Abstract
<jats:p>Modern approaches to assessing the structural complexity of forest ecosystems increasingly rely on analyzing tree-related microhabitats (TreMs), which serve as indicators of forest ecological integrity. Despite the growing number of studies in this field, data on the structure of TreMs in the primeval forest ecosystems of the Ukrainian Carpathians remain limited and fragmented. This study aimed to characterize the typological, morphometric, and ecological features of tree-related microhabitats in old-growth beech and spruce forests of the Carpathians and to analyze their microclimatic parameters. Field investigations were conducted in 2024 at four old-growth forest sites: within the Carpathian National Nature Park (Hoverla Protected Research Department, two plots), Boikivshchyna National Nature Park (slopes of the Buchok Ridge), and the primeval forest natural monument “Primeval and Quasi-Primeval Forests of the Hankovytske Forestry.” The study focused on microhabitats occurring on Fagus sylvatica and Picea abies. A total of 72 tree-related microhabitats were identified and categorized into eight types. The most common types were root buttress cavities, trunk cracks, trunk holes (without soil contact), trunk breakages, and primary soil accumulations, each accounting for 16.7 % of the total. Large woodpecker feeding cavities were recorded exclusively on Norway spruce trunks (DBH 39–79 cm, decay stage III), while dendrotelms were predominantly associated with European beech (decay stages IV–V). Morphometric analysis revealed that the formation of most microhabitats is associated with trees of substantial diameter (primarily >50 cm DBH) and advanced stages of wood decomposition (IV–V), consistent with the concept of structural forest maturity. The temperature regime of TreMs exhibited a narrow range (13–17°C), confirming their buffering function. Minimum temperatures were recorded in cavities in contact with the soil, while maximum temperatures were observed in open trunk cracks. The pH ranged from 4.29 to 7.44, reflecting the complex biochemical processes of mineralization and humification. Acidic pH values were typical of trunk breakages and cracks, which are associated with xylotrophic fungal activity, while neutral pH values were recorded in soil-contact microhabitats due to the buffering effect of the mineral substrate. Relative humidity reached its highest levels in dendrotelms and soil-contact cavities, whereas woodpecker feeding cavities were characterized by low humidity and high aeration.</jats:p>