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- Appiah Mensah, Alex, et al.
(författare)
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Taller and slenderer trees in Swedish forests according to data from the National Forest Inventory
- 2023
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 527
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Tidskriftsartikel (refereegranskat)abstract
- Changes over time in annual basal area growth and mean height for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) over the period, 1983-2020 were studied using sample tree data from temporary plots recorded in the Swedish National Forest Inventory. The annual basal area growth was derived from the last measured full ring on increment cores. Using 20 to 60-year-old dominant trees, the mean height and annual basal area growth were examined as functions of tree, stand and site conditions, and trends were assessed mainly using residual analyses over time. A significant increase in mean height at a given age was found for both species, but the annual basal area growth level remained stable over the 38-year period. Currently, at a given age of 50 annual rings at breast height, the mean heights of pines and spruces increased on average by 10.1% (i.e. similar to 2 m), compared to 50 year-old pines and spruces in the 1980s, and the increase was similar in the different regions. The results suggest that trees have become taller and slenderer in Swedish forests. Increasing tree height over time at a given age in Northern Europe has been documented in several reports and many causes have been suggested, such as changed forest management, increasing temperatures and nitrogen deposition. We suggest that elevated CO2 in the air and improved water-use efficiency for the trees might also be strong drivers.
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| 2. |
- Ara, Mostarin, et al.
(författare)
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Varying rectangular spacing yields no difference in forest growth and external wood quality in coniferous forest plantations
- 2021
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 489
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Tidskriftsartikel (refereegranskat)abstract
- Historically square or almost square spacing design has been used in plantation forest, as it has been claimed to maximize productivity. In this study, based on field experiments established in the mid-1980s, we tested the effect of square or different rectangular planting designs (2 x 2, 1.33 x 3, 1 x 4, 0.8 x 5, 1.46 x 1.46 x 4 m) on productivity, stand heterogeneity, and external wood properties of three coniferous species: Scots pine, Lodgepole pine, and Norway spruce. Stand production (volume, diameter), external wood properties (ovality, branch thickness, living crown height, height-diameter ratio), and stand heterogeneity (Gini coefficient) were not significantly affected by the different rectangular designs. Based on this evidence, we propose that more flexibility is available than previously thought for rectangular spacing layouts and consequently for the choice of planting spots and machinery operations.
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| 5. |
- Bäckström, Per-ove, et al.
(författare)
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Rehabilitering av degenererad skog i kärvt klimat : utvärdering av ett 31-årigt experiment på Ätnarova försökspark
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Olika skötselalternativ för en degenererad skog i kärvt klimat (67°N, 460 m.ö.h.) prövades i ett försök som anlades 1983/84 med 32 parceller à 0,1 ha. Det återinventerades hösten 2015. Ursprungsbeståndet var ca 100 år och höll stamvolymen 50 m³sk per hektar med 40 % gran och 60 % glasbjörk. Det växte med ca 1 m³sk per hektar och år under observationsperioden. Kalhuggning utan föryngringsåtgärder gav rikligt björkuppslag och få granplantor och bedöms på sikt återskapa ursprungsbeståndet. Fröträdsställning av gran gav fler granplantor än “ingen åtgärd” men plantorna växte dåligt. Markberedning under fröträden hade ingen signifikant effekt. Plantering under björkskärm ledde för tall och contorta till mycket höga avgångar och för gran till starkt hämmad plantutveckling. Contortaplantering på kalmark gav snabbväxande träd men höga avgångar och kraftiga snöskador. Tallplantering på kalmark klarade sig bättre och bedöms på sikt utvecklas till växtliga bestånd. Granplantering på kalmark uppvisade god utveckling, särskilt efter kemisk avdödning av björkstubbarna. Höjdbonitering av planteringarna på kalmark indikerade ståndortsindex på 20–23 m vilket in-nebär boniteter på över 4 m³sk. Rehabiliteringen av det degenererade ursprungsbeståndet ge-nom kalhuggning och plantering ser alltså ut att ha lyckats. Med stöd av observationer också i omgivande försök och bestånd bedöms tallplantering vara det lönsammaste alternativet.
