Primary succession of birch was formed on the soils where the fertile layer was completely destroyed after amber mining. To restore natural forest plantations of pine in the Klesiv forestry biotechnology of soil restoration was used. After amber mining, the area was planted with pine; birch grew on its own. The age of plantations was 7 years. At this age, birch was cut. One year after pruning, soil samples were taken to explore the species and numerical composition of micromycetes as active transformers of plant residues. The technology involved the step-by-step cutting of birch: ½ of its part on one test area, ⅓ of its part on the second, and cutting to the stump - in the third case. Pruning of birch was carried out in order to allow for the active growth of pine. Thus, the shading of the pine was eliminated. After cutting, the birch remained in the territories and was not taken out. Accordingly, the fungi assimilated the remnants of cut wood. It was important to study the composition of soil deuteromycetes involved in the destruction of wood. Pruning pine on ½ and ⅓ stimulated the development and growth of pine for two reasons: decreased shading of the pine and increased the number of nutrients in the soil. Complete pruning of birch was not effective either in terms of the effective transformation of plant residues or in terms of plantation formation, as productive pines must grow in a mixed culture with other plant species (Table 1).

The study of biodegradation processes, and the nature of biodynamic transformation of organic matter is one of the objective indicators of productivity, stability and development of biocenoses. The amount of synthesis and destruction of soil organic matter are factors that determine the level of organization of the biosphere, while the detrital block in terms of complexity of structure and variety of functions plays a key role [45]. We have identified the main genera of micromycetes that inhabit the soils where birch pruning was carried out. These are usually the genera Zigomycota and Ascomycota, whose average CFU (colonies forming organisms) ranged from 156x10⁴ to 178 × 10⁴ in the areas where birch was cut and 87 × 10⁴ in the control area. The number of colonies of fungi in one gram of soil in the territory of A₂-C - the territory of the old forest was 198 × 10⁴ CFU.

It is important to emphasize that our results comply with the works of authors who studied the Mycobiota of coniferous, mixed and deciduous forests in the Polissya, as well as Canada and Japan, and found that the predominant soil deuteromycetes were genera Mucor, Mortierella and Penicillium [46]. The nutrient layer is annually replenished with substances that are a source of nutrition for soil destructors. Globally, 95% of its flow is limited due to the soil-microorganisms-vegetation system. Thus, the main role in global biogeochemical transformations in the biosphere belongs to forest biocenoses, which occupy more than 4.1 × 10⁹ ha of land surface [47]. The main role in the destruction of ecosystems belongs to fungi [48]. The biomass of fungi in the soil is 50-70% of the share of all microorganisms, which is 90% of the total number of destructors. The maximum reserves of fungal biomass are found in the soils of the forest zone. Fungi are involved in soil formation by binding mineral particles and ensuring the stability of soil aggregates, and they are the main producers and consumers of the carbon in the soil [49, 50].

The most common type of trophic relationship of soil fungi is associated with the consistent settlement of complex organic and inorganic substrates. A typical example is the mycological degradation and transformation of plant remains, which is relevant in the study of the formation of pine stands, and which became the basis for our research.

The grouping, as a system, is characterized by the interaction between the species that are part of it. In the group of hyphomycetes, the interaction between species is primarily due to trophic relationships. Determining the ratio of micromycete species in the studied soil indicates the content of nutrients in it, their composition and the availability of essential nutrients for the plants. The first degrading agents are types of soil micromycetes that use simple carbohydrates that are formed during the degradation of cellulose. These include most species of the genus Zygomycetes. Mucor sp., Mucor hiemalis, M. angulisporus, Rhizopus nigricans, R. microsporum, and Absidia coerulea were typical and common species (from 30 to 75%) in the studied areas, in ecotopes with ½, ⅓ share of cut birch and fully cut birch. In the final stages of substrate transformation, micromycetes appear that absorb lignin. The trophic relationships of micromycetes of the studied areas occur due to the presence of a complex of specific enzymes that hydrolyze polymers of plant residues and metabolize monomer units. Facultative saprophytes that have settled on dead plant residues have a high level of growth and rapid spread of spores, which is clearly seen in the soils where ½ and ⅓ birches were cut. Here, the assimilation of dead wood was most effective, the number of fungal propagules per 1 gram of soil was 189-192 × 10⁴ CFU.

Analysis of soil mycobiota of the studied ecotopes revealed the following patterns: a total of 47 species from 15 genera of micromycetes were identified. Table 1 presents 37 species from 12 genera (excluding random species) that were constantly found in the area, and formed biocenoses of the studied areas. For natural pine plantations, the age of which is 60 years, 34 species from 12 genera are characteristic. The species composition of soil micromycetes of the parent stand - the area where amber mining did not take place - differed sharply from the species composition of soil micromycetes of the disturbed areas. The natural stand is characterized by the highest capacity of the ecosystem. Species of the genera Mucor, Rhizopus, Absidia, Aspergillus, Trichoderma, Aureobasidium, Cladosporium, and Penicillium were characteristic of all studied ecotopes. The species P. funiculosum, P. roseopurpureum, Aspergillus fumigatus, A. niger, Aureobasidium pullulans, Cladosporium macrocarpon were constantly found. The frequency of these species in extreme ecotopes is from 24 to 51%. The same species were dominant (frequency of 50% or more) and those that are constantly present (more than 30%) in radionuclide-contaminated soils of the 10-kilometer Chernobyl Exclusion Zone [51]. The authors describe this phenomenon as the formation of radiosensitive strains in the relevant species populations. In the soils of the studied ecotopes, hyphomycetes-bioindicators of radioactive contamination of P. funiculosum, P. roseopurpureum, P. nigricans, Trichoderma viride, Auerobasidium pullulans, Cladosporium macrocarpon were found (Table 1).

The constant occurrence of the described species in the Rivne region (the Klesiv forestry) may indicate an increased level of radiation. Approximately 64 TBq (1b7 Mq) of total 137Cs activity, fell on the territory of Europe in 1986, and 18% fell on Ukraine, including the Rivne region. The migration of radionuclides in forest soils is slow because they have a multilayered vertical structure. Over the course of time, due to the pool of organic acids and oxidative exoenzymes of soil deuteromycetes, hot particles decomposed [51]. Fungi mycelium, numbering from tens of hundreds of kilograms to several tons per hectare, penetrated the upper horizons of the soil and promoted the active transfer of radionuclides in its various layers. According to the authors, Zhdanova N.M. et al., the process of transfer of radionuclides along the vertical profile of soils is slowed down by their fixation on clay minerals. The rate of movement of radionuclides varies depending on the type and physicochemical composition of the soil, but in almost all cases the bulk of radionuclides remains within its rhizosphere layer. Amber mining destroys soil layers, causes harm to vegetation, and radionuclides that still remain in the rhizosphere of plants in some ecotopes migrate chaotically.

As can be seen from Table 1, the frequency of species differs greatly in ecotopes, where pine stands were formed, and in the control area, where pine stands were formed together with birch naturally without the use of technology. The species composition of micromycetes of the mother stand (A2-C) is very diverse and not dominated by species of one division or genus. Areas with cut birch are characterized by the dominance of species of Zygomycota, which indicates an active process of settlement of cut wood by destructive species and its transformation. In the control ecotope, the species composition of micromycetes indicates the gradual formation of plantations, but it is not clear which of the plantations are formed, deciduous or coniferous, as no species were identified that characterize a particular type of plantation. Our data are consistent with the studies of the authors, who noted the difference in fungal flora depending on the type of forest.

The analysis of the structure of soil micromycete groups was carried out, where the biotechnology of pine plantations formation was applied by cuts of birch. These data were compared with the indices of ecological diversity of 60-year-old pine plantations. It turned out that in the edaphotopes of pine restoration zones the species composition is depleted compared to the species diversity of microscopic fungi, which is indicated by a decrease of 2.67 (average value for all ecotopes) times the Berger-Parker index, 2.36 times the Shannon index and 2.1 times the Pisl index and a 1.9-times decrease in the Simpson index (Table 2). Regularities are set in spring and summer.

According to the obtained results, birch pruning technologies in the amount of ½ and ⅓ proved to be the most effective for the diversity of micromycetes and their number.

The structure and level of complexity of soil fungal complexes were determined using the method of correlation groups according to Terentyev [51-53]. This method involves correlation, in our case, between the frequency of occurrence of a particular genus (or species if the genus was represented by one species) and the soil where the damaged areas are restored after amber mining. The values ​​of the correlation coefficients were determined at the levels of 1.0, 0.95, 0.9 and up to 0.7 and plotted as points within a pie chart, connecting them with lines. The obtained graphic structures (correlation groups) differed in the complexity of the structure. Among them, there were closed and linear (open) groups. Closed groups belong to stable and highly organized ones. Highly organized six-membered complexes of common soil micromycetes (Fig. 2) characteristic of forest ecosystems, where the main forest-forming species is pine, were only in 60-year-old A2-C plantations (60 years).

Fig. (2). A six-member structure Penicillium, Trichoderma, Aerobasidium, Mortierella, Aspergillus, Absidia.

Fig. (3). Correlation groups in the restoration of pine plantations by correcting plant biomass:

In all research areas, where pine plantations were restored by the correction of the biomass of plants that form the primary succession (in our case, birch), less complex and stable four- and three-membered groups were formed. In areas where birch was completely cut down, only a linear method of communication was established. The structural genera of these groups were mainly species of the genus Zygomycetes - Mucor, Absidia, Rhizopus, as well as Penicillium and Cladosporium (Fig. 3).

• A – Four-member group Mucor, Cladosporium, Absidia, Penicillium;
• B – Linear group Mucor, Penicillium;
• C – Three-member group Mucor, Penicillium, Cladosporium;
• D – Three-member group Rhizopus, Penicillium, Cladosporium.

Observations of the dynamics of fungal complexes, taking into account their location, the degree of soil degradation, and seasons indicate that this structure is quite labile and constantly changing during the restoration of the fertile soil layer. Comparison of structural genera and complexity of the form of correlation groups in soils formed in the areas of pine forest restoration at amber mining sites does not correspond to the stable structure of correlation groups of pine plantations at the age of 60 years. It takes time for forest pine biocenoses to be fully formed. The proposed biotechnology of pine forest restoration is promising but requires further long-term research and constant monitoring of changes in soil mycobiota until the formation of permanent, stable complexes of soil micromycetes.

The increase in the number of different groups of micromycetes should lead to changes in the chemical composition of the soil. Therefore, we conducted a comparative analysis of soil samples taken at the studied sites 1 year after pruning. The content of various forms of Nitrogen, Phosphorus and Potassium are given in Table 3. The content of basic nutrients in the 60-year-old forest was the highest and has not changed during our research. Analysis of soils from the studied areas after birch pruning indicated a slight but dynamic increase in basic plant nutrients, indicating active processes of soil enrichment with Nitrogen, Phosphorus and Potassium, which are the result of the active transformation of dead wood remain by soil deuteromycetes (Table 3).