ill.; "July 1985."; "Final report on National Science Foundation Grant DEB-8109813"-- Cover; Includes offprints of several project-related publications by the authors; Includes bibliographical references
INFLUENCE OF FIRES, FUNGI AND MOUNTAIN PINE BEETLES ON DEVELOPMENT OF A LODGEPOLE PINE FOREST IN SOUTH-CENTRAL OREGON1 R. I. Gara, W. R. Littke, J. K. Agee, 0. R. Geiszler, J. D. Stuart, and C. H. Driver ABSTRACT Virtually pure iodgepole pine stands form an edaphic climax community over large areas of the? infertile "pumice plateau" of south-central Oregon. During our ongoing studies on the dynamics of these forests we developed the scenario that periodic fires create fungal infection courts in damaged roots; in time, advanced decay develops in the butts and stems of these trees. The mountain pine beetle preferentially selects and kills these trees during the flight season. As these outbreaks develop, additional uninfected trees are attacked. In time, the stage is set for subsequent fires as needles drop, snags fall, and logs decay. INTRODUCTION Lodgepole pine covers some 3 million acres of commercially important and scenic lands of the Pacific Northwest. The species, Pinus contorta var. murrayana (Grew and Balf.) EngeJm., has a wide ecological amplitude, and as such, it represents a valuable timber species of the region although its past commercial value has been low. Its positive establishment following tires and its rapid juvenile growth offer promise that the species can be used in short rotation management schemes (Wellner 1973, Cole 1973, Dahms 1973). Besides their potential for timber production, lodgepole pine forests provide vast recreation and wilderness areas (Despain 1973, Litton 1973), important water source areas (Hoover 1973), and range and wildlife habitats (Dealy 1973). Lodgepole pine was one of the pioneering species to occupy infertile tephra deposits at the close of the last glacial period in the southern Oregon Cascades (Hansen 1946). Franklin and Dyrness (1973) consider the virtually pure lodgepole pine stands to be an edaphic climax community on many sites of this so-called pumice plateau of south-central Oregon. Under certain circumstances the dynamics of these forests are controlled by the interacting effects of fires, the mountain pine beetle (Den-droctonus pondcrosae Hopk.), and fungal pathogens (Geiszler et ai, 1980). The main goal of the research summarized here was to assess the relative roles these ecological events play in the establishment and development ofa climax lodgepole pine forest in south-central Oregon. Study supported by XSF grant DEB vS2OS>813 RESEARCH SITES Our research sites within the Fremont National Forest and adjacent areas encompassed several discrete fire sites; these areas have been the scene of recurring epidemic infestations of the mountain pine beetle (R. E. Dolph, pers. comm. 1980). These burned sites included: I) Bald Mt.-a prescribed fire of 1982; 2) Wickiup Springs-a prescribed fire of 1976; 3) Lookout Point-a stand replacement fire that occurred in 1839 and a moderate fire in 1898; and 4) a 1980 fire at Crater Lake National Park that burned near the northern boundary of the park and eventually spread through a climax lodgepole pine stand in the Sharp Peak area of the Park. All study areas were about 1,800 m elevation with soils derived from Alt. Mazama pumice and ash, which were deposited about 6,600 years ago. The area received an additional tephra deposit from the Paulina Peak eruption ca. 4,000 years ago. Annual precipitation, largely as snow, averages 60 cm. Because of the coarse-textured surface soil and low rainfall, plant species diversity of this pumice plateau is low, and trees, shrubs and herbs are shallow rooted. The research results summarized below reflect the current status of our knowledge concerning the dynamics of these climax lodgepole pine stands. RESULTS Fire Behavior. -Climax lodgepole pine forests are more fuel-limited than other forested communities in the Pacific Northwest. The exceptionally low wood productivity (1-2 m5»ha~" ^yr-^and leaf area (1-2 m2Tn~2) result in little fuel accumulation, particularly of fine fuels that usually carry the fire. Both prescribed and natural fires in summer months have been observed to spread widely across red fir (Abies magnifica var. shastensis Lemm.) and ponderosa pine (Pinus ponderosa Doug, ex Loud.) forests without entering adjacent climax lodgepole pine stands. Where spread into lodgepole pine stands occurred, it was always along corridors of partially-decayed logs, remnants ofa disturbance several decades earlier (Agee 1981): Under the conditions we have observed, fire presence and behavior in lodgepole pine forests is more closely linked to coarse fuel dynamics than to fine fuel dynamics, and thus to the history of past disturbances. Logs often have higher fuel moistures than associated fuel classes, but the quantity and arrangement of these other fuels are such that they rarely carry the fire. For example, in the
