ISSN 0097�8078, Water Resources, 2015, Vol. 42, No. 7, pp. 922–931. © Pleiades Publishing, Ltd., 2015.Original Russian Text © A.A. Medvedkov, 2014, published in Geoekologiya. Inzhenernaya Geologiya. Gidrogeologiya. Geokriologiya, 2014, No. 6, pp. 541–552.

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INTRODUCTION

The middle taiga zone is a part of the periphery ofthe permafrost zone, in which natural landscapesshow highly mosaic character, since they have formedunder complex geological, geomorphological, andgeocryological conditions of the region. The studyfocuses on studying the Central Siberian segment ofthe area, embracing the left� and right�bank areas ofthe Yenisei, as well as the lower reaches of the Podka�mennaya Tunguska R. Yenisei left�bank area is a frag�ment of the West Siberian epi�Paleozoic plate coveredby a continuous mantle of Quaternary deposits,underlain in some places by continental Cretaceousaccumulations, and more often, by continental car�boniferous and marine Jurassic deposits. On the leftside of the Yenisei, the Middle and Late Mesosoicdeposits have a thickness of about 1 km [1] and rapidlywedge out eastward. The area east of the Yenisei is thenorthern part of the Baikal folded structure of theYenisei Ridge and the western part of the PaleozoicTungusskaya Syneclise of Siberian Platform. Tounderstand the specific landscape structure of theregion, it is important to take into account that it isdivided from the northeast to southwest by a boundaryof maximal glaciation, whose manifestation period istaken to be the Middle Pleistocene, though it can beyounger (Late Pleistocene). In the glacial zone, theparagenesis of glacial deposits includes a continental,essentially bouldery moraine, widespread at elevationsof 500–600 m and higher in the northeastern part ofthe region and at lower elevations of the order of 200 mand lower in the near�Yenisei zone. Here, it is moreoften overlain by an aqual moraine with scattered

boulders, often with clear signs of horizontal strataldifferentiation of the bed and with individual icebergbanks of coarse deposits on its surface. The aqualmoraine forms a low accumulative plain with eleva�tions mostly from 150 to 250 m. In the extraglacialzone, the surface deposits of the Yenisei left�bank areaare represented by thick glacier�dammed aleurite–pelite accumulations and sands of drainage lines, ori�ented southwest into the Ob basin. The age of theformer corresponds to the manifestation time of max�imal glaciation, while that of the later corresponds tothe stage of the break of the glacial dam by waters ofthe huge ice�dammed water body in the region wherethe Ob R. flows over a valley within Siberian Spurs. Inthe extraglacial zone east of the Yenisei, the occur�rence of surface deposits mostly follows the features ofthe layered structure of relief. Here, the top stageforms insular peneplain (J1–2), mostly trappean tablerocks with a common height of 500–700 m, its slopesand high, narrow�summit mountains (400–600 m)form an ancient stage of differentiation (J3–K1), themain peneplanation plane (K–P2) with elevations200–300 m and a valley network (P3–Q). Against thebackground of the stage–age differentiation of relief,intra�stage surfaces of superimposed dissection andplanation (Q2–4) can be identified. This are landslides,bluffs, scours (dellies), and glasises, galsis–floodplainand plain, as well as a terrace–plain—an analog of aglacier�dammed plain [2].

The mean annual air temperature in the subzone ofthe middle taiga in the Yenisei Siberia varies consider�ably depending on the landscape conditions and fea�tures of the area. In the near�Yenisei part of the middle

NATURAL AND ENGINEERING–NATURAL PROCESSES

Geoenvironmental Response of the Yenisei Siberia Mid�Taiga Landscapes to Global Warming during Late XX–Early XXI Centuries

A. A. MedvedkovFaculty of Geography, Moscow State University, Moscow, 119991 Russia

E�mail: a�medvedkov@bk.ruReceived July 17, 2013; in final form, April 3, 2014

Abstract—The response of middle boreal landscapes in the Yenisei Siberia to climate warming is considered.Changes in the systems of exodynamics, natural permafrost and nonpermafrost landscapes are analyzedbased on a series of studies. Permafrost landscapes are ranked by their susceptibility to climate warming.Changes in the habitats were identified. The aggravating problems of the local population in the sphere of theuse of taiga resources, characterizing the current stage of changes in the environment and climate are dem�onstrated.

