Soil Active Layer Research Articles

The Change Mechanism of Soil Hydrological Properties in the Permafrost Active Layer of the Qinghai–Tibet Plateau

The hydrological properties of the active soil layer are the key parameters that regulate soil water–heat–solute migration and alter hydrologic cycles in a permafrost region. To date, much remains unknown about the interaction mechanism between permafrost degradation and eco-hydrological processes in the permafrost regions of the Qinghai–Tibet Plateau (QTP). In this study, the soil texture, soil hydrological properties, and the soil moisture status of meadow soils with different degrees of degradation were analyzed in the laboratory, and hydrothermal process monitoring was conducted on the QTP. The results showed a close relationship between soil hydrological properties and soil physicochemical properties. Freeze–thaw cycles changed the physicochemical and hydrological properties, resulting in the degradation of frozen soil. In addition, vegetation on the ground delayed the degradation of frozen soil. The actual available soil water content (SWC) in the root layer was a key factor in the ecohydrological process. The actual effective SWC in the root layers of different alpine meadows was ranked as follows: non-degraded meadow (NDM) > moderately-degraded meadow (MDM) > seriously degraded meadow (SDM) (1.8–5.0% at NDM and −2.0–4.2% at SDM). In addition, the weak soil permeability in an SDM intensified the deficiency of the available SWC, thereby increasing the difficulty of ecological restoration. This study provides a basis for ecological environmental protection in permafrost regions and provides a hydrological process model for cold regions under future climate change scenarios.

The influence of soil treatment and irrigation methods on tomato yield and quality in the lowlands of Dagestan

A positive effect of irrigation of meadow-chestnut soil on soil fertility was described for the dry-steppe zone of Dagestan. The object of research was tomatoes (Gift variety) planted on irrigated lands of Dagestan. The subject of research is tillage and irrigation methods. The influence of agrotechnical methods on agrophysical soil properties, level and quality of tomatoes was determined. Maintaining the moisture of the active soil layer within 80…100 % NV can optimize agrophysical fertility indicators of the meadow-chestnut soil. In combination with tillage at a depth of 0.23…0.25 m, it ensures the tomato yield of 80…86 t/ha.

Water supply intensity during drip irrigation of vegetable crops

The paper presents the materials of field research on the study of the regularities of the development of moisture outlines on light soils during drip irrigation of vegetable crops. The correlation is found between the depth of the moistened layer and the area of the moistening outlines on the pre-irrigation threshold of the moisture content of the active soil layer, irrigation standards and the flow rate of drippers, which gives an opportunity to decline the unproductive water consumption for filtration. It is found that in light loamy and sandy loam light chestnut soils, for guaranteed rule of the moisture regime, on onion crops, it is essential to maintain the pre-irrigation threshold of 80% HB with the irrigation rate of 200 m3 / ha with the flow rate of drip water outlets of 2.8 l / h, and the depth of irrigation of 120 m3/ha with the flow rate of discharge outlets of 1.7 l/h, correspondingly. In irrigation of tomatoes grown on light-loamy light-chestnut soils, it is appropriate to apply the irrigation rate of 180 m3 / ha, which provides the level of pre-irrigation humidity in the layer of 0.6 m not lower than 80% HB, the formation of the required characteristics of the moisture contour (depth of 0.62 m and diameter of 0.37 m), as well as an enhance in the efficiency of irrigation water use by 11.1%. The results can be applied in the design of drip irrigation systems for vegetable crops.

АНАЛИТИЧЕСКАЯ ОЦЕНКА ДИНАМИКИ ПОТЕНЦИАЛА ВЛАЖНОСТИ В ЗОНЕ АЭРАЦИИ В ОРОШАЕМЫХ ЗЕМЛЯХ

The issue of forecasting soil moisture capacity using differential equation of moisture transfer in the aeration zone has been considered. An analytical approach for estimating moisture capacity per the depth of active soil layer in the irrigation period has been recommended. The obtained outcomes can be used for different soil types with various physicochemical and hydrophysical properties. To make the recommended approach more demonstrative the results of some numerical computations are introduced at the end of the current work.

Active layer depth and soil properties impact specific leaf area variation and ecosystem productivity in a boreal forest.

