Assessment of the vital state of coniferous undergrowth. Literature review Spruce undergrowth title
Assessment of the vital condition of coniferous undergrowth
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Teacher's Guide
Undergrowth can be used for reforestation of cleared areas in many cases with very great effect. The use of spruce, cedar and fir undergrowth is especially important, since the subsequent regeneration of forest stands of these species is associated with great difficulties due to the very slow growth of undergrowth in the first years of its life. [...]
Thus, undergrowth for concentrated cuttings not only itself is the basis of the future forest stand as a preliminary regeneration, but under certain conditions it serves as one of the important sources of seeding of these cuttings.[...]
The occurrence of undergrowth’ was chosen as one of the most important criteria for silvicultural and environmental requirements for the operation of logging machines during clear-cutting. Occurrence is a reliable indicator for assessing natural forest regeneration (Martynov, 1992; Tikhonov, 1979), allowing one to predict the composition and productivity of future forest stands. The occurrence rate can also be successfully used to predict subsequent forest regeneration based on the nature of forest growth conditions in fresh felled areas and the possible formation of one or another type of clearing or its fragments (parcels). The value of this indicator depends on forest conditions, biology and ecology of tree species.[...]
The use of undergrowth is of great importance for the regeneration of oak, beech, hornbeam, and linden forests. For satisfactory and good renewal, the old undergrowth of these species, which takes on a bushy, creeping form, should be planted on a stump, that is, cut down, leaving a small stump, on which shoots then emerge from dormant buds (“sit down”), characterized by more slender growth than felled old undergrowth. Planting on a stump is also quite advisable for old undergrowth of elm, maple, chestnut and other species.[...]
For example, the amount of spruce undergrowth under the mother canopy per unit area naturally changes within the range of this species: it decreases to the north and south of the areas optimal for spruce growth. The southern border of these regions extends further to the south in the western, more humid part of the European territory of the USSR, and shifts somewhat to the north in the eastern, more continental (meaning flat areas). In the sparse and northern subzones of the taiga, the amount of spruce undergrowth per unit area is less than in the southern subzones, but at the same time, spruce grows here in a wide typological range; it even enters lichen forest types. It is necessary to take into account the comparative potential productivity of undergrowth of different tree species growing in the same area in order to place the main emphasis on the species that, under given physical and geographical conditions, is capable of forming the most highly productive forest stands. Thus, in the mentioned forests of lichen types, as well as in northern lingonberries, the productivity of spruce stands significantly lags behind pine ones. A unique feature of spruce regeneration in a number of areas of the European taiga is also its ability to appear as a pioneer in burnt areas and clear-cuts under certain soil and microclimatic conditions; this phenomenon was noted and described by the author in the late twenties and early thirties.[...]
Thus, the preservation of undergrowth is an important type of regulated natural regeneration. At the same time, it cannot be considered as the only way of natural regeneration during clear-cutting. So, for example, it is not advisable to rely on spruce undergrowth growing under the pine canopy on poor soils, where the productivity of the pine tree stand is much higher than that of spruce.[...]
The number of cones and seeds in young spruce and pine trees is less than in most mature trees. However, this is compensated by a large number of undergrowth plants and a possible improvement in seed quality. The most valuable is the undergrowth that grows before felling in windows and generally under the sparse forest canopy, since it may bear fruit earlier during clearing. Such undergrowth sometimes bears fruit even before felling.[...]
Due to the fact that the preserved spruce undergrowth (20 years old at the time of felling) will subsequently occupy the first tier in the canopy of the emerging young growth, the need for thinning practically disappears. According to A. S. Tikhonov, spruce, growing from 15-20-year-old undergrowth, at the age of 70 years has the same height as birch and aspen. Thinning is necessary only in places with a predominance of small undergrowth preserved (during logging) and spruce undergrowth that is subsequently renewed. Within 10 years, the type of felling under consideration is transformed into the initial stage of the forest type - mixed-grass spruce forest (hereinafter - fresh blueberry).[...]
The growth of undergrowth in peaty sphagnum pine forests changes relatively little, which is associated with small changes in the light regime after felling and with unfavorable soil conditions.[...]
An external sign of the viability of a young tree can be its growth in height. With an average annual growth rate of 5 aa or more over the past 5 years, spruce and fir regrowth 0.5-1.5 m high can be considered quite viable, able to withstand sudden lightening of its upper canopy by clear cutting. [...]
The quality of forest stands formed from the undergrowth of preliminary generations is closely related to the nature of its damage during logging. Places of mechanical damage to spruce undergrowth are often affected by rot, which leads to a decrease in the quality of the wood. Spruce wood is affected by rot when the width of the wounds around the circumference of the undergrowth trunk is 3 cm or more. These wounds do not heal for a very long time, sometimes during the entire life of the trees. Smaller wounds heal within 15 to 20 years. Rot, formed as a result of wounds of the first kind, covers about 3 m of the butt part of the trunk over 60 - 70 years.[...]
It is much more difficult to preserve undergrowth in mountain forests than in lowland forests. A lot of undergrowth there is destroyed during unsystematic ground skidding by self-raising. Ground skidding with winches and tractors also causes more damage to undergrowth than in lowland forests. The steeper the slopes, the more undergrowth is damaged.[...]
In the forests of the taiga zone there is often a large amount of undergrowth, which is due to the high age and therefore the relatively low density of tree stands. The appearance of undergrowth under the canopy was also facilitated by ground-level runaway fires, which caused thinning of tree stands and damage to the ground cover (I.S. Melekhov, A.A. Molchanov, etc.).[...]
Sometimes, after felling, frail, although viable, spruce undergrowth remains, characterized by slow growth. Such undergrowth can only form a tree stand of low productivity. The reason for this is not only the suppression of undergrowth under the canopy and the reaction to lightening, but also soil conditions. It is advisable to replace such undergrowth by first preparing the soil by fire or some other method for subsequent artificial regeneration, for example, of pine, if this turns out to be cost-effective and leads to the formation of forest stands of higher productivity. [...]
Let's take, for example, two areas: in one there is evenly distributed coniferous undergrowth, in the other there is no undergrowth. In the first case, you can leave several insurance seeds per 1 hectare, in the other - more to ensure complete seeding of the entire plot.[...]
The study showed that the intensity of respiration of the conducting roots of spruce undergrowth, both in terms of the mass of CO2 released and the amount of absorbed O2, is higher in the clearing than under the forest canopy (Table 1). During the study period, respiration energy is subject to quite significant fluctuations, and from the second half of July, a noticeable rise in the respiration curve is observed, associated with changes in both ambient temperature and soil moisture (Table 2). However, the increase in respiration intensity does not correspond to the temperature coefficient [...]
In economic practice, it is necessary to take into account and study not only the existing undergrowth under the forest canopy, but also... deforestation, burning, etc., but also the conditions for its appearance and development. An integral part of the issues of accounting and research of forest regeneration is the scientific and practical study of forest fruiting, as a necessary condition for seed-based reforestation, natural and artificial.[...]
When visiting the Buzuluksky forest, something else is striking - the presence of viable pine undergrowth under the sparse forest canopy, usually in windows. This characteristic phenomenon prompted G.F. Morozov and other foresters on the idea of using group selective felling. This idea was practically implemented later, and in the form not of group-selective felling, but of simplified, group-gradual felling. For the first time, group-gradual logging in the Buzuluksky forest was carried out in 1928 on an experimental basis, and in 1930 on a production scale. These fellings were carried out in four stages (Table 11) in mossy pine forests on more or less dry sandy soils. [...]
The Kostroma method gives good results if the young growth consists of self-seeding and small undergrowth up to 0.5 m high. In this case, up to 50-60% of it is preserved. If large undergrowth predominates, the damage rate is higher, and in this respect the Kostroma method is inferior, for example, to the methods used in some forestry enterprises in the Arkhangelsk region and Karelia, which allow preserving up to 70% of large and small undergrowth. The use of support trees is not always effective, and not only because of the height of the undergrowth. In low-productive thin-sized tree stands, they do not save even small undergrowth from damage during felling, so it is advisable to use them in highly productive forests.[...]
