of only a few tens of centimetres would release large amounts of water and carbon. Predicting permafrost landscape changes is not straightforward; it is hindered by uncertainty, by the need to consider combined ecosystem effects, by sociocultural interactions, and by hydrothermal processes. Permafrost landscape changes will have an impact on indigenous livelihoods, as has already been noted at local and regional levels. These permafrost-related influences will amplify feedback mechanisms between the climate and water and carbon cycles through permafrost degradation and concurrent boreal ecosystem changes.
... Three main aspects of permafrost are endangered by such drastic developments: the first is permafrost-larch-forest-fire (Sofronov and Volokitina, 2010;Iijima and Fedorov, 2019), the second permafrost-freshwater , and, lastly, ecosystem services of permafrost , especially to local populations who are entirely dependent on these systems. Yakutia is the largest inhabited area situated on continuous permafrost with over 91% of its population interacting with permafrost in their daily life (GRID-Arendal, 2023). ...
... The study showed that wildfires shape the surroundings of the lakes, also contributing to the external source of erosion in the lake (Manuscript 2). Wildfires, permafrost, and larch forests can sustain each other (Sofronov and Volokitina, 2010;Iijima and Fedorov, 2019). Wildfires were mainly occurring in the Early Holocene around Lake Satagay, in a phase of shifting climate and vegetation conditions (Manuscript 2). ...
Arctic and subarctic regions face rapid warming and environmental changes. Freshwater ecosystems and their watersheds in the region are at risk of being increasingly impacted and significantly altered. The majority of lakes in the Republic of Sakha (Yakutia), eastern Siberia, are thermokarst lakes, the origin of which is defined by the harsh climate of the past and geographic locations of lowlands and plains on permafrost, which contain alaas landscapes. Alaases, non-forested permafrost basins that often feature a lake, provide not only important aquatic habitats for biodiversity, but also critical ecosystem services to local populations such as fresh water supply, recreation, cattle breeding, fishing, and hunting grounds. Although most of these lakes found in alaases are of shallow depth and cover a small lake surface area, they are predicted to undergo severe changes with continued climate change. However, data on sequential lake development and distribution in Yakutia is still scarce. This thesis aims to improve the understanding of lake development in Yakutia since the last glaciation, including the unique alaas lakes, by studying their aquatic and terrestrial ecosystems on temporal and spatial scales.
The overall research question raised within this thesis is: How can we assess the internal and external factors of lake development and, therefore, improve the understanding of natural and anthropogenic impacts on lake ecosystems? To examine the development of lakes over time and across different spatial scales, a comprehensive multi-proxy approach was applied, investigating both past and present environmental conditions. The investigation of temporal changes included the analysis of lake sediment cores, using amplicon sequencing (metabarcoding) with targeted primers to recover sedimentary ancient DNA of diatoms and plants. This approach was complemented with microscopic analyses of diatom valves, pollen, and charcoal particles, as well as biogeochemical analyses, including organic carbon, nitrogen, and XRF-derived elemental measurements. The assessment of the modern lake condition focused on the impact of the climate, permafrost, and catchment land cover on the lake water hydrochemical and isotopic conditions, macrophyte diversity, and recent sedimentary DNA from surface sediments.
The cumulative thesis consists of an introduction, four manuscripts and a synthesis. The main findings of this thesis were provided by data gained from the outlined multi-proxy approach, and presented in separate manuscripts that enabled tracing the past long-term development of two lakes since the Late Glacial and Early Holocene, and an assessment of the modern state of 66 lake ecosystems in Yakutia.
