by Boris BELASHEV, Dr. Sc. (Tech.), Senior Research Assistant of the Institute of Geology, RAS Karelian Scientific Center (KSC), Viktor BOLONDINSKY, Cand. Sc. (Biol.), Research Assistant of the Institute of Forest, RAS KSC (Petrozavodsk, Republic of Karelia)

Karelian birch, an ecological form of the drooping birch (Betula pendula Roth.), named in 1857 by Karl Merklin, a prominent Russian botanist, corresponding member of the Imperial Academy of Sciences, is known worldwide thanks to its anomalous form of branches and the trunk and a unique patterned wood grain. These external and internal declinations from the norm and their nature are well studied by scientists. However, there is still no common standpoint in the scientific fellowship on the reasons of their formation. Some specialists think they are a result of bacterial and viral attacks, others claim chemical composition of soils. Still others insist on chromosomal mutations, emphasizing that 100 percent characters of "Karelianey" are not inherited by tree seeds. The fourth support a cryogenic theory of origination of this rare species, according to which declinations are a result of light frosts on a young common birch. Authors of this article tend to support of mutagenic impact of a radioactive gas (radon) coming from the lithosphere.

Karelian birch (Betula pendula Roth. Var. carelica Merci.) is a bush or a tree up to 25 m high with a trunk with typical thickenings in the form of swellings and small tumors noticeable under a thin bark of young trees or big urceolate formations and burrs with isthmuses in between. Its main structural character is a dense patterned wood of the stem, first of all, with surface hollows--a pitted structure. This phenomenon was also identified in sugar maple, pine, alder, and other species, but it is most brightly conveyed in the Karelian birch. It has no equals among other leafy species by beauty of its pattern. It was used to decorate chambers of tsars and palaces of grandees and got its nickname--a "royal tree".

Wood grain of the Karelian birch has dark inclusions of different shape, bright "curls", and wavy bending annual layers. Heterogeneity is formed due to growing of the bark in cambial rings, and accumulations of medullar rays in the parenehima (soft tissue, one of the primary in the stems of plants, leaves and fruit pulp). The reason of anomalies is considered to be differences in cambial activities around the trunk. Attenuation of its activities results in putting aside of wood of parenchymal (roundish) elements in place of tracheal (tubular) ones. Clusters of the former make trunks tuberculate. Ornamentality and parenchymization of wood become more evident in the course of passing from

*Cambium--a formative tissue in stems and roots, generating secondary conductive tissues and ensuring their growth in thickness.--Ed.

arborescent to bushy and frutescent forms. The progeny is split into patterned and regular species in 1:1 ratio.

The area of distribution of the Karelian birch, which makes a small part of the area of a pendulous birch, is in the north-western part of Russia, including Karelia, Leningrad, Yaroslavl, Vladimir, Kaluga, Bryansk regions, Baltic countries, Scandinavia, Belarus and Ukraine. Sometimes it is found in Poland and Germany. The northern boundary of this area corresponds to the isotherm of 16 °C. According to the classical studies of the famous biologist and plant physiologist RAS Corresponding Member Yuri Gamalei, it is a temperature limit where transport of sugars from leaves to the trunk becomes less active. The southern boundary of the area of distribution is more difficult to explain. Some researchers associate it with soil fertility.

The Karelian birch grows on soils of different composition. In our republic, Leningrad Region, Baltic countries, and Scandinavia, it can be found on moraine boulder loamy soils, sandy soils with carbonates, in places with a hilly terrain. Productive plantations are found on fresh loamy or sandy soils.

This mysterious tree does not form forests, it grows isolated or in small groups. Within the area of distribution, trees can grow tens and hundreds of kilometers away from each other. However, there are areas numbering up to a hundred and more trees per one hectare. In Karelia this rare species grows in grass-gramineous, wood-sorrel, blackberry, and stony forests.

It is not easily found in nature, is lower than pendulous birch, its crown is sparser, and bark--rather rough. Wood grain of such trees is established obliquely by bulges on the trunk, patterned nature--by a relief pitted surface and ellipsoidal recesses somewhat stretched along the trunk after removal of the bark. On the inner side of the bark, there are keel-shaped bulges corresponding to the size and form of pits.

