Recovery Plan for the Northern Spotted Owl - DRAFT

WindLocal situations away from the coast may be associated with substantial winddamage over time. Forests on the lee side of Mt. Rainier, for example, in theWhite River drainage, appear to have been damaged by winds over past centuries.Trees in the Columbia River gorge area north to at least Mount St. Helensand south to Mt. Hood are "flagged" because of strong easterly winds whichdesiccate foliage on the upriver sides of the trees. North or east winds, such asoccurred in Puget Sound during December 1990, occasionally are associatedwith substantial windthrow.At Cascade Head, an exposed headland near Otis, Oregon, Harcombe (1986)found that small-scale events have a larger impact on the forest than largescaleblowdowns, comparing the canopy turnover time of 119 years from smallscaleevents to 384 years for blowdown from large-scale events (i.e., time for anarea equal to the forest area to blow down from either type of disturbance). Infact, small- and large-scale blowdown can occur. Basing long-term windthrowreturn intervals on 50 years of record, as Harcombe does, is not a very reliablemethod of prediction for such an episodic disturbance.In the Olympic Mountains, Henderson et al. (1989) suggest that wind is mostimportant in the coastal zones (Figure F.5). Substantial blowdowns have occurredin 1979 (Hood Canal Storm), 1962 (Columbus Day Storm), and 1921(Boyce 1929). Stand-level information from ridgeline stands in the westernOlympics suggests other wind-associated events in the late 1880s and early1850s (Agee, unpublished data). Although each event did not affect the entirearea, a return interval of about 30 years for major wind disturbances seems tobe operating in this area. The Columbus Day Storm also affected other standsthroughout the subregion but to a lesser extent and generally in sensitive topographicsituations (such as saddles).(Few fires, 40wind Low frequency +tires #*** High frequency& ftiresFigure F.5. Map of Olympic Peninsula showingthe relationship between groups of environmentalzones andforestfirefrequency.I 1-1 .....I. ..... I... .111.1... I.......... I I I.. 11.1.-... I.." I .447