OUR CHANGING FORESTS

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Опубликовано в библиотеке: 2021-10-08
Источник: Science in Russia, №4, 2012, C.20-27

by Andrei SIRIN, Dr. Sc. (Biol.), RAS Corresponding Member Lev RYSIN, Anastasiya GULBE, Cand. Sc. (Biol.), RAS Institute of Forest Science (Moscow Region)

 

Forest cover is an integral part of the Earth's biosphere. Its state depends on many factors, both natural and anthropogenic. Knowledge of the importance of each factor and regularities in the development of forest ecosystems enables us to predict their future. To gain the knowledge, we need stationary research carried out for dozens of years.

 

Russia has largest forest areas in the world. Forests are an important natural resource in this country, which is even more valuable than oil, gas, and coal, for it cannot be substituted. Forests contribute to the gas balance in the atmosphere, regulate many natural processes, and support life on the planet. A remarkable feature of forests is their restocking: when properly organized, forest use will not deplete its resources, but may contribute to its growth and qualitative improvement. At the same time, forests are very vulnerable and need protection. And, certainly, as living systems change incessantly.

 

To be able to assess the state of existing forests, one should remember that natural conditions are merely one of the many factors that determine their composition and structure. For many centuries, vegetation cover of the central Russian plain has been forming under an active influence of man. In accordance with a map made up in the 1920s by a renowned plant geographer, the Moscow University Professor Vassily Alyokhin, the territory was once dominated by forests. Tree species that grew there were common pines, spruces, oaks, lindens, birches, aspens, and maples. But one can only guess what these virgin thickets looked like.

 
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Almost all of them were felled many centuries ago, while what we see nowadays are secondary forests.

 

By the end of the 17th century, forest cover* of present-day Moscow, Vladimir, Ryazan, and Kaluga regions did not exceed 50 percent and was often dominated by birches. Understanding the national importance of forests, Tsar Peter I issued a set of edicts focused on the reasonable use and enhanced protection of forests. In 1719, the Admiralty was entrusted with a charge of forest observation and protection. Forest reserves were picked out and, in 1722, an Oberwaldmeister (chief forester) position was set up. Waldmeisters (foresters) were appointed in some regions. Some forest massifs were privately owned, but the legislation restricted the owners' rights to merely minor use of these plots (beekeeping, hunting, etc.).

 

The forest administration was abolished during the reign of Empress Catherine I. But in the 1730s it was restored by Empress Anna. The authorities requested forest preservation, and one of the most important instructions was to plant new trees instead of felled ones. However, in 1782, in accordance with an edict of Catherine II, private forest massifs were excluded from the jurisdiction of the Forest Department. It was assumed that "zealous landowners" would take care of their natural wealth "to the benefit of themselves and their descendants". The results were not long in coming: six months later, the Admiralty Collegium informed the Senate about increasing tree felling, particularly in the most valuable, "strategic" oak forests. The mistake had to be corrected. In late 19th century, the practice of interrelations between private landowners and the state, caring about areas of economic significance, envisages that no landowner had any right to personally decide a problem of tree felling for construction or other purposes. It was only a forester from the Forest Preservation Committee, who determined such a possibility and areas of clearings. Strict state control is typical of countries with a traditionally high proportion of private forests (e.g. in Finland). Industry development contributed to further reduction of forests in Russia. In the mid- 19th century, forest cover of the Moscow region dropped below 40 percent, Smolensk region-35.8 percent, Yaroslavl-36.2 percent, Tver-33.6 percent, Kaluga-26.5 percent, Ryazan-23.1 percent. Early 20th century and World War I were marked by further disappearance of forest massifs in Central Russia.

 

In the last two decades, despite an increasing forest cover (mainly due to overgrowth of abandoned agricultural lands), felling of the most economically attractive stands and lack of forestry planning have negatively affected species composition of the forests.

 

The state of forests requires regular government control, an integral part of which must be their monitoring. Only then one can identify undesirable processes in due time, prevent losses, and steer forest development in a right direction. How can one see undergoing changes?

