Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.
Increased human activity and development in northern Canada and other polar environments have accelerated the disturbance of vast tracts of land in an already fragile ecosystem. During the 1950s, 42 Distant Early Warning (DEW) line radar stations were built along the 70˚ latitude, and linked with stations in the Polevault line to act as an early detection system for approaching hostile aircraft during the Cold War. Construction, operation and maintenance of these sites resulted in extensive contamination of soils and ground water at numerous locations across the Canadian arctic and subarctic [
Environmental studies conducted at DYE-M between 1997 and 2001 demonstrated that contaminated soils posed a potential risk to the arctic ecosystem [
In arctic environments, plant growth is constrained by short growing seasons, harsh environmental conditions (e.g., low temperature and rainfall), low species diversity (~1000 species) and minimal soil fertility [
Assisted revegetation is an active process in which seeds from native or non-native species are selectively sowed, and/or cuttings from slow-growing woody perennial shrubs are planted onto disturbed areas to accelerate the rate of plant coverage. Species selection following disturbance is based on revegetation goals and objectives. For ecological restoration, the goal is to develop self-supporting vegetation with similar structure, function and plant communities as found in the original environment [
re-establish a plant community (reviewed in [
A four-year revegetation project was undertaken at the DYE-M beach site between 2009 and 2012 to accelerate recovery of disturbed areas. The short-term objective was to investigate the feasibility of, and devise a plan to, accelerate revegetation of disturbed areas through assisted seed dispersal and selective transplantation of slow-growing shrub species. The long-term goal was to monitor successional changes towards achievement of comparable species biodiversity and vegetation coverage in the disturbed and surrounding areas at this arctic site.
DYE-M has a high arctic ecoclimate with long cold winters with an average winter temperature of −22.5˚C, an annual temperature of −11.5˚C and short, very cold summers with an average summer temperature of 1˚C [
Plant surveys were completed in July 2009 at DYE-M to determine the density and biodiversity of different species growing in the undisturbed areas surrounding the disturbed area at the beach to define a baseline for the project and a long-term goal for revegetation. Six transects (40 - 100 m long) were established in undisturbed areas, and quadrats (1-m2) were set up every 10 m along each transect (n = 60) to determine the percent coverage of each plant species and the percent of bare soil/rocks. Plants were identified using Barrenland Beauties [
Two soil samples were collected from the disturbed area (0 - 10 cm) and two from the undisturbed surrounding
Latin Name | Common Name | Root Structure | Shoot Structure | Reproductive Method |
---|---|---|---|---|
Armeriamaritimasubsp. sibirica (Turcz. Ex Boiss.) Nyman | sea pink/thrift | taproot | evergreen perennial | seeds |
Carex bigelowii (Torr ex Schwein) | sedge | fibrous | perennial herb-graminoid | rhizomes/stolons/achenes |
Cassiopetetragona (L.) D. Don | white Arctic heather/Arctic bell heather | fibrous roots along stem | dwarf shrub-evergreen | seeds |
Cerastium uniflorum Clairv. | glacier mouse-ear chickweed | Fibrous | forb | seeds |
Chamerion latifolium (L.) Holub | river beauty/dwarf fireweed/ broad-leafed willow herb | fibrous | perennial herb-forb | rhizomes/seeds |
Dryas octopetala L. | mountain avens | taproot/lateral roots from stem | dwarf shrub | fruit, branches root |
Empetrum nigrum L. | crowberry | lateral roots from stem | dwarf shrub evergreen | seeds in fruit/branches root |
Hierochloe alpine (Sw. ex Willd.) Roem. & Schult. | holy grass | fibrous | graminoid | rhizomes, seeds |
Luzula confusa (Lindeberg) | northern woodrush | fibrous | perennial herb-graminoid | rhizomes/seeds |
Oxyria digyna (L.) Hill | mountain sorrel | taproot | perennial herb-forb | rhizomes/seeds |
Papaver radicatum L. | Arctic poppy | fibrous/taproot | perennial herb-forb | seeds |
Polygonum viviparum L. | alpine bistort | fibrous | perennial herb | bulbils/fragmentation rhizomes/achenes |
Salix arctica Pall. | Arctic willow | lateral roots from stem | dwarf shrub | seeds/branches root |
Silene acaulis L. Jacq. | moss campion | taproot | perennial herb- forb-cushion plant | rhizomes, seeds, stolons |
Vaccinium uliginosum L. | whortleberry/bilberry | roots along stem | dwarf shrub | seeds |
area and analyzed for total organic carbon (TOC) and particle sizeto determine if there were differences in the soil composition that might affect revegetation.