Specific leaf area (SLA, leaf area per unit dry mass) is a key canopy structural characteristic, a measure of photosynthetic capacity, and an important input into many terrestrial process models. Although many studies have examined SLA variation, relatively few data exist from high latitude, climate-sensitive permafrost regions. We measured SLA and soil and topographic properties across a boreal forest permafrost transition, in which dominant tree species changed as permafrost deepened from 54 to >150 cm over 75 m hillslope transects in Caribou-Poker Creeks Research Watershed, Alaska. We characterized both linear and threshold relationships between topographic and edaphic variables and SLA and developed a conceptual model of these relationships. We found that the depth of the soil active layer above permafrost was significantly and positively correlated with SLA for both coniferous and deciduous boreal tree species. Intraspecific SLA variation was associated with a fivefold increase in net primary production, suggesting that changes in active layer depth due to permafrost thaw could strongly influence ecosystem productivity. While this is an exploratory study to begin understanding SLA variation in a non-contiguous permafrost system, our results indicate the need for more extensive evaluation across larger spatial domains. These empirical relationships and associated uncertainty can be incorporated into ecosystem models that use dynamic traits, improving our ability to predict ecosystem-level carbon cycling responses to ongoing climate change.

Impacts of Arctic Shrubs on Root Traits and Belowground Nutrient Cycles Across a Northern Alaskan Climate Gradient.

Deciduous shrubs are expanding across the graminoid-dominated nutrient-poor arctic tundra. Absorptive root traits of shrubs are key determinants of nutrient acquisition strategy from tundra soils, but the variations of shrub root traits within and among common shrub genera across the arctic climatic gradient are not well resolved. Consequently, the impacts of arctic shrub expansion on belowground nutrient cycling remain largely unclear. Here, we collected roots from 170 plots of three commonly distributed shrub genera (Alnus, Betula, and Salix) and a widespread sedge (Eriophorum vaginatum) along a climatic gradient in northern Alaska. Absorptive root traits that are relevant to the strategy of plant nutrient acquisition were determined. The influence of aboveground dominant vegetation cover on the standing root biomass, root productivity, vertical rooting profile, as well as the soil nitrogen (N) pool in the active soil layer was examined. We found consistent root trait variation among arctic plant genera along the sampling transect. Alnus and Betula had relatively thicker and less branched, but more frequently ectomycorrhizal colonized absorptive roots than Salix, suggesting complementarity between root efficiency and ectomycorrhizal dependence among the co-existing shrubs. Shrub-dominated plots tended to have more productive absorptive roots than sedge-dominated plots. At the northern sites, deep absorptive roots (>20 cm depth) were more frequent in birch-dominated plots. We also found shrub roots extensively proliferated into the adjacent sedge-dominated plots. The soil N pool in the active layer generally decreased from south to north but did not vary among plots dominated by different shrub or sedge genera. Our results reveal diverse nutrient acquisition strategies and belowground impacts among different arctic shrubs, suggesting that further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing arctic.

Fine root biomass and its contribution to the mangrove communities in three saline zones of Sundarbans, Bangladesh

Globally, sea levels are rising due to climate change which would influence the salinity levels in mangroves. In the framework of this study, we focused on the influence of salinity and differences of forest structure on the fine root biomass (FRB) and carbon stocks in the Sundarbans mangrove forest, Bangladesh. Also, the relationships FRB to different stand structural parameters were investigated using the data obtained from 50 sample plots (100 sq. m each) in different salinity zones in Sundarbans. Four random soil samples (30 cm in length) were taken within study plots, which were further divided into 10 cm, 20 cm, and 30 cm to identify the most active soil layer for FRB stocks. Results suggest differences in forest structural parameters and diversity indices with salinity changes in different saline zones. The low and medium saline zone is dominated by Heriteira fomes, while Excoecaria agallocha dominates the high saline zone. The carbon stocks (Mg C ha−1) in Sundarbans show a significant decrease with increasing salinity in different saline zones, e.g. oligohaline (252 ± 60.2), mesohaline (199 ± 37.7), and polyhaline (171 ± 20.0) zone. FRB carbon (Mg C ha−1) allocation in different saline zones also followed a decreasing order, such as oligohaline (12.8), mesohaline (7.9), and polyhaline (7.3). Fine root biomass showed a decreasing trend with increasing soil depth, where the differences, however, were not significant (p > 0.05) among the soil layers. Our results provide evidence on FRB variations in Sundarbans, which has implications on the mangrove species conservation and management. The mature stands at different saline zones of Sundarbans mangrove forest, Bangladesh has a high fine root biomass, which is valuable for mangrove restoration and the studied species plantation in the shore line or coastal area which can help to decrease the erosion effects of tidal inundation.

