Current issue: 56(4)

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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles by Lars Högbom

Category: Research article

article id 1265, category Research article
Eva Ring, Lars Högbom, Hans-Örjan Nohrstedt, Staffan Jacobson. (2015). Soil and soil-water chemistry below different amounts of logging residues at two harvested forest sites in Sweden. Silva Fennica vol. 49 no. 4 article id 1265.
Keywords: clearcutting; final felling; bio fuel; conifer; fuel-adapted felling; nutrient; soil solution
Highlights: Soil-water chemistry, ground vegetation cover and water flux were affected by the amounts of logging residues stored on the ground after harvest; A strong response on soil-water chemistry was recorded at only one of the two sites; At the site showing a weak response, less residue remained after seven years in the treatments giving the most pronounced effects.
Abstract | Full text in HTML | Full text in PDF | Author Info
Logging residues (LR), i.e. tops, branches, and needles, are increasingly being harvested for energy production in Fennoscandia. These residues are temporarily piled on site awaiting transport. This study was undertaken to investigate effects on the soil and soil-water chemistry below different amounts of LR at two recently harvested coniferous sites in Sweden. Seven treatments were included and the studied amounts of LR ranged from no LR left on the ground to four times the estimated LR amount of the harvested stands. Two treatments included eight times the estimated LR amount of the harvested stands but here the LR were removed after 7 or 20 weeks. Soil-water samples were collected during the first six or seven growing seasons. Effects of treatment were detected in the soil water for 11 chemical variables at the northern site, and for the NO3- and Cl- concentrations at the southern site. The strongest response was generally found in the treatment with four times the estimated LR amount, for which the highest concentrations were recorded in most cases. In the first three seasons, the water flux through the LR decreased with an increasing amount of residue. Effects on the exchangeable store of Ca2+ in the mor layer and the upper 20 cm of the mineral soil was detected at both sites. At the northern site, the weight of the remaining LR, ground vegetation and all other material above the mor layer in the treatments with two and four times the estimated LR amount was roughly twice the corresponding weights at the southern site seven years after treatment. Although strong effects on the soil-solution chemistry were detected at one of the study sites, in the treatments corresponding to two and four times the estimated logging residue amount, the effect on the leaching from an entire regeneration area is likely to be relatively small given the percentage of the area hosting these logging residue amounts (ca. 20% after stem-only harvesting and 9% after fuel-adapted felling).
  • Ring, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail: (email)
  • Högbom, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail:
  • Nohrstedt, Swedish University of Agricultural Sciences, Department of Soil and Environment, P.O. Box 7014, SE-750 07 Uppsala, Sweden E-mail:
  • Jacobson, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail:
article id 1016, category Research article
Karin Johansson, Eva Ring, Lars Högbom. (2013). Effects of pre-harvest fertilization and subsequent soil scarification on the growth of planted Pinus sylvestris seedlings and ground vegetation after clear-felling. Silva Fennica vol. 47 no. 4 article id 1016.
Keywords: nitrogen; establishment; regeneration; Scots pine; disc trenching; carryover; competing vegetation
Highlights: Pre-harvest N fertilization had no significant effect on seedling growth and ground vegetation biomass; Scarification improved seedling survival and growth and reduced the amount of ground vegetation; Without scarification, pre-harvest fertilization increased the amount of damaged seedlings.
Abstract | Full text in HTML | Full text in PDF | Author Info
Fertilization and scarification are both performed to increase tree production at different stages of forest rotation periods. In this study, the effects of previous nitrogen fertilizations and scarification after clear felling on planted Pinus sylvestris L. seedlings and ground vegetation were investigated. Two fertilization experiments established around 1980 were harvested in 2006, after which the plots were scarified by disc trenching and re-planted. The plots had been repeatedly fertilized over a 20-year period before harvesting, with total N doses of 0, 450, 900 or 1800 kg N ha-1. After five growing seasons, the growth, survival and nutrient contents of the seedlings were measured, and ground vegetation was collected to estimate its biomass and nutrient content. Pre-harvest fertilization alone had only minor effects on the results, but scarification increased both the survival and growth of the planted seedlings. However, without scarification, seedling mortality increased with increasing fertilization intensity. The ground vegetation biomass was higher in plots without scarification, but the total biomass of seedlings and ground vegetation was similar in all treatments. Scarification thus favored seedling growth at the expense of ground vegetation. Only a few effects on nutrient content were found, but there were no signs of nutrient imbalance in any of the treatments. At higher levels of fertilization, the K:N ratio in the seedlings decreased while the K content in the ground vegetation increased. Overall, scarification had a greater impact than pre-harvest fertilization on the planted seedlings and the ground vegetation.
  • Johansson, Skogforsk, The Forestry Research Institute of Sweden, Ekebo 2250, SE-268 90 Svalöv, Sweden & Southern Swedish Forest Research Centre, SLU, Box 49, SE-230 53 Alnarp, Sweden E-mail: (email)
  • Ring,  Skogforsk, The Forestry Research Institute of Sweden, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail:
  • Högbom,  Skogforsk, The Forestry Research Institute of Sweden, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail:

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