Hanne K. Sjølie, Hans Asbjørn Kårstad Sørlie, Bjørn Tveite, Birger Solberg. (2015). The performance of two Swedish N fertilization functions evaluated on data from Norwegian fertilization experiments. Silva Fennica vol. 49 no. 4 article id 1330. https://doi.org/10.14214/sf.1330

Keywords: Pinus sylvestris; Picea abies; forest production; forest fertilization; predictive functions

Highlights: The performance of two predictive Swedish fertilization growth response functions was assessed on data from Norwegian fertilization experiments; One function performed well on the full dataset, but overpredicted the growth response in spruce plots and underpredicted in pine plots; The second function performed well in pine stands, but overestimated the growth response in spruce and in total.

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This study compares the responses of two Swedish 5-year predictive stand-level functions with the observed responses in 721 fertilization experiment plots in Norway fertilized with nitrogen (N). All plots are single-species consisting of Norway spruce (Picea abies (L.) H. Karst.) or Scots pine (Pinus sylvestris L.) fertilized with ammonium nitrate (AN) or urea. The correlations between the observed and the two predicted responses were 0.34–0.40 for all plots taken together. One response function performed well on average, but underestimated the response in pine plots and overestimated the response in spruce plots. The second function overpredicted the response on the full dataset, in spruce plots and old forest, but performed well in pine plots. Both functions overestimated the growth response in high-productive plots. Higher N deposition in Norway than in Sweden may count for parts of the deviations. Testing of fertilization functions on new datasets is rare, but important part of the evaluation of functions. As the functions are not well fit for predicting the growth response in spruce and high-productive plots in our sample, new functions that include N deposition are welcome.

Sjølie, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: hanne.sjolie@nmbu.no
Sørlie, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: hans.asbjorn.sorlie@slf.dep.no
Tveite, Norwegian Forest and Landscape Institute, P.O. Box 115, NO-1431 Ås, Norway E-mail: bjorn.tveite@skogoglandskap.no
Solberg, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway E-mail: birger.solberg@nmbu.no

article id 974, category Research note

Kristina Ahnlund Ulvcrona, Lars Karlsson, Ingegerd Backlund, Urban Bergsten. (2013). Comparison of silvicultural regimes of lodgepole pine (Pinus contorta) in Sweden 5 years after precommercial thinning. Silva Fennica vol. 47 no. 3 article id 974. https://doi.org/10.14214/sf.974

Keywords: direct seeding; forest production; corridor thinning; biomass harvest; PCT

Highlights: Management regimes can serve different purposes such as biomass production, pulp and timber production or a combination of those; 30 tons biomass or 38–45 m³ stem volume ha^–1 could be derived by schematic corridor thinning (70%) at year 20; Producing large amounts of biomass early in the rotation period does not exclude a conversion into pulp and timber production.

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Early effects (stem volume, mean diameter at breast height weighted against basal area (Dgv) (Dgv), biomass and damage frequency) of different silvicultural regimes 18-19 years after direct seeding of lodgepole pine in northern Sweden were analysed. A Conventional regime, (i) precommercial thinning (PCT) to 2200 stems ha^-1, was compared to: (ii) High biomass production (15 300 stems ha^-1, no PCT) with and without corridor thinning at year 20, (iii) production of Large dimension trees (PCT to 1700 stems ha^-1), (iv), Combined high biomass production and production of conventional round wood (PCT to 4500 stems ha^-1). PCT was done 15 yrs after direct seeding for all PCT treatments. Local biomass functions showed that the regimes aiming at High biomass production displayed ca 144-157% more biomass and 134-143% more stem volume than the Conventional and Large dimension regimes (ca 21 tons and 31 m³ ha^-1). Dgv for the 1000 (9.2 cm) and 2000 (8.3 cm) largest trees ha^-1 appeared unaffected by regime. By schematic corridor thinning (70% of the total area) at year 20 in the High biomass regime, 27-32 tons of biomass ha^-1 and 38-45 m³ ha^-1 could be derived while still having a Dgv of the 1000 largest trees ha^-1 of about 8 cm. Therefore, this study indicates that it is possible to produce and harvest large amounts of biomass and stem volume early in the rotation period without excluding later pulp and timber production. This initial regime comparison should be continued over time.

Ahnlund Ulvcrona, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: kristina.ulvcrona@slu.se
Karlsson, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: lars.karlsson@slu.se
Backlund, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: ingegerd.backlund@slu.se
Bergsten, SLU, Forest Biomaterials and Technology, Skogsmarksgränd, SE-901 83 Umeå, Sweden E-mail: urban.bergsten@slu.se

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