In these cases, almost more often the problem is to achieve the proper participation of coniferous undergrowth in the forest composition, since usually clear-cut areas here, as already indicated, are perfectly populated by birch, aspen, and alder, unless there is some admixture of them in the forest being cut down. [...]
During forced selective felling, it is not uncommon for growing trees to be damaged during felling and the undergrowth or felling of one tree when it hangs causes the need to cut down neighboring trees and the loss of the tree stand.[...]
In taiga clearings, according to V. Ya. Shiperovich, B. P. Yakovlev, A. A. Panov and others, the roots of coniferous undergrowth damage the root veins. As studies of recent years have shown (V. Ya-Shiperovich, B. P. Yakovlev, E. V. Titova), in Karelia the most common and harmful rootworms are Siberian (Hylastes aterrimus Egg.) and spruce (Hylastes cimicularius Egg.). They cause damage mainly in the process of additional feeding, attacking healthy undergrowth and young spruce and pine trees. The greatest harm from them can occur in three- to five-year-old felling areas. According to E.V. Titova, in four- to six-year-old fellings, the number of young fir trees damaged by spruce roots reaches 90%, about 20% dry out completely.[...]
Finally, if viable young growth is preserved in sufficient quantities (2000-3000 pieces of coniferous undergrowth per 1 hectare), there is no need for artificial reforestation, which is expensive. [...]
Thinning in the first years of life of young animals, called lightening, consists of freeing the undergrowth of valuable species from being drowned out by minor impurities, regulating the relationships between specimens of undergrowth of the same tree species, and improving conditions for the growth of the best specimens of valuable species. The first round of thinning for undergrowth can be carried out before the introduction of the main species into the area, an example of which is cutting corridors among elm, maple, linden, and hazel to introduce oak using the Molchanov method.[...]
Seed groups, clumps, stripes. Using materials about the composition and structure of the forest stand, the placement of undergrowth and undergrowth, and places of possible undercuts, it is possible to pre-designate intra-cutting seed clumps and seed groups for abandonment. The area of the seed group usually occupies 0.01, less often 0.03 - 0.05 hectares. The area of the curtain reaches several tenths of a hectare, and sometimes reaches 1 hectare. In this regard, the danger of decay from the wind is greater for the seed group than for the clump. The seed group is a compact biogroup, which includes several ripening or ripe trees or undergrowth and thin trees. [...]
Pine is especially hard hit by snowbreakers, and aspen is the hardest hit among deciduous trees. Heaps of snow often damage young growth in forests and clearings. A measure to prevent snow breaker and snowfall is the timely thinning of excessively dense tree stands, the creation of forest forms with a loose crown canopy.[...]
The main condition for successful regeneration of spruce during selective felling is the preservation of self-seeding and undergrowth during felling and skidding of trees.[...]
After felling (in a wet blueberry spruce forest) using a technology that ensures a fairly high preservation of the undergrowth (50-60%), the formation of the sphagnum type of felling has a certain influence on the preliminary regeneration of the spruce. Thus, in 6-year-old fellings of this type (after the operation of the LP-19, LT-157 and Timbergek-360 machines) on an intact soil surface with preserved spruce regrowth (9.6 thousand pcs./ha, average age 18 years) The projective cover of herbaceous and shrub vegetation is 35-45%. The cover is dominated by sedge (15-20%) and blueberry (4-5%). Sphagnum moss occupies 20-30%, and green mosses - 5-7% of the area. In biogroups of spruce undergrowth, the cover of herbaceous and shrub cover is reduced to 15%. Here the participation of blueberries increases (up to 6-8%), green mosses (up to 15-20%) and the area occupied by sphagnum moss decreases (up to 15-20%). This regrowth has a positive effect on the subsequent regeneration of spruce. Consequently, the spruce undergrowth preserved during felling, which is a natural drainer, promotes the subsequent regeneration of spruce and somewhat inhibits the formation of sphagnum type felling. In the taiga forests of the European part of the USSR, the nature of sphagnum and sedge-sphagnum fellings and the regeneration of forests on them (formed after the work of traditional logging equipment) were studied by many researchers.[...]
In high-density (0.8 and above) spruce-deciduous, deciduous-spruce and deciduous stands with self-seeding and undergrowth of spruce, it is justified to carry out gradual felling in three stages with an intensity of initial reception from 25 - 30%, stock (in spruce-deciduous) - up to 35 - 45% (in deciduous-spruce and deciduous), in medium-density forest stands, cutting in two steps is advisable.[...]
It is more difficult to formalize the silvicultural and environmental assessment of the operation of logging equipment in cutting areas without undergrowth than in plantations with undergrowth. The complexity of solving this problem lies in the fact that we are dealing not with the real (before cutting), but with the future (subsequent) regeneration of the forest, which immediately after cutting is predicted with a certain reliability, based on the state of forest conditions in fragments of fresh fellings and emerging ones. on them parcels of plant communities in the presence of seed sources. Therefore, for an objective assessment of the operation of logging equipment, scientific data is needed for different ecological and geographical conditions on the nature of damage to the soil cover in connection with the use of one or another type of machines and technologies, on the nature of the emergence and development of parcels and types of fellings, on their impact on the emergence of seedlings and formation of self-seeding and undergrowth. Such data is available for a number of regions. Below is an assessment of the performance of aggregate logging equipment in clear-cutting in two different regions according to soil and climatic conditions. Thus, in the conditions of a lingonberry-ledum pine forest (Tyumen region) and a fresh blueberry spruce forest (Novgorod region) after the operation of LP-19 and LT-157 machines using a technology that involves laying trees at an angle to the drag, causing approximately the same area of soil damage (80-85%), the same reed-reed type of felling is formed with different forest conditions in each region. The duration of existence and features of the formation of this type in the two regions are different (Obydennikov, 1996). The occurrence of fragments of clearings with favorable conditions for the regeneration of the main species is, in the first case, in the conditions of a lingonberry-ledum pine forest, 72-77% (Tyumen region), in the second, in the conditions of a fresh blueberry spruce forest, 4-8% (Novgorod region). The given indicators, judging by the results of the studies, correspond to the actual occurrence of undergrowth of subsequent renewal in the presence of testes.[...]
To ensure good reforestation, appropriate care of valuable, economically important undergrowth is necessary - weeding and cutting down undergrowth and undergrowth of low-value species. Ignoring these measures was one of the main reasons for the unsuccessful use of gradual logging in pre-revolutionary Russia. Forest owners or officials usually tried to get forest regeneration without any significant monetary costs, often relying only on regulating the procedure for cutting down forests. Therefore, for example, as a result of ten years of experience in using gradual felling in the Sarapul district of forests of the Specific Department, according to a special survey by Danilevsky, it turned out that the vast majority of cutting areas in pine forests resumed unsatisfactorily and only 10-20% of all fellings resumed well. A survey of gradual cutting sites in the spruce forests of the Lisinsky forestry, carried out by D. M. Kravchinsky, showed that without caring for undergrowth, the regeneration of spruce turned out to be almost the same as in clear cuttings, namely, with the dominance of deciduous species (with a change of species) , against which the gradual felling was directed. D. M. Kravchinsky himself noted that in high-productivity spruce forests, the regeneration of spruce during gradual felling is hampered by the development of cereals (mainly reed grass) and undergrowth (mainly rowan) in the cutting area.[...]
In the lichen forests of the Arkhangelsk region, under the canopy, there are large quantities of strongly suppressed (sticky) pine undergrowth, which, after felling, quickly adapts to new conditions. Already 6-8 years after felling, such undergrowth differs little from pine trees that grew in the clearing. Only on the pre-cutting part of the stem are many young branches formed (from dormant axillary buds) (Fig. 15). Small-growing, strongly oppressed, the undergrowth is well preserved (84%) from damage during winter logging - even on portages with a single pass of the TDT-40 tractor in the summer, viable specimens of the undergrowth were preserved (Listov, 1986).[...]
Foresters were not satisfied with the relationship of tree species to light, established by the density of foliage and the nature of the crown, by the speed at which trunks are cleared of branches, and by the ability of undergrowth species to survive under the shade of the upper tiers of tree stands. They tried to move experimentally to the quantitative expression of the degree of light-loving and shade-tolerance by other methods.[...]