Manuscript 1 details the reconstruction of thermokarst lake development of Lake Satagay since the Early Holocene. Using the described methods, it allows to reconstruct lake development stages throughout past millennia. The research findings provide insights into a prolonged shallowing stage, proposed as a potential new stage for conceptual thermokarst lake development. Manuscript 2 explores the environmental evolution around Lake Satagay since the Early Holocene, focusing on past relationships of wildfires and terrestrial plant composition. Open woodland vegetation is found to be more susceptible to wildfires during the Early Holocene, whereas fire occurrence decreased following the establishment of modern larch forest in the region at ca. 4.5 cal ka BP. Manuscript 3 examines major periods of past climatic warming and cooling at Lake Khamra, analyzing both aquatic and terrestrial ecosystems from a relatively stable, non-thermokarst mountain lake. The findings show that climatic trends influenced the vegetation composition, which in turn also impacted the lake ecology. This highlights the necessity for combined aquatic and terrestrial ecosystem studies. Finally, Manuscript 4 assesses the modern state of 66 thermokarst and mountain lakes. The study reveals diverse hydrochemical profiles, which are linked to the physical and morphological states and development stages of the lakes, and reflect both internal and external factors of lake development. These variations correlate with changes in aquatic and terrestrial vegetation, land cover, and land use, illustrating the lakes' complex interactions with environmental factors.
Alaas lakes are an important physical and cultural resource of Yakutia and are presently used in the daily lives of local people. Investigating both paleolimnological changes and modern conditions improves the understanding of the lake ecology in the unique permafrost zone of eastern Siberia. Findings highlight alaas lakes, directly connected to permafrost, as climate sensitive landforms, that are additionally affected by changes in vegetation, land use, and disturbances such as wildfires. They also suggest the potential inclusion of a stabilized shallowing stage, just before final alaas formation, to the conceptual alaas formation scheme.
... A number of mathematical models of soil pressure distribution caused by tire have been proposed, which are based on the finite element model of soil compaction [10], smoothed-particle hydrodynamics [11], etc. Another important aspect in studying the environmental impacts of forest machinery on the soil is the interaction of skidding system with permafrost soils of cryolithic zone forests, which represent particularly susceptible forest ecosystems [12,13], and, according to [14], significantly subjected to commercial exploitation. Skidding process is the most environmentally harmful operation in wood harvesting [15,16], which may cause significant degradation of the soil at the interaction of the tractor`s skidding and the dragging timber bunch [17]. ...
... The expression (12) suggests that the equation for rut formation by elastic tires can be written as follows: ...
An increasing demand for forest products incites a large number of log transportation operations, which may lead to negative consequences for the soil and the ecosystem as a whole. This paper is focused on establishing a mathematical model to estimate the soil deformation and compaction processes under tires of wheeled forest machines and individual components of the skidding system such as forwarder, limbs, butts, and tops of tree-lengths in high latitudes, permafrost soil and forests. The method applied is based on simulating the impact processes of elastic tires and the skidding system on the soil through a mathematical device for the measurement of the compaction parameters for different types of soil and the size of the shelterbelt. The effectiveness of the proposed models was evaluated according to experimental results. The influence of the rheological (elastic, viscous, and plastic) properties of soil were studied. The elasticity of tires and the running speed of forest machines can help to control the performance of forest machines. This can be done by reducing the pressure exerted on the soil and increasing the number of skidder passes 1.5-2-fold. Comparative analysis showed that the calculated data differ from the experimental ones by no more than 10%. The obtained results and the developed model will allow for a qualitative and quantitative assessment of technological impact on the soil during the projecting maps for logging operations.
... Furthermore, subsidence can lead to problems with equipment, soil saturation, loss of topsoil, and soil fertility, which require a large investment of labour and capital to mitigate (Ward Jones et al., 2022). Land clearing also alters the permafrost hydrology regime of surrounding uncleared areas and can lead to cascading impacts on large swathes of boreal forest (Iijima & Fedorov, 2019). ...
