Boreal Forest Restoration in the Kenai National Wildlife Refuge

Lorene Lynn (Red Mountain Consulting)

Site 1: Former Gas Exploratory Well (grandfathered into the KNWR)

Restoration of disturbed sites within the Kenai National Wildlife Refuge (KNWR) necessitates meeting regulatory requirements of the refuge. Restoration within a wildlife refuge also puts onus upon the restorationist to honor the mission of these public lands and to the people who use the land. The refuge prohibits the importation of soil or plant materials from outside the KNWR, which left me wondering how to begin restoring a 2.5-acre exploratory gas pad with a bare, compacted soil located deep within the refuge. To address the need to recontour the surface elevations and to acquire soil and vegetation, we cut the trees, harvested the vegetation mat, and used the soil from an additional 2.5 acres of virgin forest around the perimeter of the pad.

Prior to construction activities, we tied long, crumpled strips of mylar to tree branches and placed shiny pinwheel toys along the forest edge as bird deterrent and conducted a bird survey. All trees in the perimeter were cut near ground level and stored for later use in restoration. The vegetative mat was harvested as intact pieces and placed on the newly-contoured surface. The soil provided microbes and fungi adapted to local conditions, the vegetative mat provided immediate ground cover with indigenous plants, and the woody debris provided shade and improved water retention in soil. The ground surface was dimpled, creating a “rough and loose” configuration, a technique I learned from David Polster, a restoration ecologist with more than 40 years of experience in western Canada and a long-serving board member with SER. The dimpled ground provides different aspects, slopes, and water collection sites, comparable to what occurs in natural landscapes.

We salvaged hundreds of spruce saplings that were growing around the perimeter of the former pad and transplanted them into the dimpled ground with the help of the U.S. Fish and Wildlife Service (USFWS) Intern Crew. The final restoration product was described by a USFWS staff member as looking like a “nature bomb” went off. I took that as a compliment. The performance standards for this site include cover by indigenous plants that is equivalent to 60% of that found at a reference site, to be met within five years following restoration work.

We installed and operated an irrigation system for two years following restoration work. Because the site is in a remote location within the KNWR, a 40,000-gallon water truck was driven to the site twice each week to provide water for irrigation. In 2020, I took aerial photos of the site to see the area in the context of the surrounding forest.

In 2021, hundreds of naturally colonizing spruce seedlings were observed growing on the site. Approximately 60% of the transplanted vegetative mat survived. The performance standards were designed to assess whether the site is on a trajectory towards a plant community that will eventually have ecological values and aesthetic qualities that closely resemble the surrounding undisturbed plant communities. The goal is that eventually, the site will blend in with the surrounding terrain and provide suitable habitat for some wildlife species. Although 50-100 years may be needed for this site to reach this goal, it appears to be well on its way.

Site 2: 35-Acre Material Site (grandfathered into the KNWR)

During upgrades to the Sterling Highway near Cooper Landing, Alaska, the managing construction company was using an old Department of Transportation gravel pit that had been grandfathered into the formation of the KNWR. The USFWS requested the construction of two wildlife undercrossings, which required weed-free, high-quality gravel. The construction company wanted to expand the gravel pit to build the wildlife undercrossings, but the USFWS is not in the business of selling gravel. The agency staff suggested they talk to me, based on my work at the Sunrise site described above, to figure out how they might responsibly expand the gravel pit.

I suggested we use techniques similar to those used at the Sunrise site. As work progressed, this project became more complicated because mining was actively progressing as restoration work began. We first cut trees, stored them in piles along the perimeter of the future pit boundaries, and then harvested 4 acres of vegetative mat, some of which was stored on the pit floor until it could be used at a later time. I hired a local landscaping company, Moore’s Landscaping, to provide labor and heavy equipment for this project. A portion of the vegetative mat was placed directly on recontoured ground where gravel mining activities were complete. As the work was progressing, a nearby wildfire was becoming a threat to this project. In mid-summer, and in the middle of our increasingly smoky restoration work, the fire service forced us to evacuate so they could use the gravel pit as a base for the fire-fighting activities.

One worker was able to return to the pit just two days after the fire had passed through and took pictures of the burned moonscape that remained. The 287,000-acre fire ended up passing through the restoration area twice. While mining activities resumed in September, restoration activities did not resume until the following year due to safety concerns.