The regeneration of pine in concentrated fellings depends on the time elapsed after the fire (Fig. 16). As the age of the fire increases to 20 - 25 years, the amount of self-seeding and regrowth of pine increases sharply. In areas where there was a fire 30 - 40 years ago, the amount of self-seeding and undergrowth decreases as a result of the transition of part of it to the polewood stage, but still remains significant. Restoration is also proceeding successfully in areas with a longer fire duration (up to 40 - 60 years), although the amount of self-seeding and undergrowth continues to decrease. In areas where there were no fires or where they occurred more than 100 years ago, pine regeneration is usually less successful.[...]
A technological scheme with the preservation of undergrowth has found wide application at a number of enterprises in Western Siberia (in particular, at the Komsomolsky and Sovetsky timber mills in the Tyumen region) (with the installation of two timber hauling runners, Fig. 31). According to the scheme, the LP-19 feller-buncher and chokerless skidders (LT-157, LT-154, etc.) are used. Before cutting the forest, two logging trucks and two loading platforms are installed at opposite ends of the cutting area. The LP-19 machine produces forest felling in strips (the width of each strip is 15 - 16 m).[...]
Thus, silvicultural requirements for technological processes during logging are usually established based on the direct impact of logging equipment on the soil and undergrowth at the time of logging or on changes in forest conditions in fresh fellings without taking into account the emerging types of clearings and forest regeneration in connection with them. In addition, there are no scientifically based acceptable limits for the preservation of undergrowth and the size of the damaged soil surface with different densities of its upper layers. This leads to difficulty in objectively assessing the operation of logging equipment and its environmental consequences. The mentioned methodological approach to substantiating the criteria for silvicultural and environmental assessment of the operation of logging equipment is based on the use of cause-and-effect relationships between the input and output parameters of forest ecosystems and inter-level connections of plant parcels and biogeocenoses using the indicator of the occurrence of undergrowth. Of particular importance for establishing criteria are input indicators (preservation of undergrowth, degree of soil mineralization, density of its upper layers), which significantly influence the output of the ecosystem - types of felling, initial and subsequent stages of forest types. In areas with mature forest, depending on the method of regeneration after logging, different requirements are imposed on technological processes. The basis for classifying forest areas before logging to certain methods of regeneration (natural, preliminary and subsequent, artificial) after logging can be the amount of occurrence of undergrowth before logging or the likelihood of the formation of types of clearings with favorable or unfavorable conditions for the regeneration of the main species. Silvicultural and environmental requirements during the operation of logging machines in stands with undergrowth are imposed mainly on the occurrence of undergrowth (its other characteristics: density, viability and others are classified as restrictions), since this indicator is a reliable criterion for assessing the natural regeneration of the forest, allowing one to predict the composition and productivity of forest stands. The acceptable preservation of undergrowth is established by the ratio of the occurrence of preserved undergrowth under the forest canopy before felling and the occurrence of preserved undergrowth, according to which forest regeneration is assessed satisfactorily. Silvicultural and environmental requirements for the operation of logging machines in cutting areas without undergrowth are different. They depend on the method of regeneration after felling, i.e. taking into account the likelihood of the formation of one or another type of clearing and the forecast of the occurrence of undergrowth.[...]
For satisfactory regeneration of pine and larch stands on poor dry soil (in heath forests, lingonberries and similar ones), the preservation of a significant amount of undergrowth, numbering in the thousands per 1 hectare, is required. To regenerate a spruce or spruce-fir stand on fresh and moist soils (in sorrel and blueberry forests), it is often sufficient to preserve several hundred pieces of spruce and fir undergrowth per 1 hectare, if it is only more or less evenly distributed over the area.[... ]
As for ash, in its youth it is indeed more shade-tolerant than many of the species with which it grows in our forest-steppe mixed stands. Observations in these forests have shown that ash undergrowth actually often prevails over self-seeding oak and undergrowth of other species, despite the shading from above, often with three tiers (Krasnopolsky, A.V. Tyurin).[...]
Trees are felled with their tops in the direction of the movement of the fire. Branches cut off from trees are carried into the forest in the direction from which the fire is coming, and sections of cross-cut trunks are dragged in the direction opposite to the movement of the fire. Living cover, undergrowth and undergrowth are removed from the middle part of the breaking strip. The humus layer turns over, exposing the soil to the mineral layer.[...]
In place of wet blueberry spruce forest, immediately after felling, sphagnum, rush-pike and pike types of fellings are formed. The first is formed when there is damage to the soil surface on 35-40% of the cleared area and sufficiently high preservation of the undergrowth (up to 60%). This type passes into lancet-reed-sphagnum, and then into moist blueberry spruce forest. The rush-pike and pike types of clearings are formed with significant soil compaction (usually 1.3 g/cm3 or more in the upper layer) and are most often confined to places near loading areas and logging slopes. In clearings of these types, conditions for the regeneration of spruce are extremely unfavorable, and for deciduous trees (mainly downy birch) - difficult.[...]
The disadvantages of preliminary regeneration are unevenness in the width and structure of the annual layers of wood before and after felling, and the subsequent increased knottiness and curvature of the trunks. These shortcomings, especially the knotty nature, are more associated with adolescents who have experienced prolonged oppression before logging. With severe suppression of undergrowth, the annual layers are not only narrow (from hundredths to several tenths of millimeters), but often fall out altogether, and a heeling of the trunk develops.[...]
The plots are divided into apiaries with a width equal to the average height of the tree stand, with a minimum trail width of 4 - 5 m. Development of the apiary begins from the near ends. The felted trees are placed with their tops on the drag at an acute angle to it, so they do not have to be turned when pulled out. The undergrowth is preserved in the amount of 70-75% more or less evenly over the entire area of the strips. With this method, small and large undergrowth is well preserved. Working conditions made it possible to reduce the composition of small complex teams by 1 - 2 people. Labor costs for chokering and skidding over the tops in the summer are 6 - 7% higher than for choking and skidding over the butts. However, the costs are offset by savings in reducing the labor intensity of clearing cutting areas, since with this method the branches are concentrated on the drags.[...]
The first way has become more widespread. Over the past three decades, many different technological schemes for the logging process have been proposed. The ideal is still far away, but there is some progress - a number of schemes ensure the preservation of regrowth up to 60 - 70%. However, this goal is becoming less and less achievable due to the introduction of powerful logging machines, which increase the impact on the forest and forest environment. First of all, the impact of such machines as VTM-4, VM-4A, LP-49, etc., affects the soil. Its compaction, strong exposure and movement, erosion and depletion are observed, undergrowth is destroyed and damaged, and injuries are caused to the roots and trunks of trees. During clear cuttings, this can lead to the formation of types of clearings that are unfavorable for forest regeneration.[...]
Fricke fell into such a gross mistake when he came out with a categorical objection to the division of tree species into shade-tolerant and light-loving as a “scientifically unfounded dogma.” The basis for Fricke’s speech was a special experience that involved freeing undergrowth under the forest canopy from “root competition.” But this experience in itself only proves that the success of the growth and development of undergrowth depends not only on lighting conditions, but also on the conditions of soil nutrition, which in turn is a condition for air nutrition of plants.[...]
The introduction of air-suspended skidding means (Fig. 109), rational trays (Fig. PO), regulation of the direction of tree felling using technical devices (wedges, etc.), prohibition of clear felling on steep slopes, transition to regulated selective and gradual felling - Here is an incomplete list of means for preserving iodrosga in mountain forests. To this we must add much that applies to lowland forests, for example, the use of snow cover to protect self-seeding and undergrowth from damage.[...]
In clearing areas, the composition and especially the number of fauna change. In the first years after logging in the spruce forests of the Arkhangelsk region, the number of squirrels decreases, the pine marten and birds of the Galliformes order disappear. At the same time, the number of mouse-like rodents, stoats and foxes increases. The productivity of hunting lands, decreasing noticeably in the first years after logging, then increases as afforestation occurs and after 20 years becomes higher than the productivity of spruce forest lands. Clear cuttings are expanding the range of moose, hare and black grouse. The preserved undergrowth and the remaining seed clumps increase the hunting value of the clearings. Concentrated logging promotes the movement of the cockchafer to the north. Currently, it is widespread throughout the forest zone of the European part of the country and causes damage to crops and the natural regeneration of pine. This is due to favorable conditions for the May beetle: light and thermal conditions, penetration of the soil of clearings, the presence of herbaceous and other plants, the roots of which provide good and accessible food for young May beetle larvae. Grass cuttings (reed type) and some types of firewood are especially favorable for it.[...]