As the Arctic warms and growing seasons start to lengthen, governments and producers are speculating about northern “climate-driven agricultural frontiers” as a potential solution to food insecurity. One of the central ecological factors in northern spaces, however, is permafrost (perennial frozen ground), which can drive cascading environmental changes upon thaw. Considering the land requirements for expanded agriculture and the unique challenges of northern farming, national and subnational governments are grappling with and facilitating this speculative boom in different ways. Analysing agricultural land use policy instruments from the US State of Alaska and the Republic of Sakha (Yakutia) in Russia, this paper investigates if and how permafrost factors into their legal frameworks and what impacts this has on agricultural development, conservation, and food security. Alaska and the Republic of Sakha were chosen for reasons including both having at least 100 years of agricultural history on permafrost soils, both containing extensive amounts of permafrost within their landmasses and both containing permafrost that is ice-rich. Comparing legal texts as indicative of state capacities and strategies to govern, the paper finds that the two regions diverge in how they understand and regulate permafrost, and suggests that these approaches could benefit from one another. Bringing together geoclimatic and sociocultural concerns to problematise static policy divisions, this paper gestures to a path forward wherein subnational policy can balance needs for food, environmental, and cultural security in the North.
... The Yedoma ice complex is also distributed along watersheds and on some terraces in river valleys (Soloviev 1959;Iijima and Fedorov 2019), which may be also at a risk of thermokarst development. Amga is located on the left bank of the Amga River, which is one of the tributaries of the Aldan River ( Figs. 1 and 2c). ...
Thermokarst development is a topographic change in the landscape that is commonly associated with permafrost degradation in ice-rich permafrost regions. The Lena-Aldan interfluvial area in Central Yakutia in eastern Siberia has undergone extensive thermokarst development in the last three decades, particularly in the vicinity of settlements. Despite the negative effects of thermokarst development on the inhabitants of these settlements, no quantitative observation methods have been developed to investigate the surface displacement due to thermokarst development over entire towns. This study utilized interferometric synthetic aperture radar to reveal ground-surface displacement associated with thermokarst near the settlements of selected towns. The findings showed that significant subsidence was detected in disturbed areas (farming and abundant arable land) near the towns. The magnitude of subsidence in the Tyungyulyu and Mayya areas was less than that in Churapcha and Amga. Polygon density in a defined area in each town was examined using high-resolution optical images. The polygon density in Churapcha was considerably lower than that in Mayya, whereas polygonal texture in some areas in Tyungyulyu and Amga was unclear. Spatial frequency analysis using satellite optical images showed clear differences in averaged spectrum models between well-developed and less-developed polygons, which may reflect trough depths and density of vegetation between polygons. Satellite-based subsidence maps and statistics describing polygon development may be useful for evaluating both initial and subsequent stages of thermokarst development.
... Transient layer thickness varies depending on the environmental conditions and landscape disturbance, with the thickness in disturbed areas of Central Yakutia being 0.1-0.3 m (Iijima & Fedorov, 2019). Assuming that the volumetric ice content in the transient layer was 40% and the layer thawed after the fire, the estimated subsidence was 4-12 cm, which is reasonable for our observed data. ...
Forest fires significantly impact permafrost degradation in the subarctic regions. However, interannual and seasonal variations in surface deformation due to permafrost thawing in burned areas were poorly understood. Measuring the ground surface displacement in fire scars helps us understand the freeze‐thaw dynamics of near‐surface ground and predict the future state, particularly in ice‐rich permafrost regions. This study used the L‐ and C‐band interferometric synthetic aperture radar technique to reveal interannual subsidence and seasonal thaw settlement/frost heave in a fire scar near Mayya, Sakha Republic in Eastern Siberia burned in 2013. We found that the cumulative subsidence was up to 7 cm between 2014 and 2020, most of which had occurred by 2016. The magnitude of seasonal thaw settlement and frost heave varied each year from 2017 to 2020 after the fire, but the interannual change in frost heave corresponded to the temporal variation in precipitation during the thawing season from 2017 to 2020. This suggests that the precipitation amount during the thawing season is related to the magnitude of segregation‐ice formation in the sediments, which determines the frost heave amount. The observed seasonal displacements could not be quantitatively explained by models inferred from the Stefan's equation and volume changes associated with ice‐water phase change. This implies that other models associated with segregated ice (ice lens) formation/thaw are required to explain the observed seasonal displacement.
