TREE WOUND DYNAMICS IN THINNED AND UNTHINNED STANDS OF GRAND FIR, PONDEROSA PINE, AND LODGEPOLE PINE IN EASTERN OREGON

The effects of thinning (spacing) on stem-wound closure and associated wood decay, as affected by tree growth and vigor, were tested in stan ds of grand fir (Abies grandis (Dougl. ex D.Don) Lindl.), ponderosa pi ne (Pinus ponderosa Dougl. ex Laws.), and lodgepole pine (P. contorta var. latifolia Engelm.). In stands located near Union, Cove, and Lapin e, Oregon, thinning improved diameter growth and vigor. Vigor was indi cated by measuring cambial electrical resistance. Wounds on trees in t hinned stands tended to close faster than wounds on trees in unthinned stands, although differences were significant for lodgepole pine only . Stem decay occurred only in grand fir, and most of the decay was cau sed by Heterobasidion annosum (Fr.) Bref. The percentage of stem decay was significantly less in thinned (38.2%) than in unthinned (52.3%) f irs. Our results support the use of thinning to improve pine and fir g rowth and reduce losses from wound-associated stem decay.