РАСЧЕТ ТОЛЩИНЫ ТЕПЛОИЗОЛЯЦИИ И ВЕЛИЧИНЫ ЗАГЛУБЛЕНИЯ ПОДЗЕМНЫХ ПОЛИЭТИЛЕНОВЫХ ТРУБОПРОВОДОВ ТЕПЛОСНАБЖЕНИЯ В РЕГИОНАХ С МНОГОЛЕТНЕМЕРЗЛЫМИ ГРУНТАМИ

The process of thawing and freezing of the host soil of an underground polyethylene heat supply pipeline with thermal insulation, operated in areas of permafrost distribution, is considered. The task is to determine the thickness of the thermal insulation of the pipeline and the size of its depth based on the analysis of the temperature field in the ground during long-term cycle. The temperature field in the "insulated pipe-ground" system, which changes over time, is proposed to be determined by solving the heat conduction equations in polar coordinates. In this case, a bundle of pipes is considered as one pipe of equivalent radius. This approach allows to simplify the interface conditions of the pipe, thermal insulation, polyethylene shell and the host soil, as well as to use a simple numerical method for solving the equation – the finite difference method. The results of calculations of the maximum depth of soil thawing from the depth of the heat supply pipe at different thicknesses of thermal insulation are presented. It is proposed to determine the optimal depth of the underground heat supply pipeline from the condition of annual establishment of the zero isotherm of the host soil at the level of the boundary of the active soil layer by the beginning of the heating season. The possibility of finding a zero isotherm at this level is illustrated by calculations of isotherms by the beginning of the heating season (September) at various depths and thicknesses of thermal insulation. Based on the results of calculations the method of estimation the insulation thickness and depth of the pipeline from the condition of minimizing the functional that characterizes the measure of deviation of the ordinates of the zero isotherm on the left-hand boundary of the region from the depth of the active soil layer at the beginning of the heating season.

The Transition From Stochastic to Deterministic Bacterial Community Assembly During Permafrost Thaw Succession.

The Northern high latitudes are warming twice as fast as the global average, and permafrost has become vulnerable to thaw. Changes to the environment during thaw leads to shifts in microbial communities and their associated functions, such as greenhouse gas emissions. Understanding the ecological processes that structure the identity and abundance (i.e., assembly) of pre- and post-thaw communities may improve predictions of the functional outcomes of permafrost thaw. We characterized microbial community assembly during permafrost thaw using in situ observations and a laboratory incubation of soils from the Storflaket Mire in Abisko, Sweden, where permafrost thaw has occurred over the past decade. In situ observations indicated that bacterial community assembly was driven by randomness (i.e., stochastic processes) immediately after thaw with drift and dispersal limitation being the dominant processes. As post-thaw succession progressed, environmentally driven (i.e., deterministic) processes became increasingly important in structuring microbial communities where homogenizing selection was the only process structuring upper active layer soils. Furthermore, laboratory-induced thaw reflected assembly dynamics immediately after thaw indicated by an increase in drift, but did not capture the long-term effects of permafrost thaw on microbial community dynamics. Our results did not reflect a link between assembly dynamics and carbon emissions, likely because respiration is the product of many processes in microbial communities. Identification of dominant microbial community assembly processes has the potential to improve our understanding of the ecological impact of permafrost thaw and the permafrost–climate feedback.

Strong shifts in microbial community structure are associated with increased litter input rather than temperature in High Arctic soils

Rising temperatures in the Arctic and the expansion of plants to higher latitudes will significantly alter belowground microbial communities and their activity. Given that microbial communities are major producers of greenhouse gases, understanding the magnitude of microbial responses to warming and increased carbon input to Arctic soils is necessary to improve global climate change models. In this study, active layer and permafrost soils from northern Greenland (81° N) were subjected to increased carbon input, in the form of plant litter, and temperature increase, using a combined field and laboratory approach. In the field experiment, unamended or litter-amended soils were transplanted from the permafrost layer to the top soil layer and incubated for one year, whereas in the laboratory experiment active layer and permafrost soils with or without litter amendment were incubated at 4 °C or 15 °C for six weeks. Soil microbial communities were evaluated using bacterial 16S and fungal ITS amplicon sequencing and respiration was used as a measure of microbial activity. Litter amendment resulted in similar changes in microbial abundances, diversities and structure of microbial communities, in the field and lab experiments. These changes in microbial communities were likely due to a strong increase in fast-growing bacterial copiotrophic taxa and basidiomycete yeasts. Furthermore, respiration was significantly higher with litter input for both active layer and permafrost soil and with both approaches. Temperature alone had only a small effect on microbial communities, with the exception of the field-incubated permafrost soils, where we observed a shift towards oligotrophic taxa, specifically for bacteria. These results demonstrate that alterations in High Arctic mineral soils may result in predictable shifts in the soil microbiome.