A loader tractor with a tooth bucket was used to create grooves across the disturbed area which had been heavily compacted by machinery. Grooves were created by dragging the bucket perpendicular to the direction of prevailing winds, creating ridges approximately 10 - 15 cm deep, and 20 cm apart. In 2009, it was suggested by an on-site remediation design engineer that a section of the disturbed area be amended with an Agrico Canada Ltd fertilizer (available in large quantities at the site for hydrocarbon remediation in landfarms) prior to seeding. As the disturbed areas overlooked Exeter Bay, the use of this fertilizer was deemed inappropriate for this project since the MSDS literature indicated potential harm to aquatic organisms.
Salix arctica Pall. (willow) cuttings were harvested from a donor population near the beach after a frost in Sep- tember 2009. A shoot segment 30 - 150 cm long and ~1 - 2 cm in diameter was cut from the stem of each donor willow plant with pruning shears, and kept in water until time of transplantation (<10 hrs). Longer cuttings (>40 cm) were further separated into two or more cuttings before transplantation as recommended by Walter et al. [
Another 150 cuttings were transplanted in the fall of 2011. Cuttings were again collected following a frost from donor plants located in areas surrounding the disturbed area. Five plots were planted with 27 - 30 willow cuttings using the same method as those planted in 2009, whereas a sixth plot was planted with a modified approach in which willows were planted in long trenches in a staggered pattern so plants could lie in their natural orientation and nodal root growth could be encouraged [
Twenty-two kg of Lolium multiflorum (annual ryegrass; Lot L19-8-22G) obtained from Country Depot in Kingston Ontario, was seeded by hand across ~7900 m2 of the disturbed area at a rate of 29 kg/ha (commercial seeding rates = 15 - 30 kg/ha).
Ripe seeds and berries from native plants were collected by hand into five large ziplock bags (3.8 L each) from the areas above and below the disturbed area. Seeds were of different shapes, sizes, and weights based on their dispersal mechanisms. Each bag contained a different mix of seeds and berries based on the collection area; therefore seed density was not calculated prior to dispersal. Native seed was mixed by hand to create a more homogenous mix of seeds and berries and then dispersed by hand on the same area (~7900 m2) as the annual ryegrass. Seeds were not tested for germination prior to dispersal. Future studies are required to investigate seed germination and seedling survival for seeds from this area. Following seed dispersal (native and non-native), seeds were covered with soil by attaching a large metal fence section (~4 feet × 5 feet) to the back of an all-terrain vehicle, and dragging it perpendicular to the direction of the ridges to help push loose soil into the grooves to cover the seeds.
Plantassessments were conducted in late July and early August in 2010, 2011, and 2012 to determine the number of Salix arctica cuttings that survived the winter and produced new shoot growth. New shoot growth was qualified as the observation of one or more leaves, and quantified in 2010 as, i) limited growth (1-2 leaves), ii) moderate growth (3 - 4 leaves) and iii) significant growth (4+ leaves). In 2011 and 2012, cuttings were determined to be alive (one or more leaves) or dead (no leaves). Four cuttings were excavated in 2010 to observe root growth from one plant with limited growth, one plant with moderate growth, and two plants with significant growth.
Based on slow growth rates of Arctic plants, where most species are still relatively small during the first growing seasons [
Results from the initial survey of the surrounding area vegetation (i.e. prior to revegetation efforts) determined that on average, ~68% of each quadrat at DYE-M was bare soil or rock, and the remaining ~32% was a mixture of fifteen plant species (
Of the fifteen species observed on site in 2009, seven had fibrous root systems, four had taproot systems, and five were able to produce roots from prostrate shoot branches (Supplementary Information
Soil analysis determined that the particle size ranged from >0.001 mm to >4 mm; the majority of particles were <4 mm. Soil type was a mixture of sand (68%), gravel (17%), silt (11%), and clay (4%). Total organic carbon in the soil ranged from 0.22 to 0.91 for the reshaped areas, and from 0.68 to 0.86 for nearby samples from the undisturbed areas. These values are similar to carbon storage values reported for “c” horizons in various tundra environments, and for upper soil horizons in barren ground mountain tops, river gravel bar and alpine slope soil in Alaska [
Fertilizer has historically been scattered across disturbed areas during site closures in northern locations to decrease the amount of material that must be shipped back down south and to potentially improve revegetation of the disturbed areas. While fertilizer was not used in this project due to proximity to the aquatic environment,
the use of fertilizers is often deemed necessary in arctic revegetation projects to promote plant growth, especially for non-native species, as the uppermost soil layer which generally contains nutrients and soil bacteria that
help cycle nutrients has generally been disturbed or removed by human activities [
