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Patterns of Survival, Damage, and Growth for Western White Pine in a 16-Year-Old Spacing Trial in Western Washington Badege Bishaw, Oregon State University, College of Forestry, Corvallis, OR. 97331, Dean S. DeBell (retired), and Constance A. Harrington, USDA Forest Service, Pacific Northwest Research Station, 3625-93rd Ave. SW, Olympia, WA 98512-9193. ABSTRACT: Information about effects of planted spacing on growth and development of western white pine is scant because white pine blister rust disease has severely limited the survival of trees in young plantations. In the early 1980s, we established a western white pine spacing trial in the southern Cascades of Washington, using seedlings from a seedlot comprised primarily of open-pollinated seed from trees screened and certified as resistant to white pine blister rust. Initial square spacings ranged from 2 to 6 m; treatment plots were 0.4 ha in size and were replicated three times (six times for the 3 m spacing). Permanent measurement plots were installed at age 8, and the lower portion of all stems was pruned in the 10th growing season to reduce blister rust infections. The plots were remeasured at ages 11 and 16. Sixteen years after planting, survival averaged 80%; most mortality was associated with blister rust, but the rate of new infections and mortality diminished substantially between ages 11 and 16; 71% of the planted trees were free of blister rust at age 16. Trees averaged 8.4 m tall (ranging from 7.6 m in the 2 m spacing to 8.8 m in the 4 and 5 m spacings) and 12.7 cm dbh (10.3 in the 2 m spacing to 14.0 cm in the 5 m spacing). Periodic annual growth from 11 to 16 yr in the three wider spacings averaged 0.7 m in height and 1.0 cm in diameter. Antler rubbing by elk caused substantial damage to stems, but wounds on most trees were overgrown in 2 to 4 yr. Rub damage did not appear directly related to spacing but rather to stem diameter, with damage limited primarily to stems >6 and <15 cm. Early growth rates in this trial were much greater than those attained in older, natural stands (as inferred from site index curves and yield tables) and in progeny tests and other young silvicultural trials planted elsewhere. We believe rust-resistant stock of western white pine merits greater consideration for planting in the Douglas-fir region. West. J. Appl. For. 18(1):35-43. Key Words: Pinus monticola, Cronartium ribicola, pruning, rust resistance, animal damage search in that region was focused on the species (e.g., Western white pine (Pinus monticola) is one of the Haig 1932). But by the early 1940s it became largest pines in the world and among the fastest growing apparent that blister-rust disease (caused by the fungus conifers in the western United States. The species has Cronartium ribicola), would severely limit the survival widespread distribution as a component of mixed- and development of future stands of western white pine. species stands in forests of the coastal, Cascade, and As a result, most subsequent silvicultural research Sierra Nevada ranges from British Columbia to northern focused on mixed-species stands and other coniferous California. It attains its greatest commercial importance species, while forest pathologists and geneticists in the Rocky Mountains of northern Idaho and adjacent researched approaches to dealing with the exotic fungal areas of eastern Washington, western Montana, and pest. The successful development of rust-resistant interior British Columbia where it constitutes a plurality seedling stock in genetic improvement programs of the stocking in the western white pine cover type (Bingham 1983) made western white pine management (Graham 1990). High volume stands and light-weight, once again feasible in the Inland Empire and in the straight-grained, and easily worked wood made the coastal and Cascade zones of the Douglas-fir species one of the mainstays in early development of (Pseudotsuga menziesii) region. the timber industry in the Inland Empire. Much early re- Most plantations in the Douglas-fir region (i.e., west of the Cascade Range from southern British Columbia NOTE: Constance A. Harrington is the contact author and can be to northern California) have been and continue to be reached at (360) 753-7670; Fax: (360) 956-2346; E-mail: [email protected]. This article was written by U.S. planted with Douglas-fir seedlings. This focus is Government employees and is therefore in the public domain. associated with the favorable traits of Douglas-fir WJAF 18(1) 2003 35 (rapid growth, suitability for diverse sites, high value ft logs) per acre (metric equivalent not available) and wood) and with the nursery and regeneration experience represented about 10% of the merchantable timber volume available, which is considerably greater for Douglas-fir in the original old-growth forest prior to 1950 (DeBell and than for other conifer species. But as forest