Ectomycorrhizal fungal communities of black spruce differ between wetland and upland forests

Ectomycorrhizal (ECM) communities of black spruce (Picea mariana (Mill.) BSP) seedlings were characterized from three habitats spanning a moisture gradient in central British Columbia: black spruce dominated wetlands, black spruce - tamarack wetlands, and black spruce - lodgepole pine uplands. Morphological and molecular (PCR-RFLP) analyses indicated a diverse community of root-associated ECM fungi consisting of 33 morphotypes and 65 genotypes. ECM abundance varied significantly between habitats for six morphotypes. Although many occurred in all three habitats, some occurred in only one or two, and some genotypes had distributions that suggested habitat specificity across the moisture gradient. Intraspecific variation (defined as genotype variation within morphotypes) ranged from one to seven genotypes, depending on ECM morphotype. Both morphological and molecular analyses showed that ECM diversity was greater in upland than in wetland habitats and greater in black spruce - tamarack wetlands than in black spruce dominated wetlands (alpha <= 0.05). Morphological assessment captured contributions to diversity by both abundant and less abundant ECM morphotypes, whereas molecular analysis revealed patterns of genetic variation and habitat distribution at a finer resolution. The study presents the first comprehensive information on black spruce ECM and suggests that ECM community composition and richness varies across the moisture gradient in response to soil heterogeneity and alternate hosts (tamarack and lodgepole pine).