... Transient layer thickness varies depending on the environmental conditions and landscape disturbance, with the thickness in disturbed areas of Central Yakutia being 0.1-0.3 m (Iijima & Fedorov, 2019). Assuming that the volumetric ice content in the transient layer was 40% and the layer thawed after the fire, the estimated subsidence was 4-12 cm, which is reasonable for our observed data. ...
The landscape of central Europe is thought to have been dominated by steppe, forest-steppe, or tundra during the Last Glacial. This classical view is mostly based on the pollen records. However, as the pollen production and taphonomy during the cold periods are largely unknown, modern analogies of past landscapes need to be involved to provide more plausible vegetation reconstructions. Here we performed pollen analyses of recent samples from small lakes in Yakutia, eastern Siberia, a cold region where larch taiga forest is maintained by water from cyclically melting permafrost. We compared the pollen samples using multivariate (PCA) and analogue matching techniques with 830 fossil pollen samples from central Europe dated to MIS3–MIS1 (ca 35,000–11,700 cal BP). We have shown that the non-arboreal pollen proportion is around 50% in the lakes within Yakutian forested landscape, while such proportions have been interpreted as an indication of forestless landscape in European fossil records. Some central European fossil samples are more similar to samples from present-day Yakutia than to the South Siberian steppes so far considered analogous; this is especially true for samples from areas on unconsolidated bedrock with water-saturated permafrost from the Late Glacial, Bølling–Allerød interstadials. We advocate the idea of extending existing interpretations of past landscapes. The fossil pollen might not only reflect steppe–tundra vegetation, but, in addition to that, at least the Late Glacial pollen samples from central Europe may reflect a landscape forested by ‘invisible’ larch with spatially limited steppe patches, like the one found in present-day Yakutia.
The results of permafrost landscape studies on northeastern Eurasia are presented in this review. The assessment of permafrost vulnerability to disturbances and global warming was the basis for the development of these studies. The permafrost landscape, considering the morphological features of the landscape and the permafrost together, is a timely object of study. The theoretical developments of Soviet physical geographers and landscape scientists are the basis for permafrost landscape studies. Over the past four decades, numerous permafrost landscape studies have been carried out on northeastern Eurasia (and Russia). Considering the results of these studies is the main objective of this article. The analysis of the problems of permafrost landscape identification, classification, and mapping and the study of their dynamics and evolution after disturbances and long-term development were carried out. Permafrost landscape studies employ the research methods of landscape science and geocryology. Environmental protection and adaptation of socioeconomic conditions to modern climate warming will determine the prospects for studying permafrost landscapes.
This book is an attempt to understand the impact of Climate Change on the Arctic human societies from the indigenous perspectives, by focusing on the peoples living in the Republic of Sakha (Yakutia) of the Russian Federation. Historically, and also today, the livelihood of the Sakha people is closely related to permafrost. Scientific evidence shows that the thawing of the permafrost through climate change is causing severe problems on a global scale, which is alarming both international organizations and global citizens. Scientific studies confirming actual changes to the local environment, and the communities in permafrost areas are published continuously in academia. However, it is questionable whether scientists are adequately communicating this information to both the general public and the local populations. Climate change is a global phenomenon; however, it often manifests itself as regional and local natural disasters, which makes that it is essential to view climate change from a regional perspective. Therefore, focusing on particular regions and examining specific situations in detail provides a more accurate picture of the global situation.
http://www.amazon.co.jp/dp/B08ZMH66R2
Arctic and boreal permafrost ecosystems in Eastern Siberia, considered crucial to the climate system and global carbon cycle, are particularly vulnerable to climate change. This study investigates carbon dioxide (CO2) exchange fluxes over northeastern Siberia from 2013 to 2015 in a taiga–tundra boundary ecosystem for which such measurements are scarce. The growing season (May–September) net CO2 exchange flux (NEE) was −39.4 (−60.1 to −20.2) gCm⁻², with ecosystem respiration (RE) = 306.2 (288.1–317.9) gCm⁻² and gross primary production (GPP) = −345.5 (−372.5 to −317.7) gCm⁻². Microclimatic factors determining these CO2 exchange fluxes change seasonally. These fluxes are significantly affected by the timing of the onset of C uptake, which is reflected by changes in the soil temperature in spring and early summer, following which fluxes respond well to the photosynthetic photon flux density, especially for NEE. These CO2 exchange fluxes at the northeastern Siberian taiga–tundra boundary ecosystem are significantly smaller than those previously reported at southern-taiga forest sites. Spring snow meltwater-rich soil moisture conditions render southern-taiga sites as stronger CO2 sinks in June than taiga–tundra boundary ecosystem, which may be largely responsible for the pronounced north–south gradient in growing season NEE.
