Early regeneration of Populus tremula from seed after forest restoration with fire

Abstract

This study investigated the effects of biotope, substrate and coarse woody debris (CWD) shelter on Populus tremula L. regeneration from seed when restoring mature, managed, spruce-dominated stands on mesic sites. The stands were harvested using partial cuts, leaving 50 m³ ha⁻¹ of standing retention trees and 30 m³ ha⁻¹ of CWD, and burned. A direct seeding experiment was carried out 1 year later. Sowing areas were delimited on burned organic matter and mineral soil substrates, in open areas and in the shelter of CWD, on both paludified and upland biotopes. Seedling establishment was highest on mineral soil on the upland biotope, and intermediate on burned organic substrate on the paludified biotope. No seedlings established on burned organic substrate on the upland biotope. The shelter of CWD was both beneficial and detrimental to seedling emergence and establishment. Seedlings were taller on mineral soil than on burned organic substrate. The results suggest that biotope variation is important and partly explains the patchy existence of P. tremula in forests. Biotope variation should therefore be taken into account when planning forest management and restoration activities.

Keywords:

• Biotope
• germination
• mesic forest
• retention felling
• seedling
• selection felling
• substrate
• woody debris

Acknowledgments

Haapastensyrja of Metla generously provided the aspen seeds. Special thanks to Ruut Rabinowitsch, Matti Turkama, Eva Alamo Carrasco, Majella Clarke, Ilkka Taponen and all occasional help for the fieldwork. We appreciate the valuable statistical advice of Dr Hannu Rita. The study was financed by the FIRE project of the SUNARE programme and the EU project SPREAD.