Recent progress on studies on cryospheric hydrological processes changes in China

The significant changes in the cryosphere have produced a series of effects on the cryospheric hydrological processes. This paper comprehensively reviews the recent 20 years, especially the new progress in the research on the changes in cryospheric hydrological processes in China, which mainly include glacial meltwater, snowmelt runoff, and frozen ground hydrology. The main progresses in the study on changes in glacial meltwater manifest as:a comprehensive study on glacial meltwater at different scales was carried out, it was found that the glacial meltwater showed continuously increase, and whether the point of the glacial meltwater have appeared has scientifically identified and some basic understandings has obtained, and the modelling on glacial meltwater process had made significant progress. In the study on snowmelt runoff changes, the snowmelt runoff contribution rate to river runoff in various basins were basically grasped by estimating the snowmelt runoff and found that the snowmelt runoff changes in China vary greatly, and it increased in some basins while decreased in some basins. The changes in the start melting period in China are universal with other basins in the world, and the prominent feature is the advance of the peak value. In the study of frozen ground hydrology, the studies on the relationship between surface water, interflow in active layer soil, supra-permafrost water revealed the coupling mechanism of gravity and thermodynamics in the formation of runoff in permafrost regions. The impacts of permafrost change on surface runoff has already appeared, which mainly appears as increase in the winter (dry season) runoff. It also found that the permafrost degradation has a direct replenishment effect on river runoff, and the amount of recharge may have reached a certain level in some basins.

Foraging deeply: Depth-specific plant nitrogen uptake in response to climate-induced N-release and permafrost thaw in the High Arctic.

Warming in the Arctic accelerates top-soil decomposition and deep-soil permafrost thaw. This may lead to an increase in plant-available nutrients throughout the active layer soil and near the permafrost thaw front. For nitrogen (N) limited high arctic plants, increased N availability may enhance growth and alter community composition, importantly affecting the ecosystem carbon balance. However, the extent to which plants can take advantage of this newly available N may be constrained by the following three factors: vertical distribution of N within the soil profile, timing of N-release, and competition with other plants and microorganisms. Therefore, we investigated species- and depth-specific plant N uptake in a high arctic tundra, northeastern Greenland. Using stable isotopic labelling (15 N-NH4 + ), we simulated autumn N-release at three depths within the active layer: top (10cm), mid (45cm) and deep-soil near the permafrost thaw front (90cm). We measured plant species-specific N uptake immediately after N-release (autumn) and after 1year, and assessed depth-specific microbial N uptake and resource partitioning between above- and below-ground plant parts, microorganisms and soil. We found that high arctic plants actively foraged for N past the peak growing season, notably the graminoid Kobresia myosuroides. While most plant species (Carex rupestris, Dryas octopetala, K. myosuroides) preferred top-soil N, the shrub Salix arctica also effectively acquired N from deeper soil layers. All plants were able to obtain N from the permafrost thaw front, both in autumn and during the following growing season, demonstrating the importance of permafrost-released N as a new N source for arctic plants. Finally, microbial N uptake markedly declined with depth, hence, plant access to deep-soil N pools is a competitive strength. In conclusion, plant species-specific competitive advantages with respect to both time- and depth-specific N-release may dictate short- and long-term plant community changes in the Arctic and consequently, larger-scale climate feedbacks.

Irrigation management model based on soil moisture distribution profile

The article is devoted to the actual problem solving of precision irrigation in terms of an irrigation management model creating based on the soil moisture spatial variation. The research key element is that the model being created takes into account the soil moisture content variability not according the area of the irrigated plot, but in the vertical profile of the agricultural crops active root water consumption zone. This approach avoids the necessity for the irrigation equipment design complication for irrigation moisture differentiated distribution and therefore the technology application allows us to avoid unnecessary costs. The irrigation requirement assessing block according to the moisture content differentiating in the active soil layer profile is new in the proposed model architecture. The block algorithm assumes the two-stage irrigation requirement assessment, first, based on the total level of soil moisture variation in the active layer profile and second, on the layers sum of the active soil horizon with a moisture content below the threshold level. Together, these estimates allow us to make a decision about the irrigation necessity if soil moisture excessive variation in the profile layers and the moisture distribution nature in the soil profile have a significant impact on the irrigated crop productivity.