In a context of scientific and public debates on permafrost degradation under global climate change, this article provides an integrated review and analysis of environmental and socio-economic trends in a subarctic region. It focuses on Sakha (Yakut) animal husbandry as an example of indigenous land use. Within Sakha-Yakutia’s boreal forests, animal husbandry takes place in thermokarst depressions containing grassland areas (alaas) that formed in the early Holocene in a complex interplay of local geological conditions, climate changes, and permafrost dynamics. The current scale and speed of environmental change, along with shifting socio-economic processes, increasingly challenges Sakha’s adaptive capacity in use of alaas areas. The paper synthesizes information on the evolution of permafrost landscapes and on the local inhabitants’ and scientific knowledge. It also probes land-use prospects for the near future. The imminence of challenges for alaas ecosystems requires a holistic understanding between researchers and stakeholder communities, which in turn depends on a comprehensive assessment of the dynamic interaction of physical and social drivers of change.
The Central Yakutian permafrost landscape is rapidly being modified by land use and global warming, but small-scale thermokarst process variability and hydrological conditions are poorly understood. We analyze lake-area changes and thaw subsidence of young thermokarst lakes on ice-complex deposits (yedoma lakes) in comparison to residual lakes in alas basins during the last 70 years for a local study site and we record regional lake size and distribution on different ice-rich permafrost terraces using satellite and historical airborne imagery. Statistical analysis of climatic and ground-temperature data identified driving factors of yedoma- and alas-lake changes. Overall, lake area is larger today than in 1944 but alas-lake levels have oscillated greatly over 70 years, with a mean alas-lake-radius change rate of 1.6 ± 3.0 m/yr. Anthropogenic disturbance and forest degradation initiated, and climate forced rapid, continuous yedoma-lake growth. The mean yedoma lake-radius change rate equals 1.2 ± 1.0 m/yr over the whole observation period. Mean thaw subsidence below yedoma lakes is 6.2 ± 1.4 cm/yr. Multiple regression analysis suggests that winter precipitation, winter temperature, and active-layer properties are primary controllers of area changes in both lake types; summer weather and permafrost conditions additionally influence yedoma-lake growth rates. The main controlling factors of alas-lake changes are unclear due to larger catchment areas and subsurface hydrological conditions. Increasing thermokarst activity is currently linked to older terraces with higher ground-ice contents, but thermokarst activity will likely stay high and wet conditions will persist within the near future in Central Yakutian alas basins.
Data analysis on the fire occurrence and frequency in Central Yakutia (North-Eastern Russia) has been considered. Calculate the impact of socio-economic and climatic conditions of region on inflammability parameters. A close relationship was found between quantity and density of population and the frequency of fires occurence (0.95–0.99). Not so much negative correlation observed between the amount of precipitation during the fire-dangerous period and the frequency of fire (–0.53). The results of our study relating to the fire impact on microclimatic and soil conditions of the forests of Central Yakutia are brought in the article. Studies have revealed that strong changes microclimate and soil conditions in the burnt areas occur in the first 10 years after the fire. At the young burned out site, soil temperature in average increases in comparison with the forest at a depth of 5 cm in 5.2 ... 5.6 °C, at a depth of 30 cm – in 4.3 ... 6.2 °C, soil moisture – by 1.1–2.3 times in a 1–2-year – fire site, by 1.1–1.7 times in a 10–12-year-old one; seasonally thawed layer thickness is 0.3–0.8 m greater in the burned out areas than in the forest. There is stabilization of the modified conditions in the post-fire period in the course of succession. Essential changes of microclimatic and soil conditions occurring after fires and stabilizing in the progress of succession when fire-sites overgrow with plants have been found. In the burned areas of the Central Yakutia it starts at the age of 20–25 years after the fire.