In response to the fire, I amended the original restoration plan to account for the loss of vegetative mat and woody debris. This change was unfortunately paired with a reduced budget. In an amazing turn of luck, the vegetation growing along the edges of a nearby dirt road survived the fire. I shifted the focus of revegetation to transplanting the roadside vegetation into the restoration site. The roadside vegetation is regularly cut to the keep the road open, so harvesting and transplanting the roadside vegetation salvaged valuable plant materials that otherwise would have been lost. Nearly the entire 35-acre site was dimpled in preparation for transplanting.

Transplanting individual plants across 35 acres was much more labor-intensive than transplanting vegetative mats with heavy equipment. The site was supposed to be topped with a minimum of 6 inches of organic topsoil, but either topsoil was not placed on a portion of the site or too little topsoil was placed. Much of this soil was a mixture of rocks and other mineral soil and devoid of nutrients. We selected transplant sites based on the best available soil characteristics and seeded native-grass cultivars on the remaining areas where the substrates were of lower quality. We applied a granular NPK fertilizer to most of the site and will continue to do so for several years to facilitate the establishment of vegetation.

We used four-wheelers and 4×4 trucks to collect vegetation from the side of the nearby dirt road, hand-carried vegetation onto the site with 5-gallon buckets and tree-planting bags, and planted 1 or 2 plants in the bottom of each dimple to provide the best possible moisture regime, shade to minimize transpiration loss, and to facilitate plant establishment.

The first year of monitoring was in 2021. Even with irrigation, not all of the transplanted plants survived. We are currently in discussion with the USFWS about doing some additional work at the site to help meet the long-term goal for the site: to restore ecological functions and values similar to those present in the surrounding, unburned forest.

Restoring Disturbed Sites in Northern Alaska with Tundra Sod

Tim Cater

Intact blocks of live vegetation and the soil in which they are rooted (i.e., sod) provide a viable option for revegetating and rehabilitating disturbed lands in northern ecosystems. Sod harvested from tundra donor sites has been used successfully to revegetate and rehabilitate wetlands in arctic Alaska. To the best of our knowledge, the first time that sod was harvested to rehabilitate a disturbed wetland site on the North Slope of Alaska was in September 1999 when ABR, Inc.—Environmental Research and Services planted sod in ~300 sq. feet of arctic wetlands. Sod was harvested during summer at a mine site where the use of explosives resulted in scattered blocks of sod ‘flyrock’.

A distinctive feature of the tundra sodding technique is that it originated from Iñupiaq peoples’ use of sod blocks to construct traditional sod houses and to insulate entryways to ice cellars. The same characteristics that make sod useful for traditional purposes also make it useful for rehabilitating disturbed wetlands. Most importantly, the bulk mass of sod insulates the ground surface, which mitigates thawing of permafrost by immediately helping to re-establish a stable thermal regime. Preserving permafrost prevents the collapse of the ground surface which can otherwise occur due to the loss of soil volume as ice melts. In some areas, ice makes up 50% or more of the volume of the frozen soil. This subsidence due to thawing, commonly referred to as thermokarst, often leads to permanent flooding with water too deep for most rooted plants to establish. Thus, maintaining a stable ground surface is a prerequisite for successful rehabilitation of many disturbed sites in permafrost terrain. Using other rehabilitation techniques (e.g., seeding) would require a minimum of several decades to develop a surface organic mat capable of providing effective thermal insulation.

Another major benefit of the sod treatment for tundra rehabilitation is that it immediately provides a diverse community of indigenous plant species that is similar to nearby tundra wetlands. This approach effectively bypasses the long period of time (decades, and probably much longer) that is otherwise needed to develop a productive, self-sustaining community of tundra plants. Given favorable conditions, the transplanted vegetation can be expected to remain productive indefinitely.

The characteristics of sod vary on micro and macro scales, which results in variable sod quality at a donor site. In general, soil characteristics and species composition typical of wet tundra are preferred over those typically found in moist and dry tundra. The thick organic mat typical of wet tundra allows for the harvesting of 30-40 cm-thick pieces. Thick sod is preferred because plants should experience less transplant shock with rooting systems contained in a larger volume of soil (Figure 1). Also, fast-growing rhizomatous perennial graminoids are typically dominant in wet tundra. Preferred species include the grass Dupontia fisheri (Fisher’s tundragrass) and the hydrophytic sedges Carex aquatilis (water sedge), Eriophorum angustifolium (tall cottongrass), and E. scheuchzeri (white cottongrass). In contrast, the organic mat in drier tundra is usually thinner, the rooting systems are less cohesive, and vegetation typically includes evergreen and deciduous shrubs, which do not survive transplanting as well. Lichens and mosses also are not preferred because they typically die off after several years.