 

Forest layout was the main criterion of its assessment in the 20th century: huge areas were examined once in a decade to obtain invaluable information about species composition, age structure, and sanitary situation. In recent years, the traditional method was complemented with monitoring using satellite surveying. Studies carried out by a group of experts of the Center for Forest Ecology and Productivity Problems (RAS) and Institute of Space Research (RAS) headed by Academician Alexander Isayev found significant changes in species composition of forests, especially in European Russia. Coniferous massifs of the taiga zone gave way to small-leaved forests.

 

Forest is a complex system inseparably associated with habitat and environment. To fully understand ongoing forest changes, one should carry out long-term stationary studies on specially selected sites. This became a methodological base of scientific and organizational activities at the Institute of Forest, established in 1944 under the USSR Academy of Sciences on the initiative of Academician Vladimir Sukachev. In gener-

 

* Forest cover is a percentage ratio of an area covered by the forest to the total area of a region, district, etc.-Ed.

 
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Map of natural zones in European Russia and location of experimental forest areas and stations of the Institute of Forest Science, RAS:

 

1 - Onega station (Arkhangelsk region);

 

2 - Western Dvina forest-bog station (Tver region);

 

3 - Northern forest experimental station (Yaroslavl region);

 

4 - Serebryanoborskoye experimental forestry (Moscow and Moscow region);

 

5 - Tellermanovskoye experimental forestry (Voronezh region);

 

6 -Dzhanybeksky station (Volgograd region);

 

7 - Arshan-Zelmensky station (Republic of Kalmykia).

 

al, our state understood the importance of scientific support of forest restoration and preservation even during the war years. The renowned scientist noted at that time that to solve important problems of forestry, complex biogeocenotic* stations should be established in order to study all major types of our forests. The mandatory requirement is simultaneous study of phytocenoses and abiotic environmental factors.

 

As scientific problems cannot be solved without experiments and further long-term observations, two unique objects were handed over by the Government to the Institute of Forest: Serebryanoborskoye (Moscow and Moscow region) and Tellermanovskoye (Voronezh region) experimental forest areas. After the Institute was transferred to Krasnoyarsk in 1958, forest studies in European Russia were continued by the USSR AS

 

Laboratory of Forest Science (from 1991-the Institute of Forest Science, RAS).

 

Understanding of functioning mechanisms of forest ecosystems should be a basis for management of forest productivity, resistance and protective functions in the conditions of intensive nature use and climate change, scientific provision of preservation of their natural diversity; and determination of a forest management strategy. Today, the institute-based network of stations, experimental forest areas, permanent test sites and other monitoring objects includes areas of forest, marsh, and agroforest biogeocenoses in the main zones of European Russia (from northern taiga to semidesert) and is used for observations and field experiments.

 

Long-term observations are a major prerequisite of making reasoned conclusions in assessing progress of forest processes. The accumulated continuous mass of observations is used to test theoretical works related

 

* Biogeocenosis is a system comprising a community of living organisms and a totality of abiotic environmental factors closely associated with it within the limits of one territory, interlinked by circulation of substances and energy flows (the term was introduced by Vladimir Sukachev).-Ed.

 
стр. 22

 

to forest cover changes and mathematical modeling results in order to prepare recommendations on sustainable forest management.

 

According to some statements, forest that is left alone will be changing in full conformity with environmental conditions (soil and climate) and will eventually reach a "virgin" state. Such a "reserve" is supposed to have maximal productivity, be resistant, show no age-related changes, and exist forever. However, those who work in the forest know what can happen to an abandoned forest. Old trees fall, forming dirty heaps or becoming sick, infect other trees ruining many of them. Young trees of forest-forming species often lose ability of normal development and cannot replace decomposing maternal stand. As a result, once healthy massif becomes a forest graveyard.

 

Forest changes can only be identified by means of long-term observations. They are carried out on the so-called permanent sample plots-relatively homogeneous forest areas of 0.25 to 0.5 ha, where height, diameter, and other parameters of each tree are taken regularly. Undergrowth state, herbaceous layer*, and live soil cover are also described. Many plants are very precise indicators of their environment: their number, presence or absence reflect processes that go on in the focal community.

 

So what is going on with our forests? Let us discuss some of the results obtained by staff members of the institute.

