One of the most important factors influencing the growth of retained canopy lichens in managed forests is their response to canopy microclimate, particularly edge effects that extend into the surrounding forest from block margins. This is a special concern in wet Interior Cedar-Hemlock (ICH) stands of the upper Fraser River Valley (Prince George and Headwaters Forest Districts), where a unique assemblage of canopy lichens can be found. This lichen community, especially the cyanolichens, has been the focus of international conservation biology concern, in response to issues of habitat fragmentation and modification. (Goward and Arsenault 2000). Clearcutting results in 'hard' edges, characterized by an abrupt transition from a closed canopy to open conditions, and creating major changes in boundary layer climate in the surrounding forest stand. These microclimate changes can adversely affect canopy communities. Recent changes in forest harvesting practices, such as greater leave tree retention within harvest blocks, result in 'soft' edges that may reduce boundary-layer climate effects on adjacent stands. These changes in forest harvesting practices may have important implications for the conservation biology of canopy lichens, particularly when considered at a landscape level, where even small reductions in the ratio of 'edge' to 'interior' forest habitat could have large influences on canopy lichen retention. The purpose of this project is to examine the effects of variable retention and clearcutting harvest techniques on canopy lichens by comparing growth rates of Lobaria pulmonaria along transects that extend back from both 'hard' and 'soft' block boundaries into the adjacent old-growth forest. It is jointly funded by TRC Cedar Ltd. of McBride, B.C. and the Sustainable Forest Management Network.
Susan K. Stevenson and Darwyn S Coxson.
Stevenson, Susan K., Coxson, Darwyn S.. 2004. Growth rates of Lobaria pulmonaria along edges of forest harvesting blocks with different levels of retention: establishment report. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR102