AN "ENCODED CHRONICLE" OF NORTHERN NATURE

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Опубликовано в библиотеке: 2021-09-20
Источник: Science in Russia, №4, 2011, C.96-103

by Yevgeniya SIDQROVA, soil scientist

 

One of the most difficult and interesting tasks of a naturalist is to understand the formative history of a present-day object of research, be it a highland district or a biological species.

 

Sharp scientific disputes have flared up on theories of the evolution of living, nonliving and bioinert bodies of nature.

 

The soil genesis, a product of longtime interaction between organisms and the mineral substrate under the conditions of a changeable climate is no exception.

 

Therefore works, in which their authors substantiate in detail their concept of soil formation and look into the "past pages" of our planet's landscapes, are most welcome. Dr. Galina Russanova's monograph, "Polygenesis and Evolution of Soils of the Subarctic Sector (with Bolshezemelskaya tundra as an example)", brought out by Nauka Publishers in 2010 (St. Petersburg) is among such publications.

 

This book is a result of research, carried out by its author at the Biology Institute of the Komi Science Center of the RAS Ural Branch in 1992-2008 and is dealing with the history of the soil cover of Nenets District, the Archangel Region and the Republic of Komi in the Holocene (the last 11,000 years).

 

Field works in harsh permafrost areas are extremely difficult. Nevertheless in the late nineteen-hundreds scientists learned much more about cryogenic soils

 
стр. 96

 

 

Map of Bolshezemelskaya tundra vegetation zones.

 

thanks to the selfless efforts of Yevgeniya Ivanova, Dr. Sc. (Biol.), of the V. Dokuchaev Soil Science Institute of the national Academy of Sciences (in 1961 elected to the Lenin All-Union Academy of Agricultural Sciences--now the Russian Academy of Agricultural Sciences); Olga Polyntseva, Cand. Sc. (Biol.), of the Komi Biology Institute, affiliated with the RAS Ural Branch; Igor Ignatenko, Dr. Sc. (Geogr.), of Leningrad State University; Viktor Targulyan and Sergei Goryachkin of the RAS Geography Institute, and other scientists.

 

One of the pioneers of such explorations was Dr. Vera Vasilevskaya, a regular participant in expeditions to Taimyr peninsula and the northern part of Western Siberia organized in 1966-1981 within the framework of the International Program "Man and the Biosphere". All her life working at the Soil Science Department of Lomonosov Moscow State University, she shared generously her knowledge with the budding scientists. Dr. Vasilevskaya has formed a school in the field of the genesis and geography of permafrost and podzolic soils and in prognostic mapping. Remarkably, she has made her last contribution to studies of northern Russia soils as executive editor of the abovementioned book. On Taimyr and in Bolshezemelskaya tundra* they are largely formed by the same processes leaving "records" in a soil profile telling about the past and the possible future of zonal landscapes.

 

"IN CAPTIVITY OF TIME"

 

The diversity of soils described by Russanova once again indicates the relativeness of tundra gley zone borders, along the whole Arctic coast from Kola peninsula to the Bering strait, a zone painted in school atlases in the homogeneous-violet color. The real picture is more interesting because the modern soil cover in these latitudes depends not only on the diversity of mother beds but also inherits the features acquired at the time when there were absolutely other landscapes there.

 

The soil science founder, the great Russian scientist Vasily Dokuchaev (1846-1903) has deduced the law of "lasting variability of soils in time and space". He named these special organomineral bodies a mirror of ambient conditions meaning that reflected in the structure of their profile and properties are not only the features of the present landscape, but also history

 

* Bolshezemelskaya tundra-a hilly moraine plain as high as 250 m above sea level within the Nenets Autonomous Okrug (District) and the Komi Republic.--Auth.

