Predicting establishment of tree seedlings for evaluating methods of regeneration for Pinus sylvestris

Abstract

This study predicts the establishment of regeneration in 3-, 4- and 5-year-old regeneration areas planted, direct seeded and naturally regenerated, respectively, for Scots pine (Pinus sylvestris L.) in southern Finland. Establishment of regeneration was described by the number of planted, seeded and natural tree seedlings, as well as by the height of pines and the dominant height of broadleaves. In planted stands, the number of natural crop-tree conifers was also predicted. For each regeneration method, establishment of regeneration was modelled by fitting a multilevel multivariate model to regeneration survey data. Temperature sum, altitude, site fertility, soil quality and method of site preparation were used as explanatory variables in the models. Stochastic simulations that accounted for the random between-stand variation in the regeneration result were conducted to evaluate the uncertainty and risk involved in different methods of regeneration for Scots pine. Counting both planted pines and supplementary natural crop-tree conifers, on relatively fertile growing site of Scots pine (Myrtillus type), planting was more effective than direct seeding and natural regeneration. On poorer sites (Vaccinium and Calluna types), in terms of the number of pine seedlings, direct seeding proved to be the most effective method for establishing pine stands.