Fire history in Douglas-fir and coast redwood forests at Point Reyes National Seashore, California

Historical variability in tire regimes and forest age structures is necessary reference information for management of vegetation and landscape patterns in naturally managed ecosystems. In this study, we reconstructed fire history and forest age structure at Point Reyes National Seashore on the central California coast to document changes in forest conditions over the past ca. two centuries. Surface fire history was reconstructed from dendrochronologically-crossdated fire-scarred trees in two stands of Douglas-fir (Pseudotsuga menziesii var. menziesii) and one stand of coast redwood (Sequoia sempervirens). Age structure in an approximately 2000 ha area of Douglas-fir forest was examined for tree recruitment patterns. Reconstructed mean surface fire intervals and Weibull median probability intervals ranged from ~ 7 to ~13 years. Fires generally occurred late in the growing season or after growth had ceased for a year. Spatial patterns of historic fires and those reconstructed from the fire-scar record document often widespread rims in the central Olema Valley. Likely many, if not most, of the fires reconstructed from Point Reyes were ignited by humans given the long history of intensive use of this area, first by the Coast Miwok and later by European ranchers. Age structures of stands suggest that much of the Douglas-fir overstory is multiaged with little evidence of stand-replacing fire or other disturbance events. Ages of trees in Douglas-fir stands document increasing landscape coverage of Douglas-fir forest at Point Reyes and hardwood recruitment under older Douglas-fir canopies, and suggest that loss of surface fires is having cascading effects on landscape vegetation patterns, community relationships, and probably related ecosystem processes.