ill., maps; Typescript (photocopy); Thesis (M.S.)-Oregon State University, 1975; Includes bibliographical references (leaves 120-127)
AN ABSTRACT OF THE THESIS OF Robert Curlan McNeil for the degree of Master of Science in Botany and Plant Pathology presented on July 14, 1975 Title: VEGETATIOD FIRE HISTORY OF A PONDEROSA PINE-WHITE FIR FOREST IN CRATER LAKE NATIONAL PARK Abstract approved: Donald B. Zobel This thesis describes the composition of and some of the 2 environmental controls of the vegetation of a 7. 5 km area in Crater Lake National Park, Oregon. It also gives the approximate dates and locations of most fires that burned in the area between 1750 and 1974Q The vegetation was sampled in 68 plots, which were 15 m x 25 m. Trees were tallied by size classes and coverage of herbs and shrubs was recorded. The soil profile was described at selected plots. The vegetation was classified by using three techniques: (1) Daubenmire's habitat type approach, (2) Braun-Blanquet's table sorting, and (3) an ordination. This resulted in a two-level classification in which 16 communities were grouped into six habitat types. The fire history was found by cutting wedges from fire scars and counting the rings outside the sears left by individual fires. This was done for two trees within 100 m of each other at each of 24 spotsQ The dates from these two trees were combined to give dates for a single sample, Two different soil parent materials support different habitat types. Alluvial material supports the relatively dry Abies concolor/ Symphoricarpos mollis habitat type, which includes the Populus, Senecio, and Melica communities. The Populus and Senecio may be the driest and are the most recently disturbed communities, and A. concolor may not be the climax dominant. The Melica community is somewhat moister and much less disturbed. The second type of soil parent material is pumice. This supports Abies concolor/Chimaphila umbellata and Abies magnifica var. shastensis habitat types and a Mesic Species community. The Mesic Species community occurs in areas with the water table near the surface in the spring, and provides enough moisture to stop some fires. The A. concolor/C. umbellata habitat type can be subdivided on the basis of the importance of Ceanothus velutinus and other criteria. The two subdivisions are generally located on different sides of the Mesic Species community fire break, and some of the differences between them are probably due to different frequencies of fires before 1902 as well as the climatic changes associated with elevation. Other communities occur only in special topographic or edaphic situations. Fires occurred at sampling spots at intervals from three or less to more than 50 years, with the mean interval at a spot ranging from nine to 42 years. The intervals between fires generally lengthened with increased elevation. A rough estimate of the composition of the forest was gained by combining age-size data with vegetation data. Most of the study area is not near maturity, and probably never has been due to the frequent recurrence of fire. The vegetation has apparently been changing since fire suppression became effective. As the forest matures, the canopy will probably close some more, resulting in less Pinus ponderosa and decreased importance of shrubs, Reintroduction of fire can probably reverse these trends to some extent.
AN ABSTRACT OF THE THESIS OF Robert Curlan McNeil for the degree of Master of Science in Botany and Plant Pathology presented on July 14, 1975 Title: VEGETATIOD FIRE HISTORY OF A PONDEROSA PINE-WHITE FIR FOREST IN CRATER LAKE NATIONAL PARK Abstract approved: Donald B. Zobel This thesis describes the composition of and some of the 2 environmental controls of the vegetation of a 7. 5 km area in Crater Lake National Park, Oregon. It also gives the approximate dates and locations of most fires that burned in the area between 1750 and 1974Q The vegetation was sampled in 68 plots, which were 15 m x 25 m. Trees were tallied by size classes and coverage of herbs and shrubs was recorded. The soil profile was described at selected plots. The vegetation was classified by using three techniques: (1) Daubenmire's habitat type approach, (2) Braun-Blanquet's table sorting, and (3) an ordination. This resulted in a two-level classification in which 16 communities were grouped into six habitat types. The fire history was found by cutting wedges from fire scars and counting the rings outside the sears left by individual fires. This was done for two trees within 100 m of each other at each of 24 spotsQ The dates from these two trees were combined to give dates for a single sample, Two different soil parent materials support different habitat types. Alluvial material supports the relatively dry Abies concolor/ Symphoricarpos mollis habitat type, which includes the Populus, Senecio, and Melica communities. The Populus and Senecio may be the driest and are the most recently disturbed communities, and A. concolor may not be the climax dominant. The Melica community is somewhat moister and much less disturbed. The second type of soil parent material is pumice. This supports Abies concolor/Chimaphila umbellata and Abies magnifica var. shastensis habitat types and a Mesic Species community. The Mesic Species community occurs in areas with the water table near the surface in the spring, and provides enough moisture to stop some fires. The A. concolor/C. umbellata habitat type can be subdivided on the basis of the importance of Ceanothus velutinus and other criteria. The two subdivisions are generally located on different sides of the Mesic Species community fire break, and some of the differences between them are probably due to different frequencies of fires before 1902 as well as the climatic changes associated with elevation. Other communities occur only in special topographic or edaphic situations. Fires occurred at sampling spots at intervals from three or less to more than 50 years, with the mean interval at a spot ranging from nine to 42 years. The intervals between fires generally lengthened with increased elevation. A rough estimate of the composition of the forest was gained by combining age-size data with vegetation data. Most of the study area is not near maturity, and probably never has been due to the frequent recurrence of fire. The vegetation has apparently been changing since fire suppression became effective. As the forest matures, the canopy will probably close some more, resulting in less Pinus ponderosa and decreased importance of shrubs, Reintroduction of fire can probably reverse these trends to some extent.