Substrate properties, forest structure and climate influences wood-inhabiting fungal diversity in broadleaved and mixed forests from Northeastern Romania

Aim of the study: The main objective of this study was to find the factors which best explains the wood-inhabiting fungal species’ richness in beech and oak-dominated forests.Area of study: We focused on broadleaved and mixed forests found in Northeastern Romania.Materials and methods: 59 plots were randomly set up in broadleaved and mixed forest stands, in which vegetation structure, composition, and topoclimatic factors were quantified along with wood-inhabiting fungal richness. Generalized linear models were used to characterize relationship between fungal diversity and biotic and abiotic factors.Main results: 374 taxa were identified, with numerous species found to cohabitate, the highest sharing being between Fine Woody Debris and Downed Coarse Woody Debris. The best predictors of total diversity were related to the substrate, management, stand structure, and macroclimate. Higher volumes of logs and large branches in various decay stages increased fungal richness. The same effect was found in diverse forests, with large snags. Macroclimate and topoclimate positively influenced diversity, through De Martonne Aridity Index and snow cover length, both indicating macrofungi preferences for higher moisture of substrate. Silvicultural interventions had an ambivalent effect to fungal diversity, phenomenon observed through stump numbers and proportion.Research highlights: Particular environmental characteristics proved significantly important in explaining different wood-inhabiting fungal richness patterns. Substrate-related variables were the most common ones found, but they were closely linked to climate and forest stand variables.Keywords: Wood-inhabiting fungi; oak, beech and coniferous forests; substrate diversity; dead wood types; coarse woody debris; fine woody debris; climatic variables.Abbreviations used:ALT, elevation; ASPI, Aspect Index; BIO1, mean annual temperature; BIO4, temperature seasonality; BIO7, annual temperature range; BIO12, annual precipitation; BIO15, precipitation seasonality; CWD, coarse woody debris; DBH, diameter at breast height; DCWD, downed coarse woody debris; DCWD_DECAY, DCWD decay diversity; DCWD_DIV, DCWD taxonomic diversity; DCWD_SV, surface-volume ratio of DCWD; DCWD_VOL, DCWD volume; DMAI, De Martonne Aridity Index; DMAI_AU, Autumn DMAI; DMAI_SP, Spring DMAI; DMAI_SU, Summer DMAI; DMAI_WI, Winter DMAI; FAI, Forestry Aridity Index; FWD, fine woody debris; L_SNAG_BA, large snag basal area; OLD_BA, basal area of old trees; POI, Positive Openness Index; RAI, Recent Activity Index; SCL, snow cover length; SLOPE, slope; SNAG_N, snag density; STUMP_N, stump density; TPI, Topographic Position Index; TREE_BA, mean basal area of trees; TREE_DIV, tree' Shannon diversity