Keywords: climate warming and instability, permafrost landscapes, middle taiga, landscape indicators, exo�dynamic processes and phenomena, nature management in taiga zone

DOI: 10.1134/S0097807815070076

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taiga subzone, under the warming effect of the valley,this temperature averages –4.5°C, decreasing east�ward to –7.5°C. In the northern sector of the subzone,the mean annual temperature reaches –8.3°C, whilein the southern sector, it varies from –3.0 to –3.5°C.The continentality index, evaluated according toS.P. Khromov [10] is 88–90%, suggesting a high con�tinentality of climate. The mean duration of the vege�tation period with temperature above 5°C varies from100 days in the north to 130 days in the south of thesubzone; the respective periods with a temperatureabove 10°C are 65–70 and 90–100 days. The frost�freeseason varies from 60 to 85 days in the same direction.The degree of moistening of the area shows the sameregularity. The annual precipitation in the west reaches700 mm (in the windward western part of the CentralSiberian Plateau and Yenisei Range), of which sum�mer accounts for 550–600 mm. On the eastern marginof the zone, the precipitation is 350–400 mm. In thewestern part of the Central Siberian Plateau, in itswindward part, winters are most snowy in Siberia(except for the mountain areas of its southern part).The mean depth of the snow cover varies from 95 to120 cm [8]. Overall, we can conclude that the westernpart of the middle taiga shows less severe and conti�nental climate conditions than its eastern part. Themiddle boreal subzone is situated in the zone of dis�continuous and insular permafrost (from 30 to 60% ofthe area). In the Yenisei part of the central Siberia sec�tor of the middle boreal subzone, permafrost rocktemperature at the bed of the layer of annual tempera�ture variations can be evaluated at –0.1 to –1.0°C andtheir thickness, at a few meters to 25–30 m [8].

In terms of lithology and geomorphology, the terri�tory in the boreal taiga subzone is represented byaqueoglacial plains, composed of sands and aleuroli�tes; glacial plains, composed of clays; aleurites withinclusions of boulders, pebble, and sand lense, etc.;high and low trappean plateaus with a discontinuousmantle of glacial deposits in the northern part of thesubzone; and arch�block folded low�mountain areas.

The soil and vegetation cover shows the predomi�nance of pine forests on illuvial–iron podzols;spruce–fir–cedar and spruce–cedar–larch forests ontypical brown�taiga and rendzina soils; thin spruce–cedar–larch forests on cryogenic peaty–gley soils;pine–birch forests on brown�taiga thin and peaty–skeletal soils; bushy and meadow–swamp vegetationwith thin taiga on peaty–cryogenic soils; oiseries,meadow and sedgy vegetation of alluvial soils.

The objective of this study is a landscape–geoenvi�ronmental assessment of the state of middle boreallandscapes in the Yenisei Siberia under changing envi�ronment and climate.

MATERIALS AND METHODS

The first stage of the study included the processingof hydrometeorological data of local hydrometeoro�

logical observatories and All�Russia reference bookswith the aim to reveal parameter fluctuations of thetemperature regime in the Central Siberian regionsince the beginning of the XX century.

The field studies (2008–2012) included land�scape–geoenvironmental inventory of natural compo�nents on transects via the main types of forest, swamp,and burnt catenas in the left� and right�bank parts ofthe Yenisei Siberia, boreal taiga subzone (Fig. 1). Theroute profiling was carried out along transects acrossand along the geomorphological catena, taking intoaccount conjugated relief surfaces, most diverse inmorpholithogenic, soil–geographic, and landscaperespects. Detail landscape descriptions along the routewere accompanied by the determination of the upperboundary of permafrost with the use of a probe; diag�nostics of permafrost and nonpermafrost processeswas carried out. Test geobotanic sites 20 × 20 m wereanalyzed on the route to determine the composition,quality, density, and age of the timber stand (with theuse of an increment borer).

In the course of route surveys, special attention waspaid to field studies of the landscape structure of keyareas, taking into account the specifics of surfacedeposits and the character of their geomorphologicaldifferentiation; landscape indication of permafrostnatural–territorial complexes (NTC) and rankinglandscape complexes into permafrost and nonperma�frost. The comprehensive analysis of such data made itpossible to identify and outline (at the level of complexstows) the landscape complexes most vulnerable tovarious external impacts (including climatic).

