INFLUENCE OF CLIMATE ON RADIAL GROWTH AND CONE PRODUCTION IN SUB-ALPINE FIR (ABIES-LASIOCARPA) AND MOUNTAIN HEMLOCK (TSUGA-MERTENSIANA)

Thirty years of cone production records for subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and mountain hemlock (Tsuga mertensiana (Bong.) Caff.) (two sites each) in the Cascade Mountains of Washington and Oregon were compared with basal area increment and weather records to determine relationships among weather, radial growth, and cone crop. Results show that the size of subalpine fir cone crops was negatively related to large crops and positively related to radial growth in the previous 2 years. Mountain hemlock cone crops were negatively related to a large cone crop and positively related to July or August temperature in the previous year. Radial growth in heavy cone years was inhibited more for subalpine fir than for mountain hemlock. Results are explained by differences in the location of cone production between species. It is concluded that global climate warming could result in fewer and more irregular cone crops for these species.