The natural regeneration of concentrated clear-cutting areas, as shown by numerous studies (Department of General Forestry of the LTA named after S. M. Kirov, Arkhangelsk Forestry Engineering Institute, Central Scientific Research Institute of Forestry, Northern Forest Experimental Group, Institute of Forest of the USSR Academy of Sciences, etc.), takes place in many areas of the taiga zone successfully, but mainly in hardwoods. In other types of forests, the participation of conifers in the regeneration of cutting areas is rare and is mainly due to the undergrowth remaining after logging and the slow appearance of self-seeding pine and spruce under the canopy of deciduous trees, which usually populate the cutting area in the first years after logging.
480 rub. | 150 UAH | $7.5 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Dissertation - 480 RUR, delivery 10 minutes, around the clock, seven days a week and holidays
Gutal Marko Milivojevic. Viability and structure of spruce undergrowth under the canopy of tree stands and in clearings: dissertation... Candidate of Agricultural Sciences: 06.03.02 / Gutal Marko Milivoevich; [Place of defense: St. Petersburg State Forestry University named after S.M. Kirov http://spbftu.ru/science/sovet/D21222002/dis02/].- St. Petersburg, 2015.- 180 p.
Introduction
1 Problem status 9
1.1 General information about spruce phytocenoses 9
1.2 Spruce juvenile 11
1.2.1 Features of the age structure of spruce undergrowth 12
1.2.2 Features of the light regime under the canopy of spruce forests 16
1.2.3 Viability of spruce undergrowth 22
1.2.4 Number of spruce undergrowth 25
1.2.5 Influence of forest type on spruce regrowth 27
1.2.6 Features of the development of spruce undergrowth under the canopy 30
1.2.7 Influence of vegetation of lower tiers on spruce regrowth 33
1.2.8 The influence of economic activities on spruce juveniles 35
2 Research program and methodology 39
2.1 Research program 39
2.2 Study of forest phytocenosis by structural elements 40
2.2.1 Determination of the main characteristics of the forest stand 40
2.2.2 Accounting for teenagers 41
2.2.3 Accounting for undergrowth and living ground cover 46
2.2.4 Determination of biometric indicators of needles 49
2.3 Research objects 51
2.4 Scope of work performed 51
3 Dynamics of the state of spruce undergrowth under the canopy .
3.1 Dynamics of the vital state of spruce undergrowth based on the results of long-term studies 53
3.2 Patterns of changes in the viability of spruce undergrowth in connection with the type of forest 69
3.3 Influence of the maternal canopy on the dynamics of the state and structure of spruce undergrowth
3.4 Relationship between the viability of spruce undergrowth and the value of average growth over a period of 3, 5 and 10 years.
3.5 Age structure as an indicator of the state of adolescence 86
3.6 Structure according to the height of undergrowth as an indicator of condition 89
3.7 Comparative analysis of the state and structure of spruce undergrowth in the spruce forests of the Lisinsky and Kartashevsky forest districts 93
4 The influence of economic activities on the number and viability of spruce undergrowth
4.1 The influence of thinning on the dynamics of viability of spruce undergrowth 105
4.2 Thinning the undergrowth - as a measure to promote the natural regeneration of spruce 122
5 Dynamics of the state of spruce undergrowth in the felling area 127
5.1 Features of the structure and condition of spruce undergrowth 127
5.2 Dependence of the dynamics of the state of spruce undergrowth on the recency of felling 134
6 Biometric characteristics of needles as an indicator of the viability of spruce undergrowth
6.1 Biometric indicators of needles under the canopy and in cuttings 140
6.2 Biometric indicators of needles of viable and non-viable spruce undergrowth.
Bibliography
Features of the light regime under the canopy of spruce forests
Spruce is one of the main forest-forming species in the Russian Federation, occupying fourth place in terms of area, second only to larch, pine and birch. Spruce grows from the tundra to the forest-steppe, but it is in the taiga zone that its forest-forming and edificatory role is most manifested. The genus spruce (Picea Dietr.) belongs to the pine family (Pinacea Lindl.). Individual representatives of the spruce genus date back to the Cretaceous period, that is, 100-120 million years ago, when they had one common habitat on the Eurasian continent (Pravdin, 1975).
Norway spruce or common spruce (Picea abies (L.) Karst.) is widespread in northeastern Europe, where it forms continuous forests. In Western Europe, coniferous forests are not a zonal vegetation type, and vertical differentiation occurs there. The northern border of the range in Russia coincides with the forest border, and the southern border reaches the black earth zone.
Norway spruce is a tree of the first size with a straight trunk, a cone-shaped crown and not strictly whorled branching. The maximum height reaches 35-40 meters in flat conditions, and in the mountains there are specimens up to 50 m high. The oldest known tree was 468 years old. However, age over 300 years is very rare, and in the zone of coniferous-deciduous forests it decreases to 120-150 (180) years (Kazimirov, 1983).
Norway spruce is characterized by relatively high plasticity of the root system, capable of adapting to various soil conditions. The root system is most often superficial, but on well-drained soils relatively deep vertical branches often develop (Shubin, 1973). The trunk of the Norway spruce is full wood, covered with relatively thin green-brown, brown or gray bark. The bark of the common spruce is smooth, but with age it becomes scaly and furrowed.
Growth buds are small - from 4 to 6 millimeters, ovoid-conical, red with dry scales. Reproductive buds are larger and reach 7-10 millimeters.
The needles of the common spruce are tetrahedral, sharp, dark green, hard, shiny, up to 10-30 mm long and 1-2 millimeters thick. It stays on shoots for 5-10 years and falls throughout the year, but most intensively from October to May.
Norway spruce blooms in May–June. The cones ripen in the fall of the following year after flowering, the seeds fall in late winter and early spring of the following year. Male spikelets of elongated cylindrical shape are located on the shoots of the previous year. The cones are spindle-shaped, cylindrical, 6 to 16 cm long and 2.5 to 4 centimeters in diameter, located at the ends of the branches. Young cones are light green, dark purple or pinkish, while mature ones take on a different shade of light brown or red-brown. Mature cones contain from 100 to 200 seed scales on the stem. Seed scales are lignified, obovate, entire, finely serrated along the upper edge, notched. Each seed scale contains 2 seed cavities (Kazimirov, 1983). The seeds of the common spruce are brown in color, relatively small, 3 to 5 millimeters long. Weight of 1000 seeds is from 3 to 9 grams. Seed germination varies from 30 to 85 percent depending on growing conditions. Growing conditions also determine the presence of repetition of productive years, which occur on average every 4-8 years.
Norway spruce is a species that grows over a relatively large area, in different soil and climatic conditions. As a result, Norway spruce is distinguished by high intraspecific polymorphism (in the type of branching, color of cones, crown structure, phenology, etc.), and therefore by the presence of a large number of ecotypes. In relation to air temperature, the common spruce is thermophilic, but at the same time it is a cold-resistant species, growing in a zone of temperate and cool climates with an average annual temperature of -2.9 to +7.4 degrees and the temperature of the warmest month of the year from +10 to +20 degrees (Chertovskoy, 1978). The distribution range of Norway spruce ranges from 370 to 1600 mm of precipitation per year.
The issue of soil moisture is closely related to its aeration. Although common spruce is capable of growing in conditions of excess moisture, good productivity should be expected only in cases where there is running water. On damp soils, spruce falls out at a speed of 6-7 meters per second, and on fresh and dry soils it can withstand wind flows at a speed of 15 meters per second. Wind speeds of more than 20 meters per second cause a massive fall.
The most intensive growth of common spruce occurs on sandy and loamy soils, underlain at a depth of 1-1.5 meters by clays or loams. It should be noted that there are no strict rules for the requirements for soil composition and mechanical composition as such, since the requirements of spruce for soil are of a zonal nature. Norway spruce has a high tolerance threshold to soil acidity and is able to grow at pH fluctuations from 3.5 to 7.0. Norway spruce is relatively demanding in terms of mineral nutrition (Kazimirov, 1983).
