Lumbricoid fauna of cryosolic soils of Yakutia.
Lumbricoid fauna of earthworms of cryosolic soils of Yakutia is represented by one specie Eisenia nordenskioldi. Main areal of this specie covers Asia part of Russia (from The Far East to Ural). On the north is extends to the banks of Arctic Ocean [15,3,2].
It is one of the few species of Lumbricidae that inhabits the regions of permafrost . The most frequent form in conditions of Yakutia's cryolite zone is soil and litter form [15,11,17].
But lumbricoid fauna of many regions of Yakutia haven't yet been studied. There are also a few works accounting Lumbricoid fauna as a component of soil mesofauna of cenosises. In the course of research ecological profile across Lena River has been set. Automorphic (native shore), semihydromorphic (slope) and flood lands' soils (near terrain, central and near river bed parts of flood lands) were objects of research. Sides with radically different soils and vegetation were selected as points of observation of earthworms, starting from the most dry habitats with weak spoils to well wetted, fertile and further to overwetted places.
G.T. Belimov article "On distribution and hibernation of earthworms in middle course Lena valley" covers first researches of earthworms of Yakutsk district. According to observations lumbricids typically inhabit upper layers of turfy meadow and humus meadow alkaline of sandy and sandy-load and loamy soils under gramineous and rich in herbs vegetation. The greatest abundance (25-30 pieces/[m.sup.2]) was observed in July in meadows with normal wetting. Diapause state of earthworms lasts for 7 months (from the end of September till the first days of May) and this process is caused by the course of autumn and spring. In Yakutia conditions they easily resist winter freezing as low as t = - 14-21 [C.sup.0] .
There are also some scattered works of different times covering earthworms of tundra and taiga ecosystems of Yakutia [15,18].
We have researched earthworms in cryosolic soils of tundra, middle taiga, alas, flood land ecosystems of Yakutia [10,17]. Morphologic and ecological groups of earthworms have been defined, their distribution in different natural and climate zones, correlation between abundance of lumbricids, features and ecological conditions (regimens) of different soil types have been revealed, etc. .
The aim of the work is to reveal the mail functioning patterns of earthworms Eisenia nordenskioldi,  that inhabits various cryosolic soils of tundra, taiga, alass and flood and meadow land ecosystems of Yakutia.
1. Material And Research Methods:
Description of research region:
Sakha republic is situated in north-eastern part of Sibaria. Yakutia is the largest subject of RF.
Total area of continental and insular (Lyakhovskiye Ostrova, Anjou and De Long Islands that are the part of Novosibirsk islands of Arctic Ocean) Yakutia is 3103.2 thousand [m.sup.2]. More than 2/5 of the territory lies within the Polar circle. Yakutia spreads in latitude over 2500 km and in longitude is over 2000 km.
Yakutia is characterized by variety of natural conditions and resources that results from physiographic position of its territory. Most part of the territory--over 2/3 of it is covered with mountains and plateau that and only 1/3 of the territory lies in lowlands.
Almost all continental Yakutia is the zone of continuous centuries-old frozen subsoil that and only in the most southern part it is distributed discretely. Average capacity of frozen layer of about 300-400 m and in Vilyuy River basin it equals 1500 m. It is the greatest layer of frozen rocks in the Earth.
Yakutia has acutely continental climate that is characterized by long winter and short summer periods. Greatest amplitude of average temperature of the coldest month--January and the most warm--July is 70-75 [degrees]C. The republic has no analogous in North hemisphere in absolute value of low temperature (up to minus 700C in eastern mountain range in hollows, pits and other low areas) and its total duration (from 6.5 to 9 months a year).
Yakutia territory extends over four geographical zones--taiga forest (about 80% of territory), tundra, foresttundra and arctic desert. Dahurian larch is the most frequent tree (85% of forest area). Pine tree, dwarf Siberian pine, fir tree, birch, aspen grow almost everywhere and Siberian cedar grows in southern regions and fragrant poplar and Chosenia in mountains.
Objects and methods of research:
We have been researching abundance of earthworms in cryosolic soils of Yakutia in 1993-2010. Results of quantitative research in soils of tundra, middle-taiga, alas, flood lands ecosystems are summarized in the present article. Besides we analyze material gathered near settlements.
Cryosolic soils of three geographic zones of Yakutia: taiga forests, tundra and forest-tundra were objects of research (see Fig. 1).
Collections of local populations of earthworms Eisenia nordenskioldi  were material of research. Specie was defined according T.I. Vsevolodova-Perel's definition .
Materials gathered in route researches were used for comparative characteristics of lumbricide of different soil types. Earthworms' population structure, correlation of hydrothermic conditions and earthworms abundance were studied in semiportable lab. About 900 soil samples had been taken with more than 6 thousand specimen received from them. Morphologic and ecological types (life forms) have been analyzed.
