Ectomycorrhizal and fine root foraging across European forests: the concept of complementarity within “root-mycorrhiza-bacteria” continuum

This study examined ectomycorrhizal and fine root foraging mechanisms in 38 stands along climate gradient representing northern boreal, hemi-boreal and temperate forests: 13 Scots pine forests covering a latitudinal range from 69? to 49? N; 11 silver birch forests covering a latitudinal range from 53? to 66? N; 15 Norway spruce forests covering a latitudinal range from 68? to 48? N; the data for twelve spruce sites were published in Ostonen et al (2011). The absorptive fine roots association with fungal and microbial networks in northern boreal and temperate birch forests were studied in more detail. The birch stands` ages varied from 9 to 74 years. The soil samples were taken from the upper (0-20 cm) organic layer of the birch stands soils. The bulk soil and rhizosphere bacterial communities were analysed separately. Bacterial community profiling was performed using Illumina® HiSeq 2000 sequencing of the combinatorial sequence-tagged PCR products amplified from V6 hypervariable region of the 16s rRNA gene (Gloor et al. 2010). Bacterial community structure in birch forest soil was affected by the environmental conditions in a given geographical location. The bulk soil and rhizosphere bacterial communities were different and responded differently to the environmental changes. Soil chemical composition, birch roots physiological status and composition of the ectomycorrhizal fungal community were the factors related to the structural changes in bacterial community. Complementary changes in „root-mycorrhiza-microbes continuum“ revealed in the forest ecosystem adaptation to the local geographically defined environmental conditions.