Forest management and maintenance of ectomycorrhizae: A case study of green tree retention in south-coastal British Columbia

Abstract

Assessment of ectomycorrhizal (EM) colonization was carried out in a variable green tree retention experimental block near Powell River, British Columbia. We hypothesized that increasing retention level enhances colonization of EM fungi onto seedlings in harvested areas. We also investigated the role of isolated trees in EM maintenance. Transects were established in treatments where 0% (a clearcut), 5%, 10%, and 30% of trees were retained. Douglas-fir seedlings (Pseudotsuga menziesii) were planted at 5, 15, 25 and 45 m from the remaining forest edge and excavated 18 months later for analysis of EM colonization. Within the forest, soil cores and sporocarp surveys provided information on EM species potentially available for colonization of seedlings. We observed a total of 85 EM morphotypes. The edge effects—declines with distance from the forest, observed in the 0% retention treatment—were diminished in the higher-retention treatments. EM richness and root colonization increased insignificantly with increasing tree retention when the influence of ubiquitous early-stage EM fungi and inherent microsite differences were accounted for. EM diversity next to isolated trees was greater than at 10 m from the trees, but lower than at 5 m from the forest edge. We discuss the implications of these relationships and the role of isolated trees in the context of these exploratory findings. While these results suggest certain trends, they are for a single installation and their applicability to forests elsewhere in the region needs further study.