 

Forest massifs of the central Russian plain show a steady trend towards species composition changes, which affects their protective and social functions and timber consumption pattern. Lower intensity of forest management earlier focused on restoration of valuable commercial tree species, air and soil pollution with toxic substances, increasing recreational pressure on forests, overgrowth of abandoned agricultural lands and changing climate during the last decades have led to an increased proportion of deciduous stands.

 

Magnificent century-old pine forests with the second layer of oaks and lindens and undergrowth of hazel, rowan, honeysuckle, spindle-tree, and other shrubs have been preserved in the Serebryanoborskoye experimental forest area on the Moskva River terraces. Having reached the height of 30-35 m, the pines stopped growing and are gradually falling out. Broad-leaved trees that are much younger than the pines keep growing and occupy the first layer in some areas. Over 50 years of observations, the pine number decreased almost by half, but they have not been replaced by young trees due to heavy shading made by crowns of oaks, lindens, and filberts. There appeared linden, oak, or filbert groves, with no pine at all. Thus, one can see a gradual transformation of pine forests to broad-leaved forests.

 

This process also affects lower layers that become a domain of shade-hardy and shade-loving plant species, while light-loving ones decrease in number or even disappear. An interesting result was obtained in a test with sprouting plant seeds buried in the soil. Having no opportunity to sprout immediately, they remain anabiotic until favorable conditions evolve. Sprouting seeds of plants absent at present in herbage indicate that the forest used to be different in the past-with a less closed stand and more illumination under its canopy.

 

Half a century ago, areas of pine forests with blueberry and red whortleberry shrubs were not rare on these terraces of the Moskva River. Now, these forests look differently, have the second layer of deciduous trees (mainly birch) and undergrowth of tall large-trunk rowan trees. Pine lost its ability to reproduce. There is every indication that pine will be replaced by deciduous tree species, though it still sounds incredible.

 

* Layer is a vertical structure element of a vegetable community. The layer structure enables an optimal use of natural conditions, such as light, heat, and soil, by plants.-Ed.

 
стр. 23

 

What has caused the expansion of deciduous species? We are not sure so far, but, obviously, there are several reasons for that.

 

Our forests have been altered by man. By now, the human influence has been minimal (when no cuttings are conducted) and vegetation is gradually returning to its "initial" state that corresponds to the environment. In the past, linden was intensively felled for commercial purposes. When felling was no longer economically attractive, the linden began to expand. Earlier, fires were an important forest-forming factor that promoted forest "restoration", while now they are rare in central Russia (droughts like in 2010 are an exception). Fires are usually rapidly extinguished and do not have enough time for large-scale changes.

 

One can see many examples of a "tricky" position of pine in these forests. It is only stable in extreme situations (on poor dry sands or in up-river peat bogs). In other cases, older pines can be replaced by other tree species.

 

Some people would probably find the conclusion about instability of pine forests in the central Russian plain surprising. However, spruce forests can be as unstable. Alexander Abaturov, senior researcher of the Institute of Forest Science, having surveyed many spruce forests in the Moscow region, established that the stands were clearly of the same age and of artificial origin. Spruce forests of various ages appeared to be quite rare. The thorough analysis of one such area has shown that, in future, this species is likely to remain present, but not dominant in the tree layer, even if the existing young trees survive. Growing spruces, oaks, birches and aspens will fall out to be replaced by linden, as its young trees can be seen everywhere (probably together with Norway maple). In fact, this point of view was expressed back in 1968 by Sergei Kurnayev, who wrote the most renowned book on forest vegetation zoning of the country, and believed that the formation of southern taiga spruce forests was related to mass felling of linden and intensive cattle grazing in

 
стр. 24

 

the forest. After elimination of these factors, one can expect formation of the second layer of linden. This conclusion has not been generally accepted and, obviously, should be confirmed by future studies.

 

As a result of economic activities over a considerable area, highly productive spruce forests were replaced by stands of small-leaved trees (birch, aspen, etc.). It is believed that secondary (i.e. newly grown) forests occupying felled areas should once develop a spruce regrowth. But this is not always possible. There should be nearby fruit-bearing spruces, giving enough healthy seeds, although even their shoots do not ensure a viable regrowth, as the environment under the canopy of deciduous trees may change substantially and irreversibly.

 

The observations that have been carried out since the early 1990s on a series of sample plots under supervision of Mikhail Rubtsov, corresponding member of the Russian Academy of Agricultural Sciences, show that natural regrowth of spruce has taken place under the canopy of birch stands. However, spruce restoration as a result of demutation succession* is a lengthy process.

 

To boost restoration of spruce forests where they used to grow, one should apply measures aimed at providing favorable conditions for emergence and development of viable spruce regrowth in birch forests, including "cleaning cutting".

 

It is difficult to make prognoses about the future of present-day birch forests, primarily because they are mostly very young and therefore sufficiently resistant. Observations made on the sample plots have shown that they can last for a long time even in the conditions of intensive technogenic pollution and recreational loads. However, in some cases, general state of the birch is gradually deteriorating, with more and more trees becoming weakened.

 

Very serious changes have been observed in oak forests in the forest steppe zone that are mostly located in Russia. The oak, an acknowledged edificator* of such broad-leaved massifs, very rarely is found in new tree stands. Oak seedlings cannot compete with herbs and abundant shoots of other species of trees and shrubs (maple, ash). As a result, oak restoration is rather rare

 

* Demutation is a vegetation succession that starts after an anthropogenic transformation of a biocenosis and is directed to the restoration of the former community.--Ed.

 

* Edificator (from Latin aedificator-builder) is a plant species with a pronounced environment-forming ability that determines structure and composition of a vegetable community.-Ed.

 
стр. 25

 

in the forest steppe without human help, oaks can be replaced by broad-leaved forests of other less valuable species. But oak forests can be saved with human help.

 

Let's point out that a system of narrow (25-50 m wide) clearings that was developed in early 20th century by the renowned Russian scientist Grigory Kornakovsky gave excellent results in the Tellermanovsky forest in the years of regular and abundant oak fruiting. There one can see a series of cutting areas made over a century ago and in the 1930s that provide very good oak renewal according to this technique. Cutting in the years of abundant self-sown plants, sowing acorns, planting additional seedlings, and looking after the seedlings after felling provide most favorable conditions for renewal. In such secondary plantations this valuable species regains its importance as an edificator of the forest biogeocenosis in just 30-50 years after cutting.

 

Social processes taking place in Russia affect the situation in nature management. Since the early 1990s, areas of abandoned agricultural lands have been intensively growing and reached 50 mln hectares in 2012, which is over 1/3 of their total agricultural area. They are over grow with the forest and we observe forest vegetation returning to its former territories. Species that naturally take over these lands in the forest zone are weeping birch, grey alder, aspen, and, less often, pine. The problem of the fate of young forests on abandoned lands is a sensitive issue. Restoration of agriculture on these lands requires considerable economic costs and is mostly unjustified. However, as it was shown by studies performed at the Northern Forest Experimental Station of the Institute of Forest Science, RAS (Yaroslavl region), these areas require urgent, scientifically substantiated forest management measures in order to form highly productive stands with due account for their designation purpose. Otherwise we can end up with thickets difficult to traverse and devoid of economic and ecological value.

 

Due to urbanization and intensive construction development in central European Russia, large forest

 
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areas turned out within limits of human settlements or in the immediate proximity to them. It is difficult and not always possible to conserve forest ecosystems there without transforming them into artificially maintained plantations. It is vital to identify mechanisms of anthropogenic dynamics of forest biogeocenoses by means of long-term stationary observations. Such works have been carried out in the Serebryanoborskoye experimental forest area for over 65 years. Studies of impacts of air and soil pollution, various types of recreation are in progress as well. The obtained results help conserve unique biogeocenoses of urbanized areas that are steadily and increasingly affected by the megacity, as well as protect them from managerial decisions that are not always reasonable and scientifically sound.

 

Long-term field works have traditionally been used in forest studies, as natural and anthropogenic changes in forest ecosystems are almost impossible to identify during aerial and other occasional surveys. We would like to place special emphasis on the following: it is only results of long-term empiric observations over permanent objects that give an opportunity to understand a complex nature of forest biogeocenoses, to predict their future development, and to elaborate methods of economic management and sustainable development. To protect a unique network of forest scientific bases and objects in contemporary economic conditions and provide a consistency of stationary studies and experimentation are the most important objectives of forest science and practice in early 21st century.


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© Andrei SIRIN () Источник: Science in Russia, №4, 2012, C.20-27

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