SUBALPINE TREE REESTABLISHMENT AFTER FIRE IN THE OLYMPIC MOUNTAINS, WASHINGTON

Rates of subalpine tree reestablishment were measured on the 1978 Hoh burn (3 yr old), the 1924 Mount Wilder burn (55 yr old), and the 1891 High Divide burn (88 yr old) in Olympic National Park, Washington, USA. All 3 sites were Abies lasiocarpa/Tsuga mertensiana forest at the time of burning; Vaccinium spp. were dominant after the fire. Tree establishments rates were higher on burned sites during periods with generally above-average to average spring/summer precipitation than during below-average periods. Highest rates of tree establishment occurred close to fire edges. Current species composition on the older burns closely reflects the composition of residual trees. Drought resistance of the residual tree species may interact with climate to affect establishment rates. Tsuga mertensiana establishes best during wet periods; Abies lasiocarpa, Pseudotsuga menziesii and Pinus monticola establish well during normal periods. These patterns are quite different from tree invasion into heather (Phyllodoce/Cassiope) meadows, which occurred during a fairly discrete 1920-1940 regional drought when extended snow-free periods apparently existed in these meadows.