Restoring whitebark pine ecosystems.

PRINCIPLE INVESTIGATOR

Robert E. Keane, Deputy Program Manager, Fire, Fuel, and Smoke Science (FFS); Research Ecologist; Director, Fire Modeling Institute (FMI)

Staff: Russ Parsons, Jhen Rawling, Violet Holley, Signe Leirfallom, Laurie Dickinson, Curtis Johnson, Eva Karau, Lisa Holsinger

INTRODUCTION

Whitebark pine (Pinus albicaulis) forests are declining across most of their range in North America because of the combined effects of three factors: 1) several major mountain pine beetle epidemics that occurred over the last 70 years, 2) effects of an extensive and successful fire exclusion management policy, and most importantly, 3) extensive invasion of the exotic white pine blister rust fungus (Cronarium ribicola). The loss of whitebark pine would be serious for upper subalpine ecosystems because it is considered a keystone species across most of its range, producing large seeds that are an important food source for over 110 animal species. Therefore, the restoration of this dwindling species is important to many species that depend on it for existence. This is an extensive, long term study, called Restoring Whitebark Pine Ecosystems (RWPE), where the effects of several ecosystem restoration treatments were evaluated on five high elevation sites in the northern Rocky Mountains. These treatments included prescribed fire, thinning, selection cuttings, and fuel enhancement cuttings. The main effects evaluated for these treatments included fuel consumption, tree mortality, and vegetation response measure at three time periods: prior to the treatment, 1 year after the treatment(s), and 5 years post-treatment (10 year post-treatment measurement is available for one site).

Whitebark pine is a long-lived, seral tree of moderate shade tolerance. It can take approximately 50 to 250 years for subalpine fir to replace whitebark pine in the overstory depending on the local environment and previous fire history. Whitebark pine forests are found in two types of high mountain biophysical settings. Most common are upper subalpine sites where whitebark pine is the major seral species that is successionally replaced by the shade-tolerant fir, spruce or hemlock, depending on geographic region. Sites where whitebark pine is the only tree species able to successfully reproduce and mature (the indicated climax) are found at lower timberline on relatively dry, cold slopes, where trees often occur in elfin forests, clusters, groves or tree islands. Whitebark pine comprises about 10‑15 percent of the forested landscape in the upper subalpine zone of the northern Rocky Mountains. Although this species has limited use as a commercial timber species because of its diminutive stature, gnarled growth form, and remote setting, it produces seeds that are highly prized for food by many species of wildlife, including the threatened grizzly bear (Ursus arctos horribilis), red squirrel (Tamiasciurus hudsonicus), and most importantly, the Clark's nutcracker (Nucifraga columbiana). The Clark's nutcracker plays a critical role in the whitebark pine regeneration process because this bird is essentially the only dispersal vector for the heavy, wingless seed. Whitebark pine also protects snowpack in high-elevation watersheds and delays snowmelt, providing high quality water to valleys below throughout the summer.

GOALS AND OBJECTIVES

The RWPE study was started in 1993 to explore the use of prescribed fire, mechanical cuttings, and planting treatments to restore whitebark pine forests by enhancing regeneration success and prolonging whitebark pine cone production. The primary assumption in the RWPE study is that whitebark pine ecosystems can be restored from the damaging effects of blister rust, mountain pine beetles, and fire exclusion by implementing treatments that emulate wildland fire processes in stands where the species has been declining. The objective of these treatments are to 1) to increase whitebark pine regeneration potential that to provide for future whitebark pine cone crops and 2) improve the vigor of surviving whitebark pine to promote future cone crops. We assume that those living, cone-producing whitebark pine seed sources at or near the restoration sites will possess some degree of blister rust-resistance because they have already survived decades of rust infection. These apparent rust-resistant whitebark pine trees would provide the seed for the nutcrackers to plant in the treated units and the subsequent regeneration would be somewhat resistant to the rust.