In addition, the field studies included monitoringdifferent types of permafrost and nonpermafrost stowsin terms of the specifics of their response to climatewarming, which were compared with the dataobtained by S.P. Gorshkov in the course of field studiesin the 1970s, 1980s, 1990s, and 2000s.

Special attention was paid to observations of spe�cific informative natural objects and phenomena.

—Stone streams. In the zones of occurrence ofactive stone streams, the specifics of local overgrowingby moss–lichen cover were studied, and the number ofunstable boulders was determined. For low�activity,closed stone streams, the degree and character of for�estation and the specifics of stand timber, in particular,the share of inclined trees, were determined. Succes�sion changes in the taiga vegetation within the rela�tively stale covers and stone�stream–defluction (blockstructures with loam colmatage) were examined;

—Soliflual deposits. The signs of weakening ordegeneration of solifluction were assessed, includingthe presence of inclined trees with vertical tops, as wellas the overgrowth of solifluction hollows–disruptionsin the above�soil cover. The cases of replacement ofsolifluction slopes and glacises on river banks by locallandslides–creeps because of a recession of permafrostroof and an increase in the instability of bank massifs;

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—Relic permafrost relief forms. the cryogenicmorphosculpture of the Upper Pleistocene forms ofsolifluction origin, the signs of thermokarst, and thefeatures of their landscape occurrence were analyzed.Analogous modern formations were sought for andstudied;

—Undergrowth of parvifoliate species (birch,aspen). The causes of explosive rise of the undergrowthof parvifoliate species in dark and light coniferous for�ests were studied and analyzed, in particular, in thehabitats that have not been typical of such before.

The changes in the resource–environmental func�tions of the natural systems of the middle taiga (at thelevel of complex stows) under warming climate wereassessed using monitoring data based on interviews offamilies of kets—representatives of a native minorityof the North. The traditional ket household is rigidlybound to landscape, and any stress situation in thenatural complex will immediately affect their self�pro�duction and social welfare, thus making the informa�tion we have collected quite reliable. The total numberof interviewed families was 25 (as was the number ofhunting areas in the hunting community of Sulomayakets; the number of interviewed people was 57, abouta half of the population of Sulomai Settlement, EvenkiMunicipal District, Krasnoyarsk krai).

Ket families, which have their heritable huntingarea, collect important data on the dynamics of catchof some animal species or the yield of berries over along period of several decades. Many kets (mostly old�timers) keep ecological calendars to record importanthydrometeorological and phenological phenomena.In the absence of a reliable monitoring system in thetaiga zone of Central Siberia, such data are of impor�tance for identifying the response of the natural–envi�ronmental resources of taiga and traditional economyof the local population to climate warming. Theauthor carried out route harvesting–resource observa�tions (during five field seasons starting from 2008),including the assessment of the yield and floweringpercent of berry�beds, the resources of food plants indifferent types of natural complexes (at the level ofstows).

RESULTS AND DISCUSSION

Climate changes. Climate warming in the CentralSiberian region has been recorded for more than30 years since the early 1980s (Fig. 2). Warming wavesseem to be due to the stronger western transport fromthe Atlantic (this is most clearly seen in winter becauseof the inflow of warm air masses) and the weaker Asiananticyclone (its western branch or the Voeikov axis)because of a considerable decline of Arctic ice cover.Here, the mean annual temperature increased by 1–2°C and more compared with the previous, colderperiod from the late 1940s to the late 1970s. Since theearly 1980s, the winter became warmer, and the spring

and autumn, longer. Years with shorter summer alsooccurred.

In the cold 1974, the minimal mean monthly airtemperature in January at Bor Settlement was found tobe –35.1°C, while that in the warm 1995 was –17.8°C.at the same time, the difference between the mean Julytemperatures in the same years did not exceed 1.7°C.The increase in the mean annual temperature in warmyears is due to both the higher temperatures in the coldseason (see Fig. 2) and the longer warm season.

