Abstract
The effects of intensifying the management of 15% of the Swedish forest land on potential future forest production over a 100-year period were investigated in a simulation study. The intensive management treatments, which were introduced over a period of 50 years, were: intensive fertilization of Norway spruce (IntFert); bulking-up Norway spruce elite populations using somatic embryogenesis (SE-seedlings); planting of lodgepole pine, hybrid larch, and Sitka spruce (Contorta, Larch, and Sitka); fertilization with wood ash on peatlands (Wood ash); and conventional fertilization in mature forests (ConFert). Potential sites for applying intensive forest management (IFM) to sites with low nature conservation values were determined with a nature conservation score (NCS). Four different scenarios were simulated: “Base scenario”, which aimed at reducing the negative impact on nature conservation values, “Fast implementation”, “No IntFert” (IntFert was not used), and “Large Forest Companies”, where the majority of plots were selected on company land. Total yields during the 100-year simulation period were about 85–92% higher for the intensive forest management scenarios than for the reference scenario (business as usual). In the “No IntFert” scenario total production was 1.8% lower and in the “Large Forest Companies” scenario total production was 4.8% lower than in the “Base scenario”. “Fast implementation” of IFM increased yield by 15% compared to the “Base scenario”. Norway spruce SE-seedlings and IntFert gave the highest yields, measured as total production during the 100-year simulation period, but relative to the yields in the reference scenario, the highest increases in yield were for Contorta. The “Base scenario” and “No IntFert” gave the highest yields for plots with the lowest NCS, but plots with higher NCS had to be used in the “Fast implementation” and “Large Forest Companies” scenarios. More than half of the effect on future growth of IFM methods was because of increased intensity in the regenerations. It took a relatively long time (40–60 years) for the simulated IFM treatments to result in a significant increase in stem volume production.
Highlights
Numerous experiments and observations spanning centuries have shown that both silvicultural methods and the choice of tree species can significantly affect forest yield and profitability [1]
Our results indicate that assigning this proportion of the regeneration area each year for intensive forest management (IFM) may be done without resulting in a significant loss of nature conservation values since plots with nature conservation scores >300 were not used in the ―Base scenario‖
Among the studied IFM treatments intensive fertilization of Norway spruce (IntFert), planting of lodgepole pine, and planting of Norway spruce SE-seedlings appear to have the largest potential to increase future growth and harvest potential, mainly because they could be applied to large areas
Summary
Numerous experiments and observations spanning centuries have shown that both silvicultural methods and the choice of tree species can significantly affect forest yield and profitability [1]. Examples include experiments with new tree species during the 18th century [2], seed transfer trials to identify better adapted and faster growing alternatives to local provenances, and observations of the effects of various forest management practices, such as drainage and fertilization with wood ash [2]. Classical Swedish forest management methods intended to increase forest yield include: (i) the introduction of exotic, fast-growing tree species; (ii) forest fertilization; (iii) drainage of peatlands; and (iv) tree breeding. But the most widely introduced species was lodgepole pine Forest companies in central and northern Sweden started to plant lodgepole pine on a large scale in the mid-1960s.
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