Silva Fennica : quarterly issues : 40(1) : sa401083.htm

Jaakko Repola, Hannu Hökkä & Timo Penttilä. 2006.

Thinning intensity and growth of mixed spruce-birch stands on drained peatlands in Finland

Silva Fennica 40(1): 83–99

The impacts of thinning at various intensities on the growth and mortality of mixed spruce-birch stands were investigated in thinning experiments on spruce swamps in northern and south-eastern Finland. At the time of establishment, three of the stands had recently reached the first commercial thinning stage and four were more advanced. The monitoring period was mainly 15 years, and the thinning intensity varied from heavy thinning (ca. 46 per cent of the basal area removed) to no thinning. Basal area removals of light and moderate thinning were ca. 22% and 39%, respectively.

Unthinned plots had the highest volume increment. Light and moderate thinning slightly decreased the 15-year volume increment by, on an average, 1% and 8%, respectively. Heavy thinning led to a greater reduction (22%) in volume increment.

The growth response to thinning intensity was evident as a higher relative volume and mean diameter increment of the living trees with decreasing stand density. Part of the volume increment on the unthinned plots was lost through natural mortality. Even light thinning significantly decreased natural mortality.

Keywords
thinning, Picea abies, Betula pubescens, spruce swamps, growth, forest drainage

Addresses
Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland. E-mail jaakko.repola@metla.fi

Received 22 June 2005 Accepted 30 December 2005
ISSN 0037-5330

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