Production of hybrid aspen on agricultural land during one rotation in southern Sweden
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ORIGINAL PAPER
Production of hybrid aspen on agricultural land during one rotation in southern Sweden Nils Fahlvik1 · Lars Rytter1 · Lars‑Göran Stener1
Received: 10 July 2019 / Accepted: 16 October 2019 © Northeast Forestry University 2019
Abstract High potential productivity together with short rotation periods have made hybrid aspen an interesting option for wood production on former arable land in Nordic countries. In this study, some of the oldest active experimental plots with hybrid aspen in Sweden were remeasured at 23–30 years of age. A main aim was to assess age and productivity at the time of maximum mean annual volume increment. In addition, the influence of commercial thinning on stand development and differences in genetic gain among clones were investigated. Data from five experiments in southern Sweden were used, including three genetic trials, one demonstration stand with a clone mixture and one stand regenerated from root suckers. The three genetic trials were treated as single plot experiments, subject to a standard thinning program. In the remaining experiments, different thinning strategies were tested in a balanced block design. Volume growth had culminated or was close to maximum at age 25–30 years. Mean annual stem volume increment at culmination was 20–22 m3 ha−1 a−1. Dominant height reached 30–35 m at 28–30 years of age. Mean diameter at breast height was 27–29 cm after 29–30 years in the genetic trials. Clonal ranking based on diameter at age 7–9 years was positively correlated with the ranking at the final measurement
Project funding: The study was funded by the Skogssällskapet Foundation (Grant number: 2018-466-Steg 2 2017). The online version is available at http://www.springerlink.com Corresponding editor: Zhu Hong. * Nils Fahlvik [email protected] 1
The Forestry Research Institute of Sweden (Skogforsk), Ekebo 2250, 268 90 Svalöv, Sweden
in the genetic trials, 20 years later. This indicates that clones can be selected for superior growth based on results from young trials. More intense thinning programs increased the mean diameter compared to light thinning. The study indicates that one or two early and relatively heavy thinnings can promote the development of crop trees, without jeopardizing total volume production during a rotation of 25–30 years. Keywords Populus tremula × Populus tremuloides · Rotation length · Thinning · Biomass
Introduction Biomass is an important renewable resource as a substitute for less climate-friendly products, and forest species have the potential to sequester large amounts of carbon in northern latitudes. An increased use of woody biomass is probably a prerequisite to meeting future climate goals in the Nordic countries (IEA 2013; Nordic Energy Research 2016). Woody biomass can, for example, be used as biofuels and substitute for other materials in house building. To increase available amounts of biomass, sustainable forest productivity must also increase. One way of doing this is to introduce fast-growing tree species, and species
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