 
стр. 97

 
стр. 98

 

of its formation. Subsequently this idea was furthered in works of Dokuchaev's pupils and followers. Today Ilya Sokolov, Dr. Sc. (Agr.) (the Soil Institute), and Viktor Targulyan, Dr. Sc. (Geogr.) (Institute of Geography of the Russian Academy of Sciences), have introduced such classical terms as "soil-memory" and "soil-moment" (1976), designating the two forms of time as a soil formation factor. Beginning research into a new object, a scientist proceeding from its characters (morphological, physical, chemical etc.) seeks to identify the underlying processes, and see, which of them still hold. Just as a good doctor does examine and sound his patient, Russanova's book deals exactly with this difficult diagnostics.

 

Why is it so important to work to identify the soil genesis? Why understand the intricacies of its past and present?

 

For someone the answer may be unexpected: first of all, organomineral bodies fall ill just as biological ones do, and the cause may be, for example, oil spills, heavy metals pollution in industrial areas jet fuel spills near military objects, radioactive discharges and many other events in modern civilization. In the north of our country, where many oil and other deposits are concentrated, large metallurgical enterprises are at work; the biological circulation is rather slow there. Dire effects on nature are fairly frequent, and the aftermath is especially hard.

 

Serious problems cropped up in an attempt to clean and recultivate over 70 hectares of soil in Usinsk Region of the Komi Republic polluted by oil hydrocarbons when the main pipeline burst in 1994*; the destruction of wood biocenoses in a radius of 70 km round the Norilsk metallurgical industrial complex** was irreversible. Soils are both vulnerable and mortal beyond permissible loads, that is why it is necessary to study the "patient" beforehand, while he is "still alive" (as a 20th-century classic, Alexei Tolstoy, said). And secondly, according to some researchers, episodes of climatic fluctuations in the late Holocene (last 2,5 thousand years) may recur in connection with the predicted global warming. Hence, scientists should understand changes in processes bearing on this very important landscape component.

 

However, it is very difficult to "read" soil history without special approaches. In particular, micromor-

 

See: M. Markarova, "The Far North: Cleaning of Soil From Oil", Science in Russia, No. 5, 2006.--Ed.

 

** See: L. Leontyev, "Ecological Problem of Norilsk: Ways of Solution", Science in Russia, No. 6, 2006.--Ed.

 

phological research* is of great help here. Russanova is a big expert in this field. Her works on the micro-structure of taiga soils in the Komi Republic have essentially expanded the knowledge on their genesis. Turning to Bolshezemelskaya tundra objects, quite new to her, she spent 15 years in detailed studies of their ultrathin sections and came to interesting conclusions: some processes which have left well-formed traces in the microstructure of these soils at present cannot continue for lack of the necessary external (climatic, first of all) conditions. Which means that relicts of the bygone stages of landscape evolution are still there.

 

Russanova compared these materials with the data of spore-pollen analysis, radiocarbon dating of samples, the characteristics of organic matter. They need a special, critical approach, because even in soils buried under eolian sediments, humus is renewed (in time the microflora changes its structure, there is an inflow of organic matter brought in by surface solutions), and then the age of an object of research determined by carbon radioisotopes should be corrected. The author has succeeded in "connecting all the threads" and get a picture of the evolution of soil-forming process.

 

EXHIBITS OF NATURAL HISTORY

 

In the profile of present soils of Bolshezemelskaya tundra the relict and modern lines, the markers notorious "soil-memory" and "soil-moment", are distributed differently. Only by studying natural objects will it be possible to see such surprising examples of mutual penetration of the present and past over thousands and thousands of years of natural evolution. Let's look at them as unique museum exhibits.

 

As suggested by some scientists, Yuri Liverovsky (1933) for one, in the late Atlantic time (6,000-4,600 years ago) Bolshezemelskaya tundra up to the Barents sea coast was covered with a taiga and soils peculiar to it--podzols (their profile brightened, as if the horizon is strewn with ashes). Russanova and colleagues have detected islets of a fir forest on leeway side, well-drained terraces of river valleys; however, this forest grows on sabulous brown subsoils (podbur) not having apparent color and textural differentiation, as silt and sesquialteral ferric oxides accumulate in the top and middle parts of their profile. The thick, clayey,

 

* When the micromorphological method is used, ultrathin soil sections of intact structure (microsections) are examined with a microscope at 40-80-fold magnification.--Auth.

