About thinning in the Arkhangelsk region

. An analysis was made of the growth of birch-spruce plantations, passed through three stages of thinning (in 1966, 1974 and 1984) in the Northern district forestry (in the Obozersky forestry) in the Arkhangelsk region. The duration of observations is 54 years at the time of the last count in 2020. The results of past studies by employees of the FBU "SevNIILKh" were taken into account. During the period under review, the forest stand in the control section (without thinning) developed quite dynamically. The birch element of the forest prevailed at all stages of growth and was characterized by the highest productivity (I-II quality class) at the age of 40-50 years. At present, the period of active growth has already passed, the stands are approaching the age of natural ripeness, as evidenced by the decrease in the quality class to IV, the decrease in the average height, and the decrease in stock. Spruce in the second tier and in a depressed state. With the continuation of the decay of the birch element and with an increase in the light regime, the spruce will actively grow. The research data show that in stands that have been thinned, the trees become larger, the yield of large-sized marketable wood is greater than in non-sparse ones. Since the main place in the cost of timber belongs to quality indicators, the economic efficiency of plantations with thinning is obvious. Through thinning, it seems possible to form plantings of optimal composition and density, better growth rates and at the stage of main felling, providing a greater economic effect compared to control


Introduction
The dynamics of forests in the study area under consideration shows a significant decrease in the area of conifers with an increase in the area of deciduous plantations over the past 10 years. This indicates the need for a transition from extensive to intensive forestry. The projected average increase in 2030 is 0.8 m 3 /ha per year. On a vast area of forests in the north-taiga forest region of the European part of the Russian Federation, a change of species is taking place. Analysis of forest deaths from fires, adverse environmental conditions and soil and climatic factors (FSL and SCF), pests and diseases of the forest showed that there are high risks of forest fires and extreme natural phenomena.
According to the forest planning materials, thinning in young forests (clarification and clearing) was actually carried out over ten years with the implementation of planned indicators by 95%, passing felling by 3.0 times, and thinning -by 8.0 times exceeded the planned figures. Renewal felling is also carried out on an area of 433 ha, reshaping on an area of 36.5 ha, and landscape formation felling on an area of 124.4 ha. At the same time, due to the remoteness of the forest inventory, based on surveys of the current year, within the framework of budget projections, reduced volumes of clarification and cleaning were agreed annually. Incomplete implementation of the entire scope of activities is also associated with the termination of contracts with tenants of forest plots.
In this regard, it is necessary to prevent the change of species, to improve the conditions for the restoration of coniferous trees through thinning forest care. These measures should be aimed at forests of different structure and origin. Changing the period (term) of forest care purposefully leads to an increase in the natural resource potential of forests. Thinning makes it possible to organize a farm in natural and artificial plantations for growing wood and green mass, to obtain sawn timber and building assortments, raw materials for the pulp and paper industry, energy raw materials, etc. [1-3, 5, 7-8, 10].

Materials and methods
The article studied birch-spruce plantations (Northern district forestry, Obozerskoye forestry, Arkhangelsk region), where three methods of thinning were carried out (in 1966, 1974 and 1984), in 2020 plantings were examined on trial plots -PPP 2RU PPP 19 (control PPP 1K), PPP 20 RU (control -PPP 20 K). As an experiment, by creating and growing pine forests without a spruce layer in a 50-year-old mixed pine forest (PPP 20), all spruce was previously cut down, the sampling rate for pine was 24%, for birch -90%. Based on the research, the characteristics of the forest stands of the experimental sections -trial plots from the moment of laying by the employees of SevNIILKh (based on the reporting materials of previous years) until 2020 were predicted.
One of the birch-spruce stands as a control (PPP 1K -control). Here, the ratio of tree species was initially preserved, no maintenance was carried out. The main task is to track the indicators of the emerging forest stand with the initial predominance of birch. In other areas, thinning was carried out from 2 to 3 steps, with different thinning parameters (PPP 2RU, PPP 19). On the first test (PPP 2RU), 3 stages of thinning were performed, the number of birch trees and other associated species was significantly reduced. The purpose of thinnings is the development of a mixed stand with a predominance of spruce.
On the third test (PPP 19), the modes of use for the formation of a clean spruce forest. The task of the first thinning techniques performed was to remove all associated species, to monitor the development of the spruce element of the forest.

