Beyond seedlings: ectomycorrhizal fungal networks and growth of mature Pseudotsuga menziesii

1. Mycorrhizal networks are conduits for the transfer of resources between hosts. While ectomycorrhizal networks (EMN) are known to influence seedlings, their effect on adult tree growth remains unknown and may have important implications for forest responses to future climates.

2. We used annual basal area increment of trees and previously described Rhizopogon vesiculosus and Rhizopogon vinicolor EMNs to examine an association between the number of connections between trees through an EMN and the growth of adult interior Douglas-fir. We compared this relationship for the year the networks were mapped, in 2008, with eight years previous and eight years afterward. We also compared the variation in standardized growth (2000–2016) to examine the association between growth variability and EMN variables.

3. Greater growth was positively associated with 1) the number of connections to other trees via a Rhizopogon vinicolor EMN, and 2) the number of genets of Rhizopogon vesiculosis by wh...