From useless thickets to valuable resource? – Financial performance of downy birch management on drained peatlands

Abstract

Highlights• The most profitable management regimes for pulpwood and energy wood production in dense downy birch stands on drained peatlands include no thinnings, but final cutting at the stand age of 40-45 years as whole-tree harvesting, or as integrated harvesting of pulpwood and delimbed energy wood stems about 10 years later depending on applicable harvesting method.• A competitive management regime is early precommercial thinning at 4 m dominant height to a density of 2500 stems per hectare and production of pulpwood with a rotation of 55-65 years. Equal profitability is achieved with or without traditional first thinning, which can thus be included for other reasons, for example to improve regeneration of spruce. AbstractDowny birch (Betula pubescens Ehrh.) stands on drained peatlands are often considered useless because they typically do not yield good-quality sawn timber. However, covering an area of ca. 0.5 million hectares and with total yields of up to 250 m 3 ha -1 , downy birch stands on peatlands in Finland have a potential for pulpwood and/or energy wood production. We examined the financial performance of alternative management regimes (with or without thinnings, different thinning intensities, several rotation lengths) combined with alternative harvesting methods (pulpwood, energy wood, or integrated, energy wood being delimbed stems or whole trees). We used data from 19 experimental stands, monitored for 20-30 years. For harvesting removals we considered both actual thinning removals and final-cutting removals with alternative timings that were based on the monitoring data. We assessed the profitability as a combination of the net present value of the birch generation and the bare land value of future generations of Norway spruce (Picea abies (L.) Karst.). The most profitable management was growing without thinnings until wholetree final cutting at the stand age of 40-45 years with an advanced multi-tree harvesting method. In contrast, the standard method in whole-tree final cutting resulted in the lowest profitability, and an integrated method with the energy wood as delimbed stems was the best of the standard methods. Thinnings were unprofitable especially when aiming to produce energy wood, whereas aiming for pulpwood, light precommercial thinning was competitive. Commercial thinning at the traditional "pulpwood stage" had little effect on profitability. The best stand age for final cutting was 40-65 years -earlier for very dense stands and whole-tree energy wood harvesting with advanced method, later for precommercially thinned stands and pulpwood harvesting.

Stump diameter and age affect coppicing of downy birch (Betula pubescens Ehrh.)

“…Energy wood production by growing dense downy birch stands with rotations of 23-26 years, assuming that second birch rotation can be achieved through sprouting, has been calculated to be economically feasible on cutaway peatlands (Jylhä et al 2015). Additionally, for dense downy birch stands on peatlands, the most profitable management option is to grow them for energy without thinnings until whole-tree final cutting at the stand age of 40-45 years (Niemistö et al 2017). If sprouting is successful, a second rotation birch stand could be established without costs, provided the development of the sprouts is favourable.…”