 
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brownish clots, amorphous for the most part, are visible under a microscope whereas in classical podzols this material "is washed off into the lower, illuvial horizon, where after a forced "journey" it is placed in the form of clay and glandular-clay layers on mineral grains. And yet soils, whose shape betokens a more active carry-over of iron oxides and other elements from the top layers, are still there in Bolshe-zemelskaya tundra, though buried under a present-day profile. The point is that a dramatic fall of atmospheric precipitation, and that against the background of negative temperatures in a cold snap (3,200-2,200 years ago), intensified an eolian carry-over of dust particles, and an upper level was added to podzols which appeared out of the line of woods that receded to the south.

 

Similar multilevel profiles in Bolshezemelskaya tundra are formed not only on sandy, but also on clayey, more deep-frozen soils. It is very difficult to find* high-quality "exhibit": Evidence of the past evolutionary stages kind of "shade" the phenomenon of cryoturbation when horizons take the form of eddies, bends and rings with the thawing of the organomineral mass; it froze in the wake of superfluous humidification. Russanova has found and described the soil formed during the Atlantic time and preserved thanks to the "screen" of sediments, as a result of water erosion and solifluction**. This relict object has been conserved 50 cm deep.

 

This is a typical podzolic sod soil: the aggregative features in its top horizon, humus microforms, characteristic dark stains and roundish biopores studied under a microscope at 70-fold magnification are its positive proof. Besides, according to chemical analy-

 

See: G. Russanova, "Bolshezemelskaya Tundra (Cold Desert): Flashback", Science in Russia, No. 1, 2007.--Ed.

 

** Solifluction--slow movement of soils and loose ground under the effect of alternate freeze-thaw periods and gravity, taking place mainly within frozen rock areas.--Auth.

 
стр. 100

 

sis, its organic substance is a product of taiga soil formation. On top of all, there is the illuvial horizon, easily identifiable by fine-dispersed sinters in micro-sections: pores and channels in structural jointings (all of the material aggregated) are filled by clay, and their surface "dressed" by membranes of two or several layers (dust on clay). Proceeding from long-term observations and literary data, the author proposed: Textural differentiation of buried soil proceeded in the late Atlantic time, when the mean July temperatures were by 3-4°C higher compared with the present ones, the precipitation total was 100 mm higher, and the border of cold-resistant broad-leaved trees--an elm, for example, extended further north. Then came the cold snap of the subboreal period and the well-nigh formed profile started degrading. Such are the episodes of the Holocene climate.

 

MUTUAL PENETRATION OF THE PAST AND PRESENT

 

These multilevel objects of Bolshezemelskaya tundra occur side by side with profiles superposed on one another. Researchers come up against great difficulties there. For example, under the recent brown subsoils (podbur), 8 to 30 cm deep, are podzols of the Subatlantic age (2,200 years ago), formed in the same

 
стр. 101

 

layer where before that, in the middle subboreal interval (4,300-3,200 years ago), podzols with a well-expressed illuvial horizon had taken body and form. A similar combination of soils of different ages can be explained by the low accumulation rate of Aeolian sediments; that is why the separating layer, serving as a "crosspiece" in "many-storeyed" objects, could not be formed yet.

 

Another variant of the combination of the modern and inherited signs in "a diurnal" soil profde is the preservation of humic soil genesis relicts (fragments of more ancient soil material, including "the conserved" parts of an extinct horizon). They can be detected at an microlevel only. The formations described by Russanova are represented by dark clots on the surfaces of mineral grains or within structural jointings. As to the recent organic substance, it occurs at the same depths in complexes with mineral components and, morphologically, is identified as fdms under a microscope.

