Trip Report by Leader David Cook
On Sunday, 6 October, 2019, seventeen persons participated in this field trip to Cypress Bowl Provincial Park, jointly organized by Nature Vancouver and Friends of Cypress Provincial Park. Objective was to learn the characteristics of an old-growth forest and the role that fungi play in it.
We proceeded to the upper Sunset Trail where there is a little known old-growth forest. Some of the characteristic features of an old-growth forest are trees of uneven age from saplings to veteran trees, coarse woody debris on the forest floor, snags or wildlife trees, pit and mound topography, canopy gaps and multi-layered canopy.
The roles that fungi play in an old-growth forest are three-fold; symbiotic or mycorrhizal, decomposers of dead woody tissue, and parasitic. Examples of symbiotic fungi were the numerous species of Russula scattered across the forest floor while decomposers were represented most commonly by the red belt conk or Fomitopsis pinicola. Fomitopsis causes a brown, crumbly rot of a wide range of hosts in British Columbia but most commonly in western hemlock. No parasitic fungi were found. One interesting find was a truffle dug up and left to dry on a stump by a squirrel. It was about a centimeter in diameter and was probably a deer truffle. Numerous holes in the forest floor indicated where squirrels had been digging for truffles.
On the return we passed through the Yew Lake old-growth loop to see the old-growth western hemlocks. This is the upper limit for western hemlock and is one of the few places where old-growth trees can be seen. This is probably due to the relative absence of the parasitic dwarf mistletoe which is common at lower elevations and stresses the trees thus shortening their life span.
We returned via Yew Lake and noted the white pine blister rust that infects most white pines in the area by girdling the tree thus killing the tree above the girdle. The rust is prevalent throughout the Yew Lake area due to the presence of its telial host, Ribes spp. We also noted another rust Pucciniastrum vaccinii which is common on blueberry bushes whose telial host is both western and mountain hemlock.