Terminal leader failure in white spruce plantations in northern Minnesota

Terminal leader failure from bud mortality occurred in 46% of plantation white spruce (Piceaglauca (Moench) Voss) trees, 19-43 years old. Frost damage was identified as the causal factor of bud mortality, with all plantations being established from seed sources of local origin. Large differences in terminal bud failure rates were noted between year of observation, tree size class, and stand age-class. Dominant trees, 33-43 years old, had a 3 year failure rate ranging from 16 to 51 %. For dominant trees, an 18% (9 cm) height growth reduction per year of incidence was noted. The lateral replacement process could account for greater than a 2 m height reduction for dominants at age 50 years, confounding estimates of potential site quality. The height growth of overtopped trees responded differently to frost damage than dominants, with replacement laterals averaging 38% (8 cm) greater height growth than apical terminals of undamaged trees.