Factors affecting the success of autumn direct seeding of Pinus sylvestris L. in Finnish Lapland

Abstract

Spring and early summer have been regarded as the biologically best direct seeding dates for Scots pine. The study focused on finding out if late autumn is also a reasonable period for direct seeding of pine in Finnish Lapland and what factors affect the success of seeding. In all, the inventory-based data consisted of 50 regeneration stands and 908 sample plots sown in the autumn; the data were hierarchically structured at the levels of stand and circular plot. The method used was to construct models for the seedling establishment and seedling height. Modeling was used to analyze the principal ecological factors influencing regeneration success. The density and height models were developed using the Generalized linear mixed model (GLMM). The most significant variables affecting seedling establishment were temperature sum, proportion of prepared area, thickness of humus layer, stoniness, and distance from forest edge. Contrary to the hypothesis, late autumn can be regarded as a reasonable alternative period for direct seeding, at least in northern Fennoscandia. For confirmation of the results, more experimental research is needed. One must remember that the success of regeneration results from the combination of direct seeding and natural regeneration.

Keywords:

• Pinus sylvestris
• artificial regeneration
• direct seeding
• autumn direct seeding
• main crop seedling
• seedling establishment model
• seedling height model

Acknowledgements

The study was conducted in cooperation between the Finnish Forest Research Institute and Metsähallitus. We are grateful to the organizations and their personnel for technical and financial support. Raimo Pikkupeura deserves our special thanks for assisting in technical details. We also thank Sauli Valkonen for reading the manuscript and providing valuable comments, and Zoe Koivu for checking the English language.