This study was conducted as part of the LTER-BG (Long-Term Ecosystem Research) project—the Bulgarian Long-Term Ecosystem Research Network—involving the Petrohan-Ponor site team, and aims to monitor the species diversity of macrofungi. Unfavourable climatic conditions — prolonged summer drought followed by sudden cooling and early snowfall — significantly limited fruiting body development in most species typical of Bulgarian beech and spruce forests. Nevertheless, in early autumn, partially retained moisture in the highest-elevation site (a spruce culture) supported a relatively good fungal biodiversity, especially among species with shorter developmental cycles (e.g., Mycena spp.). A total of 106 species were recorded across the five sites; sites 1 and 4 were the most diverse, whereas sites 2 and 3 yielded the fewest records due to a cold, drying microclimate and steep terrain, respectively. Notable findings include Cantharellus friesii , a rare chanterelle listed in the Bulgarian Red Data Book as "Endangered"; Elaphomyces papillatus , registered for the first time at this elevation in association with spruce; and Chamonixia caespitosa , a rare hypogeous bolete whose presence confirms the successful naturalisation of the small-area spruce culture. Regarding the methodology, nuclear ribosomal DNA isolation and sequencing were performed on 14 specimens. These results confirm the impact of climate change on fungal adaptive mechanisms, as the reduced prevalence of traditional species creates conditions for rarer taxa to emerge.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: fungi Calvatia cyathiformis, Gastrosporium simplex, Hypomyces chlorinus, and Schenella pityophila, mosses Buxbaumia viridis, Didymodon de­sertorum, Heterocladium wulfsbergii, Leucobryum glaucum, Microbryum floerkeanum, Sphagnum obtusum, and Ptychostomum schleicheri var. latifolium, dicots Corylus colurna, Galatella linosyris, Menyanthes trifoliata, and Polygonum albanicum, and mono­cots Dactylorhiza saccifera, Epipactis helleborine subsp. distans, Ophrys apifera, and Orchis × hybrida