Effects of Nitrogen Fertilization on Young Jack Pine (Pinus banksiana) and on its Suitability as a Host for Jack Pine Budworm (Choristoneura pinus pinus) (Lepidoptera. Tortricidae)

1991

S. 1447-1458

4 Abb., 4 Tab., zahlr. Lit. Ang.

Unselbständiges Werk

200089562

Effects of nitrogen fertilization on growth, foliar nitrogen concentration, and monoterenes were determined on 7- to 11-year-old jack pine (Pinus banksiana Lamb.) on two sites in northwestern Wisconsin. One site established after wildfire; the other after clear-cutting. Jack pine budworm (Choristoneura pinus pinus Free.) larvae were caged on fertilized and unfertilized trees on each site. Relations among foliar nitrogen, monoterpenes, larval survival, and adult budworm weight were examined. Foliar nitrogen concentration, needle weight, shoot and diameter growth, and monoterpene production were lower on wildfire site trees than on clear-cut site trees, and were significantly increased on both sites by fertilization. Fertilization increased production of staminate cones on the wildfire site. Height growth differed between sites but was unaffected by fertilization. Contrary to expactions based on the resource availability theory, foliar nitrogen and monoterpene levels were positively related. Survival of jack pine budworm larvae was greater on clear-cut than on wildfire site trees, but was significantly affected by fertilization. Larvae on low-nitrogen trees on the wildfire site clipped more foliage than those on the clear-cut site, suggesting compensatory feeding. Adult female weight was higher for larvae on wildfire than clear-cut site trees. Two monoterpene compounds and site-related differences were the best predictors of adult female weight based on regression.