management Franklin 1987). By the 1980s, however, bleached-out snags objectives have shifted in response to changes in of western white pines killed by blister rust and mountain ecological, economic, and social conditions, there is pine beetles (Dendroctonus ponderosae) and a few seedlings greater interest in managing tree species previously and saplings infected with blister rust were all that neglected in westside forestry. Thus, there is a need to remained of the species. The study site was, and the develop information that will help forest managers choose surrounding stands are, dominated by old-growth Douglas- among a greater number of species and cultural options. In fir, western hemlock, and Pacific silver fir, much of which the early 1980s, spacing trials were established for several is defective with high incidence of broken tops, dwarf conifer species on the Wind River Experimental Forest in mistletoe, root rots, and other diseases. Natural the southern Cascades of Washington; one of these trials regeneration of coniferous tree species in the area includes was with western white pine. At the time, there were no Douglas-fir, western hemlock, Pacific silver fir, western ongoing spacing trials for the species. Few such trials for redcedar, and western white pine; the latter, however, western white pine had been previously established, and usually succumbs to blister rust prior to growing beyond those established had been abandoned because of severe the small sapling stage. mortality caused by white pine blister rust. Study Installation and Design This article reports performance of western white pine The western white pine spacing trial was installed on the during the first 16 yr after planting in the Wind River lower half of a 32 ha clearcut that was harvested in 1979. spacing trial. Patterns of survival and growth as well as Residual slash was machine piled and burned, and much of incidence of blister rust and animal damage are the area was also scarified to remove a dense cover of salal summarized. Trends in tree growth and stand development and vine maple that had developed as a result of openings and are then compared with limited published data on young sparse canopies created by Phellinus weirii root rot. The plots white pine stands elsewhere. were laid out and seedling positions marked with small wire Materials and Methods pin flags a year before the area was planted. To minimize shading and other edge effects, all plots were established at Site Description least 35 m from mature timber on the south side of the unit and The spacing trial is located in a gentle mid-slope position 25 m from other boundaries. (elevation 680–720 m) on the west-facing aspect of Trout Western white pine seedlings were grown as bareroot Creek Hill in the Wind River Experimental Forest, about stock (2-0) at the USFS Wind River Nursery. The seedlot 20 km north and slightly west of Carson, WA (lat. consisted of wind-pollinated seed collected from 13 trees 45°50’N, long. 122°0’W). The soil (mapped as a medial, growing in a seed production area near Mount Adams, some amorphic, mesic, Vitric Hapludand similar to the Stabler 65 km from the study site. Twelve trees had been screened soil series) is derived from basaltic lava that has at the USFS Dorena Tree Improvement Center and weathered rapidly to produce a uniform, moderately deep determined to be rust-resistant, but one bushel came from a (1 to 2 m) loam over cobbly or gravelly loam. At the tree that had been selected for phenotypic resistance but had nearby Wind River weather station (about 7 km distant not been screened. Thus, the seedlot—though not certified with an elevation 200 m below the study site), the average as “improved”—was assumed to have a moderate amount of frost-free growing season is 140 days, and average annual resistance. Planting was done in the spring of 1982 using a precipitation is 2,550 mm. Nearly 75% of the annual power auger. Nominal spacing was very close to prescribed precipitation (1,850 mm) occurs as rain or snow during spacing except where large stumps or logs prevented the November through March period. Mean annual planting at the designated planting spot. Dead trees were temperature is 9°C; mean temperature during the growing replaced with similar western white pine seedlings every season is 16°C. Vegetation is intermediate between the spring for 3 yr following the initial planting, but relatively western hemlock (Tsuga heterophylla) and Pacific silver fir few required replacement. Thereafter, a nearby naturally (Abies amabilis) zones (Franklin and Dyrness 1973). The seeded or volunteer tree, usually Douglas-fir, was selected forest cover type on Trout Creek Hill ranges from for retention and measurement so as to maintain competition predominantly Douglas-fir (Site class III to Site class IV, levels approximating those initially established for testing.

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