Seed-cone and pollen-cone production models for young black spruce seedling seed orchards: a first approximation

Abstract

Seed orchard managers wanting to predict potential seed-cone (Sc) and pollen-cone (Pc) production 1 year in advance of seed release and pollen dissemination need predictive models. The present study proposes the use of cone-crop models based on tree age in young black spruce (Piceamariana (Mill.) B.S.P.) orchards. Sc and Pc production was monitored from 1987 to 1993 in each of five seedling seed orchards. Some trees began bearing Sc and Pc by tree age 6. The relationships of Sc and Pc production with tree age were each represented by three sigmoid equations: one for light crop years, one for heavy crop years, and one for light plus heavy crop years. The rate of cone increase for heavy and light crop years differed for both Sc and Pc. Sigmoid equations representing heavy Sc and Pc crop years in orchards had the highest r2 (0.8462 and 0.9381, respectively) and the lowest standard error. Sigmoid model of heavy crop years with plantation data also had the highest r2 value (0.8066) and the lowest standard error. The rate of Sc and Pc increase versus tree age was higher for orchards than for plantations. To select the best of three sigmoid models, one must take into account the early buildup phase of cone production in young trees, the yearly fluctuation in cone crops, previous-year cone production, and environmental factors that can affect cone crops.