Recognizing palsa and high-centered polygonal peatlands based on the carbon-to-nitrogen ratio

Vasil'chuk Alla Constantinovna ORCID: 0000-0003-1921-030X Doctor of Geography Leading Researcher; Laboratory of Geoecology of the Northern Territories; Lomonosov Moscow State University 119991, Russia, Moscow, Leninskie Gory, 1,, of. geographical Faculty, NIL Geoecology of the North alla-vasilch@yandex.ru Other publications by this author

Vasil'chuk Yurii Kirillovich ORCID: 0000-0001-5847-5568 Doctor of Geology and Mineralogy Professor; Department of Landscape Geochemistry and Soil Geography; Lomonosov Moscow State University 119991, Russia, Moscow, Leninskie Gory str., 1, office 2009 vasilch_geo@mail.ru Other publications by this author

Introduction

SP 502.1325800.2021^[1] and SP 493.1325800.2020^[2] indicate that engineering surveys for construction in areas of permafrost distribution primarily take into account engineering geocryological conditions, i.e. a set of characteristics of geocryological components of the geological environment in areas of permafrost distribution, influencing design decisions, construction and operation of structures and etc. However, in the areas of distribution of bumpy peatlands, this task is significantly complicated by the difficulty of recognizing their different types. According to paragraph 6.2.4.2. SP 493.1325800.2020^[2] engineering and environmental surveys for the preparation of design documentation for capital construction projects in the areas of permafrost mounds are performed at the second stage, if necessary, to identify areas of increased environmental danger and areas of environmental restrictions due to adverse conditions. Earlier, when characterizing the difficulties of engineering surveys for the construction of pipelines within the bumpy landscapes of the zone of sporadic permafrost distribution, the authors showed^[3] that convex-bumpy landscapes change at a high rate both under the influence of natural changes, global and local, and under the influence of linear objects themselves, as well as as a result of the consequences of construction and other man-made impacts. At the same time, the danger of pipeline operation, even within point-to-point permafrost hilly landscapes, is associated with a large range of vertical displacements during seasonal freezing and thawing in the contact zone of the hillock and the surrounding melt space, reaching 1-2 m. A noticeable, abrupt and sudden loss of bearing capacity of frozen soils within limited areas of bumpy landscapes leads to uneven subsidence and depths and to a serious local change in the curvature of the pipeline radius.^[3]. Bumpy peatlands are one of the most common forms of permafrost relief and represent a complex peat-bog formation, the main components of which are frozen peat mounds and the wells separating them ^[4-11]. There are several types of hummocky peatlands, the most characteristic of which are flat-hummocky and convex (large-hummocky), differing in height and shape, and most importantly in the distribution of their main engineering and geological properties, in particular, iciness. The height of flat mounds is 1-1.5 m, convex mounds reach a height of 3-5 m or more (up to 10 m), the configuration of the mounds is diverse: rounded, ridge-shaped, lobed and can occupy an area of units and several tens to hundreds of square meters. Among geocryologists, there are ideas according to which flat-rimmed peatlands were formed as a result of thermal erosion over re–vein ice (Fig. 1), and convex-rimmed (Fig. 2) - as a result of heaving processes.

Fig. 1. Peat polygonal flat-rimmed massifs with the development of mounds as a result of thermal erosion over re–vein ice: a - exposure of the first terrace on the Shchuchya River, southwestern Yamal; b – exposure of the first terrace near the village. The new Port of the Shchuchya river, southeastern Yamal; in – lake-marsh tab on the third terrace near the village. Seyakha, east coast of Yamal, in – lake-marsh tab on the third terrace, Vaskin Cottages, central Yamal. Photos of the authors (a, c), L.P. Kuzyakin (b) and A.P. Ginzburg (d)

Flat-edged and convex-edged peat massifs

Flat-rimmed peat massifs are mainly confined to the zone of continuous development of permafrost rocks and occur in the zone of their intermittent distribution and are often confined to areas of development of Holocene re-vein ice in peatlands.

Polygonal flat-edged peat massifs are found mainly in large lowlands and watershed basins. The thickness of peat bogs varies; most often it is 0.5-1.5 m, but sometimes it reaches 3-4 m. There is a gradual transition of peat into the underlying lake loams on which they lie. Such a gradual transition indicates the genetic relationship between lake sediments and peat: the completion of lakes by precipitation resulted in the formation of swamps with subsequent peat accumulation and the growth of re-vein ice.