Results
The research methodology includes generally accepted silvicultural methods for studying forests. Over the past period after the start of the research, the staff of the institute found that the forest plantation in the control was formed quite dynamically. Birch dominated, having high productivity (I-II quality class) at the age of 40-50 years. It should be noted that the period of active growth has already ended and the stage of approaching natural ripeness has begun, since the quality class is decreasing to IV, average height, reserve. Spruce remains in the second tier, for the entire period it was in a depressed state. With the continuation of the decay of the birch element and the increase in light space, it is more likely that the spruce will grow. The research methodology includes generally accepted silvicultural methods for studying forests. Over the past period after the start of the research, the staff of the institute found that the forest plantation in the control was formed quite dynamically. Birch dominated, having high productivity (I-II quality class) at the age of 40-50 years. It should be noted that the period of active growth has already ended and the stage of approaching natural ripeness has begun, since the quality class is decreasing to IV, average height, reserve. Spruce remains in the second tier, for the entire period it was in a depressed state. With the continuation of the decay of the birch element and the increase in light space, it is more likely that the spruce will grow.
In the second plantation (trial constant area 2RU), the stand is the most productive of the presented options. Thanks to timely care, due to the fact that the proportion of birch is insignificant, spruce has just begun to increase its performance (absolute fullness, height, and stock), overtaking other species in terms of stock over a period of 50-70 years and subsequently having excellent growth. At the same time, the spruce in the second tier is the first of pine and birch. On the trial permanent area 19, there is a pure spruce forest, birch and pine were previously cut down. But birch grows faster, complementing the upper tier with pine. The results confirm the expediency of timely care, especially with the participation of economically valuable breeds. Examples of wood yield by size categories are presented on the example of a 20K control plot for the study periods (Tables 1-5). The average volume of the whip in pine was 0.116 m 3 , in birch -0.052 m 3 , and in the plot -0.090 m 3 . The average volume of the whip in pine was 0.159 m 3 , in birch -0.059 m 3 , and in the plot -0.124 m 3 . The average volume of the whip in pine was 0.159 m 3 , in birch -0.071 m 3 , and in the plot -0.127 m 3 . The average volume of the whip in pine was 0.245 m 3 , in birch -0.089 m 3 , and in the plot -0.200 m 3 . The average volume of a tree-whip was 0.306 m 3 for pine, 0.080 m 3 for spruce, 0.123 m 3 for birch, and 0.226 m 3 for the plot. According to the data, the following dynamics can be seen that in the control plot 20K in 1991, 1997, 2002, small wood prevailed, and from 2010 to 2020, medium wood.
On the trial plot of 20 RU from 1991 to 1997, small wood prevailed, and from 2002 to 2020 -medium wood. On the control trial plot 1K in 1966, 1974, calculations were not carried out, from 1986 to 2010, small wood size is small, in 2020, data on small and large wood are at the same level.
No calculations were carried out on the trial plot 2RU in 1966,1974. From 1986 to 2001, small timber dominated, and from 2010 to 2020, medium timber.
On trial plot 19, there is an increase in medium-sized wood, a decrease in small wood. After analyzing all the histograms, we can conclude that over the periods of research, the proportion of large and medium wood only increases with age, while the proportion of small wood, waste and firewood decreases. The patterns obtained will be useful for developing standards for the marketability of forest stands of secondary generation.

Discussion
The disadvantage of the current standards for forest maintenance felling is the lack of an integrated approach:  Appointment of forest management measures is carried out with the averaging of the standard, compiled for very large areas that do not take into account the characteristics of the forest conditions of each specific planning object.
 The standards were created according to the types of forest. The scheme of forest types does not take into account the nature of soil-forming rocks, on which the reforestation process (the course of succession) largely depends.
 It is impossible to predict the development of a unit for the full cycle of forest growing.  The standards do not take into account the economic efficiency of the activities.  Appointment of forest management measures in the course of forest management is carried out according to the state of the allotment at the time of taxation, without taking into account past years.
 Activities are not linked.  The standards are designed for tree-length technology.

Conclusion
For forest care felling:  Data on the main indicators of forests, stages of plantation formation, ways of selling and selling timber.
 Research and evaluation of forests.  Studying the state of forest plantations after felling, what is the effect of felling, determining the intensity of felling by the number of trunks of the remaining part. The results as a basis for the protection, protection, reproduction and use of forests, which allows them to be applied in the form of an algorithm for felling, while not harming the environment and increasing productivity. In the course of work on the topic, it was revealed that the main indicators in the formed forests are: species composition, commodity structure, volumes of use and costs. All this should determine the work plans for logging and for each taxation unit, the feasibility of logging, their parameters, and the profitability of logging. The main taxation indicator for thinning planning is relative density [4,6,9].
Controlling the number of trees by intensity through thinning increases stand productivity without increasing phytomass stock or carbon sequestration per unit area. At the same time, the quality of the assortments can be improved to obtain sawlogs while minimizing the carbon accumulation in wood products with a long service life.
Properly performed thinning does not cause a decrease in growth. This has been shown by long-term experiments. And the dropout losses are significantly reduced. In experiments with a duration of more than 60 years, laid down in the Plesetsk forestry of the Arkhangelsk region, the losses on mortality after thinning amounted to 30 to 50% of mortality in the control areas where there were no fellings. In the new experiments set up in the Plesetsk forestry, care was more regular, and mortality losses over 25 years are 4-14% control mortality. Consequently, after thinning, the rate of carbon accumulation is maintained, and the rate of return largely depends on the way the wood obtained in the process of thinning is sold. In addition, the positive impact of thinning is manifested in obtaining larger-sized wood at a ripe age, which is used for the manufacture of durable products. Undoubtedly, the improvement of the composition of forest stands and the increase in the share of economically valuable species also play a certain role.
Since climate change mitigation measures are largely related to forests (combating forest fires, forest pests and diseases and other disasters, intensive reforestation and afforestation, etc.), it is obvious that the organization and planning of forestry activities are an important tool in adaptation and climate change mitigation. By increasing the intensity of cutting, it is possible to increase the participation of conifers in the species composition. This will increase the productivity and quality of wood, as well as reduce the risk of fires. Further, using more wood from thinnings only contributes to the conservation of forests.