INITIAL AND CONTINUED EFFECTS OF A RELEASE SPRAY IN A COASTAL OREGON DOUGLAS-FIR PLANTATION

Portions of a 4-year-old Douglas-fir (Pseudotsuga menziesii var. menzi esii (Mirb.) France) plantation were sprayed with herbicide. Five year s after spraying, we established 18 plots and used several means to de termine retrospectively that six plots probably received full spray tr eatment and six others received no spray. Various portions of the rema ining six plots probably were sprayed. Herbicide reduced number and si ze of red alder (Alnus rubra Pong.), increased number and size of plan ted Douglas-fir, damaged terminal shoots of Douglas-fir resulting in m ore abnormal boles and branching, and increased number of volunteer co nifers. Fifteen of the eighteen plots were thinned. In the subsequent 6 years, thinned plots that had received full release at age 4 average d 9 percent more volume growth (all species) than plots not released.