Flat-edged peat blocks are remnant landforms that were formed “passively” due to thermokarst processes along the frost-breaking cracks with vein ice separating them. In the same peat massif, flat-edged landforms can be observed, bounded by steeply sloping ditch-shaped depressions and, on the continuation of the latter, on the flat surface of a polygonal peat bog, a network of frost-breaking cracks with ice veins that have not yet thawed.^[12]

Bulbous peat massifs are distributed mainly in the zone of island permafrost, although they are often observed in the zone of intermittent and even in the zone of continuous development of permafrost rocks – for example, in the area of Norilsk, on the Putorana plateau, in the area of Mirny in Yakutia, Chukotka and Kamchatka, etc. ^[4]. The peat thickness, both on flat and convex peat mounds, is usually high and is 1-3 m, reaching in some cases 5 m, and sometimes 8-9 m on convex mounds.^[4]

Fig. 2. Peat bulbous massifs: a – Circumpolar Urals, the valley of the Lekjelets River, photo A.Titova; used by the village of Yeletsky, photo by N.Budantseva

In the conditions of non-pressurized cryogenic systems, freezing follows a migration-segregation type, and heaving was determined by the conditions of accumulation of texture-forming ice. This mechanism of areal and local heaving is probably associated with the formation of a large-bumpy relief of peat massifs at the initial stage of their formation.

Migration heaving mounds on convex–bumpy permafrost peat massifs (palza) are a convex mesoform of relief that occurs during the upward development of permafrost rocks as a result of the combined course of injection, migration and segregation processes. Such mounds would even be more logical to call injection-segregation-migration, since all three processes – moisture segregation (separation of pure ice from water–saturated soil during freezing), its migration from surrounding and underlying water-saturated soils, and injection from closed volumes during expansion as a result of freezing - are undoubtedly present in almost every case the formation of bulges of this type.^[4] A.I.Popov ^[6] used the term migration heave mounds to characterize bulbous permafrost peat massifs. I.D. Danilov ^[12] believed that there was a genetic relationship between flat-hummocky and convex-hummocky peatlands. N.I. Piavchenko ^[13] believed that all hummocky peatlands were the result of thermal erosion.

Research methodology

In 2023, field studies of new sections of polygonal flat-edged peatlands were carried out: 1) on the first and second lagoon-sea terraces in the south-east of the Yamal Peninsula near the village of Novy Port of the Yamal district of the Yamalo-Nenets Autonomous Okrug; 2) near the village of Lorino, located in the east of Chukotka, on the shore of the Mechigmen Bay of the Bering Sea; 3) on the Chara River in Transbaikalia; 4) at Cape Phlox, on the shore of the Baydaratskaya Bay. Sampling was carried out from the cleaned wall, in the case of sampling below the seasonal melting layer (STS), peat was cleaned to a frozen surface. Special attention was paid to the accuracy of the selection, the selection tool was thoroughly cleaned before selecting the next sample.

To determine the content of organic carbon (C) and nitrogen (N), samples of peat and soil horizons with a volume of about 1-0.5 ^cm3 were taken from the sections. The samples were freeze-dried for two days, then crushed in an agate mortar and dried again at 60 ° C for 2 hours. The samples were placed in tin foil capsules and weighed with an accuracy of 5 digits. Measurements of the values of organic carbon (C) and nitrogen (N) were performed in the Instrument Analysis Room of the A.A. Borisyak Paleontological Institute of the Russian Academy of Sciences (PIN RAS). Measurements were carried out using an analytical complex consisting of a Delta V Plus isotope mass spectrometer, an EA Flash 2000 elemental analyzer and a ConFlo IV interface (Thermo, USA, has been operating since 2010). The degree of decomposition of peat is the content of a structureless part in peat, including humic substances and small particles of inhumified plant residues - it was determined using a microscope in accordance with GOST 10650-2013.

Results and discussion

The rate of formation of mounds within polygonal peatlands. Within polygonal peatlands, as a result of the activation of thermal erosion, mounds can form over several decades. The polygonal bumpy massifs formed in the XX century near the village are indicative in this regard. Churapcha (Fig. 3). Back in the second half of the century, the village had an airport that received small planes. On June 18, 1976, Yakut aviators flew for the first time on a new Czechoslovakian L-410 aircraft to Churapcha. However, in subsequent years, the runway was almost destroyed, as a result of intense thermal erosion and the formation of numerous plaskobugristy forms (Fig. 4).