Prior to revegetation efforts at DYE-M, all fifteen species observed in the initial study were investigated to determine their revegetation potential based on: i) their ability to tolerate sandy soil, ii) their potential to improve the growth substrate, iii) whether they were perennials, iv) whether they were native to the Cape Dyer region, v) whether they could be obtained commercially or locally in sufficient quantities, vi) whether they had previously been shown to be successful in revegetation studies, and vii) whether they had the ability to prevent further erosion on the site (adapted from [
Ninety-four percent of the 540 S. arctica cuttings planted in 2009 survived the winter and produced new shoot growth in 2010. First year survival rates greater than 80% are considered successful for Salix sp. cuttings [
Root growth assessments determined that roots ranged in length from non-existent (plant with limited shoot growth), to extensive (plant with significant shoot growth) with roots >10 cm long and secondary and tertiary root development. Maximum root growth was observed in damp but not flooded areas. Visual observations of S. arctica from other areas around the site support the observation that plant growth is greatest in areas that offer refuge from strong winds (along rocks and boulders), as well as providing a significant source of soil water content (near water pools and along water run-off areas). Furthermore, these S. arctica tend to have well-developed secondary root growth along the full length of the stem (
In 2011, two landslides, one in June and one in late August, carrying rock and sediment debris from the road and hillside above the beach impacted six of the revegetation plots. Only thirty-five of the 88 willow cuttings from these plots survived. Initial observations from late July indicated that most cuttings in the other areas were producing leaves, but that secondary root development and shoot length growth was limited. This is to be expected as growth in the arctic is slow and significant change in size may take years of observation. Plant surveys were conducted six weeks later in September, and it was determined that some cuttings that had been judged unsuccessful in July had multiple leaves and appeared to be in significantly better health. Based on the September observations, 84% of the 428 S. arctica cuttings found in 2011 had survived since 2009. Results from 2010 and 2011 indicate that end-of-season observations provide a more realistic indication of overall plant health and survivorship than early or mid-season observations.
Plant surveys were conducted in August 2012, following another landslide in July which impacted a similar area as in 2011. Another two plots were compromised by this third landslide, leaving only 29 of the 128 willows in this area. In addition, road work destroyed another two plots (24 cuttings). Of the remaining 388 cuttings not impacted by landslides or other disturbances, 82% survived to year three. This three year survival rate of 82% is similar to observations from a revegetation effort following an oil spill along the Trans-Alaska pipeline in 2001, where 80% - 88% of transplanted willow cuttings survived after three years [
Lolium multiflorum (annual ryegrass) seeded at a planted density of ~29 kg/ha in 2009, was observed in 85% of
all quadrats, with a maximum density of 198 plants/100 cm2. While the majority of L. multiflorum germinated and grew in 2010, a minority of seeds germinated in 2011 and 2012. No plants had developed spikes or inflorescences by the end of July, 2010, and all plants appeared so be stunted by the cold climate, with heights between 5 - 10 cm, in comparison to normal heights up to 125 cm [
Previous studies have used various guidelines to determine the success of revegetation projects, including colonization by native plants and establishment of seedlings, increased species diversity, reproduction by colonizing species, development of a moss layer, accumulation of ground litter, and 85% total plant cover [
New species observed on the disturbed areas included Cochlearia officinalis L., Melandrium affine (J. Vahl ex Fr.) J. Vahl, and M. fontana [
Despite the harsh climate and unpredictable weather patterns in the arctic that make revegetation work difficult, visual observations of the disturbed areas in 2012 indicated that patches of new vegetation are becoming more predominant compared to the almost complete lack of vegetation in 2009. Arctic plant communities are slow growing and seedling distribution tends to be skewed towards those sites that offer favourable conditions and are in close proximity to native tundra. Germination sites or microsites may be created naturally such as by desiccation cracks in the ground [
As seedling growth is a slow process, monitoring over ten or more years will likely be required before conclusively declaring the disturbed areas partially or wholly revegetated. The information and techniques developed for this project can be used to guide the long-term remediation and revegetation strategies at other DEW line and high arctic sites following large scale disturbances. Future studies could incorporate assessment of native seed germination and survival rates, germination rates from the seedbank, permanent monitoring plots and use of other shrub species to improve diversity and long term monitoring of disturbed sites.
The authors are indebted to members of the Environmental Sciences Group (ESG) who have been involved in the DYE-M Clean up project over the years. We are grateful for the help provided in the field, and for the funding provided by North Warning System Office (NWSO) for this project.