Active-layer thickness (ALT) is one of the most robust measures used to assess the impact of climate change on terrestrial permafrost. Testing of a handheld dynamic cone penetrometer showed that it was capable of measuring ALT with the same level of accuracy as conventional methods in boreal and tundra sites in eastern Siberia. The penetrometer also characterised the vertical structure of ground hardness within the active layer. The vertical profile of penetrometer measurements corresponded closely with soil plasticity and the liquid limit in high-centred polygons produced by thermokarst subsidence in dry grassland areas at a boreal site at Churapcha. The ALT was markedly deeper (>70 cm) at gravelly slope points adjacent to a wet tundra plain (<50 cm) in a CALM grid (R8) at Tiksi. Overall, the penetrometer is considered to provide an accurate and informative proxy for rapidly assessing the spatial heterogeneity and interannual changes in ALT. Copyright
Permafrost landscape dynamics were investigated between 1998 and 2012 at Neleger, near Yakutsk, in central Yakutia, to determine the effects on permafrost of clear cutting of larch forest. Changes in ground temperature, soil moisture, seasonal thaw depth and surface subsidence at a control (forest) site and a site cleared of forest were associated with vegetation recovery and climate change. Before clear cutting (1998-2000), permafrost temperatures were similar to the 1998-2012 average. After cutting (2001-04), permafrost temperatures decreased in the undisturbed forest site, but increased in the cleared site. The thermal disturbance of clear cutting caused increases in thaw depth and led to 4.8cm of ground surface subsidence. Significant warming of permafrost in 2005-08, coincident with maximum snow depth and precipitation, caused up to 14.6cm of additional ground subsidence, which represented the maximum changes observed in the landscape. Between 2009 and 2012, permafrost began to stabilise and subsidence was restricted to 1.8cm. The reduced thaw depth and the growth of young birch shoots during this period indicated stabilisation of permafrost conditions and the beginning of landscape restoration.
Long-term (up to 25 years) seasonal thawing depth observations have been fulfilled on permafrost stations in Northern Russia. Analysis of the obtained data has shown that contemporary climate warming is not always accompanied by an increase in the depth of seasonal soil thawing. For different landscape conditions statistically significant trends of perennial changes in seasonal thawing depth can be characterized both as positive and negative values. Correlation coefficients between the seasonal thawing depth and the possible determining meteorological factors (sum of summer air temperatures, mean annual air temperature, precipitation for summer period, maximum height of snow cover) have been found. It turned out that the perennial changes in seasonal thawing depth and in the sums of summer air temperatures do not correlate neatly enough. Hence, it is necessary to specify the supposed perennial changes in air temperature as well as other meteorological factors (precipitations, solar radiation, snow cover) as an upper boundary condition, when forecasting the changes in seasonal thawing depth subject to climate changes.
The contemporary 1965-1995) air temperature increase on the north of Russia as a whole makes 1.1°C while the global average meaning is 0.5°C. The permafrost monitoring data show the beginning of the tendency to the contemporary increase of the soils temperature in cold regions. On the North of the West Siberia the increase of the soils temperature on 10 meters depth of 1979-1995 is estimated at 0.2-1.2°C. Starting from 1996 small decrease of the temperature of upper horizons of permafrost caused by some cold snap was fixed here. In Central Yakytia in spite of strong contemporary climate warning the frozen soils temperature increase is marked weakly and not everywhere. The high thermal stability in the Central Yakutia is caused mainly by the marked tendency to the reduction of snow caver in the region for the last 15-25 years. The response of the depth of seasonal thawing to the climate changes is poor, it does not serve as a sensetive indicator of air temperature rising. The appreciable degradation of continuous permafrost is not expected for the next 25-50 years. However complete or part thawing of island permafrost can take place, mainly in the areas of intensive technogenesis.