Hastening the Return of Complex Forests Following Fire: The Consequences of Delay

Above: In July 2002, the Biscuit Fire burned through the 1987 Silver Burn. Note the snags igniting ahead of the fire front. Photo by Tom Link, Siskiyou National Forest Hastening the Return of Complex Forests Following Fire hasten regrowth of structurally complex conifer-dominated forests, we examine prefire forest conditions, what exists now in the aftermath of the fire, and the likely consequences and tradeoffs of natural ecosystem recovery versus management interventions. This examination of forest policy was prompted by Douglas County commissioners who asked Oregon State University to examine costs of management delay following the large fires in southwest Oregon during 2002. Landscape Condition The area of the Biscuit Fire is a geologic patchwork, characterized by rough terrain, deeply incised valleys, and geologic strata that vary in resistance to erosion. Soils in the burned area can be loosely grouped into two categories, those derived from serpentine base rock and those that are not. The serpentine-derived soils are the most erosion prone. They are high in magnesium and low in calcium, and their water-holding capacity is low. Vegetation on these soils is sparse, and they are low productivity for conifer forests. About 25 percent of the soils in the Biscuit Fire perimeter are serpentine-derived. The remainder are derived primarily from sandstones and schists; their productivity for conifer forests is low to medium. Within the Biscuit Fire, mature forests (>100 years) comprised Douglasfir (Pseudotsuga menziesii), white fir (Abies concolor), tanoak (Lithocarpus densiflorus), Jeffrey pine (Pinus jeffreyi), and Port-Orford-cedar (Chamaecyparis lawsoniana), with scattered western white pine (Pinus monticola), sugar pine (Pinus lambertiana), ponderosa pine (Pinus ponderosa), madrone (Arbutus menziesii), and other species. Few stands reached great ages (>300 years) because of frequent fires, and most of the older stands were on north slopes, which do not burn readily. The prefire timber volume within the fire perimeter was estimated to have been about 10 billion board feet, Scribner scale. One-third of the burned area may return to the desired forest conditions with minimal human intervention because it retains seed sources and elements of structural complexity. But on about 345,000 acres, according to the USDA Forest Service (2003), there now are more dead than live conifer trees (fig. 2, p. 40). At least 25 percent of the canopy was killed on more than two-thirds of the fire area. The affected area includes about 20 percent of the entire natural range of Port-Orford-cedar and is also an important area for sugar pine and western white pine (Don Goheen, pers. commun., July 2, 2003). If naturally seeded, these five-needle pines have little resistance to an exotic blister rust, and naturally seeded Port-Orfordcedars have almost no resistance to Port-Orford-cedar root disease, another exotic. These species can be successfully established on sites within the Biscuit Fire area only if disease-resistant seedlings from improved stock are planted. Of the 300 wildlife species that meet at least part of their yearly needs on the Rogue River–Siskiyou National Forests, three are listed as threatened or endangered: the bald eagle, the marbled murrelet, and the northern spotted owl. Habitat for the owl is the most significant consideration, as about 25 percent of the 202 known spotted owl activity centers on the Siskiyou are within the fire area. The fire transformed 23 of the 40 “functional home ranges” to “nonfunctional” habitat and made 75,000 to 80,000 acres of nesting habitat unsuitable (USDA Forest Service 2003). In addition, some 460 miles of streams 39 April/May 2004 • Journal of Forestry Figure 1. The 2002 Biscuit Fire, encompassing 500,000 acres, affected critical habitat for the northern spotted owl, as well as other species . Source: USDA Forest Service (2003). Siskiyou National Forest