Fire is the keystone disturbance that shaped most whitebark pine landscapes, so treatments should be designed to emulate fire’s historic effects on the landscape (Keane and Arno 2001). While prescribed fire is the obvious tool, mechanical cutting treatments can also be effective. Properly designed silvicultural thinning can simulate the effect of non-lethal surface fire in whitebark stands (Keane and Arno 2001). Treatment unit sizes and shapes should be similar to the patterns left by past fires and need to reflect the amount of available whitebark pine seed source in surrounding stands (Keane and Parsons 2008[in press]). Do not design treatments that create large areas for whitebark pine regeneration if there is little seed available for caching unless planting rust-resistant seedlings is possible.
Whitebark pine is regenerated almost exclusively from Clark’s nutcracker seed caches. Therefore, restoration treatments that optimize regeneration are those that optimize conditions that attract Clark’s nutcracker caching. The optimum caching habitat for the Clark’s nutcracker is recently burned over areas (birds may like the pattern created by the fire for remembering cache sites) greater than 50 meters diameter. These were found to be attractive to Clark’s nutcrackers (Keane and Arno 2001; Tomback et al. 2001, Norment 1991). Seedling survival of whitebark depends on open stand conditions for as much of the rotation as possible (whitebark pine is an early seral species, and is shade-intolerant).
As whitebark pine continues to decline across its range, there will be fewer seeds produced and available for nutcracker caching, resulting in fewer caches across the landscape, which in turn will reduce potential whitebark pine regeneration. Furthermore, those seeds produced in damaged stands are highly sought after by pre-dispersal seed predators, especially pine squirrels but also nutcrackers, leaving few seeds for nutcracker caching. In high rust mortality areas, there may not be sufficient seed to naturally regenerate whitebark pine and planting may be the only option for regeneration the species.
Seedlings for planting should be grown from seed collected from “plus” trees known to be rust-resistant– identified by seedling progeny in rust screenings– or at least from phenotypically rust-resistant cone-bearing trees that are healthy with 30 percent or more live-green crown in otherwise highly rust-infested stands.
Once seed is available from seed orchards, cone collections should shift from the field to the orchards, which have been designed for improved blister rust resistance, broad adaptability, and minimal inbreeding. It may be beneficial to plant whitebark pine on a variety of sites and to refine planting guidelines for a specific geographic area or stand condition that will optimize survival and growth of future plantings. On the broad-scale, planting should be done on a variety of sites, including the more productive seral sites. When practical, planting crews should attempt to remove non-whitebark conifers to make planting more effective in the long-term.
Whitebark pine seedlings take five to seven years to become fully established and start significant height growth. It may be useful to inoculate whitebark pine seedlings with ectomycorrhizal fungi for survival in nature since whitebark pine share a complex, mutualistic ecological relationship with various species of ectomycorrizhae. Inoculation of nursery seedlings with native fungi should be considered when soils lack appropriate fungi and it is unlikely they will be imported in a timely manner (Brundrett and others 1996; Khasa and others 2009). Areas at high risk for absence of ECM fungi for whitebark pine are: ghost forests, severe burns, and species shift areas (not previously in whitebark pine). This is particularly true for they are a long distance from an inoculum sources with few animal vectors present.
There are basically two major types of restoration treatments that can be implemented at the stand level: prescribed burning and mechanical cuttings, or some combination of both. Other minor treatments can be used to augment or compliment the two major treatment types. Most restoration treatments are designed to eliminate or reduce competing species and increase the regeneration opportunities for natural-selection to produce white pine blister rust-resistant seedlings. The primary objective of these treatments is to mimic some natural disturbance process, mainly wildland fire, to facilitate whitebark regeneration and cone production. Two sources are available as detailed references for evaluating, designing, and implementing whitebark pine treatments. Keane and Parsons (2008) summarized results of a 15 year whitebark pine estoration study by treatment across five diverse sites. Keane and Arno (2001) present additional summarized material that can be used for the same purpose.
Mechanical cuttings include treatments that manipulate the stand by cutting trees. To date, there have been three types of mechanical cuttings. Keane and Parsons (2008[in press]) created a series of nutcracker openings in successionally advanced subalpine fir stands containing dying, rust infected whitebark pine. These nutcracker openings were near-circular areas within which all trees except whitebark pine were cut. The size of these areas can vary but they can be anywhere from 1-30 acres based on a study by (Norment 1991) who found nutcrackers appeared to favor burn patches less than 15 ha in size. The nutcracker openings are a cutting treatment that attempts to mimic patchy, mixed severity wildfires. Other cutting treatments include group selection cuts where all trees except whitebark pine are sawn down, and thinnings where all non-whitebark pine trees below a threshold diameter are cut (Chew 1990, Eggers 1990). One last cutting is a fuel augmentation or fuel enhancement treatment where subalpine fir trees are directionally felled to increase fuel loadings and contagion (Keane and Arno 1996, Keane and Arno 2001).
Keane and Parsons (2008) found that lodgepole pine trees could be left on site if they occur in low densities (<50 trees acre-1). Whitebark pine can compete with lodgepole pine on most upper subalpine sites with acceptable regeneration and grow underneath scattered lodgepole pine (Arno and Hoff 1990). It is also important to reduce or remove the slash from the treatment area to allow nutcrackers access to the ground for caching. This can be done by piling the slash and then burning the piles, or it can be done by whole tree skidding the tree to a landing to remove the branches, or it can be done by augmenting the cutting with a prescribed fire. (Waring and Six 2005) found some Ips beetle activity killing live whitebark pine trees from piles that were left for one year. Cutting treatments can be commercial timber harvests if 1) the trees are large enough, 2) the area is accessible by road, and 3) there is a market for the timber. Often, National Forest ranger districts have implemented cutting treatments using outside funding from various foundations or institutions.
Prescribed burning may be the most desirable treatment because it best emulates wildland fire, but it is also the most difficult and risky to implement. Prescribed burns can be implemented at three intensities to mimic the three types of fire regimes. The primary objective of low intensity prescribed fires is to kill the subalpine fir understory and perhaps overstory and to preserve the whitebark pine component.
The ignition method is important in this ecosystem. Most prescribed fires were ignited using strip head-fires where the width is increased if higher fire intensities were desired. However, some study sites are so moist when they need to be burned with very wide strips. Keane and Arno (2000) used both the terratorch and heli-torch in their study and burned large areas with the target high intensities. However, these techniques may not always be available. That leaves drip torches as the primary ignition technique and, to be effective, these ignitions should be done in dry conditions if high intensity fires are the objective of the burn. Another way to achieve high severity prescribed fires is multiple burns if possible.
We recommend a fuel enhancement cutting be implemented one year prior to a prescribed burn to ensure burn objectives are fully realized. The addition of cured slash to discontinuous fuel beds facilitates burn effectiveness by providing additional fine fuel to 1) aid fire spread into all areas of the stand and 2) augment quickly drying fine fuel levels so the burn can be implemented in moister conditions. Prescribed burns have a greater coverage and higher severity in stands where the fuels were enhanced. Fuel enhancement is an easy, cheap, and fast treatment that can be done by timber crews, fire crews or contractors. Keane and Parsons (2008[in press]) also found that shrub and herbaceous fuels were much drier after the first hard frost in late summer or early autumn. This frost kills the above ground foliage that allows the plants to take water from the soil so the entire plant structure can dry sufficiently for burning.