Forest Investment Account

Abstract of FIA Project

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Grizzly bear forage trial review: trial assessment summary and discussion

Author(s): Johnson, Tom; McLennan, Donald
Imprint: Smithers, BC : T. Johnson and Associates, 2000
Subject: Forest Investment Account (FIA), Grizzly Bear, British Columbia, Food, Adaptive Management
Series:  Forest Investment Account (FIA)


In the mid to late 80's a number of research projects identified alluvial floodplains and lower slope seepage ecosystems as key seasonal foraging areas for grizzly bears in coastal British Columbia. Grizzly bears utilize herbaceous species such as skunk cabbage and lady fern early in the year, and berry producing shrubs such as devil's club, salmonberry, elderberry, and red raspberry later in the summer. Studies completed in the mid eighties identified grizzlies as solitary foragers with extensive home ranges and, consequently, identified the need to provide foraging areas across watersheds slated for harvest. Subsequent analyses of the silviculture activities required after harvesting and the grizzly's dependence on extensive forage sources identified a potential conflict between these two management objectives. The silvicultural activities needed to establish free growing conifers on high brush hazard sites were considered incompatible with the need to maintain extensive supplies of grizzly forage across the landscape. The stocking standards of the day required intensive control of non crop vegetation to establish the required number of seedlings within free growing timeframes. To aid crop tree establishment, control of non crop vegetation was achieved using aerial applications of herbicide, glyphosate in particular. Treatment of non crop vegetation with glyphosate was shown to negatively impact the quality and quantity of available grizzly forage and create short-term forage deficits. The use of herbicides was predicted to further exacerbate the forage deficit because they increased survival of crop trees and resulted in a continuous distribution of seedlings. These evenly spaced, relatively dense, conifer stands close canopy more quickly than discontinuous natural stands and create light environments too low for production of healthy forage communities. Thus, the initial short-term forage reductions caused by herbicide application were predicted to eventually become long-term deficits. In many drainages this deficit is heightened by historic harvest patterns of progressive clearcutting at low elevations. The front to back, bottom to top mentality of the day reduces overall forage availability as old growth stands with variable canopy closure and frequent canopy gaps are replaced with dense young homogeneous closed canopy managed forests. To alleviate the conflict between the need for an extensive long-term supply of grizzly forage and continued timber harvest from alluvial floodplains and seepage ecosystems, the Ministry of Environment Lands and Parks (MoE) proposed a compromise between these demands. As a result of industry and Ministry of Forests (MoF) input at the summer meeting of the Coast Silviculture Committee in June of 1991, it was agreed that stocking standards on alluvial and seepage sites would be reduced to lengthen the time it took for canopy closure. To increase the area capable of producing forage and localize conifer production to optimal microsites, the concept was further modified by suggesting that conifers be planted in clusters of up to eight trees. In 1992, a contract was awarded to Johnson - Schwarz Forest Management and Oikos Ecological Services Ltd. to develop silviculture systems using the reduced stocking standards and to design and establish a series of adaptive management trials. The trials would be structured to determine the impacts of the stocking standards on grizzly forage and conifer growth and yield. As the trial design developed, the initial concept of cluster planting was expanded to include a range of clusters from seven to thirty trees. The expanded number of trees per cluster was required to create a sufficiently wide range of gap openings and light regimes that would produce measurable differences in forage production and species composition. Initially, trees in clusters were planted at an inter-tree distance of one meter to maximize the amount of area in gaps. In later trials, inter-tree distances were expanded to include a range of distances from 1.0 to 2.5 meters to allow measurement of conifer performance and yield as a function of inter-tree spacing. To match the available site conditions with the trial design, three levels of trial establishment were proposed for this project. Formal trials were designated for freshly disturbed areas where homogeneous site factors allow implementation of the full experimental design. Informal trials were designed for blocks where site heterogeneity due to site series variation or stock distribution prevented establishment of the full trial. Monitoring areas were proposed for sites which fell within the grizzly stocking guidelines and could indicate trends in the relationship between forage quality and gap size without management intervention. From the fall of 1992 to the spring of 1997, candidate sites were reviewed and a number of trials were established with the co-operation of licensees and MoF staff. Trial sites range in size from 1.2 hectares to 54.7 hectares. Eighteen trials totalling 280 hectares were established throughout the Coastal Western Hemlock (CWH) Zone of the Vancouver and Prince Rupert Forest Regions over the five year period. The status of trial sites at the time of establishment included recently logged and backlog sites and sites scheduled for fill planting. Following the project working plan, first year monitoring was completed on 80 percent of the established trials. However, due to a lack of funding, the remaining 20% of the trials have not been monitored and no baseline data has been collected. Funding constraints have also prevented completion of two and five year monitoring as scheduled in the trial working plan.

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Updated August 3, 2006 

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