Woody fibres grow at different angles, which makes a cut wavy, curly and originally colored. A decorative part of the tree is usually its lower section. Upper parts are less patterned the plane surface of the trunk and branches predominate there. However, sometimes thickenings are found there too. On rare occasions a section with a decorative wood grain can reach 10 m. The transition from arboraceous to bushy forms is accompanied by changes from big to small patterns.

The Karelian birch is characterized by a wide variety of forms even within one area. Scientists identify a long-stemmed, short-stemmed and shrubby (by growth form), patterned and ribbed (by surface of the trunk) forms. There are forms failing to match a conventional classification: giant bushes, dwarf trees with spherical or cylindrical "burrs" on branches, lyrate trunks with a spiral ribbing, bushes of 10-12-year-old wood without any signs of "Karelian origin", and a numerous transitional species. Natural micro-populations are usually represented by trees of different configurations. Diversity of forms proves a unique variability and plasticity of the Karelian birch, its adaptation capacities.

The life cycle of bushy and short-stemmed trees is 40-60 years. At the age of 3-5, first patterns appear, which form and develop in the course of a generative

period and slow down by 30-35 years. Patterns and high density of wood pulp are determined by a rate of division of cambial cells, saccharose content in floema (conductive tissue of vascular plants, which transports products of photosynthesis), inability to excrete sugars, reserving metabolites in forming parenchymal cells.

Adaptation CO₂ absorption mechanisms allow the Karelian birch to effectively use solar radiation in terms of competition, stress, soil and atmospheric draught. In hot days, given a wet soil, evaporation of water per unit of leaf surface of 8-year trees under consideration is about 80 percent less as compared with a pendulous tree, which is explained by a hampered movement of water along the trunk with anomalous wood. At the same time, the photosynthesis level is almost the same as in the pendulous birch due to metabolism. In two-year old species structural changes are not so evident, and difference in evaporation of water is insignificant. In terms of soil draught, when normal trees save water, the Karelian birch consumes water rather rapidly due to failures of water processes and photosynthesis. In the habitat of this valuable species, where long-term draughts are quite rare, taking into account potential limitations of growth, the risk of water loss is justified. Wasteful consumption of water during a long draught accompanied by high temperatures results in mortality of shoots. These experimental facts somehow explain location of the southern border of its area of distribution and frequency of its occurrence in the regions with their aridity.

There is a number of hypotheses explaining the origin of the Karelian birch. Proceeding from its ability to grow in mountains, on rocks, bleached and stony soils, it is considered a relic preserved on the hills formed by glaciers. Wood anomalies are explained by individual peculiarities of the development and diseases affecting a plant genotype, and an "abnormal" development of the pendulous birch under bacterial and viral attacks. Deputy Director of the Institute of Experimental Botany of the National Academy of Sciences of Belarus Alexander Pugachevsky together with his colleagues regard "Karelian nature" as a result of the impact of frosts on a common young birch. Head of the Laboratory of Physiology and Cytology of Woody Plants of the Institute of Forest under the RAS Karelian Scientific Center Lyudmila Novitskaya and her students experimentally

proved: formation of structural anomalies of wood and bark is a result of increased contrations of transported sugars in tissues and disorders in the rhythms system of cambial activity.

Specialists made attempts to tie up the anomalous activity of cambium and soil composition by growing the pendulous birch from seeds on the substrate of old Karelian birches exposing them to mutagenous substances. Deviations from normal growth of two-year old trees and electromagnetic radiation identified in 3 Karelian birches near the city of Elgava (Latvia) allowed the Latvian researcher Verners Banders to speak about the effect of radiation background and electromagnetic fields on growth processes of the pendulous birch as early as in the 1960s.

The attractive element of this hypothesis is that it coordinates anomalies of woody plants and tectonic manifestations. Among the abiotic factors (of inorganic nature) of such environments capable to affect the plants are: radioactivity, electromagnetic fields, flows of fluids: hydrogen, methane, carbon dioxide, and radon. The latter (²²²Rn)--a colorless tasteless inert gas, 9 times heavier than air, soluble in water--is of special interest.

Like its "parents"--uranium (²³⁸U) and radium (²²⁶Ra), radon is an alpha radiator with a half-life of 3.82 days, generator of a series of unstable daughter isotopes of lead, bismuth, polonium and thallium-sources of α-, β-, and γ-radiation. Inert gas together with its decomposition products and water get into the plant via roots and cause mechanical damages, stimulate generation of stress proteins and intensive division of cambial cells. Radioactivity destabilizes the biological environment towards mutagenesis and formation of species. Thus, location of forest belts (narrow, long, twisting forest areas on the foothills) in Altai coincides with fractures of the earth's crust along which emissions of radon are registered. An unusually high frequency of burrs, "witches' brooms" (plant disease characterized by formation of numerous thin springs, mostly unfertile, usually growing out of dormant buds) makes it possible to assume: anomalies are of mutant, not infectious character.

Our task was to study volumetric activity of radon in areas of natural growth of the Karelian birch and mani-

festations of structural anomalies in other plants. In 2010-2012, we carried out measurements 50 km away to the north from Petrozavodsk, 2 km to the west from the settlement of Konchezero near the lake Gabozero in the village of Vendery, Kondopoga District. Additional sampling was carried out in the outskirts of the capital of Karelia in the settlement of Solomennoe, where the so-called Solomenskaya breccia (agglomeration tuff)*, extending from Lake Onega southeast to the island of Munak, starts.

Selected plots are located on the western coast of Lake Onega in a 100 km belt at a similar distance from each other. Traces of tectonic and volcanic processes have preserved in this territory. Paleovolcanic manifestations are represented by lava volcanic fields, alternating streams of different types of basalts interlaid by ash and tuff agglomerates. Cracked structure of the cover forms transportation channels for endogenic fluids. In the Onega structure, there were discovered uranium-vanadium and shungite deposits**, areas of discharge of radionuclides to the day surface; volumetric activity of radon is also high there.

Radiation measurements were effected using a scintillation radiometer SRP-68, seismic radon station SRS-05, detectors SIRAD M 106 N and gamma spectrometer SGS-200. Radon detectors were placed in holes 0.4-0.6 m deep with narrow vertical channels of the same length. To prevent ingress of moisture, they were covered with polyethylene and turf. To study natural radio-

* See: A. Prokhorov, Ye. Platonova, A. Lantratova, "Gardens on the Rocks". Science in Russia, No. 3, 2009; L. Kuleshevich, "History Silent, Stones Speak". Science in Russia. No. 5, 2010.--Ed.

** See: Yu. Kalinin. "Ecological Potential of Shungite", Science in Russia, No. 6, 2008.--Ed.

activity of soil and indigenous rocks, samples were crushed to 5 mm, dried to a stationary mass, weighed and put into special containers, and according to the measurement results calculated their specific activity.

Samples taken in the immediate vicinity of the roots of a Karelian birch growing near Konchezero showed mostly 250-350 Bq/m³. Within a 100 m-coastline line of Gabozero, the registered values were 150-190 Bq/m³. In the late summer of 2012, increased values up to 600 Bq/m³ were recorded, which was the result of seismic activity. Background values also increased to 350-400 Bq/m³. Increased concentrations of radon in soil (up to 500 Bq/m³) were also registered in the southern outskirts of Petrozavodsk, i.e. tectonic activity affected a vast territory. This fact means that the concentration of inert gas in soil may increase manifold within one season. Much of it is consumed by plants together with water available in soil. Measurements carried out by the Karelian geophysicist Alexander Savitsky on the Zaonezhsky Penin-

Map of prevalence of the Karelian birch, deposits and ore manifestations of uranium and radon-bearing areas. Red circles--frequency of occurrence (small diameter-- 1-2 trees/ha, big--over 10 trees/ha). Black triangles: small triangles--uranium ore manifestations, big triangles--deposits. Blue line-borders of radon-bearing areas.

