## 3 Results
### Mycobione Abundance Analysis  
The amplicons were assigned to 373 OTUs. Two-hundred-and-one genera and two-hundred-and-ninety-one species were found. Most of the fungi belonging to the _Ascomycota_ group were found in the control group, and the fewest after mulching the plots with the pine bark compost. On the other hand, the growth of fungi belonging to the _Basidiumycota_ group was stimulated by applying the same compost under the pine roots (Figure 3, Appendix A). It is also noteworthy that a considerable proportion of the fungi could not be identified. Of the group _Ascomycota_, most of those found belong to the _Leotionycetes_ (Figure 4). Fungi of the class _Eurotionycetes_ were also highly represented. The _Sordariomycetes_ were much less represented and were mainly found after soil treatments with sawdust and wood residues left after fellings (S and WW). Figure 2: Rarefaction analysis of coverage of OTU detected for different soil conditions studied: C—control, BCR—dark compost under the roots, BCS—dark compost on the surface, WW—wood waste and S—sawdust. The rarefaction curves for each sample are represented by different colours. The x-axis represents the sequencing depth in number of reads and the y-axis represents the estimate of OTU richness determined at species level. Among the _Basidiomycota_, however, the largest number of fungi was found in the _Agarino-omycetes_ present both in treatments (less in BCS than BCR, S, and WW) and the control. The second abundant class of fungi in treatments (BCS and WW) was _Tremellomycetes_; in this case, they were more frequent in BCS. From the _Mucoromycota_ group of fungi, most belonged to _Mortierellomycetes_ (Figure 4). They were found in both control and treatments, but the least amount was found in BCS. Figure 4: Relative abundance of detected fungi class versus various studied soil conditions: C—control, BCR—bark compost under the roots, BCS—bark compost on the surface, S—sawdust, and WW—wood waste. Three most abundant phylum are plotted. Fungi phylum is indicated in the charts. Figure 3: Relative abundance of detected fungi phylum versus various studied soil conditions: C—control, BCR—bark compost under the roots, BCS—bark compost on the surface, S—sawdust, and WW—wood waste. Among _Mucoromycota_, the _Umbelopsidomycetes_ were particularly common in BCS in contrast to _Mortierellomycetes_. The analysis carried out shows that OTUs belonging to 18-22 genera account for between 32% and 41% of all reads (Table 1, Figure 5). Fungi, which are characteristic of forest communities, such as fungi of the genus _Russula_ (which form mycorrhizal associations with tree roots), were found after S and especially WW treatments as well as other mycorrhizal fungi (Appendix A). Fungi of the genus _Penicillium_, which are antagonistic to the pathogen _H. annosum_, also colonised these variants and especially BCS. Fungi of the genus _Inocybe_ preferred BCS as a substrate, and BCR even more. They also formed mycorrhizal associations with tree roots, similar to _Tricholoma_ spp., which were also abundant in BCR. Control was dominated by the mycorrhizal fungi genus _Wilcoxina_. Some fungi, such as the genus _Amphinema_, only appeared or dominated in the variant of compost applied to the soil surface (BCS), e.g., _Hyaloscopylpha_ (Figure 5). If, on the other hand, the same compost was spread under the roots of the trees, fungal genera specific to this variant (BCR) only occurred, e.g., _Apiotrichum_, or were present there in the greatest quantities (_Cenangium_, _Geomyes_, _Inocybe_, and _Tricholoma_). The genus _Penicillium_ occurred everywhere but was strongly represented in the case of BCS, while the genus _Russula_ dominated after WW wood residues were used. Overall, the fewest taxa were found in the control (C-14) and in sawdust (S-13), while the most were found after the application of compost (BCR and BCS, 18 each) and wood residues (WW-17).