The impacts of broadcast burning after clearcutting on the diversity of ectomycorrhizal fungi associated with hybrid white spruce seedlings in central British Columbia using morphological and molecular characterization techniques

In British Columbia, broadcast burning following clearcutting has been used to meet forest management objectives such as site preparation for restocking timber species. However, effects of broadcast burning on ectomycorrhizae (ECM), which facilitate nutrient and energy cycling within forests, is poorly understood. Difficulties include a complex soil environment and uncertainties in ECM identification. To determine effects of broadcast burning following clearcutting on the diversity and abundance (percent colonization) of ectomycorrhizal fungi, morphological and molecular (PCR-RFLP) methods were used to assess naturally regenerating and outplanted hybrid white spruce seedlings growing in clearcut, clearcut plus burned, and adjacent mature sites in the Interior of British Columbia. Morphological characterization resulted in 24 fungal morphotypes. Significant treatment effects and seedling differences occurred between naturally regenerating seedlings in clearcut and mature sites and between naturally regenerating and planted seedlings in clearcut sites. The abundance of some morphotypes differed on planted seedlings in clearcut compared with clearcut plus burned sites and for planted seedlings in treated (clearcut and clearcut plus burned) compared with regenerating seedlings in untreated (mature) sites. A Russulaceae type and Thelephora were the most abundant morphotypes on regenerating seedlings in the mature and clearcut sites, respectively. Molecular characterization showed no significant differences for treatment effects or seedling type. Amplification of the ITS region for eight commonly occurring morphotypes revealed 12 genotypes (having a shared band pattern for one or none of three restriction endonucleases) with 18 variants (having similar band patterns for two restriction endonucleases). Cenococcum, Tuber, Hebeloma and Thelephora had only one genotype, however, Amphinema, E-strain, MRA, and a Russulaceae type each exhibited two or three genotypes. Morphology showed differences in occurrence and abundance of some ECM fungi following clearcutting, and clearcutting plus burning, suggesting that disturbance may be altering the fungal composition of hybrid white spruce seedlings on these sites towards ECM best able to adapt to changing environmental conditions. Using both characterization techniques provided a comprehensive estimate of diversity, specifically for total species richness when using morphology, and for increased understanding of inter- and intra-specific variation with respect to molecular characterization of ectomycorrhizal associations.