Sampling of earthworms was done manually by generally accepted methods . Soil samples dimensions are 50x50x40 sm. Soil was sorted manually in layers 10 sm thick. Number of samples in each test was not less than 10 (June-October). Statistical technology was applied.
Lumbricidelogical tests were carried out on 18 types of soils. 50 soil cutting were made and sampling of 900 samples. Granulometric composition and physicochemical characteristics of soils were defined in accordance with methods accepted in soil science. Analysis was made in laboratory of Soil Science and Agricultural Chemistry Institution of Agricultural Branch of the Russian Academy of Sciences in Novosibirsk and in the Republican Design and Exploration Agricultural Chemistry station of Nature Conservation Ministry of Sakha Republic .
Research results were processed by variation-statistical and correlation analysis ("Statistika" software).
2. Research Results:
Digging and route research in soils of tundra, middle-taiga, alas, flood land ecosystems allowed us to observe one species of earthworms Eisenia nordenskioldi  that was represented by two morphologic and ecological forms (soil and litter and burrowing). The greatest abundance of earthworms was observed in Central and South-West part of Yakutia. The farer from polar latitudes (72[degrees] North) and closer to boreal temperature zone (51[degrees] North) the greater is abundance of earthworms .
Earthworm Eisenia nordenskioldi  is also usual but rare in settlements' regions and belong to soil and litter earthworms. Belonging to another than typical form morphologic and ecological group is has the possibility to inhabit the same biotopes , but in conditions of cryolite zone of Yakutia both forms are being observed only in flood land cenosis and rarely in watersheds .
Singulary finding of Eisenia nordenskioldi  were made on the banks of Vostochno-Sibirskoye Sea, Bolshaya Nerpichia lake near Pokhodsk settlement of Nizhnekolymsk region and in Khromskaya bay of Allaikhovski region.
Lumbricoid fauna of tundra cryosolic soils is represented only be soil and litter forms (2-4 specimen/[M.sup.2]).Lumbricoid fauna of alas ecological systems of Central Yakutia is highly scanty. We have researched cryosolic soils of alas ecosystems of interfluves of Lena and Amga and interfluve of Tiung and Tiukyan rivers in left-bank part of Vilyuy River. In middle zones of these alases life conditions (wetting, density) are better for lumbricide. Mechanical composition of soils here is light loamy. All described specimen of earthworms belong to soil and litter morphologic and ecological group.
In alas bog soils of interfluve of Lena and Amga volume weight across the whole profile varies from 0.71 to 1,05 g/[sm.sup.3]. Soil moisture varies from 49.77 to 77.17 %. These indicators show optimal life conditions of all invertebrate inhabitants of alass soils of low zone including earthworms.
Research of earthworms in alas soils showed that their abundance varies in the range 11-16 specimen in boggy over-wetted soils, 25-53 specimen/[M.sup.2] in meadow optimal wetted soils. In soils with insufficient wetting (cryosolic alas meadow-humus) earthworms are absent (see Table 1).
In flood lands of middle Lena valley the greatest density of earthworms is characteristic for biogeocenosis of central flood land. The most favorable conditions for earthworms are developing here in cryosolic alluvial turfing humus soil.
In flood land earthworm abundance is caused by wet well drained soils with light mechanical composition. Greatest density (85 specimen/[M.sup.2]) is observed in near river bed and central parts of flood land. In upper parts of near river bed flood land density is lower (53 specimen/[M.sup.2]) due to worse soil wetting. Lowering of density of earthworms in central flood land is caused by heavier mechanical composition of soils. In near terrain part unfavorable conditions for proper soil animals (burrowings) develops that is manifested in lower density of this morphologic and ecological groups of earthworms in general.
Research of biotopic distribution of earthworms in natural forest cenosis had shown that the greatest density of those is observed in cryosolic soils of South-West of Yakutia.
The greatest number of lumbricide among taiga soils is observed in humus-carbonate (56 specimen/M2) and sod-carbonate (26-43 specimen/[M.sup.2]) soils under coniferous forests and mixed forests.
These soils are characterized by high content of organic matter, close to neutral medium reaction, saturation of soil absorbing complex with bases and soil wetting in the range of HB (semihydromorphic soil) that is optimal for earthworms functioning. These soils have automorphic positions in spacial distribution and they are wetted mainly due to atmospheric precipitation. So upper layers are often affected by typical for Yakutia drought periods.
