Below-ground ectomycorrhizal community structure in two Picea abies forests in southern Sweden

Ectomycorrhizal community structure is likely to be influenced by factors s uch as anthropogenic stress, site history and degree of isolation. Informat ion about the mycorrhizal community at the level of individual mycorrhizal roots is needed, since these are the organs for nutrient exchange. To ident ify mycorrhizal species we used morphotyping based on colour and external a natomy of the mycorrhizal roots. The morphotypes were further divided using restriction fragment length polymorphism (RFLP) analysis of the internal t ranscribed spacer (ITS) region of the ribosomal DNA extracted and amplified from the mycobionts colonizing single mycorrhizal roots. The communities s tudied were in two similar 60-year-old Picea abies (L.) Karst. forests loca ted in southern Sweden approximately 50 km apart at sites with different N deposition. The level of mycorrhizal colonization was almost 100% at both s ites, but the total number of mycorrhizas was 30-42% higher at the northern site. Six morphotypes were distinguished at the northern site with the low er N deposition (Vedby), and four at the southern site (Skrylle). Some morp hotypes consisted of several ITS types and identical ITS types were also fo und in roots assigned to different morphotypes. The RFLP data revealed a to tal of 16 ITS types. Eleven of these were identified at least to genus by c omparison with local or regional reference material. Five ectomycorrhizal t axa, Cenococcum geophilum, Thelephora terrestris, Tylospora fibrillosa, Tyl opilus fellelus and Ve-95-3 were common to the two sites but the total numb er of taxa recorded at Vedby was twice as high as at Skrylle. Possible reas ons for the differences between sites are discussed.