Ectomycorrhizal community structure of the admixture tree species Betula pendula, Carpinus betulus, and Tilia cordata grown in bare-root forest nurseries.

Highlights • ECM fungal communities of nursery grown admixture tree species are highly diverse. • Hornbeams and limes hosted 23 ECM fungal taxa each, while birches hosted 21 taxa. • ECM communities of hornbeams and birches were the most divergent. • Limes hosted the most consistent ECM communities regardless of the soil chemistry. • Most abundantly found fungal species belonged to genera Tuber and Hebeloma. Abstract In many European countries, recent policies and forest management have been striving to restore and increase forest biodiversity. One of the ways to achieve this goal is by increased planting of admixture tree species, such as birch, hornbeam or lime, after clearcutting or in older, otherwise homogenous forest stands. However, because admixture forest tree species present less economical value than trees such as pine or oak, they are object of fewer studies, and in this context their mycorrhizal relations are not fully known. Describing them would further aid the use of such trees in forest management. This study focused on the ectomycorrhizal (ECM) fungal communities of two-years-old silver birch (B. pendula L.), European hornbeam (C. betulus L.) and small-leaved lime (T. cordata Mill.) seedlings under bare-root forest nursery conditions. The ECM fungal partners of the studied trees were identified based on the molecular approach, and the uncovered community structure was analyzed in context of the local soil chemical parameters. We found that the ECM fungal communities of admixture tree species in bare-root nurseries are of high diversity, and contain a wide array of fungal species. Our study identified the highest taxa richness (23 taxa) associated with the roots of hornbeams and limes, followed closely (21 taxa) by birch. Surprisingly, ECM fungal communities of lime (family Malvaceae) were more similar to hornbeam and birch (family Betulaceae) than the two were to each other. The lime ECM fungal communities were also the least divergent across the five tested nurseries, showing little response to differences in the soil chemistry. The most abundant and frequent fungi found in the study were Tuber (average relative abundance: 18.9%) and Hebeloma (average relative abundance: 18.4%) species. Some of the fungal taxa we recorded have never before been identified under nursery conditions (e.g., Lactarius pubescens , Leccinum holopus , Pachyphloeus melanoxantha , Russula grata). Pachyphloeus melanoxantha is a rare species in Europe, and this study recorded one of its first records in Poland. Our results present not only a description of ECM associations of tested trees (providing the first ever description of young hornbeam ECM communities), but also may have practical implications both for producing planting stock of these admixture trees, and for the later replanting of those into forest stands. [ABSTRACT FROM AUTHOR]