Microscale spatial distribution patterns of red oak (Quercus rubra L.) ectomycorrhizae

The microscale spatial distribution patterns of ectomycorrhizal (ECM) morphotypes of red oak (Quercus rubra L.) were analyzed over a 600 × 6 × 3 cm (length x width x depth) soil monolith. For this purpose, the soil monolith was divided into 2 × 2 × 1 cm cuboids. Each cuboid was assigned to an organic sublayer, namely the F- or H-layer. A new classification method was used to combine morphotypes with similar distribution patterns into five different groups. For identification of the ECM fungi, internal transcribed spacer (ITS) regions from nuclear rDNA were sequenced and compared with sequences from the international GenBank. Twenty-eight ECM types were identified in the soil monolith. Using this new classification method, it was found that the majority of morphotypes (16) appeared in a scattered horizontal distribution and that only 5 morphotypes formed clusters. In addition, it was found that many morphotypes had a clear preference for a specific organic sublayer: 14 morphotypes preferred the F-layer, 5 the H-layer, and only 4 morphotypes showed no preference for a given layer. Analysis of the distribution patterns showed that ECM fungi either exclude each other or occur together. The most frequent morphotypes, Cenococcum geophilum and Tomentella spec. 01, were associated with the whole ECM community. In contrast, the frequent morphotype Tomentella terrestris showed the lowest degree of association among the identified morphotypes.