Stabilization of organic material from soils and soil-like bodies in the Lena River Delta (13C-NMR spectroscopy analysis)

The Arctic ecosystem has a huge reservoir of soil organic carbon stored in permafrost-affected soils and biosediments. During the short vegetation season, humification and mineralization processes in the active soil layer result in the formation of specific soil organic substances – humic substances. Humic acids are high molecular, specific, thermodynamically stable macromolecules. The study was conducted in the Lena River Delta, the largest river delta located in the Arctic. Cryosol-type soils on alluvial deposits of the river form an area of about 45 thousand km<sup>2</sup> under permafrost conditions. The vegetation cover is represented by moss-lichen communities with the presence of <em>Salix glauca</em> in the flooded areas, as well as <em>Betula nana</em> in the areas not subject to flooding. The paper presents the elemental and molecular composition of humic acids isolated from soils, integral indicators of humification (stabilization) of organic matter in the soils of the Lena River Delta. The study was conducted using the <sup>13</sup>C (CP/MAS) NMR spectroscopy method. In the work, it was revealed that up to 33% of aromatic and up to 15% COOR fragments are accumulated in humic acids. The AR/AL ratio ranged from 0.69 to 0.89. The studied soils are variants of modern soil formation (not subjected to alluvial processes) and soil-like bodies that melted from the IC of the river delta. A relatively high degree of condensation of humic acid macromolecules in comparison with other polar regions of the Arctic and Antarctic was noted.

Innovative technologies in the effective use of water resources

Global warming in the arid region is currently exacerbating water scarcity. The use of groundwater for crop irrigation is one of the major problems in the world. In this context, the use of rivers and ponds with varying degrees of mineralization is especially important for the irrigation of crops. About 300 km3/year of collector-drainage water (CDW) is formed in the world, which causes great damage to the economy and nature of all countries of the world. In this regard, one of the important tasks is the development of measures for the reuse of collector-drainage water for irrigation, the first demineralization, and disinfection, or their use in combination with river water. To solve these problems, a neutron-active analysis of the composition of the soil and trace elements were studied, as well as the dynamics of the distribution of water in the active soil layer to determine the patterns of water absorption in active soil during irrigation based on a new innovative method of nuclear physics and irrigation of cotton plantations with the addition of drainage water and as a result of which, there was provided the efficiency of water use and increase the productivity.

The effects of warming and soil chemistry on bacterial community structure in Arctic tundra soils

Soil microbial communities in the Arctic play a critical role in regulating the global carbon (C) cycle. Vast amounts of C are stored in northern high latitude soils, and rising temperatures in the Arctic threaten to thaw permafrost, making relatively inaccessible C sources more available for mineralization by soil microbes. Few studies have characterized how microbial community structure responds to thawing permafrost in the context of varying soil chemistries associated with contrasting tundra landscapes. We subjected active layer and permafrost soils from upland and lowland tundra sites on the North Slope of Alaska to a soil-warming incubation experiment and compared soil bacterial community profiles (obtained by 16S rRNA amplicon sequencing) before and after incubation. The influence of soil composition (characterized by mid-infrared [MIR] spectroscopy) on bacterial community structure and class abundance was analyzed using redundancy and correlation analyses. We found increased abundances of Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes [Sphingobacteriia] post incubation, particularly in permafrost soils. The categorical descriptors site and soil layer had the most explanatory power in our predictive models of bacterial community structure, highlighting the close relationship between soil bacteria and the soil environment. Specific soil chemical attributes characterizing the soil environments that were found to be the best predictors included MIR spectral bands associated with inorganic C, silicates, amide II (CN stretch), and carboxylics (C–O stretch), and MIR peak ratios representing C substrate quality. Overall, these results further characterize soil bacterial community shifts that may occur as frozen environments with limited access to C sources, as is found in undisturbed permafrost, transition to warmer and more C-available environments, as is predicted in thawing permafrost due to climate change.