Accounting for undergrowth and living ground cover
The heterogeneity of the qualitative and quantitative characteristics of adolescents is expressed, first of all, through the concept of adolescent viability. The viability of adolescents according to the Encyclopedia of Forestry (2006) is the ability of the younger generation of maternal adolescents to exist and function in changing environmental conditions.
Many researchers, such as I.I. Gusev (1998), M.V. Nikonov (2001), V.V. Goroshkov (2003), V.A. Alekseev (2004), V.A. Alexeyev (1997) and others noted that the study of the qualitative parameters of spruce forests, by and large, comes down to studying the condition of the stands.
The state of the tree stand is a consequence of the complex processes and stages through which the plant passes from its primordium and seed formation to its transition to the dominant tier. This long process of plant metamorphosis requires division into various stages, each of which must be studied in a separate order.
Thus, it can be stated that relatively little attention is paid to the concept of vitality and state of the undergrowth (Pisarenko, 1977; Alekseev, 1978; Kalinin, 1985; Pugachevsky, 1992; Gryazkin, 2000, 2001; Grigoriev, 2008).
Most researchers claim that there is a sufficient amount of viable spruce undergrowth under the canopy of mature forest stands, but most often the interdependence of the state of the undergrowth and its spatial distribution with the characteristics of the maternal tree stand is not revealed.
There are also researchers who do not claim that under the canopy of the maternal tree stand there should be viable undergrowth capable of fully replacing the mother tree stand in the future (Pisarenko, 1977; Alekseev, 1978; Pugachevsky, 1992).
Fluctuations in height and group distribution of spruce undergrowth allowed some authors to argue that spruce undergrowth as a whole is not capable of providing preliminary regeneration under the condition of intensive logging operations (Moilanen, 2000).
Another study by Vargas de Bedemar (1846) established that the number of trunks sharply decreases with age, and that of the sprouted seedlings, in the process of natural selection and differentiation, only about 5 percent are preserved to the age of ripeness.
The process of differentiation is most pronounced in the “youth” of the planting, where the oppressed classes are distinguished to the greatest extent by status, and gradually takes over the “old age”. According to G.F. Morozov, who refers to earlier works by Ya.S. Medvedev (1910) in this direction, a common feature of undergrowth growing in a plantation is depression. Evidence of this is the fact that at the age of 60-80 years, spruce undergrowth under a canopy very often does not exceed 1-1.5 m, while spruce undergrowth in the wild at the same age reaches a height of 10-15 meters.
However, G.F. Morozov (1904) notes that the productivity and productivity of individual specimens of undergrowth can change for the better, as soon as the environmental conditions change. All specimens of undergrowth, of varying degrees of depression, differ from undergrowth in the wild in the morphological characteristics of the vegetative organs, incl. fewer buds, a different crown shape, a poorly developed root system, and so on. Such morphological changes in spruce, such as the formation of an umbrella-shaped crown developing in a horizontal direction, are an adaptation of the plant to the most efficient use of the “scarce” light penetrating to the undergrowth. Studying cross-sections of the stems of spruce undergrowth growing in the conditions of the Leningrad District (Okhtinskaya Dacha), G.F. Morozov noted that in some specimens the annual layers were densely closed at the initial stage of life (which indicates the degree of oppression of the plant), and then sharply expanded as a result of some forestry measures (in particular thinning), changing environmental conditions.
The spruce youngsters, abruptly finding themselves in open space, also die from excessive physiological evaporation due to the fact that in open areas this process occurs with greater activity, to which the youngsters growing under the canopy are not adapted. Most often, this teenager dies as a result of a sharp change in the situation, but, as G. F. Morozov noted, in some cases, after a long struggle, he begins to recover and survives. The ability of a young plant to survive in such circumstances is determined by a number of factors, such as the degree of its oppression, the degree of severity of changes in environmental conditions, and, of course, biotic and abiotic factors affecting the growth and development of the plant.
Individual specimens of undergrowth often vary greatly within the same massif in such a way that one specimen of undergrowth, marked before felling as nonviable, recovered, while another remained in the category of nonviable. Spruce regrowth, formed on fertile soils under the canopy of birch or pine, often does not respond to the removal of the upper tier, because did not experience light deficiency even in its presence (Cajander, 1934, Vaartaja, 1952). After a buffer period of adaptation, the height growth of undergrowth increases many times, but small undergrowth requires more time for the functional restructuring of vegetative organs (Koistinen and Valkonen, 1993).
Indirect confirmation of the fact of the expressed ability of spruce undergrowth to change the category of condition for the better was given by P. Mikola (1966), noting that a significant part of rejected spruce forests (based on the state of undergrowth), in the process of forest inventory in Finland, was later recognized as suitable for forest growing.
Age structure as an indicator of the state of adolescence
Depending on the structure of the planting, from 3 to 17 percent of photosynthetic active radiation can penetrate under the canopy of spruce forests. It should also be noted that as edaphic conditions worsen, the degree of absorption of this radiation decreases (Alekseev, 1975).
The average illumination in the lower tiers of spruce forests in blueberry forest types most often does not exceed 10%, and this, in turn, on average provides the minimum energy for annual growth, which ranges from 4 to 8 cm (Chertovskoy, 1978).
Research in the Leningrad region, conducted under the direction of A.V. Gryazkina (2001) show that the relative illumination on the soil surface under the canopy of tree stands is 0.3-2.1% of the total, and this is not enough for the successful growth and development of the young generation of spruce. These experimental studies showed that the annual growth of the young generation of spruce increases from 5 to 25 cm with an increase in light penetrating under the canopy from 10 to 40%.
Viable spruce undergrowth in the overwhelming majority of cases grows only in the windows of the canopy of a spruce stand, since in the windows the spruce undergrowth does not experience a lack of light, and besides, the intensity of root competition there is much lower than in the near-trunk part of the stand (Melekhov, 1972).
V.N. Sukachev (1953) argued that the death of undergrowth is largely determined by root competition of mother trees, and only then by light deficiency. He supported this statement by the fact that in the very early stages of a teenager’s life (the first 2 years) “there is a strong decline of spruce regardless of the light.” Authors such as E.V. Maksimov (1971), V.G. Chertovsky (1978), A.V. Gryazkin (2001), K.S. Bobkova (2009) and others question such assumptions.
According to E.V. Maksimov (1971), undergrowth becomes unviable when illumination is from 4 to 8% of full. Viable undergrowth is formed in the gaps between the crowns of mature trees, where illumination averages 8-20%, and is characterized by light needles and a well-developed root system. In other words, viable undergrowth is confined to gaps in the canopy, and strongly suppressed undergrowth is located in the zone of dense closure of the upper tiers (Bobkova, 2009).
V.G. Chertovskoy (1978) also claims that light has a decisive influence on the viability of spruce. According to his arguments, in medium-density stands, viable spruce regrowth usually accounts for more than 50-60% of the total. In tightly closed spruce forests, nonviable undergrowth predominates.
Research in the Leningrad region showed that the lighting regime, i.e. The canopy closeness determines the proportion of viable undergrowth. When the canopy density is 0.5-0.6, undergrowth with a height of more than 1 m predominates. In this case, the proportion of viable undergrowth exceeds 80%. When the density is 0.9 or more (relative illumination less than 10%), viable undergrowth is most often absent (Gryazkin, 2001).
However, other environmental factors should not be underestimated, such as soil structure, soil moisture, and temperature conditions (Rysin, 1970; Pugachevsky, 1983; Haners, 2002).
Although spruce is a shade-tolerant species, spruce undergrowth in high-density plantings still experiences great difficulties in low light conditions. As a result, the quality characteristics of undergrowth in dense plantings are noticeably worse compared to undergrowth growing in medium-density and low-density plantings (Vyalykh, 1988).
As the spruce tree grows and develops, the threshold of tolerance to low light decreases. Already at the age of nine years, the need for light in spruce trees increases sharply (Afanasyev, 1962).