Fig. 3. Mounds formed as a result of thermal erosion near the village. Churapcha (177 km east of Yakutsk), Central Yakutia. Photo B. Isaeva

Fig. 4. The mounds formed within the village. Churapcha. Photo from the website^[14]

Fig. 5. Active thermal erosion on the outskirts of the village. Churapcha

The rate of thawing and subsidence of mounds within the convex peatlands. One of the most important characteristics that should be taken into account when designing structures, and therefore predicted during surveys, is the rate of thawing and subsidence of hillocks. If flat-hummocky massifs are divided into separate mounds under the influence of thermal erosion for hundreds and sometimes thousands of years, then convex-hummocky peatlands in the zone of rarely insular and sporadic distribution of MMP can completely thaw for decades, which was confirmed by direct observations in Sweden.^[10,15] It has also been established that individual arrays of convex peatlands can disappear within just a few years.^[4,8,9,16] These differences in the rate of degradation of the two named types of peatlands are due to two factors. Firstly, it is the temperature of the MMP: in flat−sided peatlands it is usually lower than −3 ° C, and in convex-sided peatlands it is often higher than -1 ° C. Secondly, this is the distribution of ice content: in flat-rimmed peatlands, the bulk of the ice is concentrated under the inter-polygonal grooves between the mounds, and in convex-rimmed ice is concentrated in the cores of the mounds. During the operation of structures, these two types of bumpy permafrost peatlands react significantly differently to anthropogenic impact and require different protective actions. In this regard, it is necessary to develop methods for more accurate identification of mounds already at the first stages of engineering and environmental surveys.

The dynamics of convex finger-type bulges was studied^[16] in the area of the village. Abez (66°31' s.w., 61°46' v.d., 2098 km of the Moscow-Vorkuta railway), located in the central part of the area of the distribution of heaving mounds, in the Bolshezemelskaya tundra. Frozen rocks here have an insular distribution. There are no frozen rocks up to a depth of 10-12 m within high watersheds. Within the limits of the second above-floodplain terrace of the river.Whiskers, permafrost rocks are found on islands and are confined mainly to peat bogs.

Within the vast lake basin in 2001, there were both young mounds growing in the center of the draining reservoir, and ancient ones, signs of destruction of which were the sliding of peat blocks into the inter-mountain depression, a sickle-shaped shape in plan. Several heave mounds of different sizes and heights were examined in detail. There were large mounds up to 3-4 m high with a strongly acidic core, overlain from the surface by peat, with a thickness of up to 1 m.^[16]

Fig. 6. A large convex bulge of heaving up to 3 m high with a strongly acidic core, overlain from the surface by peat near the village. Abez, Bolshezemelskaya tundra in 2001. Photo by the authors

In September 2001, a bulbous massif with heaving mounds in the area of the village. The lake was in a relatively stable condition, the height of the mounds varied from 3 to 1.5-1 m (Fig. 7, a). In September 2016, repeated studies of the massif with heaving mounds in the area of the village. The results showed that the height of the mounds has significantly decreased (Fig. 7, b) compared to 2001 and or they have completely disappeared.^[16]

According to calculations, the average C/N value for peatlands located north of 45 degrees north latitude was 45-49.^[17-19] This parameter differs significantly within the zone of development of permafrost rocks.

One of the possible ways to assess the ecological features of convex mounds is to assess the content of carbon (C) and nitrogen (N), as well as the ratio of these elements (C/N). Previously, we justified the differences between the finger and the lithalse by studying the distribution of these elements in peat.^[20] In particular, it was found that, unlike lithals, the carbon content in the surface horizons of convex and flat-edged peatlands is many times higher than the values obtained for both surface and buried organic horizons of the lithals soil cover. The value of C/N less than 13 has not been recorded for the peat cover of the palm, this indicator for the litals never exceeds 10-12.^[20] A detailed study of the nitrogen and carbon content in peat allows using this indicator to identify peatlands of both types. Since flat-sided peatlands accumulate and turn into a permafrost state sequentially, the nitrogen content depends not only on the composition of the phytocenosis and the activity of microorganisms, but also on the rate of freezing. While several phases are distinguished in the formation of bumpy peatlands, at the same time a sufficiently thick layer of peat with sphagnum moss, which provokes heaving, accumulates in conditions of increased watering and remains in a thawed state much longer than peat of flat-hummocky peatlands.^[4,21]. The formation of mounds is not necessarily a unidirectional process. They often melt, and then, when favorable conditions arise for the formation of an ice core, they bulge again.^[4]

The ratio of carbon and nitrogen content within polygonal flat-edged peatlands

Flat-edged polygonal peat massifs are noted both in the zone of continuous development of permafrost rocks and in the zone of intermittent distribution of MMP.^[21] The thickness of peat bogs varies from 0.5-1.5 m to 3-4 m. According to new data from the authors, in one of the polygonal peat bogs near the village. The New Port on Yamal has an average C _content of 47.18% and ranges from 49.73% to 39.27%.^[22] The average N content is 2.64% and ranges from 1.51- 3.15%. The C/N values are in the range of 17.6-30.3, averaging 24.5. In another peat bog located in the same place, but on the coast of the Gulf of Ob, these indicators are different. The average content of C or is _44.14% (from 53.37% to 15.72% in the upper peat layer); the average content of N is 1,51% (2,50% - 0.44%). Significant variations in nitrogen content affected the value of the C/N index, which varies between 24.1-65.8, the average value is 36.4.^[22] The polygonal peat bog in the Bovanenkovsky GKM area in Yamal is characterized by a fairly high content of C _org = 45.4-28.1%, the average value is 38.1%, and a lower content of N. The average N content is 1.77% and is in the range of 1.12-2.96%. The average value of the C/N ratio is 26.4, within the peat layer this value varies from 13.7 to 44.7.^[23] Studies of the carbon and nitrogen content on the Taz Peninsula have shown that the active layer contains 42-48% carbon, in the upper frozen layer – 44-49%. The minimum nitrogen content is observed in the pockets of grass-sphagnum wells (0.9%), the highest is in the upper frozen layer of polygonal peat bogs and willow sedges (2.2%).^[24,25]

Fig. 7. Thawed and sagged large convex bulge of heaving up to 2 m high with a strongly acidic core near the village. Abez. Direct comparison of the morphology of the same finger, in 2001 (a) and 2016 (b). From ^[16] Photos of the authors

According to the new data of the authors, the peat bog on the first sea terrace on the coast of the Baydaratskaya Bay near Cape Phlox is characterized by a high content of _sulfur (24.49-51.82%, average value 40.33%), and a slightly lower nitrogen content compared to the peatlands of the New Port (0.99-1.66%, average value 1.3%).^[22] The value of C/N is in the range of 28.36-36.42, the average value is 35.8. In the peat bog located on the coast of the Mechigmen Bay in Chukotka, according to new data from the authors, the average content of C / _org is 19.8% (varying from 8.16 to 30.99%), the nitrogen content is also low, the average content of N = 0.9% (varying from 0.48 to 1.51%), the average value of the C /N ratio = 24.8 (varying from 19.2 to 31.1).

In the peat bog on the coast of Onemen Bay in the same place in Chukotka, the average content of C _org = 31.53% (varying from 1.19 to 59.09), the average content N = 1.33 (varying from 0.13 to 2.18%).^[26]

The peat of the polygonal peat bog accumulated in very continental conditions on the Chara River in Transbaikalia is characterized by a very contrasting distribution. The carbon content, according to the new data of the authors, varies widely (2.11-41.32%, the average value is 28.23%), the nitrogen content is lower than even that of the polygonal peat bog at Cape Phlox (0.11-1.88%, the average value is 0.98%). The C/N ratio varies widely (from 13.68 to 73.75, the average value is 35.82). Note that the highest values of the C/N ratio are recorded in the active layer in all described peatlands.

Polygonal flat-rimmed peatlands within the Indigir and Kolyma lowlands demonstrated similar values of carbon and nitrogen content. Thus, in the peat of the landfill in the delta of the Kolyma River, these indicators vary within the following limits: C = 10-30%, N = 0.5-2.3%, the value of the ratio C / N = 10-33. The polygonal peat bog in the vicinity of the WWF Kitalyk research station is characterized by the following indicators: C = 10-40%, N = 0.5-2%, value C/N = 15-20.^[27]

The studies, including the analysis of carbon and nitrogen content, were conducted on polygonal peat bogs on the Yukon coastal plain. The content of nitrogen and carbon in the peat of the central parts of the polygons and in the inter-polygonal grooves was studied. In a polygonal peat bog located 1.5 km from the coast of the Beaufort Sea, the average C content is 40%, the average N content is 2.5%, the average C/N ratio is 5.5. A polygonal peat bog near the coast of Ptamigan Bay is characterized by similar values: the average C content is about 36%, N is about 2%, the average value of the C/N ratio does not exceed 5.^[28]

