|Sponsor:||ANC Timber Ltd.|
Object & Deliverables
The overall purpose of this Project was to monitor the effects on terrestrial lichens of three different levels of commercial thinning in lodgepole pine stands.
The Final Report, completed in February 2009, studied the responses of understory and ground layer vegetation and flora using 180 plots placed in three thinning regimes (20, 40, 60% removal by volume). Stands were operationally thinned in the winter of 1997-1998, and we have results from several post harvest fields campaigns, the last of which was in summer 2005 (seven years post harvest). We addressed four questions:
- What effect did the thinning treatments (n=3) have on canopy cover?
- What effect does canopy opening have on the following:
- Species diversity;
- Vegetation after seven years after thinning treatment;
- Canopy opening; and/or
- Species interactions limit ground layer establishment.
The study concluded the following:
- Thinning operations did not produce effective canopy cover treatment groups at the plot level, however ranking of post-harvest plots revealed a significantly different set of canopy cover change groups.
- Species richness was not affected by the changes in canopy cover.
- Decreases to the moss and vascular plant vegetation are evident at even the lowest canopy cover change regime; lichens remain unaffected; and as a result, bare ground and ground covered by woody material both increase. At seven years post harvest, there is no evidence that lichens have colonized areas left bare by moss death.
- Our results appear to suggest that both lichen and bryophyte fragments are readily available for establishment in both native and thinned stands surrounded by native forest.
- When lichen diaspores are introduced, they establish well under both native and thinned regimes. Lichens also perform better than mosses under all conditions in our trial except under control conditions that were originally dominated by mosses. It appears that mosses are limited by reflections of their past substrates whereas lichens are able to establish under a variety of disturbance regimes.
- Canopy changes, even small ones, affect abundances of understory vascular plants and ground layer mosses, but there is no evidence from our study that species richness has been affected after seven years post-harvest. Lichen abundances after seven years post-harvest have not changed. When diaspores of lichens are provided, lichens appear to be able to establish on a number of disturbed substrates, whereas mosses are more limited to areas that originally were dominated by moss, thus moss occurrence may partially be a reflection of the history of the habitat whereas lichen occurrence is strongly influenced by stochastic events. Lichen and moss diaspores appear not to be limiting in either thinned or native forest stands.
The complete findings of this project are contained in a report entitled “Lodgepole Pine Thinning Regimes in Relation to Lichen Abundance, Growth, Establishment, and Species Richness: Final Report”