Analysis of Fig. 3 suggests that the amplitude ofvariations of winter temperatures is much larger thanthose in other seasons, a feature that determines theirleading role in the annual temperature. It can beclearly seen that the last 20 years of the XX century canbe distinguished by their winter maximums. Note thata concentration of high winter temperatures falls ontothe period from the late 1980s to the mid�1990s, while,since 2009, the mean annual air temperature decreasesallove the Central Siberian region, suggesting the pos�sible end of the cycle of climate warming.

Such temperature variations can be attributed tothe character of atmospheric circulation in the middlereach of the Yenisei and the lower reaches of the Nizh�nyaya and Podkamennaya Tunguska. The low temper�atures in the cold season in the Central Siberia are dueto the onset of the stable western branch of the Asiananticyclone with the formation of inversions in winterand strong cooling of the surface layer under a thinsnow cover. With the weakening of the Asian anticy�clone and the shift of its western wedge, commonlysoutheastward, it is replaced by less stable and warmeranticyclones either of local origin or arriving from thewest, southwest, or northwest. They can significantlychange the air temperature in the mid�winter.

Characteristic features of permafrost landscapesand their tolerance to climate warming. The permafrost

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landscapes are very sensitive to climate warming,though to a different degree. Of importance in this sit�uation are their indication and the identification ofoccurrence specifics. Permafrost processes in boreallandscapes often manifest themselves under favorablesubstrate conditions, irrespective of the heat supply torelief elements. Thus, the lithological–geomorpho�logical and landscape–geographic analyses showedthat permafrost stows in the lower reaches of the Pod�kamennaya Tunguska occur in the surface deposits ofaleurite–pelite composition [5]. This demonstratesthe priority role of the lithological factor. Of greatdemarcation importance in terms of landscape is thesouthern boundary of the Upper Pleistocene glacia�tion, which separates the modern boreal natural com�plexes into the landscapes of glacial and nonglacialzones. In the glacial zone, permafrost landscapesdominate within the upper stage of the relief, wherethey occur on the summit plains, near�summit slopes,and the slopes and beds of valleys, where disperserocks overlie traprock outcrops. The situation in thenonglacial zone is different: here, permafrost land�scapes are confined to the lower stage of relief (a com�bination of erosion valley network and water�dividedepressions) because of their higher watering due tothe concentration of surface runoff, high occurrenceof subsoil water, etc. (Fig. 4). The next is the aspectfactor: permafrost lies on the slopes of cold aspect(northern and eastern) with traprock outcrops. Theseareas show higher watering, the development of stone�

stream–creep and, at the most developed stage of theprocess, peat bed increase [5]. An example of a combi�nation of several factors, leading to the formation ofpermafrost stows, is a hanging bog. Hanging bogs aremostly situated on steep near�river slopes with lowheat supply. A stone flow underlies a thin peat layer ineach such bog. The permafrost peatery shows highsegregation ice content. The most impressive are iceinclusions with a size of a walnut. The permafrost layeris overlain by ground vegetation, consisting of mosses,lichens, and dwarf shrubs with abundance of ledumand dwarf arctic birch. However, under the conditionsof global warming, the permafrost in the area canaggradate because of the longer vegetation period,resulting in a thicker peat–vegetation layer, whichserves as a heat insulator.

Our studies show that permafrost rocks manifestthemselves in different stows, which feature dystrophy,suppression, and species poverty, appreciable distur�bances of the day surface, specific soil profile with gleysigns, higher watering of soils and surface deposits,and the manifestation of cryogenic processes and phe�nomena (Fig. 4).

Thus, the key characteristics of permafrost land�scapes include

(1) vegetation character: suppressed thin taiga withappreciable tilt of trees, sparse stands and dwarf birchthickets, moss–brush vegetation with the predomi�nance of sphagnum mosses (Sphagnopsida);

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Fig. 3. Distribution of mean air temperature over seasons based on data of ZGMOS in Bor Settl. (Turukhansk raion, Krasnoyarskkrai) over 1900–2009.