 

There are other variants of polygenetic "exhibits" in Bolshezemelskaya tundra, too. Experts believe lowland eutrophic* peat deposits in the subarctic region are a suite of buried soils. Russanova has studied in detail a peatbog on the lakeside terrace in the river Vorkuta basin and has established that its formation began 8,000 years ago under the cover of woods. The rates of organic substance accumulation were the highest then--about 1 mm a year. However, 6,290-5,010 years ago the gain slowed down to 0.4 mm a year because of the higher intensity of biochemical and microbiological processes of decomposition. A sudden dramatic cold snap and lower humidification 3,200-2,200 years ago caused a further decrease in the peat accumulation rate down to 0.1 mm a year.

 

A stratigraphie analysis of the paleobotanical structure and radio carbon age dating of the peatbog allowed the author to restore the chronology of Bolshezemelskaya tundra soil evolution in the Holocene, even though development stages of sandy and loamy objects differ somewhat.

 

For sandy soils the reference point is warmer middle subboreal period (4,300-3,000 years ago). Under the taiga canopy classical podzols were formed then.

 

* Eutrophic (lowland) bogs-a type of bogs with rich water-mineral alimentation by groundwater for the most part. They are located in flood-plains, along the shores of lakes, in the places of the springs in low places.--Auth.

 
стр. 102

 

But 3,000-2,200 years ago it became colder, the woods fell back, and cryogenic deformations of soils and their burial under aeolian deposits set in. In the warm phase of the middle subatlantic period (2,100-1,700 years ago) the situation recurred, and the repeat process of podzol formation came to an end only 1,000 years ago, when the present brown subsoils became a basic "product" of combined interaction.

 

On loamy deposits the best conditions for humus formation and carry-over of silt-dust aleurites were available at late atlantic stage (6,000-4,600 years ago). Sod-podzol soils were formed then. However, in the subboreal period (4,600-4,300 years ago) a harsh cold snap touched off their degradation and burial as a result of solifluction freeze processes and sedimentation. In the warming phase (4,300-3,000 years ago), modern soil formation processes must have set in. And at the end of the subboreal period and during the subatlantic period (over the last 3,000-2,200 years) they definitively took shape in the form of gley soils characterized by anaerobic water conditions, that is why compounds of iron and other elements stay here in the reduced form and impart a bluish color to the profile.

 

FEWER "BLANK SPACES"

 

The author's conclusions largely fall in with the present views, on soil formation evolutionary processes that took place in the north of the Russian plain in the Holocene. But a wealth of analytical material on tundra soils, collected by Russanova, allowed her to rank them in evolutionary series for the first time ever. Besides, she studied in detail the specifics of processes in the ecotone (boundary) wood-tundra zone, during the Holocene, a zone that changed shape many times and "memorizing" its eventful history thanks to the conservative component of a landscape, the soil.

 

The objective picture of natural life is fleshed out the more we know about it. There are still many "blank spaces", including soils and landscapes in the north of the Russian plain--that is why such works are so important. In soil science the ability of an inquisitive scientist to synthesize depends on his or her outlook and grows with research into new objects. This calls for broad experience in field studies, and an ability to navigate in a huge data array. The author of the book under review, a research scientist of great involvement and experience, does certainly have all that.

 

As the executive editor of this book Vera Vasilev-skaya, on being quizzed by the questionnaire of Lomonosov Moscow State University graduates ("Self-Portraits of the Generation of Biologists of Moscow State University in 1950-2000"), what she considered a basic contribution to science, said: "Study of poorly explored areas." This is a job of work calling for great selfless application and intellectual involvement. To Russanova, the author of the monograph we have reviewed, it was her life work. We cannot but admire women-scientists, who have given themselves up to the exploration of the harsh nature of the Far North.


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