## 4 Discussion
### Observed Positive Changes in Soil Mycobiomes after Treatments  
The Venn diagram shows that the control contained fewer OTUs, especially compared to BCR (2.6 times more) and S (about 2 times more). These two variants also dominated in terms of the number of OTUs compared to other organic matter. Compost and sawdust also had the highest number of common organisms, e.g., BCS/S--156 and BCR/S--163. The fewest OTUs were detected in wood waste (WW) or its combinations with other treatments. This is probably since wood waste, unlike compost, was colonised by lignin- and cellulose-degrading fungi, but these are also the most characteristic of the forest environment. Hydrolysis of cellulose requires synergism of several organisms, including bacteria, actinobacteria, filamentous fungi, and plants [47]. Among these organisms, filamentous fungi stand out, with the genera _Penicillium_ and _Trichoderma_ known as models for cellulase production at laboratory and industrial scales [48]. Under our experimental conditions, the expected species of forest mycorrhizal fungi occurred in WW and S, such as _Russula_ and _Inocybe_ in BCS and BCR (Table 1, marked in yellow). Other fungi antagonistic to the pathogen _Heterobusiation_, such as _Penicillium_, were more frequent or even twice as frequent in WW or S than in the control group. On the other hand, filamentous fungi of the _Ascomycota_ group of the genus _Sagenomella_, which cause diseases in animals (e.g., _Sagenomella chlamodopa_, which causes systemic diseases in dogs), were predominant in the soils after agricultural use. In our study, _Penicillium_ accounted for between 4% and 10% of sequence reads, and the highest abundance was found in soils enriched with bark compost under the roots (10%) (Table 1). Soil enrichment also increased the abundance of _Trichoderma_ from 0.2% in the control to 0.9% in bark compost under the roots and wood waste groups. Coarse woody debris consisting of pits, stumps, root mounds, and logs, that are formed as a result of tree fall, also supported the development of ectomycorrhizae [49]. The control after 20 years of the experiment differed from the treatment variants, as shown by the Bray-Curtis dissimilarity index (Figure 8). Thus, the addition of organic matter accelerated the changes in the forest soil environment. Sawdust (S) and logging residues (WW) were particularly favourable concerning the Shannon index (Figure 7). The latter certainly contained fungal spores, including mycorrhizal spores, and were covered with the mycelium of wood decomposing fungi, which are thus antagonists of _H. annosum_. The forest habitat, assessed as fresh coniferous forest, is not very fertile but is suitable for growing pines. By adding organic material, we created an organic horizon (characteristic of forest soils) and restored the natural interactions between the fungi so that none of them dominates. The above research findings are in line with the studies of [PERSON] et al. [17]. As we did, they investigated the effects of pine sawdust, composted bark, or coarse woody postharvest waste from conifers on the abundance and diversity of cultivable fungi to increase soil suppression of _Armillaria_ and _Heterobasidation_. The soil was found to be colonised by saprotrophic fungi of _Ascomycota_ and _Zygomycota_, including species known to be potential antagonists of _Armillaria_ or _H. annosum_ (e.g., _Clonostachys + Trichoderma_ spp., _Penicillium commune_, _P. daleae_, _P. janczewskii_) or to stimulate _Armillaria_ (e.g., _Pseudogymnocus roseus_, _Trichocladium opacum_). Three years after treatment, fungal abundance and diversity, the abundance of _P. commune_ and, locally, _P. janczewski_ increased, while _Clonostachys_ + _Trichoderma_ spp. and, locally, _P. dalae_ and _T. opacum_ decreased [50]. The addition of organic matter to soils established 10 years ago after agricultural use had a positive effect on the growth of bare-root pine seedlings. The larger annual increases in shoot, needle length, and biomass (compared to control plants) were clearly visible.