| 1. |
- Bergh, Johan, et al.
(författare)
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Long-term responses of Scots pine and Norway spruce stands in Sweden to repeated fertilization and thinning
- 2014
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 320, s. 118-128
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Tidskriftsartikel (refereegranskat)abstract
- Recent investigations have shown that annual wood production in Sweden can be increased by 30 million m(3) per year in a long-term perspective (>50 years) by using new forest management methods such as new tree species or seedling materials. However, to meet the increased demands during the next 20 years, Sweden will have to rely on silvicultural methods available today. Growth in boreal and cold temperate forest is with only few exceptions limited by nutrients availability, primarily nitrogen, and one way to satisfy the increased demands in a short-term perspective is nitrogen fertilization. A set of thinning and fertilization experiments were started in the 1960's in Scots pine and Norway spruce stands over the whole of Sweden representing different soil, moisture and vegetation types. We used data from these experiments to examine the long-term effects of repeated fertilization in thinned stands on growth, stand development, and yield. The 34 Scots pine sites and 13 Norway spruce sites included in our analyses had at least four treatment plots (no thinning, repeated light thinnings, repeated light thinnings with repeated N fertilization, and repeated light thinnings with repeated N + P fertilization). In northern Sweden, 100 kg N ha(-1) and 150 kg N ha(-1) were applied at each fertilization event for Scots pine and Norway spruce stands, respectively. In southern Sweden, 150 kg ha(-1) N was applied in Scots pine stands and 200 kg ha(-1) N in Norway spruce stands. Phosphorus was applied at the rate of 100 kg ha(-1). Several sites also included non-thinned fertilized plots. Pine stands but not spruce stands were responsive (up to 25% more growth depending of the attribute assessed) to repeated fertilization. Surprisingly, the non-thinned pine stands showed strong continuing response to fertilization throughout the 30+ year observation period resulting in higher cumulative volume response than the thinned stands. In thinned stands incremental volume response to fertilization continued but slowly diminished with time indicating that fertilization and thinning effects were less than additive. However, thinning and fertilization effects were additive for diameter growth. Fertilization accelerated stand development with significant shifts in diameter distributions to larger and potentially more valuable trees. Conclusively, repeated nitrogen fertilization is a silvicultural practice that will result in significant and sustained increases in Scots pine production. (C) 2014 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Drössler, Lars, et al.
(författare)
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Stand structure and future development of a managed multi-layered forest in southern Sweden : Eriksköp - a case study
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A heterogeneously structured forest stand with pine overstory and naturally regenerated spruce and oak trees in different size classes was documented. The effect of target diameter cutting on stand structure and growth was analyzed as a case-study. Both, systematic sample plots and forest gaps were used to describe the stand structure after cutting. Target diameter cutting in different treatments reduced the standing volume from ca. 320 to 180 m³/ha. Forest canopy gaps were created on more than 15% of the stand area. The seedling number of advanced natural regeneration was low (less than 500-1000 individuals per ha). Based on the advanced regeneration in gaps, three different scenarios for future ingrowth into the tree layer were defined. The extreme minimum ingrowth scenario assumed about 10 cm annual height growth and rather high mortality reported in literature from other experiments (resulting in one tree annually reaching 5 cm DBH during the next 50 years). Two other scenarios assumed 20 and 30 cm annual height growth. While no mortality was presumed within the latter scenario, moderate mortality rates (reported in literature) were chosen for the intermediate scenario. The maximum scenario postulates ten trees per year and ha reaching 5 cm DBH (equal to ingrowth reported from boreal single-tree selection forests). The moderate scenario assumes four new trees per year and he. Additional scenarios after soil preparation in gaps were used, defined on the base of shelterwood experiments. To describe the future basal area growth and continued target diameter cutting in the next 50 years, a single-tree growth model was applied, using stand age-independent estimations of the age of single trees. Thereby, a mean annual increment of 0.53-0.64 m2/ha was projected, similar to 5.6-6.8 m³/ha volume. Some errors to estimate the standing volume in multi-layered stands were detected during the simulation process. Compared to an evenaged spruce stand planted on the same site, the expected growth of the study stand during the next 50 years was one third lower. In average, about 120 m3/ha standing volume was removed in 20-25 years-cutting cycles. To continue without longer harvest intervals after the 50 years-simulation period, soil preparation seems necessary to achieve a sustainable number of small trees. Beside timber production, profitability was also lower by selective cutting. But, the important advantage of target diameter cutting can be more equally distributed income over time, with investments costs that can be covered by profit from timber harvest at the same time. A regular income of 17000-28000 SEK per ha every 20-25 years seems possible from today´s perspective. An additional treatment with alternative target diameters to promote particular tree species did not affect the amount of removals and the length of cutting intervals substantially. But simulations with 5 cm reduced target diameters caused very heavy removals and 35-40 years to reach 300 m³/ha standing volume again. The study includes discussions of tree species composition and development as well as a sensitivity analysis of the applied growth model.
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| 4. |
- Fahlvik, Nils, et al.
(författare)
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Development of single-storied mixtures of Norway spruce and birch in Southern Sweden
- 2011
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 26, s. 36-45
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Tidskriftsartikel (refereegranskat)abstract
- In a stand with planted Norway spruce (Picea abies (L.) Karst.) and naturally regenerated birch (Betula pendula Roth and B. pubescens Ehrh.) in southern Sweden, the proportion of birch was reduced in 0.1-ha plots at pre-commercial thinning to 0%, 20% or 50% of the total stem number (2000-2500 stems ha(-1) after the thinning). The growth of both species was surveyed 4 and 10 years later. No significant between-treatment differences were observed on either occasion in total yield or in spruce diameter (apart from a more negative skewness of the diameter distribution of Norway spruce in the mixture with 50% birch compared to pure spruce). Birch retained its initial advantage in dominant height (of about 2 m) throughout the 10-year measurement period; hence, height growth rates of Norway spruce and birch were very similar. After three, four and 10 growing seasons, whipping damage to Norway spruce caused by birch was registered in the 20% and 50% birch mixtures, in which the proportions of damaged spruces were found to be similar, with 17% and 15% of damaged trees at the last inventory, respectively. In addition, simulations of the stands' development from the time of the last measurement until final felling at a total age of 66 years indicated that growth, yield and net present value decrease with increasing birch proportion, but if the proportion of birch removed in subsequent thinnings is increased, the between-treatment differences are reduced.
