High Biodiversity Cedar Stands at Risk? The Importance of Topographic Position in the Inland Rainforest.
By Darwyn Coxson
The Ancient Forest Trail provides an exceptional opportunity to walk through a rare very old cedar grove in the upper Fraser River watershed. Recent research now points to the high biodiversity value of these very-old wet forest stands (see New lichen species described from the canopy of inland temperate rainforests and Stand structural attributes and canopy lichen diversity) and suggests that they represent a globally significant biodiversity resource.
Although iconic images of giant cedars from sites like the Ancient Forest Trail have long been a common part of our cultural heritage in B.C.'s central-interior (see Socio-economic Benefits of Non-timber Uses of the Inland Rainforest and Cultural Forum), in reality, large stature cedars like those on the Ancient Forest trail do not occur widely in landscapes of the upper Fraser River. These ancient forest stands are largely confined to sites where topography provides protection from fire and rich soils support lush tree growth. In the upper Fraser River valley these sites occur primarily in wet toe-slope topographic positions, where abundant groundwater flow and high humidity nurtures tree growth and reduces fire risk.
Unfortunately, this affinity for wet toe-slope positions has had very negative consequences for ancient cedar stands in the upper Fraser River valley. Historically, most roads and railroads were placed at the base of mountain slopes, in toe-slope positions where ancient cedars grew. The easy access afforded by these transportations corridors has meant that ancient cedar stands were typically among the first to be chosen for logging. As a result, toe-slope topographic positions in many of the mountain valleys in B.C.'s upper Fraser have now been heavily fragmented by road-side logging.
Above: The placement of access roads and logging blocks in toe-slope positions in mountain valleys can be seen in this Google-Earth image (©2009 Google Earth) of the McGregor River Valley in B.C.'s northern inland rainforest.
The cumulative loss of toe-slope ancient forest stands in the upper Fraser river watershed has now reached a critical threshold. Geographic Information Systems (GIS) studies by the B.C. government's Integrated Land Management Bureau (B.C. Integrated land Management Bureau 2008) found that Ancient Cedar stands now represent less than 3% of the upper Fraser River landscape (see also Stand structural attributes and canopy lichen diversity). Surprisingly, very few of the "high-biodiversity" cedar stands identified by the 2008 ILMB report are represented within B.C. provincial parks. Of the 9482 ha remaining very-old wet forests (including all cedar, hemlock, and spruce stands) in the Upper Fraser, only 356 ha fall with designated Provincial Parks (assessments from the 130,571 ha ICHvk2 climate zone) (from Radies 2009).
Above: The location of remnant very-old cedar stands in the upper Fraser River Valley (ICHvk2 region) is shown in red (from B.C. Integrated land Management Bureau 2008). Provincial parks (from left to right in light blue) are (A) Sugar-Bowl Grizzly Den and Grand Canyon of the Fraser, (B) Slim Creek, (C) Erg Mountain, and (D) Ptarmigan Creek Provincial Park. Map center at 53° 49' 09.76" N, 121° 14' 06.52" W.
Although the site of the Ancient Forest trail itself has been given a limited form of protection through designation as a provincial Recreational Area, most of the remaining "high-biodiversity" cedar stands have been designated as "Guidance" Old Growth Management areas, a voluntary designation that is not legally binding on forest companies (see Legislation not Guidance Needed to Help Forest Professionals), and places these stands at continued risk for timber harvesting. In reviewing this practice of using "guidance" management designations, the B.C. Forest Practices Board concluded that "there is a gap in the ability to manage for, and maintain, old growth values because government's 'old forest' targets can currently be met without conserving any forest older than 140 years. Biodiversity targets need to be representative of the ecosystem but the current targets are not refined enough to capture old forest stands that have specific moisture regimes and slope positions" (from Post 2009)
These emerging research findings were summarized by Radies and Coxson (2009) in the international forestry journal Forest Ecology and Management as follows:
"cedar-leading stand types of exceptional age and stature should be immediately designated for protection, given their rarity in the landscape, and their lack of representation in protected areas ... these sites represent significant biodiversity hotspots for canopy lichens, and are key to the maintenance of biodiversity within regional landscapes".
The challenge for public policy land managers in B.C. is now that of insuring that these emerging research results can be used to guide forest management policy, providing "science-based" solutions for long-term sustainable forest management (Hollstedt 2001).