Holocene peatlands with re-vein ice have been studied on the east coast of Herschell Island. The values of the C content of _org are in the range from 17.8 to 39.0% (average value: 30.2%), the average value of the C/N ratio is 22, it ranges from 8-31. The minimum C/N values are noted in the lower 2.0 m 8-14, and in the active layer (0-0.32 m) this value ranges from 19 to 31.^[29]

In the north-west of Canada,^[30] studies were conducted on polygonal flat-rimmed peatlands 400, 200 and 75 km from the forest boundary, as well as on one peatland in the forest tundra. The C content in them ranges from 15 to 50%, the average value is 24-39%, the highest values of the C content are noted in the active layer. The N content is in the range of 0.6 -3.1%, the average values are from 1.3% to 2.5%. The highest C/N values are observed in vegetation and the active layer, regardless of the composition of peat. The average values were 17.5–37.9 in the active layer, and 13.7–21.1 in permafrost peat in all four peat layers. The highest C/N ratios are observed in vegetation and newly formed peat in the surface aerobic layer, regardless of the composition of the peat. It is noted that there are no differences between peat with high and low C/N values, except for the permafrost state of peat with a low index.^[30] The differences in the composition of carbon and nitrogen in peatlands located at different distances from the northern border of the forest are not so great and are due, according to the authors, to the different age of peatlands.

The ratio of carbon and nitrogen content within convex peatlands. Convex peat masses (palm arrays) are common in the zones of intermittent and insular distribution of MMP, sometimes they occur in the zone of continuous development of MMP.^[21] The thickness of convex peatlands of peat bogs varies from 0.5-1.5 m, up to 5-6 m. In the surface layer of the palm near the village of Yeletsky on the periphery of the drained lake basin, the maximum value of C/N was 31.12 in the layer belonging to the mesothelm (the boundary layer between acrotelm and katotelm), below this layer the roots of modern vegetation were absent. The minimum carbon content and C/N values (13-14) are observed at the top of the finger and below in the active layer, where peat consists mainly of the remains of sphagnum mosses, as well as Ledum decumbens, Vaccinium vitis-idaeae and Rubus chamaemorus, which contain a minimum amount of carbon (23-38%). Fluctuations in the values of the C/N ratio are mainly associated with changes in the carbon content, which varies in the range of 29.48-55.36%. Variations in nitrogen content are less noticeable: there is a minimum value at the base of the peat bog of 1.78%, a maximum value in the middle of 4.48%, and an average value of 3.3%. According to E.M.Lapteva and co-authors^[31], variations in the content of C in the bumpy peat bog in the north-west of the Bolshezemelskaya tundra are 28.8-48.3%, variations in the content of N = 0.88-1.90%, the minimum content of both elements is observed in the upper upper 4 cm of peat. The value of the C/N ratio varies from 25 to 40, the minimum values relate to the active layer. The bumpy peatlands in the southeast of the Bolshezemelskaya tundra in the valley of the Seida River are characterized by a stable carbon content of 40-50%,^[32] the N content is low. In the active layer, the value of the C/N ratio is in the range of 5-25, which indicates a relatively higher degree of decomposition of peat and enrichment of the surface layers of peat with nitrogenous substances, the maximum value of the C/N ratio = 38 is noted at the boundary of thawed and frozen peat, in frozen peat this value varies from 21 to 25. In the vicinity of the city of Nadym, the peat of the palza massif contains C from 58.01 to 59.86%, and the content of N is from 0.13 to 0.21%, the C/N values in the upper part of the profile are 41.75-59.41, and in the lower 41.75-21.67.^[33] In the Igarka area^[34.35] in the studied finger, the C content varies from 17.3 to 54.7%, and N - from 0.37 to 3.26% the value of the C/N ratio 14-134. The lowest C/N values in the peat of the palm are noted in the upper 100 cm, since there is an unusually high nitrogen content (2.5-3.2%). Nitrogen enrichment in the upper part of the palm is associated with the participation of the remnants of the roots of Ledum palustre and the dominance of lichens, which are characterized by an increased nitrogen content. At a depth of 300-450 cm, a decrease in nitrogen content to 0.4-0.5% and a corresponding increase in the C/N ratio corresponds to the initial stage of the formation of the hillock represented by sphagnum peat.

