Reducing wind damage in the forests of the Oregon coast range /

Abstract

A study of damage in the Cascade Head Experimental Forest since 1948 and on 225 sample plots in the Oregon Coast Range in summer 1952 showed that: (I) Storm winds causing windthrow came from the S.S.W. (2) On the borders of clear-felled areas 93 % of the wind damage occurred along the N. and E. boundaries, especially when these boundaries were on the leeward side of the ridge. (3) There was no correlation between wind damage and size of tract felled, but areas down to 2 acres and less sustained considerable loss. (4) In stands from which 16-24% of the volume had been removed in thinnings, losses from windthrow averaged 80 bd. ft./ acre/year, while losses were heavy in other areas from which most of the dominant and co-dominant trees had been removed. (5) Douglas Fir and Sitka Spruce are more windfirm than Western Hemlock, and trees infected with root rot are particularly liable to windthrow. (6) Windthrow is more severe on areas with a high water-table or very shallow soil. (7) In virgin stands heaviest damage occurred on the lee side of ridges, beginning near the crest of the ridge and extending for some distance down the lee slope, and also on small ridges and level areas in the lee of higher ridges. Recommendations are made on felling practices to reduce windthrow. KEYWORDS: Picea sitchensis windthrow resistance \ protection \ forests \ Pseudotsuga taxifolia \ Pseudotsuga menziesii \ windthrow \ Rooting depth \ soil rooting depth \ Tsuga heterophylla windthrow \ Wind damage \ effects \ root rot \ Wind damage \ shallow \ soil \ Wind damage silvicultural precautions again