Absence of burrowing earthworms in tundra soils of Yakutia is caused mainly by close bedding of permafrost's rocks, overwetting and poor aeration of soils. Overwetting of upper layers of soils and severe thermal conditions are limiting factors for earthworms functioning in soils of hydromorphic type. In soils that were analyzed biologically active temperatures are almost absent . Physicochemical characteristics of soils (acid and strong-acid medium reaction, exchangeable cations' compound, heavy granulometric composition) are not optimal for earthworms functioning. Dietary intake, low content of fossils are addition unfavorable factors of lumbricide functioning.
Comparative analysis of alas meadow soils of alases Lena-Amga and Lena-Vilyuy River interfluves showed that the most optimal conditions for earthworms functioning develop in meadow soils of alases of Tiung and Tiukyan rivers' interflude. These alases develop on medium loamy deposits, they are better wetted, soils contain great amount of humus and are saturated with exchangeable cations. Content of lumbricide in interflude of Lena and Amga rivers are significantly lower. This results from low exchangeable cations' capacity and lower wetting of soils.
Burrowing earthworms inhabiting flood land biogeocenosis of cryosolic alluvial soils are characterized by capability of using all soil profile from litter to pedogenic rock. This morphologic and ecological group of earthworms Eisenia nordenskioldi  actively use soil humus as food. Burrowing earthworms are less active than earthworms of litter and soil forms, poorly pigmented and have cylindrical form .
So integrity of soil covering and the absence of factors limiting earthworms distribute in this or that part of soil profile is necessary conditions of their living . In flood lands' biogeocenosis these are light mechanical composition of near river bed soils, overwettting in near terrain soils as well as salification processes in some parts of central flood land. So morphologic and ecological group of burrowing earthworms Eisenia nordenskioldi  inhabiting flood land cryosolic soils of Yakutia may be considered as an indicator of integrity of soil profile.
In middle-taiga earthworms in watersheds tend to north oriented slopes. It is caused by hydrophilous nature of this specie. So on northern slopes of watersheds favorable hydrothermal conditions for earthworms develop.
High abundance of earthworms on watershed of middle-taiga is highly dynamic and varies significantly during single season and is characterized by instability from year to year. So it is difficult to reveal strict fidelity of earthworms to a certain type of biogeocenosis if it exists. Most likely earthworms in general prefer forest type of vegetation and in favorable even short wetting conditions may reach high density in forest assemblages of the region that differ in typological indicators. High migratory capability of burrowing forms of morphologic and ecological group may promote this situation.
Extensiveness of the territory and related to it heterogeneity of natural conditions of researched region led to irregularity of distribution of earthworms in cryosolic soils of Yakutia with tendency to habitats with regular wetting, temperature and food regimen.
Morphologic and ecological group of burrowing earthworms Eisenia nordenskioldi,  inhabiting cryosolic soils of flood lands and watersheds of Yakutia may be considered as indicator of integrity of soil covering.
In the long term obtained materials may be used as biological indicator for evaluation of the level of anthropogenic load on biogeocenosis as in organization of ecological monitoring. Complex research of all main indicators of cryosolic soils is required for this purpose.
Hereinafter revelation of distribution of earthworms will all information about the fauna of cryosolic of Yakutia and significantly extend existing information on distribution of this specie in the territory of the North of Russia that is important from the point of view of inventory and preserving of biodiversity of soils of northern regions. Obtained results may give view of mechanisms of dispersion and development of earthworms' fauna in northern latitudes and on the specifics of lumbricide ecology in zonal and anthropogenically disturbed soils of the North.
Received 15 April 2014
Received in revised form 22 May 2014
Accepted 25 May 2014
Available online 15 June 2014
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Vasily Boeskorov and Grigory Savvinov
M.K. Ammosov Research Institute of Applied Ecology of the North North-Eastern Federal University, Lenina 43, Yakutsk 677980, Russia
Corresponding Author: Vasily Boeskorov, M.K. Ammosov Research Institute of Applied Ecology of the North NorthEastern Federal University, Lenina 43, Yakutsk 677980, Russia
Table 1: Statistical parameters of lumbricide content in alas soils. Soil type, alas M  m Lim [sigma] M  t0, 95m V,% Alas humus fen soil 16  2 0-28 9 12-20 56 (alas Siullyakh) Alas meadow boggy 11  2 0-32 9 6-15 86 soil (alas Timofie) Alas meadow-humus 53  5 7-89 22 42-63 41 alkaline soil (alas Muosaany) Alas meadow soil 32  6 0-78 25 20-43 80 (alas Muosaany) Alas gleyey soil 32  3 0-50 15 25-39 46 (alas Angala) Alas meadow gleyey 25  2 10-37 8 21-29 33 soil (alas Angala)
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|Author:||Boeskorov, Vasily; Savvinov, Grigory|
|Publication:||Advances in Environmental Biology|
|Date:||Jun 1, 2014|
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