In the north of Sweden and Norway, the palm massifs are also characterized by a fairly low nitrogen content (0,7-3,7%),^[36] at the same time, the maximum carbon content of 53-56% is noted in the upper part of the finger sections, composed mainly of gypsum mosses, therefore, in the finger sections of these regions, the maximum C/N values are noted in the upper part of 40-56%. In the rest of the section, as well as in the sections of the finger near the village of Yeletsky^[37], C/N values fluctuate around magnitude 25.^[36] Low nitrogen content determined high values of the C/N ratio in bumpy peatlands on the coast of Hudson Bay in western Canada. The carbon content in the peat bog near the lake. Selvine is almost constant (42.2%-44.9%), the average content of _organic matter is 43.5%. The average N content in this peat bog is 0.4%, it varies between 0.2–0.5%. The value of C/N varies from 82 to 240, averaging 131. Fluctuations in C/N values are mainly associated with changes in carbon content, which varies in the range of 29.48-55.36%. Variations in nitrogen content are less noticeable: there is a minimum value at the base of the peat bog of 1.78%, the maximum in the middle part of 4.48%, averaging 3.3%.^[38] In the peat bog near the lake.Ennandai carbon content ranges from 40.7% to 47.7%, averaging 44.1%. The nitrogen content varies from 0.3% to 0.8%, and the average value is 0.5%, except for the lowest sample, which has a value of 1.8%. The C/N ratio varies from 26 to 144, with an average of 96. For the Selvin peat bog, the C/N ratio is relatively constant throughout the profile, with three exceptions: one peak with an increased C/N ratio occurs at a depth of 25-30 cm; an even more pronounced peak occurs at an interval of 55-60 cm. For the Enandai peat bog, the value of the C/N ratio increases from the surface to a depth of about 30-50 cm, below which this ratio remains relatively stable and is about 135.^[38]

The authors' experience of studying flat-humped peat massifs in the Bolshezemelskaya tundra, Yamal and Chukotka showed that differences in the mechanism of formation of mounds are reflected in the value of C/N, despite the fact that the peat-forming agents for both peatlands are the same plant species in various combinations. Flat-hummocky peatlands are characterized by an average carbon content of 35-40%, and convex-hummocky 50-55.5%, the average nitrogen content in flat-hummocky peat massifs is 1.8-2.2%, and in convex-hummocky peatlands 0.5-2.0%. That is, on average, in convex peatlands ^{[11,16,20,37]}, the carbon content is higher and nitrogen is slightly lower compared to flat-sided peatlands ^[22,23,26]. The value of the C/N ratio in these peatlands obviously also differs: for convex peatlands, this value is in the range of 30-36, and in flat-sided peatlands, if we exclude the indicators of the seasonal melt layer, it rarely exceeds 25-27.

Conclusion

1. In the areas of distribution of bumpy permafrost peatlands, engineering-geological and engineering-ecological surveys for construction are significantly complicated by the lack of clear criteria for the separation of mounds of different types, and primarily flat-hummocky and convex-hummocky peatlands.

2. Flat-hummocky and convex-hummocky peatlands differ in genesis, height and shape, and most importantly in the distribution of their main engineering and geological properties, primarily ice content.

3. During the operation of structures, these two types of bumpy permafrost peatlands react significantly differently to anthropogenic impact and require different protective measures.

4. It is necessary to develop methods for more accurate identification of mounds already at the first stages of research. One of the methods may be to study the distribution of the ratio of carbon and nitrogen in the peat covering the mounds.

5. In convex peatlands, the carbon content is on average higher than 50-55%, and nitrogen is slightly lower below 0.5-2.0% compared with flat-sided peatlands in which the carbon content is on average 35-40%, and nitrogen 1.5-2.5%.

6. The value of the C/N ratio in these peatlands also differs: for convex peatlands, this value is in the range of 30-36 (reaching — 240), and in flat-sided peatlands, if we exclude the C/N indicators for the seasonally thawed layer, rarely exceeds 25-27 (and often amounts to 10-20).

Thanks

The authors thank Senior researcher S.N.A. Budantseva, senior researcher S.V.A. Litvinsky, senior researcher S.A.A.Maslakov and M.N. S. A.P. Ginzburg for their assistance in field and laboratory research.