Use of low nitrogen fertilizer as a strategy for maintaining mycorrhizal colonization on whitebark pine seedlings inoculated with native fungi in the greenhouse

Abstract

Inoculation of whitebark pine (Pinus albicaulis Engelm. [Pinaceae]) with native ectomycorrhizal fungus Suillus sibiricus (Bonard.) Singer was investigated under a variety of nursery scenarios. Because fertilization often prevents mycorrhizal colonization in the greenhouse, we tested a low nitrogen (N) fertilizer. In general, ectomycorrhizal abundance was greater in longer containers (21 cm compared with 14 cm); when inoculum (slurry) originated from fresh, rather than dried, sporocarps; and when seedlings were subsequently given very low (13 ppm N every other week) or no additional N fertilizer. Slurry type interacted with container length, and fertilizer rate and colonization rates were all low on seedlings in short containers, except for those that were not fertilized and given slurry from dried sporocarps. Results show that drying and storing sporocarps for future use in slurry is possible although certain conditions might apply. No differences were observed in colonization for the inoculation methods tested, and injection is recommended over the drip method for ease of application. Further research is necessary to refine and optimize fertilizer regime and container type and size for whitebark pine seedlings to be inoculated in the greenhouse prior to outplanting on high-elevation restoration sites. Whitebark pine is currently awaiting official listing as an endangered species in the US and is already listed as such in Canada.