The size, age and condition of the undergrowth depend on the density of forest stands. Most mature and overmature coniferous plantations are characterized by different ages (Pugachevsky, 1992). The largest number of juvenile specimens is found at a density of 0.6-0.7 (Atrokhin, 1985, Kasimov, 1967). These data are confirmed by the research of A.V. Gryazkina (2001), who showed that “optimal conditions for the formation of viable undergrowth with a population of 3-5 thousand individuals/ha are formed under the canopy of tree stands with a density of 0.6-0.7.”
NOT. Dekatov (1931) argued that the main prerequisite for the appearance of viable spruce regrowth in the sorrel forest type is that the completeness of the maternal canopy is in the range of 0.3-0.6.
Viability, and therefore growth in height, is largely determined by the density of the planting, as evidenced by the research of A.V. Gryazkina (2001). According to these studies, the increase in non-viable undergrowth in sorrel spruce forests with a relative stand density of 0.6 is the same as the increase in viable undergrowth when the sorrel spruce forest density is 0.7-0.8.
In blueberry-type spruce forests, with increasing stand density, the average height of undergrowth decreases and this dependence is close to a linear relationship (Gryazkin, 2001).
Research by N.I. Kazimirova (1983) showed that in lichen spruce forests with a density of 0.3-0.5, spruce undergrowth is rare and qualitatively unsatisfactory. The situation is completely different with sorrel forests, and especially with lingonberry and blueberry forest types, where, despite the high density, there is a sufficient amount of undergrowth that is satisfactory in terms of vital condition.
Dependence of the dynamics of the state of spruce undergrowth on the recency of felling
As the relative density of the tree stand increases, the proportion of medium and large viable spruce undergrowth also increases, since competition for light in such a closed canopy most affects the small undergrowth. With a high stand density, the proportion of non-viable small spruce undergrowth is also very large. However, this proportion is significantly larger when the relative density is low, since in such light conditions competition increases, from which small juveniles primarily suffer.
With an increase in the relative density of the forest stand, the share of small non-viable undergrowth changes as follows: at low density, the share of small non-viable undergrowth is greatest, then it falls and reaches a minimum at a density of 0.7, and then increases again with increasing density (Figure 3.40).
The distribution of spruce undergrowth by condition and size categories confirms that the life potential of undergrowth grown in the conditions of the Lisinsky forestry is greater than that of spruce undergrowth in the Kartashevsky forestry. This is especially clearly seen in the altitudinal structure of the undergrowth, since the proportion of medium and large spruce undergrowth is, as a rule, greater at the Lisisinsky sites under similar forest conditions (Figures 3.39-3.40).
The better life potential of spruce undergrowth at the Lisinsky sites is also evidenced by the growth rates of undergrowth, which are shown in Figures 3.41-42. For each age group, regardless of life state, the average height of spruce undergrowth at the Lisinsky sites is greater than the average height of undergrowth grown in the conditions of the Kartashevskoe forestry. This once again confirms the thesis that in relatively less favorable environmental conditions (in terms of soil moisture and fertility - closer to the blueberry type of forest), spruce young trees are more able to demonstrate their competitive abilities. It follows that changes occurring in the canopy as a result of anthropogenic or other impacts give a more positive result in the context of improving the condition of spruce undergrowth in the conditions of Lisinsky rather than Kartashevsky forestry.
1. At each stage of development, the number of undergrowth, as well as the structure in height and age in the experimental plots, change in different directions. However, a certain pattern has been identified: the more the number of undergrowth changes (after fruitful seed years it increases sharply), the more the structure of undergrowth changes in height and age. If, with an increase in the number of undergrowth due to self-seeding, a significant decrease in the average height and average age occurs, then with a decrease in the number as a result of mortality, the average height and average age can increase - if predominantly small undergrowth goes into decline, or decrease - if predominantly large undergrowth goes into decline teenager
2. Over 30 years, the number of undergrowth under the canopy of the sorrel spruce and blueberry spruce forests has changed; in this component of the phytocenosis, the change of generations is continuous - the main part of the older generation goes into decline, and the undergrowth of new generations regularly appears, and first of all, after a bountiful seed harvest.
3. Over three decades, the composition of undergrowth at the observation sites has changed significantly, the share of deciduous trees has increased markedly and reached 31-43% (after cutting). At the beginning of the experiment it did not exceed 10%.
4. In section A of the ecological station, the number of spruce undergrowth increased by 2353 specimens over 30 years, and taking into account the surviving model specimens, the total number of spruce undergrowth by 2013 amounted to 2921 specimens/ha. In 1983 there were a total of 3049 specimens/ha.
5. Over three decades, under the canopy of the blueberry spruce and sorrel spruce forests, the share of undergrowth that moved from the “nonviable” category to the “viable” category was 9% in section A, 11% in section B and 8% in section C, i.e. on average about 10%. Based on the total number of undergrowth on the experimental plot of 3-4 thousand/ha, this proportion is significant and deserves attention when carrying out accounting work when assessing the success of natural regeneration of spruce in the indicated forest types. 103 6. From the category “viable” to the category “non-viable” over the specified period of time, from 19 to 24% moved, and immediately from the category “viable” to the category “dry” (bypassing the category “non-viable”) - from 7 to 11%. 7. Of the total amount of growing undergrowth in section A (1613 specimens), 1150 specimens of undergrowth of different heights and different ages were lost, i.e. about 72%. In section B – 60%, and in section C – 61%. 8. During observations, the proportion of dry undergrowth increased with increasing height and age of the model specimens. If in 1983-1989. it accounted for 6.3-8.0% of the total amount, then by 2013 dry undergrowth already accounted for from 15 (blueberry spruce forest) to 18-19% (sorrel spruce forest). 9. Of the total number of certified undergrowth in section A, 127 specimens became trees of reduced size, i.e. 7.3%. Of these, the majority (4.1%) are those specimens that moved in different years from the “non-viable” category to the “viable” category. 10. Repeated recording of the same specimens of spruce undergrowth over a long period of time allows us to indicate the main reasons for transitions from the “non-viable” category to the “viable” category. 11. Changes in the structure of undergrowth in height and age, fluctuations in numbers are a dynamic process in which two mutually opposite processes are simultaneously combined: the decline and arrival of new generations of undergrowth. 12. Transitions of adolescents from one category of condition to another, as a rule, occur more often among small adolescents. The younger the teenager is, the more likely a positive transition is. If during the first 6 years of observation, about 3% of specimens moved from the “VF” category to the “F” category. (with the average age of a teenager being 19 years), then after 20 years - less than 1%, and after 30 years - only 0.2%. 13. The dynamics of the state of undergrowth is also expressed by forest type. The transition of non-viable undergrowth to the “viable” category is more likely in the blueberry spruce forest than in the sorrel spruce forest.
Development of self-seeding
The young generation of woody plants up to 3-5 years old, and in the north up to 10 years old, formed from seeds naturally, is called self-seeding. Shoots that appear on the soil surface as a result of sowing seeds are called seedlings.
In the first year of its life, the size of self-seeding is far from the same. The height of a 2-year-old seed pine varies from 2 to 14 cm, and the height of 2-year-old seed birches varies from 11 to 76 cm. The significant difference in height, diameters and other external signs of self-seeding and undergrowth was explained by Charles Darwin. He explained fluctuations in growth and development primarily by individual variability. The hereditary characteristics of organisms within the same species are different.
Individual plant variability is most pronounced at a young age. For seedlings or seedlings, the external environmental conditions are grass cover, rainfall, snowfall, snowfall and other factors. They enhance the process of differentiation. which ultimately ends in failure. Natural thinning occurs, i.e. the loss of part of the self-seeding, which lasts in the planting throughout the life of the tree stand, but has a maximum at a young age.
The growth of seedlings also depends on the thickness and density of the litter. As the thickness of the forest floor increases, the total amount of self-seeding and undergrowth decreases. In forest types where the litter consists of litter from deciduous trees - ash, oak - and conifers, the development of self-seeding pine can be successful. In the presence of a dense litter of maple, aspen, linden, and elm leaves, seedlings covered with these leaves die. Mother trees in the forest create favorable conditions for the development of self-seeding, protecting, for example, tender shoots from the sun, preventing herbaceous vegetation from growing wildly.
A negative role in the process of natural regeneration is played by the cereal ground cover, especially reed grass, meadow grass, bluegrass, etc. Cereal plants form dense turf, preventing the emergence and development of seedlings. However, grasses and mosses do not always have a negative meaning. In the early stages of its development, sphagnum can be an additional moisturizer for downy birch seedlings.