WATER RESOURCES Vol. 42 No. 7 2015

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(2) specific soils: cryogenic peat–gley, alluvial–swamp with signs of gley and cryogenic skeletal(stone�stream soils);

(3) relief microforms: solifluction windows–breaks(holes–breaks) (Fig. 5), solifluction ledges, frostmounds, thermokarst subsidence;

(4) relief mesoforms and their outline: solifluctionswells (foot plumes); watered and low�mobility stone�streams; hanging bogs; ditch�type channels of creeksand rivers with land�slide signs;

(5) the state of surface deposits: viscous–flow con�sistency of disperse soils; active and watered stonestreams (individual boulders are unstable);

(6) the composition of surface deposits: moraineclays, loams, lacustrine–glacial and alluvial clays,aleurites, frozen peat, solifluction disperse deposits,highly watered boulders of stone�stream fields;

(7) higher watering of a stow due to groundwateroutcrops.

Nonpermafrost landscapes show(a) the presence of full�scale erect tree vegetation;(b) the high occurrence of hard rocks under a thin

mantle of surface deposits;(c) relatively good drainage.As to the stability of permafrost landscapes, it was

found to show some differentiation of occurrencetoward the south. If some type of permafrost stowsoccurs furthest to the south, then, other conditionsbeing the same, it can be regarded as the most tolerantto climate warming [5]. In this context, three types ofstows can be identified in the region under study bytheir tolerance to climate warming:

—low�stability stows of glacises with good watersupply and slopes with open stone flows and summitplains;

—stable stows of slopes, glacises1 and glacis–flood�

plains2;

—highly stable—polyfactor permafrost stows onslopes with poor heat supply: hanging bogs and for�ested floodplains of large rivers.

Thus the most stable permafrost stows are hangingbogs of cold slopes and forested floodplains of majorrivers.

The response of permafrost landscapes. In the lowerreaches of the Podkamennaya Tunguska, the least sta�ble permafrost is confined to the landscapes of low(200–250 m) summit plains and gentle slopes, com�posed of clays, loams with inclusion of individualboulders, and aleurolites–fine�sand deposits of glacialcomplex [3]. Common in such places are bog com�plexes with low thin (crown density of 40–50%)cedar–fir taiga with birches and larches on peaty–gleycryogenic soil with most–brush and, sometimes,lichen ground cover.

At the depth of zero annual temperature variations,the cryogenic soil is cooled to 1°C and even to frac�

1 Glacises are accumulative surfaces with slopes from a fewdegrees to a few tens of minutes, composed of decerption, solif�luction, and diluvium, forming foot plumes or occupying valleybeds.

2 Glacis–floodplain includes areas of glacises near river bed,which are inundated during spring flood, under meadow–bog ordwarf birch vegetation on alluvial–gley and peaty–permafrostsoils.

Fig. 5. Solifluction hole–break in ground vegetation filled with cold water on the surface of a high (14–17 m) floodplain of thePodkamennaya Tunguska. Water is a sign of the presence of a permafrost aquiclude near the day surface.

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tions of degree below zero. The active layer in loamsand clays is the layer of seasonal freezing and thawing,which is 0.8–1.0 m in thickness [3, 6]. Since the mid�1990s until now, the top of permafrost shifted 1.5–2 mand more down, demonstrating the process of perma�frost degradation because of the warming of its strata.

The beginning of permafrost degradation had animmediate effect on the appearance of permafrostlandscapes, i.e., the disappearance of water in solifluc�tion holes�breaks; fallen trees can be seen with theentire spreading�root assemblage torn out of the earth,because they fall more easily under wind impact, andtheir root base lost the support of the solid frozen sub�strate. The result was an increase in the occurrence ofrelief forms of biogenic origin (the so�called, iskor’s)in the landscapes of insular�permafrost subzone.Local replacement of solifluction by landslide pro�cesses was observed in the zones of intensification ofriver erosion. Because of draining, some plants, pri�marily, horsetail, lose their green color, making theground vegetation cover yellowish–golden. Smallthaw lakes with collapssed and dead forest stand.