INTERACTION OF POST FOUNDATIONS AND FROZEN SOILS

The frozen soils’ stress-strain state varies with time due to the internal soil rheological processes. Those processes become active within the thawing period of the active soil layer causing increase in settlement of the engineering structures’ foundations. Hence, creep processes and thawing of frozen soils should be considered when designing the transportation facilities for regions of the Far North and Siberia.The objective of the research is to develop a procedure for evaluating the variation in time of the stress-strain state of the frozen soil under the post footing of a bridge pier’s foundation considering the frozen soil creep and thawing. The interaction of the bridge pier post foundations and frozen silt-loam soil is modelled and studied. The research is based on the example of an existing overpass over the M‑56 Lena motor road situated at Amga–Samyrdah stage of Tommot–Yakutsk section of the Berkakit–Tommot–Yakutsk railway line. This overpass has piers with post foundations. The above railway line is in the area of hard frozen soils.The study focuses on changes in principal normal compressive stresses with the course of time, as well as on the frozen soil movements under the post footing. The time allotted for the above system behavior study is limited to five months. There are two design cases: a) considering the frozen soil thawing up to a depth range of 1,5 to 4 m; b) without considering the frozen soil thawing.The research has shown that the thawing of the frozen soil up to a comparatively low depth as compared to natural level results in a significant increase (by 2÷2,5 times) in the values of post foundation settlement as compared with the design case without thawing. At the same time, it was found that small values of thawing have a subtle effect on the frozen soil’s stress state under the post footing. Besides, all reviewed design cases (with / without thawing revealed that stress of the frozen soil under the post footing decreases with time (stress relaxation).

Prospects of spring wheat cultivation in the conditions of arid Volga region

The article analyzes the experience of the impact of the system of forest belts and mineral fertilizers on the yield of spring wheat, including on irrigated lands. Vegetation irrigation is designed to maintain the humidity of the active soil layer from germination to maturation at the lower level of the optimum-70-75%, and in the phases of tubulation-earing - flowering - 75-80% NV. However, due to the large differences in zones and microzones of soil and climate conditions and due to the weather conditions of individual years, wheat irrigation regimes require a clear differentiation. In the Volga region in the dry autumn rainfalls give the norm of 800-1000 m3/ha, and in saline soils – 1000-1300 and 3-4 vegetation irrigation at tillering, phases of booting, earing and grain formation the norm 600-650 m3/ha. the impact of the system of forest belts, mineral fertilizers on the yield of spring wheat is closely tied to the formation of microclimate at different distances from forest edges.

Prospects of peat development in the Arctic and Subarctic zones of Russia

The vital infrastructure of Russia’s Arctic and Subarctic, in view of severe nature and climate, consumes much energy sources, mostly, coal shipped from central Russia by water transport via the Northern Sea Route (2-3 thousand kilometers) in summer. This raises the cost 3-4 times. A good alternative to the imported fuel is local peat. The principal consumer of peat as a fuel can be the Verkhoyansk Region in the Republic of Sakha (Yakutia), which is the subject of research. This article describes the promising deposits of peat in this region, peat occurrence conditions and possible production output. The scope of the discussion embraces the most popular methods of peat production: milling, hydraulic, dredging, scraper-elevator, cutting, milling-and-forming, shoveling, etc., with field curing and harvesting. However, because of high bogginess of the tundra zone, the listed methods of peat production are unusable. In this regard, the most promising approach is winter production of frozen peat with preliminary monitoring of the frozen thickness by ground penetrating radar. The earlier studies into the temperature conditions of the active soil layers, including peat beds, are presented. The chosen technology will ensure maximum preservation of landscape and ecological safety.

Sources of seasonal wetland methane emissions in permafrost regions of the Qinghai-Tibet Plateau

In this study, systematic soil methane cycle geochemical monitoring was carried out in a typical gas hydrate region in the Qinghai-Tibet Plateau. Soil gas samples were collected for hydrocarbon components and carbon isotope analysis. Meanwhile, soil-methane fluxes from the upper active layer (20–30 cm) were monitored during six months of one year. The results of this research provide evidence of a new source of methane emission from wetland soils in permafrost regions: gas hydrate release. Sites with large methane emissions were found using flux monitoring, the characteristics of thermogenic methane were identified using carbon isotope tracing, and the relationship between emission by soils and effusion from gas hydrates was determined through correlation analyses of soil-adsorbed hydrocarbons. Seasonal variation of methane emissions are also discussed by considering the emission of bacterial methane, thermogenic methane, and the absorption of methane from the soil active layer. These comprehensive findings provide valuable information for carbon cycle research of wetlands in permafrost regions.