Dense moss cushions made of cuckoo flax or sphagnum in the taiga coniferous forest prevent the successful development of self-seeding. Emerging seedlings with strong growth of moss or grasses may die due to lack of moisture. The upper soil horizons are drying out. If there is a forest under the canopy or heather is cleared, the appearance of turf grasses is excluded and favorable conditions are created for the growth and development of pine. Plants such as fireweed, heather, European hoofweed, kupena, and crow's eye help loosen the soil.
The growth of some plants in the ground cover can cause the risk of certain diseases of woody plants. Thus, in the northern regions of the taiga, spruce is affected by a rust fungus that spreads from wild rosemary.
Living ground cover in cleared areas can be useful for tree seedlings, as it protects them from frost, sunburn, and the drying effects of wind. Fireweed, etc., have a protective effect on the self-seeding of conifers. However, the cover is dangerous for tree seedlings as a competitor, taking away moisture, food, light and heat from them. Some plants (for example, lupine and clover) enrich the soil with nitrogen, improving the conditions for forest development. Knowing the nature of the grass cover, you can easily prevent its negative effects on the growth of self-seeding main tree species.
Adolescence development
The young generation of woody plants under the forest canopy or in clearings, capable of forming a forest stand, is called undergrowth. The presence of a sufficient amount of undergrowth under the forest canopy or in clearing does not mean that the forest needed for the farm has been formed. There are a number of factors that directly or indirectly negatively affect the further course of forest formation. Low temperatures and frosts often damage young growth, causing plants to grow poorly and take on a crooked shape. On heavy, damp and damp soils, the undergrowth is squeezed out of the soil by frost. Among young teenagers there is a large number of injuries and diseases.
The closing of the crowns of the undergrowth marks a new qualitative stage in the formation of the forest. In the case of uniform distribution of undergrowth arising from seeds of one seed year, a uniform closure is formed. From this period, undergrowth is considered a plantation, and the area occupied by it is classified as covered with forest. In the case of clump placement of undergrowth, the closure of crowns occurs later than with uniform placement. Clump regeneration is typical for multi-aged coniferous forests.
The undergrowth of individual tree species is classified taking into account their characteristics. Thus, spruce undergrowth is divided into three categories of reliability: stable, dubious and unreliable. (208;5)
The condition of the undergrowth (its growth and development under the forest canopy) depends on the closeness of the crowns of the maternal canopy. The largest amount of reliable undergrowth in coniferous forests occurs at a density of 0.4-0.6. A decrease or increase in canopy density negatively affects the reliability and abundance of young growth. In highly dense plantings, little light and heat penetrates the soil surface, there is not enough moisture in the soil, and the top layer of soil remains in a supercooled state for a long time. Therefore, those seedlings that are “lucky enough” to appear here almost all die in the future. In a sparse forest there is another extreme. Abundance of light and heat promotes growth
turf. Under these conditions, the pine undergrowth, having acquired independent significance, cannot withstand competition with the grass cover and dies either from frost or from the sun.
Various tree species under a closed forest canopy can remain in a state of oppression for a long time. For example, spruce and fir undergrowth up to 60 years or more. Pine, birch and aspen do not tolerate prolonged shading. Undergrowth plays a positive role in forest regeneration.
Undergrowth under the forest canopy reacts to sudden lightening to varying degrees. Young coniferous trees after removal of the parent forest canopy can get burned or significantly slow down growth and accelerate development.
According to OST 56-108-98, the following terms are distinguished:
Seedlings are plants of tree species up to one year old, formed from seeds.
Self-seeding is young woody plants of natural seed origin at the age of two to five, and in northern conditions up to ten years.
The undergrowth is the young generation of the forest, capable in the future of entering the upper tier and taking the place of the old forest stand, under the canopy of which it grew. Undergrowth refers to the generation of woody plants older than two to five years, and in the conditions of the North - older than ten years, before the formation of young growth or a layer of the forest stand.
Young growth includes viable, well-rooted trees of the main species with a height of more than 2.5 m and a diameter at breast height below the release diameter established in the regional logging rules, capable of participating in the formation of a stand, and therefore the logging of such trees is prohibited.
The undergrowth can be of seed or vegetative origin.
Seed reforestation is considered the most advanced, allowing new generations of trees, as a result of the splitting of characteristics, to successfully improve in response to a changing environment.
Vegetative regeneration, in its essence, is an absolute copying of the properties of the parent organism with the absence of genetic differences. This reduces the adaptive abilities of the new generation of such plants. Among tree species, almost all deciduous trees renew themselves vegetatively, unlike conifers. In this case, new individuals appear from the vegetative organs of the parent plant: dormant and adventitious buds on the trunk, branches, roots. This ability is used in forestry to propagate particularly valuable clones or individual specimens. The formation of adventitious roots on shoots of conifers in a natural environment is a rare phenomenon. Therefore, vaccinations are used for their vegetative propagation.
The process of accumulation of undergrowth under the canopy of a tree stand is called preliminary regeneration, i.e. renewal that occurs before the forest is cut down (before its death). The undergrowth under the canopy is called pregeneration undergrowth
Regeneration that occurs after forest cutting is called subsequent. Accordingly, the undergrowth that appears after felling is called undergrowth of the subsequent generation.
The undergrowth of all tree species is divided into:
· in height - into three categories of size: small up to 0.5 meters, medium - 0.6-1.5 meters and large - more than 1.5 meters. Young animals to be preserved are counted together with large juveniles;
· according to density - into three categories: rare - up to 2 thousand, medium density - 2-8 thousand, dense - more than 8 thousand plants per hectare;
· by area distribution - into three categories depending on occurrence (the occurrence of undergrowth is the ratio of the number of counting plots with plants to the total number of counting plots laid out in a trial plot or cutting area, expressed as a percentage): uniform - occurrence over 65%, uneven - occurrence 40-65%, group (at least 10 small or 5 medium and large specimens of viable and closed undergrowth).
Viable undergrowth and young growth of coniferous forest plantations are characterized by the following characteristics: dense needles, green or dark green color of the needles, noticeably pronounced whorl, pointed or cone-shaped symmetrical dense or medium-density crown extending at least 1/3 of the trunk height in groups and 1/2 trunk height - with a single placement, height growth over the last 3-5 years has not been lost, the growth of the apical shoot is not less than the growth of the lateral branches of the upper half of the crown, straight intact stems, smooth or fine-scaly bark without lichens.
Undergrowth and young growth of coniferous forest plantations growing on dead wood can be classified as viable according to the indicated characteristics if the dead wood has decomposed and the roots of the undergrowth have penetrated into the mineral part of the soil.
Viable undergrowth of hardwood forest stands is characterized by normal foliage of the crown and stems proportionally developed in height and diameter.
Paragraph 51 of the Timber Harvesting Rules states “When felling mature, overmature forest plantations, the preservation of regrowth of forest plantations of economically valuable species in areas not occupied by loading points, highway and apiary trail routes, roads, industrial and domestic sites, in an amount of at least 70, is ensured. percent when carrying out clear cuttings, 80 percent when carrying out selective cuttings (for mountain forests - 60 and 70 percent, respectively).”
In connection with this requirement, if there is a sufficient amount of viable undergrowth, the technological map for the development of a cutting area indicates the need to preserve it throughout the entire area of the cutting area or on parts of it if the undergrowth is arranged in clumps. Felling of undergrowth is permitted:
· when cutting sights;
· when cleaning hanging and dead trees;
· on the territory of upper warehouses and loading points;
· on logging roads;
· on skidding roads;
· in places where mechanisms are installed;
· during mechanized felling of trees within a radius of up to 1 m from the tree being felled;
· on routes up to 3 m long to allow the feller to move away from the tree.
Paragraphs 13 and 14 of the Reforestation Rules read:
Measures to preserve the undergrowth of forest plantations and valuable forest tree species are carried out simultaneously with the felling of forest plantations. In such cases, felling is carried out mainly in winter on snow cover using technologies that make it possible to ensure that the amount of undergrowth and young growth of valuable forest tree species is not less than that provided for during the allocation of cutting areas from destruction and damage.