In the basements of stone streams and detritus,called kurums, the permafrost retreats downwardfaster than in the areas of permafrost thin forest. Stud�ies in key areas show that bald�peak ice melted, smalldepressions formed, and cold subsurface creeks disap�peared in the kurums, primarily on slopes with south�ern and western aspects. The kurums overgrow withlichens, dwarf shrubs, and individual trees (Fig. 6). In

the low reaches of the Podkamennaya Tunguska R.,the kurums not covered by forest, even on slopes withpoor heat supply, on valley beds, on slopes and summitplains with elevations not exceeding 400 m, have losttheir bald�peak ice. Warm kurums are common in thenorthern part of the Yenisei Range and the westernpart of Central Siberian Plateau up to the NizhnyayaTunguska R. in the zone of Severnyi kamen' trappeanmassif, which is as close as 70 km south of the polarcircle. The permafrost on the beds of deep valleys andon steep slopes of northern and eastern aspects withlow heat supply is more tolerant to warming. The per�mafrost roof is still stable on the upper plateau of thewestern Central Siberia with absolute elevations of550–700 m.

The analysis of the collected material allows us tosuggest that protection response in the form of nega�tive feedbacks form in the kurums of the boreal taigasubzone. At the first stage, bald�peak ice melts andkurums overgrow with mosses, lichens, and tree spe�cies. At the gradual overgrowth of a kurum, fine soilaccumulates, filling gaps between boulders and form�ing more impressive soil profile A1–AB–C of browntaiga skeletal soil. The accumulation of fine earth andthe rate of kurum overgrowth were found to increase inthe zones of concentration of black cristose lichens. Atthe farther accumulation of fine earth, the brown taigaskeletal soil transforms into peaty brown taiga soil, theshare of disperse deposits and the thickness of peat–vegetation layer increase, and the watering of kurum

Fig. 6. A kurum overgrown by lichen and young birches on the right�hand bank in the middle reaches of the Bol’shayaChernaya R. (the left�hand tributary of the Podkamennaya Tunguska).

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and its isolation from the lower air layer grow. The for�mation of hanging peat bogs at the second stage isaccompanied by aggradation of permafrost because ofa growth of icy rocks.

Our studies show that in 1980–2012 in CentralSiberia, only high�temperature permafrost experi�enced degradation: kurums in all subzones of the per�mafrost zone, though not including the upper pene�plain, and the high�temperature permafrost in peliterocks—only in insular�permafrost zone and furthersouthward.

Changes in habitats. Changes were found to havetaken place in the habitats of encephalitic tick, whichhas been detected as far as 63° N [3, 9]. Ixodid (Ixodesperculcatus) have shifted 250 km northward over thepast 25 years, covering the subzone of central taiga inthe zone of our studies. The probability of tick�induced diseases increased. Tick activity has beenespecially high in the recent decade. Our interviewsshow that this worries the inhabitants of Vorogovo V.,Bor Settl. in the southern Turukhanskii raion, Sulo�main V., Kuz’movka V. in the southwestern Evenkiiskiidistrict, and other populated localities in Krasnoyarskkrai, who repeatedly request tick�borne encephalitisvaccination. Many insects in the forest steppe andsouthern taiga have been described by A.V. Kuvaev inthe lower reaches of the Podkamennaya Tunguska andthe middle reaches of the Yenisei R. in the central�taiga subzone.

In the third quarter of the XX century (a periodwith stable cold winter), there were nearly no vipers(Vipera berus L.) in the central taiga part of the Yeniseiright�bank area. The expansion of those poisonoussnakes became the topic for the local population afteranomalously warm years of the second half of the1990s, which coincides with the period of mass thaw�ing of bald�rock ice in kurums. Now vipers are almostever�present on thawed kurums.

Coney (Ochotona), which plays a significant part inthe nutrition of sables, leaves kurums. This is facili�tated by late spring cold spells and the loss of subsur�face water resources at the base of kurums.

Problems of conventional nature development. Cli�mate warming, which features more frequent warmwinters and prolonged springs and autumns had astrong effect on taiga biological resources. Thus, in1997 and 1998, there were almost no berries of black�berry, blueberry, cowberry, honeysuckle, red and blackcurrant in the Central Siberian Reserve (within one ofthe largest wildlife reserves of the planet with a sizeequal to the territory of Lebanon or Jamaica). Theiryields were also scarce in 1999, the situation remainingnearly the same now, as follows from the data of mon�itoring studies and interviews with local people. Theynote that pine nuts were difficult to find in years withcool summer and warm winter, despite the ubiquitouspresence of cedars in the dark coniferous forest. Simi�lar trends were recorded in the yield of berry beds.Thus a relationship was found to exist between the

yield of cowberry and the weight of its leaves in sum�mers of different type [4]. The weight of leaves is min�imal in warm and moderately humid summer becauseof water consumption by the growing fruits, while,during cold summers, the situation is inverse (the ber�ries are few, so they do not compete with leaves formatter); dry or very humid summer also is not favor�able for fruit formation.

