Golder
January 2018
Executive Summary
To meet habitat targets within boreal caribou ranges, the federal Recovery Strategy for the Woodland Caribou, Boreal Population in Canada (Environment Canada 2012) identifies coordinated actions to reclaim woodland caribou habitat as a mitigation step to meeting current and future caribou population objectives. Actions include restoring industrial landscape features such as roads, seismic lines, pipelines, cut-lines, and cleared areas in an effort to reduce landscape fragmentation and the changes in caribou population dynamics associated with changing predator-prey dynamics in highly fragmented landscapes. Based on the federal recovery strategy habitat targets and current range conditions, it is expected that boreal caribou range plans in Alberta will have a requirement to restore significant amounts of habitat along linear disturbance features. Habitat restoration (i.e., mechanical site preparation, planting and/or seeding of tree species) as well as implementing access control measures are considered the primary mechanisms to enhance the rate of recovery of linear disturbance features to naturally occurring vegetation. Through the Alberta Caribou Action Plan (GOA 2016), the Alberta government has committed to restoring 10,000 km of seismic lines within the Little Smoky and À La Peche caribou ranges over the next five years.
As caribou habitat restoration initiatives have become more widespread across Alberta in the last decade, key uncertainties have been recognized regarding what treatment types are appropriate for habitat restoration, how to measure success, and timelines to reach functional habitat. To that end, a collaborative research initiative was initiated by Golder Associates with support from the Foothills Landscape Management Forum (FLMF), the Petroleum Technology Alliance of Canada (PTAC) and the Government of Alberta to monitor the vegetation attributes on restoration treatment sites implemented from 2001 to 2007, as part of the Caribou Range Restoration Project in the Little Smoky caribou range.
The study approach for this project attempted to understand how planted and naturally regenerating tree seedling species (primarily black spruce and lodgepole pine) responded to site treatments in order to answer the following questions:
Growth patterns (i.e., individual tree height-age trajectories) were also modelled for both planted and naturally regenerating tree species to determine their growth trajectories within both treated and naturally revegetating sites.
Permanent vegetation sampling plots along regenerating seismic lines were sampled in 2008, 2015, and 2017. A total of 126 plots were sampled over the three survey years; 59 of these plots occurred on naturally revegetating lines while the remaining 67 plots occurred on seismic lines that had received some form of preparation treatment to speed vegetation recovery (i.e., treated lines). A variety of parameters representing physical site properties and vegetation community conditions were measured at each plot including conifer seedling height and leader growth. Data analysis was made up of three main components using the data collected during the three survey years:
Along treated seismic lines, planted black spruce seedlings showed greater leader growth and higher average heights than the naturally regenerating spruce seedlings growing on the same lines. Planted black spruce seedlings were tallest and showed the greatest leader growth at lowland sites, and both naturally regenerating and planted individuals performed better at lowland sites than at upland sites. The candidate models created to explain variation in seedling height and leader growth indicated that seismic line age (i.e., time since disturbance or treatment occurred) was likely the most important factor affecting seedling growth. Site treatment also had a significant effect on black spruce seedling height and leader growth but had a variable effect depending on the site type that the treatments were applied to. Black spruce seedlings seemed to benefit from a mound and planting treatment if they occurred in lowland sites whereas they appeared to gain limited benefits from mounding treatments when they were applied in upland sites. Lodgepole pine seedling growth was most affected by seismic line age but line orientation was also identified as an important factor in explaining variation in pine seedling height.
Growth trajectories created using the heights and leader growth measurements of conifer seedlings indicated that treatments did not speed up the time required for seedlings growing at upland sites to reach height thresholds, compared to naturally revegetating sites. Treatments applied to lowland sites did however speed up the time required for black spruce seedlings to reach height thresholds compared to non-treated lowland sites. Black spruce seedlings growing in lowland habitats were projected to reach the 1.4 m, 2.7 m, and 5.0 m thresholds by age 17.7, 27.8, and 43, respectively, and were projected to reach these thresholds approximately 2 years faster than seedlings growing on naturally revegetating lines sites. Lodgepole pine seedling growth trajectories did not seem to benefit from treatments applied to upland sites as seedlings growing on naturally revegetating lines were projected to reach height thresholds faster than equivalent seedlings growing on treated lines.
Applying mounding treatments to upland habitats seemed to have little benefit to black spruce or lodgepole pine seedling growth and instead seemed to act as a detriment to seedling regeneration at these sites. These results suggest that treatment applications need to be more targeted to natural regenerative systems and applied based on an understanding of site limiting factors and conditions to achieve the most optimal results. Thus, consideration for whether an upland site should be planted with seedlings, seeded, or left for natural seed ingress, as well as which species to introduce within upland sites of higher mineral and lower moisture content, and the use of coarse woody debris or other soil enhancements, or placement of seedlings lower down in a mound, should be considered in future restoration trials within upland sites.
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