During felling of forest plantations, viable undergrowth and young growth of pine, cedar, larch, spruce, fir, oak, beech, ash and other valuable forest plantations must be preserved in their corresponding natural and climatic conditions.
The undergrowth of cedar, and in mountain forests also the undergrowth of oak and beech, are subject to recording and preservation as the main species for all logging methods, regardless of the quantity and nature of its distribution over the cutting area and the composition of the forest stand before felling.
To protect the undergrowth of the main forest tree species from unfavorable environmental factors in clearing areas, more successful growth and formation of forest plantations of the required composition, the undergrowth of accompanying forest tree species (maple, linden, etc.) and shrub species are fully or partially preserved.
In pine forests growing on sandy loam soils, the regrowth of spruce forest plantations is preserved provided that the spruce plantation does not reduce the quality and productivity of the forest stand. When restoring pine and spruce forest plantations, undergrowth is, if necessary, retained in the felling to protect the soil and form stable and highly productive pine and spruce forest plantations.
Undergrowth affected by pests, underdeveloped and damaged during logging must be cut down at the end of logging work.
When carrying out selective felling, all undergrowth and young growth under the forest canopy must be counted and preserved, regardless of the number, degree of viability and the nature of their distribution over the area.
To determine the amount of undergrowth, conversion factors from small and medium undergrowth to large undergrowth are used. For small undergrowth, a coefficient of 0.5 is applied, for medium-sized ones - 0.8, for large ones - 1.0. If the undergrowth is mixed in composition, regeneration is assessed based on the main forest tree species corresponding to the natural and climatic conditions.
Counting of undergrowth and young animals is carried out using methods that ensure the determination of their number and viability with an accuracy error of no more than 10 percent.
In all cases, it is necessary to maintain predetermined distances between sites on the sights and counting tapes. On plots of up to 5 hectares, 30 registration plots are laid out, on plots from 5 to 10 hectares - 50 and over 10 hectares - 100 plots.
Currently, it is believed that of all the measures to promote natural reforestation, the most effective is the preservation of undergrowth, i.e., the emphasis is on preserving the results of preliminary reforestation. To preserve undergrowth, special methods of wood harvesting have been developed (“Kostroma method” with mechanized felling, shuttle method when working with VTM, etc.), which make it possible to preserve up to 65% of the undergrowth available in apiaries, but at the same time significantly reducing the productivity of the main work.
Preservation of undergrowth and young growth during logging ensures the restoration of forests from clearings with economically valuable species and prevents unwanted change of species, reduces the period of forest restoration and the time of growing technically mature wood, reduces the costs of reforestation work, and contributes to the preservation of the water protection functions of forests. In the scientific literature, for example, in the works of prof. V.N. Menshikov, there is information that this method of promoting reforestation can reduce the turnover of cutting the main species by 10–50 years.
However, as practice shows, a primary focus on preserving adolescence is not always justified for the following reasons:
· on most of the forested flat lands of the forest fund of the Russian Federation, the main species are conifers;
· in forests where light-loving conifers (pine, larch) are chosen as the main species, the regrowth of these species is almost absent due to their inability to develop normally under the maternal canopy;
· in forests formed by shade-tolerant conifers (spruce, fir), there is a large amount of undergrowth, however, according to our observations and according to other researchers, a large amount of undergrowth preserved during logging dies in the first 5–10 years after clear cutting due to a sharp change in the microclimate and light regime after removal of the maternal canopy (burning the needles and root collar, squeezing the roots, etc.). Moreover, the percentage of dying undergrowth directly depends on the type of felling, and, consequently, on the type of forest that preceded it;
· the undergrowth dying off within 1–2 classes of age litters the cutting area, increasing its fire hazard and increasing the risk of forest damage by pests and diseases.
In connection with the above, it can be argued that in certain types of forest, when focusing on natural forest regeneration, refusal to preserve undergrowth, with the obligatory abandonment of sources of contamination, can give more positive than negative results for the following reasons:
· logging technologies without preserving undergrowth are more productive than technologies with its preservation;
· the abandonment of a strictly defined network of apiary skidding tracks means that the load work of the skidding routes (one track) can be significantly reduced (depending on the distance from the upper warehouse, the forest stock per hectare and the carrying capacity of the skidding tractor), which will contribute to the improvement of forest soil due to its mineralization, as well as bringing the soil density to optimal for seed development, i.e. improving conditions for subsequent natural reforestation);
· when clearing cutting areas from logging residues, it becomes possible to use high-performance rake-type pick-ups;
· refusal to preserve undergrowth will allow for a wider use of tree skidding technology, dramatically increasing the productivity of the operation of clearing trees from branches (using mobile delimbing machines), and will allow concentrating most of the logging residues in the upper warehouse, significantly facilitating their further disposal and reducing the labor intensity of cleaning cutting areas.
A number of scientific publications devoted to the success of natural reforestation note that in clearings in Western and Central Siberia, 15–95%, and sometimes 100% of the preserved viable coniferous undergrowth perishes. The same data were obtained on some types of clearings for the conditions of the North-Western region of the Russian Federation V.I. Obydennikov, L.N. Rozhin. They note that “the mortality of spruce undergrowth (20 years old at the time of felling) over a five-year period after clear felling (in the conditions of the Krestetsky private farm) amounted to 18.5% in the emerging forb-reed type of fellings, and 57% in the reed-reed type. 3%, in Sitnikovovoye – 100% .
In addition, as a result of large-scale studies carried out in the 80s of the twentieth century, it was found that in general in the North-West region the area of forest plantations with a sufficient amount of undergrowth of main species for sustainable reforestation does not exceed 49.2%, and in some areas it does not exceed 10% (Novgorod region - 9.0%, Pskov region - 5.9%).
The above facts allow us to assert that in large forest areas the preservation of undergrowth is unprofitable due to poor prospects for its development or its insufficient quantity. In this case, subsequent natural reforestation comes to the fore, based on the mandatory preservation of sources of seeding and supported by such assistance measures as soil preparation, cleaning of cutting areas, etc.
From the point of view of subsequent natural reforestation (germination of seeds that have fallen into the soil), the condition of the soil will be one of the main factors influencing the success of this process. It is also obvious that the use of machines and mechanisms to perform special technological operations to prepare the soil for natural reforestation will increase the cost and complexity of the logging process. Therefore, when carrying out logging operations, it is necessary to strive for such an impact on the forest environment, in particular on the soil of the cutting area, which would provide optimal conditions for subsequent reforestation.
This approach is reflected in the Timber Harvesting Rules, in paragraph 56 of these rules it is stated: “In lowland forests, with clear cuttings without preserving young growth in forest types where the mineralization of the soil surface has a positive impact on forest regeneration, the area of the trails is not limited. The types (groups of types) of forest where such logging is allowed are indicated in the forestry regulations of the forest district or forest park.”
At the same time, the regulatory documents do not yet provide more specific instructions in which cases it can be considered that the mineralization of the soil surface has a positive effect on reforestation.
Caring for a teenager
After the completion of logging operations during summer harvesting and after the melting of snow and thawing of the soil during winter felling, the preserved undergrowth is trimmed and cared for. Undergrowth and young growth are freed from logging residues, and the root systems of plants that have lost contact with the soil are pressed to the ground. Broken, shriveled and severely damaged specimens during the logging process are cut down and removed from apiaries or landed along with logging residues.
After the main mortality, after 2-3 years, shrunken, severely damaged individuals of the main species are removed, for example, those with stripped bark wider than 2 cm, undergrowth of undesirable species or their trees of subsequent renewal and shrubs that interfere with the growth of the main species. In the first year after felling, such work should not be carried out, because unwanted tree and shrub vegetation serves as protection for the undergrowth from the sun, frost, and wind, which increases evapotranspiration. Caring for young trees, as a measure of promoting natural reforestation, is especially necessary for light-loving species: pine, oak, larch.
Under conditions of normal moisture supply, reliable (light) undergrowth increases not only transpiration, but also photosynthesis, metabolism increases, and root respiration is activated, which contributes to the development of the root system and assimilation apparatus. It is important that from the buds laid under the forest canopy, needles are formed in clearings, which are close in anatomy and morphology to light ones. New needles also arise from dormant buds.