| 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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Natural Regeneration in a Multi-Layered Pinus sylvestris-Picea abies Forest after Target Diameter Harvest and Soil Scarification
- 2017
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Forest management in Sweden can be characterized by even-aged silviculture heavily relying on three established harvest regimes: clearcutting, the seed-tree method, and the shelterwood system. Less intense, small-scale retention harvest systems such as single tree and group selection harvest are rarely used. In addition, natural regeneration dynamics without enrichment planting have barely been studied. Consequently, this study examined natural regeneration establishment in a multi-layered Pinus sylvestris-Picea abies forest stand in southwest Sweden after target diameter harvesting and soil scarification. The creation of forest canopy gaps had a positive effect on total seedling density five years after harvest, mainly due to a significantly higher number of Betula pendula individuals. Seedling density of more desirable tree species suitable for continuous cover forestry such as Fagus sylvatica, Quercus petraea and Picea abies also increased substantially in gaps when compared to pre-harvest conditions or the unharvested plots. In contrast, soil scarification did not increase the number of seedlings of desired tree species due to a significant decrease in Picea abies abundance. Soil moisture and gap size significantly improved Betula pendula seedling establishment while a larger number of Quercus petraea seedlings were observed in Vaccinium myrtillus patches. We conclude that canopy gaps are beneficial under the encountered stand conditions to initiate forest regeneration, and that soil scarification without the timely occurrence of a mast year of desired tree species is not effective in the type of forest studied.
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| 4. |
- 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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| 5. |
- Egbäck, Samuel, et al.
(författare)
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Modeling early height growth in trials of genetically improved Norway spruce and Scots pine in Southern Sweden
- 2017
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Genetically improved Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) are used extensively in operational Swedish forestry plantations to increase production. Depending on the genetic status of the plant material, the current estimated genetic gain in growth is in the range 10-20% for these species and this is expected to increase further in the near future. However, growth models derived solely from data relating to genetically improved material in Sweden are still lacking. In this study we investigated whether an individual tree growth model based on data from unimproved material could be used to predict the height increment in young trials of genetically improved Norway spruce and Scots pine. Data from 11 genetic experiments with large genetic variation, ranging from offspring of plus-trees selected in the late 1940s to highly improved clonal materials selected from well performing provenances were used. The data set included initial heights at the age of 7-15 years and 5-year increments for almost 2000 genetic entries and more than 20 000 trees. The evaluation indicated that the model based on unimproved trees predicted height development relatively well for genetically improved Norway spruce and there was no need to incorporate a genetic component. However, for Scots pine, the model needed to be modified. A genetic component was developed based on the genetic difference recorded within each trial, using mixed linear models and methods from quantitative genetics. By incorporating the genetic component, the prediction errors were significantly reduced for Scots pine. This study provides the first step to incorporate genetic gains into Swedish growth models and forest management planning systems.
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| 6. |
- Fahlvik, Anton, et al.
(författare)
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Hydrothermal alteration, lithogeochemical marker units and vectors towards mineralisation at the Svärdsjö Zn-Pb-Cu deposit, Bergslagen, Sweden
- 2022
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 144:3-4, s. 177-195
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Tidskriftsartikel (refereegranskat)abstract
- The Svärdsjö Zn-Pb-Cu deposit is situated in the heavily mineralised Bergslagen lithotectonic unit of the Fennoscandian shield, south-central Sweden. Intense hydrothermal alteration followed by a strong overprint by deformation and metamorphism during the Svecokarelian orogeny complicate interpretation of the local geology. Integration of whole-rock lithogeochemical and petrographic methods has allowed the mainly dacitic volcanic host succession and effects of ore-related hydrothermal alteration to be characterised. Mineralisation is hosted by 2–15 m thick, commonly skarn-altered dolomitic marble interbeds. Zones of strong–intense hydrothermal chlorite-sericite alteration envelop the marble units, recording mass gains of Fe and Mg, as well as Na depletion. Minerals such as cordierite, anthophyllite and sillimanite formed in these rocks during regional metamorphism. Mineralisation via sub-seafloor replacement is suggested for the deposit based on alteration zoning and the irregular, stratabound, marble-hosted style of sulphide lenses. It is inferred that mineralisation formed via neutralisation of hot, acidic metalliferous fluids. Geochemically and lithologically distinct units adjacent to the mineralised zones can serve as marker units to aid further exploration in the area. Mass change calculations reveal that Fe and Mg enrichment, as well as Na depletion exhibit detectable changes extending up to 100 m from the mineralised lenses, providing exploration vectors.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Fahlvik, Nils, et al.
(författare)
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Effects of precommercial thinning strategies on stand structure and growth in a mixed even-aged stand of Scots pine, Norway spruce and birch in southern Sweden
- 2015
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- Four different management strategies were applied to a young mixed stand of Scots pine (Pinus sylvestris L.), Norway spruce (Pices abies (L.) Karst.) and birch (Betula pendula Roth and Betula pubescens Ehrh.) in southern Sweden. All strategies included an initial precommercial thinning to ca. 2400 stems ha(-1). The different aims were: (i) a conifer-dominated stand with focus on high productivity; (ii) a conifer-dominated stand with high quality timber; (iii) keeping a stem-wise species mixture; (iv) a mosaic-wise species mixture. Stem selection according to the different strategies were simulated with a starting point from plots with a 5 m radius. All strategies were applied to all of the plots. A growth simulator was used to simulate the stand development up to final felling. This study illustrates the possibilities for influencing the structure of a mixed stand through precommercial thinning. The study also illustrates the long-term effects on stand structure and volume yield by consequently applying a management strategy from precommercial thinning until final felling. Precommercial thinning was found to be a useful tool to influence the stand structure in accordance to the aims set. However, the opportunities for influencing the stand by precommercial thinning were restricted by natural settings and unconditional considerations (e.g. tree vitality, stem quality, regular spacing), beyond what could be judged from stand average data. The stem volume production during a rotation was 6% lower for (iii) and (iv) compared to (i) and (ii), mainly due to a greater proportion of birch in the former strategies.
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| 10. |
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