LOCAL AND REGIONAL VEGETATION CHANGE ON THE NORTHEASTERN OLYMPIC PENINSULA DURING THE HOLOCENE

The postglacial vegetation history of the northeastern Olympic Peninsu la was investigated at different spatial scales by comparing the polle n, macrofossil, and charcoal records from a low elevation lake (Crocke r Lake) and a nearby forested swamp (Cedar Swamp). The regional pollen record from Crocker Lake revealed a parkland of coniferous species wi th divergent modern ecological tolerances, including Pinus contorta, P icea sitchensis, and Abies lasiocarpa during the late glacial period ( similar to 13 000 - 10 000 BP). Disturbance-adapted species such as Al nus rubra and Pseudotsuga menziesii dominated forests during the early Holocene (10 000 - 7000 BP). Modern forests containing mesic late-suc cessional species such as Tsuga heterophylla and Thuja plicata were es tablished during the late Holocene (7000 BP to present). During the la te glacial period, the local vegetation at Cedar Swamp was dominated b y Alnus sinuata. Hydrologic changes resulted in the establishment of a deep marsh during the early Holocene. Hydrosere succession from an op en aquatic environment to a forested wetland and disturbance-mediated alternations between Thuja plicata and Alnus rubra characterized the l ocal vegetation during the late Holocene. Throughout the Holocene, the vegetation of the northeastern Olympic Peninsula was governed by broa d climatic and physiographic parameters at the regional scale and the effects of local geomorphologic constraints and disturbance history at the finer landscape scale.