Sod develops over many growing seasons when a new layer of plant litter is produced and previous additions of litter begin to decompose, adding to the increasingly thick layer of organic matter that accumulates at the ground surface. The process of sod development is slow in arctic ecosystems because cold temperatures and low oxygen levels in soil limit microbial activity, especially when the soil pore space is flooded.

Harvesting sod may require a permit from the U.S. Army Corps of Engineers, a State of Alaska Material Sales Contract issued by the Alaska Department of Natural Resources, or a harvest permit from the Bureau of Land Management, depending on local land management. Donor sites have typically been areas that were slated for development of gravel mines (Figures 2–3), but other donor sites could include vehicle parking lots or trenches excavated for the burial of power cables or telecommunications lines. In these situations, harvesting sod should be considered a best management practice, as it results in beneficial use of a valuable resource that would otherwise be wasted. Harvesting sod from areas not slated for development is not a viable option because it does not result in a net benefit to the environment.

Tundra sod can be harvested and transplanted using heavy equipment and/or hand labor. Maximizing the use of heavy equipment minimizes costs for most projects and improves worker safety (Figures 4–8). Both techniques produce immediate results, with the treated areas resembling undisturbed tundra (Figures 10–12). Innovations continue to improve the efficiency of this technique. In particular, the techniques developed in summer 2020 by Red Mountain Consulting appeared to be more efficient than all previous attempts. This approach included using a standard excavator fitted with a 4-ft wide frost bucket modified with plates welded to the bucket’s sides. This equipment allowed the extraction of thick, intact pieces of sod that could be loaded directly onto standard 4-ft × 4-ft pallets, which could then transported with a loader (Figure 9).

In a typical tundra sod harvesting operation at a gravel mine, the live vegetation and rooting zone (i.e., tundra sod) must be separated from the rest of the “overburden”, a term that refers to all of the material overlying the gravel. The 30–40-cm thick pieces of sod generally make up a small fraction of the overburden, which often is a 3–10 meter-deep mixture of silt, sand, and gravel. The density of tundra sod is similar to that of water (1 g/cm3), which means that relatively small pieces must be used if a person must carry blocks to the transplant site by hand. In practice, sod often includes substantial amounts of mineral soil, making it heavier and more difficult for a person to handle.

Restoration in Alaska’s North Slope Oilfields

Sue Bishop

Oil and gas exploration in northern Alaska began in the 1960’s, and the first discovery of oil in the Prudhoe Bay field was announced in March 1968. The Trans-Alaska Pipeline System was constructed during 1975-1977, to bring the oil to the tidewater port at Valdez, 800 miles south on the coast of Alaska. The first oil flowed through the pipeline in June 1977, and took about 30 days to reach Valdez.

ABR, Inc.—Environmental Research and Services has been involved in research, planning, and implementation for land rehabilitation in Prudhoe Bay and other North Slope oilfields since the early 1980s. For most of the sites we’ve worked at, complete restoration to pre-disturbance conditions is not a realistic goal, due to the nature of the disturbances and the harsh environmental conditions. We tend to focus more on rehabilitation; i.e., promoting the development of a stable, self-sustaining community of indigenous plants, although typically not the same community that existed before the disturbance.

Disturbance types within the oilfields that may require rehabilitation include gravel roads and pads (intact, partially, or completely removed), excavations (intact or backfilled), spills (petroleum, seawater, chemicals), off-road vehicle traffic (intentional or accidental), and tundra affected by the removal of ice roads and pads. In some cases (e.g., intact gravel pads), the original tundra vegetation has been completely lost, and the new substrate provides very different conditions. In other cases (e.g., disturbance by off-road traffic), the surviving tundra vegetation may be capable of recovery.

Northern Alaska is a challenging environment for land rehabilitation or restoration, for several reasons:

• The North Slope is in the zone of continuous permafrost, meaning that any disturbance may result in thawing of the frozen soil and loss of surface stability. In some areas the soil may contain well over 50% ice by volume, so thawing can lead to dramatic changes in site conditions.
• The growing season is short (about 2 months) and cool, resulting in slow plant growth. The short, cool summer also limits the rate at which dead plant matter decomposes, leading to low soil nutrient levels.
• There are no commercial sources for plant materials native to the region.
• Heavy grazing, primarily by flocks of temporarily flightless geese, limits plant growth at some rehabilitated sites.
• Until recently, northern Alaska has been largely free of non-native, potentially invasive plant species. As the climate warms, there is increased concern that invasive species may be more likely to survive in the Arctic if they are inadvertently introduced.
• The logistics of land rehabilitation projects in the Arctic can be difficult for a number of reasons, including; Lack of road access to many sites, limited communication (e.g., no internet and/or cell phone coverage), short season for fieldwork, weather (frosts or snow can occur even in summer), and wildlife (bear safety is a concern at many locations).