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| 5. |
- Fahlvik, Nils, et al.
(författare)
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Early thinning of energy wood in dense mixtures of Norway spruce and birch in Northern Sweden
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Naturally regenerated silver birch (Betula pendula) and downy birch (Betula pubescens) commonly appears in mixtures with conifers and constitutes a considerable part of the growing stock of young forests in Sweden. The proportion of birch is traditionally heavily reduced during pre-commercial thinning to promote the development of conifers. In dense mixtures where no pre-commercial thinning has been carried out and where the average tree dimension is small, thinning of energy wood might be an alternative to conventional pulp wood thinning. Moreover, the goals for future management might need to be revised due to a pronounced interspecific competition. An experiment was established in Northern Sweden to study the potential of energy wood thinning in unthinned mixtures of naturally regenerated Norway spruce (Picea abies) and birch. The stem number before thinning was 13800 and 3200 stems ha-1 and the dominant height was 15 and 7.5 m for birch and spruce, respectively. The treatments included an unthinned control and three thinning strategies resulting in pure plots of spruce and birch and a mixture of spruce and birch, respectively. Within the thinned plots the stem number for each species was kept constant where they appeared. The same number of spruce and birch trees was also marked and followed within the unthinned plots in order to study the influence of thinning on the development of main stems. Whole trees were harvested and a strip road was established in the centre of each plot. The presentation focuses on the early development and survival following the alternative courses of action and on the comparison of extractable volumes between energy wood thinning and conventional thinning of pulp wood. Influence of strip roads on the development of the adjacent trees in young stands will also be discussed.
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| 6. |
- Fahlvik, Nils, et al.
(författare)
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Evaluation of growth models used in the Swedish Forest Planning System Heureka
- 2014
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 48
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Tidskriftsartikel (refereegranskat)abstract
- The performance of growth models implemented in the Swedish Forest Planning System Heureka was evaluated. Four basal area growth models were evaluated by comparing their predictions to data from five-year growth records for 1711 permanent sample plots of the National Forest Inventory (NFI-data). Also, two alternative implementations of Heureka, including a combined stand- and tree-level basal area growth model and a single tree-level model, respectively, were evaluated using data from 57 blocks in a thinning experiment (GG-data) involving Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) in which the trees were monitored for 30 years after the first thinning. The predicted volume growth was also compared to observed values. Growth models based on data from 1970's and 1980's overestimated growth in the NFI test plots from the early 2000's by about 3%. Stand-level models had larger precision than tree-level models. Basal area growth was underestimated in dense NFI-plots and overestimated in non-thinned GG-plots, illustrating an un-solved modelling problem. Basal area growth was overestimated by 2-5% also in the GG-plots over the whole observation period. Volume growth was however accurately predicted for pine and underestimated by 2% for spruce. The relative prediction error did not increase with increasing length of prediction period. Thinning response models calibrated with GG-data worked well in the total application and produced growth levels for different thinning alternatives in line with observations.
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| 7. |
- Nilsson, Urban, et al.
(författare)
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Simulation of the Effect of Intensive Forest Management on Forest Production in Sweden
- 2011
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 2, s. 373-393
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Tidskriftsartikel (refereegranskat)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
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| 8. |
- Nilsson, Urban, et al.
(författare)
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Thinning of Scots pine and Norway spruce monocultures in Sweden: effects of different thinning programmes on standlevel gross- and net stem volume production
- 2010
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Ingår i: Studia Forestalia Suecica. - 0039-3150. ; 219, s. 1-46
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The effect of thinning intensity, thinning interval, thinning form and timing of the first thinning on stand level gross- andnet stem volume production in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst) was investigatedin a nationwide field experiment across Sweden. In total, 35 Scots pine sites distributed from the south to the north ofSweden and 13 Norway spruce sites located in the south and central parts of Sweden were investigated. Thinning treatments ranged from unthinned control, to light and moderate repeated thinnings, to a treatmentwhere 60-70% of the basal area was removed in a single thinning. In addition, thinning from above was compared tothinning from below and delayed first thinning was compared to early first thinning. The average measurement period was31 years for Scots pine and 30 years for Norway spruce. All Scots pine thinning treatments reduced the total gross stemvolume production compared to the unthinned control, whereas only the heaviest thinning treatments, in which a largeproportion of the basal area was removed, reduced the total gross stem volume production for Norway spruce. Thinningfrom above did not affect total gross stem volume production of Scots pine, but there was a tendency towards lowerproduction in Norway spruce. For Norway spruce, thinning from above resulted in lower net stem volume production thanthinning from below. Delaying the first thinning did not affect gross stem volume production for either Scots pine orNorway spruce. Net volume production and volume production in trees with diameter at breast height > 8 cm was higher forthe light thinning treatment than for the unthinned control in Norway spruce. In Scots pine, there was no differencebetween the light thinning treatment and unthinned control in net volume production. For cots pine, the heavy thinningtreatments decreased net volume production compared to the unthinned threatment whereas there were no differences innet volume production between the heavy thinning treatments and unthinned control in Norway spruce
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