INFLUENCE OF FIRES, FUNGI AND MOUNTAIN PINE BEETLES ON DEVELOPMENT OF A LODGEPOLE PINE FOREST IN SOUTH-CENTRAL OREGON1 R. I. Gara, W. R. Littke, J. K. Agee, 0. R. Geiszler, J. D. Stuart, and C. H. Driver ABSTRACT Virtually pure iodgepole pine stands form an edaphic climax community over large areas of the? infertile "pumice plateau" of south-central Oregon. During our ongoing studies on the dynamics of these forests we developed the scenario that periodic fires create fungal infection courts in damaged roots; in time, advanced decay develops in the butts and stems of these trees. The mountain pine beetle preferentially selects and kills these trees during the flight season. As these outbreaks develop, additional uninfected trees are attacked. In time, the stage is set for subsequent fires as needles drop, snags fall, and logs decay. INTRODUCTION Lodgepole pine covers some 3 million acres of commercially important and scenic lands of the Pacific Northwest. The species, Pinus contorta var. murrayana (Grew and Balf.) EngeJm., has a wide ecological amplitude, and as such, it represents a valuable timber species of the region although its past commercial value has been low. Its positive establishment following tires and its rapid juvenile growth offer promise that the species can be used in short rotation management schemes (Wellner 1973, Cole 1973, Dahms 1973). Besides their potential for timber production, lodgepole pine forests provide vast recreation and wilderness areas (Despain 1973, Litton 1973), important water source areas (Hoover 1973), and range and wildlife habitats (Dealy 1973). Lodgepole pine was one of the pioneering species to occupy infertile tephra deposits at the close of the last glacial period in the southern Oregon Cascades (Hansen 1946). Franklin and Dyrness (1973) consider the virtually pure lodgepole pine stands to be an edaphic climax community on many sites of this so-called pumice plateau of south-central Oregon. Under certain circumstances the dynamics of these forests are controlled by the interacting effects of fires, the mountain pine beetle (Den-droctonus pondcrosae Hopk.), and fungal pathogens (Geiszler et ai, 1980). The main goal of the research summarized here was to assess the relative roles these ecological events play in the establishment and development ofa climax lodgepole pine forest in south-central Oregon. Study supported by XSF grant DEB vS2OS>813 RESEARCH SITES Our research sites within the Fremont National Forest and adjacent areas encompassed several discrete fire sites; these areas have been the scene of recurring epidemic infestations of the mountain pine beetle (R. E. Dolph, pers. comm. 1980). These burned sites included: I) Bald Mt.-a prescribed fire of 1982; 2) Wickiup Springs-a prescribed fire of 1976; 3) Lookout Point-a stand replacement fire that occurred in 1839 and a moderate fire in 1898; and 4) a 1980 fire at Crater Lake National Park that burned near the northern boundary of the park and eventually spread through a climax lodgepole pine stand in the Sharp Peak area of the Park. All study areas were about 1,800 m elevation with soils derived from Alt. Mazama pumice and ash, which were deposited about 6,600 years ago. The area received an additional tephra deposit from the Paulina Peak eruption ca. 4,000 years ago. Annual precipitation, largely as snow, averages 60 cm. Because of the coarse-textured surface soil and low rainfall, plant species diversity of this pumice plateau is low, and trees, shrubs and herbs are shallow rooted. The research results summarized below reflect the current status of our knowledge concerning the dynamics of these climax lodgepole pine stands. RESULTS Fire Behavior. -Climax lodgepole pine forests are more fuel-limited than other forested communities in the Pacific Northwest. The exceptionally low wood productivity (1-2 m5»ha~" ^yr-^and leaf area (1-2 m2Tn~2) result in little fuel accumulation, particularly of fine fuels that usually carry the fire. Both prescribed and natural fires in summer months have been observed to spread widely across red fir (Abies magnifica var. shastensis Lemm.) and ponderosa pine (Pinus ponderosa Doug, ex Loud.) forests without entering adjacent climax lodgepole pine stands. Where spread into lodgepole pine stands occurred, it was always along corridors of partially-decayed logs, remnants ofa disturbance several decades earlier (Agee 1981): Under the conditions we have observed, fire presence and behavior in lodgepole pine forests is more closely linked to coarse fuel dynamics than to fine fuel dynamics, and thus to the history of past disturbances. Logs often have higher fuel moistures than associated fuel classes, but the quantity and arrangement of these other fuels are such that they rarely carry the fire. For example, in the