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Plant Communities and Environmental Interrelationship in a Portion of the Tillamook Burn, Northwestern Oregon

Bailey, Arthur W., Poulton, Charles E.
Ecology 1968 v.49 no.1 pp. 1-13
Acer circinatum, Acer macrophyllum, Alnus rubra, Gaultheria shallon, Lotus, Polystichum munitum, Pteridium aquilinum, Rubus parviflorus, Symphoricarpos, Vaccinium, environmental factors, forest fires, plant communities, shade tolerance, soil, species diversity, vegetation, Oregon
Major post—burn communities were characterized and environmental relationships investigated on an area burned by forest fires in 1933, 1939, and 1945. Results that seral vegetation developing after three forest fires is classifiable, and the communities show consistent relationships to environmental factors. Both shade—intolerant, early seral species and shade—tolerant, late seral or climax species revealed specific environmental requirements for growth and survival. Species composition and dominance data were recorded in 42 stands. Six associes were recognized. The Alnus rubra/Polystichum numitum associes occurs predominantly below 1,200 ft elevation, on north—facing, lower slope positions. These stands usually occupy the stony phase of the Hembre or the Astoria soil series. The Alnus rubra/Rubus parviflorus associes is found on steep, north—facing slopes usually at slightly higher elevations than the Alnus/Polystichum associes. These stands are predominantly associated with the stony phase of the Hembre soil series. The Acer circinatum/Polystichum munitum associes, found on all aspects between 700 and 1,200 ft, was arbitrarily classified into xeric and mesic phases. However, the community is usually associated with steep, lower slope positions. It is also found on the stony phase of the Hembre or the Astoria soil series. The Rubus parviflorus/Trientalis latifolia associes is found on all aspects, on steep, upper slope positions and above 1,200 ft elevation. It occurs predominantly on the Kilchis soil series. Stands of the Pteridium aquilinum/Lotus crassifolius associes usually occupy gentle, middle, and upper slope positions on all aspects above 1,200 ft elevation. It is found on the deep, stone—free Hembre soil series. The Vaccinium parvifolium/Gaultheria shallon associes is found on south—facing, convex slopes or ridgetops from 700 to 2,100 ft. It occurs to some degree on all soil series in the area. Two provisional associes were recognized: the Acer macrophyllum/Symphoricarpos mollis associes occupying partially—vegetated, south—facing, rock outcroppings and talus slopes, and the Acer macrophyllum/Alnus rubra associes limited to stream bottoms. Some of the cause of vegetation heterogeneity are discussed, and a dichotomous key to the vegetation is presented.