To produce timber from birch and harvest birch for energy biomass in the first thinning of birch-spruce mixed stands can generate positive net revenues, especially on medium-fertile sites. The results are shown in a new study by PhD student Swastika Chakravorty and her research colleagues.
”The key message for forest owners is that birch can be economically viable with active management and the right market conditions”, says Swastika Chakravorty, PhD student at Luleå University of Technology and within Trees For Me.
The results were retrieved from 45 experimental forest plots from Svalöv in Skåne to Vindeln in Västerbotten, including planted but not genetically improved birch. Results from mixed forest stands with a checker-board pattern of spruce and birch patches were compared to larger Norway spruce and silver birch monocultures.
Birch timber justify management costs
The study highlights the importance of developing birch timber markets to increase the economic viability of birch management. Mixed birch-spruce forestry can be economically competitive but only if markets, logistics, and management practices evolve together.
”The inclusion of birch timber in final harvest assortments consistently improved land expectation value relative to pulpwood-only management”, says Swastika Chakravorty.
The management simulations, which were done in the forest management simulation tool Heureka, assume that the planted seedlings were of good initial quality (e.g., without double stems or major defects) and that active, selective thinning was applied throughout the rotation. This implies that the most suitable and well-formed trees would be retained and promoted for timber production over time. Costs for e.g. soil scarification, planting and thinning were included in the simulations.
Consistent management increase land value
”One of the more surprising findings was that even when birch pulpwood from the first thinning was used for lower-value energy biomass, and even with more frequent thinning, it was still possible to maintain a positive land expectation value”, Swastika Chakravorty explains.
The study also examined the timing of thinning based on stand basal area versus species-specific criteria.
”The results once again demonstrate site-specific potential. In cases where basal-area-based thinning would delay birch interventions, species-specific thinning improved economic outcomes”, Swastika Chakravorty comments.
Potential for forestry actors
The results could impact the forestry sector in several ways.
”Bioenergy actors can potentially rely more on early thinnings from mixed stands. Wood-processing industries have a clear role to play in strengthening birch timber markets. And harvesting contractors may find opportunities in developing more efficient systems for patch-based mixed management”, Swastika Chakravorty concludes.