sula (northern extremity of Onega), where this valuable species is common, showed high values of radon exceeding manifold our results. Thus, near the Church of the Veil making part of the world-famous religious and historical center Kizhi (18th-19th centuries), scientists registered concentrations of ²²²Rn over 10 kBq/m³, on the islands of the Kizhi Archipelago and other territories of Zaonezhye--up to 31 kBq/m³. There are deposits of shungite and a major uranium-vanadium field "Srednyaya Padma" on the peninsula. Volumetric activity of radon in the drifts of mountain workings exceeds 1,000 Bq/m³, in potato pits--300-700 Bq/m³. External radiation background at the level of 1 m from the daytime surface measured by the scintillation survey radiometer SRP-68 did not exceed 10 mck/h, and in general the radiation environment was safe. It is characteristic that similar values were registered by researchers of the Belorussian anticlise and Pripyat deflection (thickness of sedimentary and volcanogenioc-sedimentary formations), where Karelian birches are also predominant.

After comparing the tectonic diagram of the Onega structure with the maps of the area of distribution of the Karelian birch, it was established that natural habitats of this species in Karelia to a considerable extent coincide with tectonic zones and areas of emission of radionuclides. It is particularly evident in the Onega area with its uranium polymetallic deposits and prevalence of this valuable species. On the contrary, in the south-eastern part of the Pudozh District, quite big in area, no radionuclides have been registered there except for a narrow strip along the eastern bank of Onega, large fractures and areas of emission. Consequently, the Karelian birch is rather rare there.

Surveys of seismic and radiation conditions in its natural habitats are also of great help to find a key to its origin. A geological history of the region plays an important role here. It is clear that the concentration of radon in soils with uranium deposits is still very high. The species under consideration, like other woody plants with different anomalies, frequently occur in such areas. But such phenomena happen in other regions too, but there they are occasional, sometimes localized, and sometimes rather evenly distributed along the territory and are not numerous. Concentration of subsoil radon in these places under normal seismic conditions does not exceed 200-300 Bq/m³. The probability of its dissemination using seeds away from its concentration area is very low. It is likely that the identified trees are residual samples of populations formed hundreds of years ago when radiation was much higher. After deglaciation of Karelia and the Leningrad Region, there happened earthquakes of magnitude 8. The last major event that caused grave damages on the

Onega Peninsula was recorded in 1542. The discharge of tectonic energy in pre-fractures and other stressed areas was accompanied by emissions of methane, carbon dioxide and helium forming radon aerosols. It is well-known that concentrations of radon in a period before and after earthquakes may increase hundreds of times.

At the same time, natural seed propagation of the species is insignificant even in places with high concentrations of subsoil radon. Mutagenic processes in the pendulous birch do not have a considerable effect on the increase of population of the Karelian birch. Perhaps, this is connected with a sizeable reduction of its number. Starting from the first half of the 19th century, the number of this species, growing in the natural environment, has been constantly decreasing in Karelia. While in the 1920s-1930s Nikolai Sokolov, the first scientist to take an inventory of the Karelian birch in Russia, professor at the Leningrad Forest Technology Academy, registered about 7,000 trees, after the excessive cuttings of 1941-1944 in the time of occupation of the republic the number of trees decreased and is still rapidly decreasing. Nevertheless, surveying of functioning and development of the mysterious tree of the North in the territories characterized by high concentrations of radon could lift the veil of secrecy and offer valuable data for its artificial growing.

The prominent researcher of anomalies of woody plants, professor of the Moscow State University Vladimir Korovin who dedicated over 50 years to this problem, wrote: "The Karelian birch is still 'taking scientists in'. It is absolutely unclear why such non-specific structural anomalies occur, what are they, what are they for? Most likely these anomalies are regarded as such, as we do not understand them. We are facing a great many of pending questions. That is why we are eager to find a key to the problem and no doubt, a lot of important discoveries are in store for us."

Illustrations supplied by the authors