Early revegetation projects in the oilfields relied on cultivars of native grasses that were developed for the purpose, but we no longer recommend this approach in most situations, for several reasons:

• The grass cultivars require relatively high nutrient levels, so live cover typically begins to decline after 5–7 years unless fertilizer application is repeated. At most sites, periodic fertilization is not a realistic option.
• Most natural tundra communities are dominated by sedges and/or shrubs, rather than grasses.
• There is some evidence that a heavy cover of grass (living and/or dead) may inhibit natural colonization by indigenous tundra plants, by preventing seeds from reaching the soil surface, intercepting precipitation, or competing for water or nutrients in the soil.
• Commercial seed mixes may be contaminated with seed of non-native, potentially invasive species.

Much of our work in the past several decades has focused on developing plant cultivation techniques for sites in the North Slope oilfield that promote the recovery or establishment of communities dominated by indigenous tundra plants. Several of these techniques are described below.

Natural Colonization — Natural colonization (with or without the addition of fertilizer) may be appropriate for sites with considerable surviving vegetation (e.g. minor damage from off-road traffic, or a spill site where impacts are not severe). We also typically recommend natural colonization for narrow, linear disturbances (e.g. backfilled trenches) where there is good potential for both seed input and vegetative spread from the adjacent tundra.

Fertilize Adjacent Tundra — This treatment may promote seed production in the adjacent tundra, resulting in higher seed input to the disturbed site. It is only recommended for sites where the adjacent tundra contains species that are both 1) adapted to the conditions in the disturbed area and 2) likely to increase seed production in response to the added nutrients (e.g. wetland sedges adjacent to a moist or wet site). Fertilizer is not added to flooded areas where it might enter ponds or streams.

Seed or Transplant Wetland Sedges — Wetland sedges are dominants in many tundra plant communities, so re-establishing them is a priority on sites with suitable hydrology and soil conditions. Seed must be hand collected, typically in the season before sowing, to allow time for cleaning and germination testing. Alternatively, tundra plugs can be harvested from nearby natural stands and transplanted onto the rehabilitation site. This technique is somewhat labor intensive, but we have had good success with it where conditions are favorable. The impact to the source population is minimal in wet tundra, if the harvest rate is limited to one plug per square meter or less. The plugs are typically dominated by Carex aquatilis and/or Eriophorum angustifolium, with a few forbs and the occasional willow.

Seed Native Forbs — Some sites (e.g. gravel pads, road embankments) provide soil and hydrologic conditions that are completely different from the surrounding tundra. Plants that are adapted to similar habitats include legumes and other forbs that occur naturally on riparian gravel bars. The legumes have the additional advantage of potentially contributing nitrogen to the soil that may benefit natural colonizers. Occasionally seed of some of these species is available from the Alaska Plant Materials Center, but for the most part we hand collect seed from nearby natural populations. Over the winter we send the seed to the PMC to be cleaned and germination tested, in preparation for sowing the following summer. Species we’ve successfully seeded on rehabilitated sites include Artemisia arctica, A. borealis, Chamerion latifolium, and the legumes Astragalus alpinum, Oxytropis borealis, and O. deflexa.

Seed salt-tolerant species — Some sites within the oilfields that need rehabilitation have elevated soil salinity, due to either the residual effects of a spill or naturally occurring salts. This is a coastal area, so there are natural populations of species that are adapted to moderately high soil salinity. We have had some success with seeding several of them, including the sedge Carex maritima, the grass Puccinellia angustata, and the forb Cochlearia officinalis.

Transplant willow cuttings — Shrubs are a desirable addition at many rehabilitated sites to increase species diversity, enhance habitat value for wildlife, and/or help to stabilize slopes or shorelines. We have primarily focused on willows, as they are relatively easy to harvest and transplant and can survive well as long as soil moisture is adequate. Cuttings may be harvested either in the spring before they break dormancy or in the fall after the leaves have dropped. However, the cuttings cannot be planted in the spring as the soil remains frozen well into June. We prefer to harvest and transplant in the fall to avoid storing the cuttings over the winter.