Years with low reproduction of game�animalresources have become a standard, rather than excep�tion, especially in areas east of the Yenisei. This can beattributed to the higher degree of freeze�hazard of theright�bank areas as compared with left�bank areasbecause of the geomorphological features of the area:its high roughness, the presence of deep valleys, higherabsolute elevations, etc. Cold air enters the valleys;recurrent frosts in springs are more frequent. Animportant feature is the lesser thickness of the snowcover on the right�bank compared with the left�bankarea. Thaws became more frequent in the period ofclimate warming. For example, the kets, representa�tives of indigenous peoples of Siberia, note that 20–25 years ago, frosts lasted for at least a month, whilenow they last not more than 2–3 weeks. Ket’s observa�tions are supported by the data of meteorological sta�tions in the area, showing an increase in the frequencyof thaws and a warmer winter period (see Fig. 3). Theresult is the lesser thickness of snow cover, which couldnot but affect the yields of berry beds. A decrease insnow cover thickness is known to increase the likeli�ness of freezing of blueberry and blackberry. Ket hunt�ers also notice that the thickness of snow cover hasdecreased, making it more difficult to hunt for elk. Theresult is the phenomenon of “hungry taiga” observedin the two recent decades. I.I. Krupnik [7] called suchphenomena “life crises,” commenting that, accordingto interviews and chronicles, they occur in years withextreme weather conditions, which mostly accom�pany the periods of warming and climate instability.

The decrease in the life�supporting function of thefeeding landscape (as L.N. Gumilev called it) requiresus to focus on the comprehensive development of tra�ditional types of taiga nature development and theirdiversification; support of their resource and produc�tion–technological base; and the organization of pro�cessing of conventional trades [9].

CONCLUSIONS

A vast body of data was obtained suggesting thebeginning of permafrost degradation in the middleboreal subzone in the Yenisei basin (not less than 70%of the area it occupies within the ecotone).

The most significant response processes to climatewarming in the boreal landscapes of the MiddleYenisei area include

an increase in the thickness of the active permafrostlayer (10–15 cm/year within low�stability stows) andthe intensification of solifluction;

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cases of local replacement of solifluction by land�slide motion of soils in the zones of active river ero�sion;

anomalously frequent fall of trees that have spread�ing�type root systems in areas where clay soils arewaterlogged, have viscoplastic consistency, and are1.5 or more meters in thickness;

better drainage on summit plains and adjacent gen�tle slopes;

higher mobility of large boulders on kurums (NTCsthat are most vulnerable to climate warming) becauseof melting of bald�peak ice, as well as the number andarea of overgrowth spots of mosses and lichens;

depletion of subsurface streams under kurum boul�der cover;

the intensification of thermokarst processes withinswampy areas;

the deterioration of forest and game resourcesbecause of an increase in the share of birch and aspenin the dark coniferous taiga;

more frequent episodes of forest diseases and theirspreading over wider areas, poor yields of berries andpignoli nuts, a drop in the populations of game ani�mals;

changes in the habitats and northward displace�ment of some representatives of the animal kingdom(ixodids, adder, etc.);

a decrease in the efficiency of nature developmentby the local population.

The ecotone under consideration is situated in thewestern part of the Central Siberian Plateau and theeastern margin of the West Siberian Plain. Theresponse to climate warming causes changes in thepermafrost–landscape conditions, exodynamic pro�cesses, the production of natural systems and affectsthe life support of the local population. The under�standing of processes taking place in a permafrost eco�tone is of importance for assessing the changes inmodern boreal landscapes in the Northern Eurasiaand the state of its natural–environmental resourcesin the future.

ACKNOWLEDGMENTS

The author is grateful to Prof. S.P. Gorshkov for hishelp in field studies and processing the obtained mate�rial underlying this article.

The study was financed by the RF Presidents Sci�entific grant (project �7614.2015.5).

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