EFFECTS OF THINNING AND NITROGEN-FERTILIZATION ON SUGARS AND TERPENESIN DOUGLAS-FIR VASCULAR TISSUES - IMPLICATIONS FOR BLACK BEAR FORAGING

The chemical constituents of coniferous vascular tissues play a role i n bear forage selection. In particular, bear foraging preferences are related to the concentrations of simple sugars (nonstructural carbohyd rates) and terpenes in the forage. Analyses of vascular tissue samples from trees collected in test plots indicated that both thinning and f ertilization caused the sugar concentration of vascular tissues in the lower bole to increase. However, these treatments had no effect on th e concentrations of hydrocarbon monoterpenes, oxygenated monoterpenes, or sesquiterpenes. These results may explain the observations that bl ack bears prefer to forage in thinned and fertilized stands.