Beech coppice conversion to high forest: results from a 31-year experiment in Eastern Pre-Alps

Abstract

Selective thinning is a more viable method for beech coppice conversion to high forest when compared with thinning from below as it enhances tree growth, reduces mortality of the remaining trees, and allows to obtain stands with a higher mechanical stability and larger crowns. Beech forests in North-East Italy have been largely managed as coppice. Due to socio-economic changes, a large conversion to high forests program started in the second half of the past century. A long-term experiment testing the effects on tree growth and stability of two different conversion methods (thinning from below—method A; selective thinning—method B) was implemented. Both silvicultural treatments started in 1979 with a first thinning followed by a second one in 1997. All trees were periodically measured in order to assess mortality, stability, and growth during the period 1979–2010. In 2010, an assessment of stem quality and crown size was also performed. Both methods were economically viable, but method B acted with a higher intensity both in 1979 and in 1997, thus making the harvest more profitable for the owners. Moreover, method B enhanced tree growth, especially in the period after the first thinning, reduced mortality, and allowed to obtain stands with a higher mechanical stability and with larger crowns. It would be possible to adopt some of the criteria prescribed with method B in future thinnings over the large areas actually managed with method A, as prescribed by the law.