METHODS AND RESULTS

We implemented the RWPE study on five sites in the northern Rocky Mountains. Three sites are on the Bitterroot National Forest (two on the Stevensville Ranger District and one on the Darby Ranger District), one on the Salmon-Challis National Forest, and the largest study site is on the Clearwater National Forest. Whitebark pine is declining on all sites except for the Blackbird Mountain site on the Salmon-Challis National Forest where there were few rust infections and no observed mortality. We installed 10 plots within each treatment unit to describe changes in a diverse range of ecological conditions within the treatment unit. We systematically located these plots across the treatment units based on fixed distances and compass bearings. Plots in this study were circular in shape and 0.1 acre (0.04 ha) in size and they were permanently located using three foot (1 m) rebar driven 2 feet (0.7 m) into the ground. For all trees above 4.5 in DBH, we measured species, DBH (tree diameter at breast height), tree height, height to crown base, and health (live, sick, dying, or dead) for each tree and then recorded the percent crown volume killed by blister rust for all whitebark pine trees. The same characteristics were measured for all live trees less than 4.5 in DBH and higher than 4.5 feet tall except DBH was estimated to 1 inch diameter classes. Tree seedlings (trees less than 4.5 feet) were counted by 1 foot height classes on a 1/300 acre circular plot in the middle of the tenth acre plot using the same plot center. Surface fuels were measured on two 50 foot (15.2 m) transects that originated at the plot center rebar and extended in opposite directions. Vertically projected foliar cover of each vascular plant species was visually estimated within each of four, 1 m2 (1.41 m by 0.71 m) microplots at each plot using 12 cover classes: <1%, 1-5%, 5-15%, 15-25%, up to 95-100% (see FIREMON for details). Ground cover for rock, bare soil, wood, duff/litter, and moss was also recorded for each microplot using the same cover classes. We took the tree, fuel, and plant species measurements described above prior to the treatment (pre-treatment), then one year after the treatment(s) and five years after the treatment (5-yr post-treatment).

All high and moderate intensity prescribed fire-cutting treatment combinations were effective at creating desirable nutcracker caching habitat as evidenced by the abundant nutcracker caching observed on nearly all sites. However, the expected whitebark pine regeneration from this caching has not materialized as yet with nearly all sites having few or no whitebark pine seedlings. We also found it difficult to implement low severity prescribed fires to mimic non-lethal surface fires for a number of reasons. First, shrub and herbaceous fuels on sites without fuel were rarely dry enough to sufficiently carry a fire under our fire prescriptions (desired conditions of burning) resulting in a light fire with low tree mortality and low burn coverage. In contrast, the fire intensity on those sites where we used fuel enhancement to increase fine fuels and contagion was too high because of the high fuel loadings and this resulted in high whitebark pine mortality and extensive reductions in the stabilizing undergrowth plant community. Most treatments actually increased fuel loadings on most sites, especially the coarse woody debris (logs > 3 inches diameter). This is primarily because the prescribed fire burned through the bases of the abundant rust-killed whitebark pine snags in the treatment stands. These newly fallen logs pose a low fuel hazard because of the lack of fine fuels, and their presence might actually improve the potential for whitebark pine regeneration by providing safe sites for cached whitebark pine seed. The planting of whitebark pine seedlings was marginally effective (approximately 40 percent survival after 3 years) because nursery techniques and planting guidelines for whitebark pine at the time of planting were not as extensive as they are today. Our seedlings were small and they were planted in mid-summer just after snowmelt and had to endure three hot, dry months. There is now extensive reference material for growing whitebark pine in nurseries and recommendations for planning whitebark pine so our success would definitely be improved using today’s technology.

PUBLICATIONS AND PRODUCTS

Keane, Robert E.; Parsons, Russell A. 2009[in press]. Management guide for ecosystem restoration treatments: Whitebark pine forests of the northern Rocky Mountains, USA. General Technical Report RMRS-GTR-XXX. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, XXXX pp

Keane, Robert E.; Parsons, Russell A. 2009[in prep]. Restoring whitebark pine ecosystems. Ecological Restoration.

Keane, R.E. and S.F. Arno. 1996. Whitebark Pine (Pinus albicaulis) ecosystem restoration in western Montana. In: Arno, S.F. and Hardy, C.C., editors, The use of fire in forest restoration, a general session at the annual meeting of the Society of Ecosystem Restoration "Taking a broader view". Sept 14-16, University of Washington, Seattle, WA. USDA Forest Service General Technical Report INT-GTR-341. Pages 51-54.

Keane, R.E., S.F. Arno and C. Stewart. 1995. Restoration of upper subalpine whitebark pine ecosystems in western Montana. In: Mathiasen, R.L. editor, Proceedings of the 43 annual Western International Forest Disease Work Conference, Whitefish, Montana, USA. August 29-31, 1995. Pages 105-112.

Keane, R.E. and S.F. Arno. 2000. Restoration of whitebark pine ecosystems in western Montana and central Idaho. In: Proceedings of the Society of American Foresters 1999 National Convention. Portland, OR. Society of American Foresters, Bethesda, Washington DC. Pages 324-330.

Keane, R.E., S.F. Arno, and C. Stewart. 2000. Ecosystem-based management in the whitebark pine zone. In: Smith, H.Y. (ed.) 2000. The Bitterroot Ecosystem Management Research Project -- what we have learned: symposium proceedings; 1999 May 18-20; Missoula, MT. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Proceedings RMRS-P-17 Pages 36-41

PROJECT STATUS

This study is nearly finished. All field data are collected and the final set of publications is being written. We plan on conducting a 10 year remeasurement of all plots when the time has elapsed.

FUNDING ORGANIZATIONS

This work is currently being funded by RMRS and Missoula Fire Fuels and Smoke Program.