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| 6. |
- Dahlberg, Jenny, et al.
(författare)
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Ten years transmission of the new variant of Chlamydia trachomatis in Sweden : prevalence of infections and associated complications
- 2018
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Ingår i: Sexually Transmitted Infections. - : BMJ Publishing Group Ltd. - 1368-4973 .- 1472-3263. ; 94:2, s. 100-104
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: In 2006, a new variant of Chlamydia trachomatis (nvCT) was discovered in Sweden. It has a deletion in the plasmid resulting in failed detection by the single target systems from Abbott and Roche used at that time, whereas the third system used, from Becton Dickinson (BD), detects nvCT. The proportion of nvCT was initially up to 65% in counties using Abbott/Roche systems. This study analysed the proportion of nvCT from 2007 to 2015 in four selected counties and its impact on chlamydia-associated complications.METHODS: C. trachomatis-positive specimens collected from 2007 to 2015 were analysed by a specific PCR to identify nvCT cases. Genotyping was performed by multilocus sequence typing (MLST) and ompA sequencing. Ectopic pregnancy and pelvic inflammatory disease records were extracted from the national registers.RESULTS: In total, 5101 C. trachomatis-positive samples were analysed. The nvCT proportion significantly decreased in the two counties using Roche systems, from 56% in 2007 to 6.5% in 2015 (p<0.001). In the two counties using BD systems, a decrease was also seen, from 19% in 2007 to 5.2% in 2015 (p<0.001). Fifteen nvCT cases from 2015 and 102 cases from 2006 to 2009 had identical MLST profiles. Counties using Roche/Abbott systems showed higher mean rates of ectopic pregnancy and pelvic inflammatory disease compared with counties using BD systems.CONCLUSIONS: The nvCT proportion has decreased in all counties and converged to a low prevalence irrespective of previous rates. Genotyping showed that nvCT is clonal and genetically stable. Failing detection only marginally affected complication rates.
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| 8. |
- Elfving, Björn, et al.
(författare)
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Biomass equations for lodgepole pine in northern Sweden
- 2017
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Ingår i: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 47, s. 89–96-
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Tidskriftsartikel (refereegranskat)abstract
- Biomass equations for cultivated lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were developed based on data from destructive biomass sampling of 164 trees collected from 13 sites at latitudes 61.9 degrees N-66.2 degrees N in northern Sweden. Stand age varied between 20 and 87 years and top height varied between 8 and 32 m. Seeded and planted stands with different densities were included. Allometric biomass equations for all above-stump components were constructed, expressing dry mass of stem, bark, living and dead branch wood, foliage, and cones, as well as total mass. Equations with one to three independent variables were constructed for each component, accounting for variances within and between sites. Estimated values for trees of different sizes were compared with corresponding estimates for lodgepole pine in Canada and Scots pine (Pinus sylvestris L.) in Sweden and Finland. Residual variation of our equations was lower than that of equations from other sources. Our equations predicted average biomass levels similar to the predictions from Canadian equations for natural stands. In comparison with Scots pine, at given stem dimensions, lodgepole pine had 50%-100% more foliage biomass and greater dead branch biomass with increasing tree size. The wide amplitude of our data and the flexible form of our equations should make them useful for wider application.
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| 10. |
- Elfving, Björn
(författare)
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En plantering med poppel, björk och gran på nedlagd jordbruksmark vid Umeå
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Med syfte att vinna insikt om olika trädslags etablerings- och produktionsförmåga på nedlagd jordbruksmark planterades jättepoppel (Populus trichocarpa), vårtbjörk (Betula pendula) och gran (Picea abies) på några inägor öster om Umeå 1986 och 1989. Våren 1986 planterades en parcell med två poppelkloner i systematisk blandning och en parcell med förädlad finsk och svensk vårtbjörk i systematisk blandning. Våren 1989 planterades två parceller vardera med björk och gran och en med poppel. Planteringsförbandet var genomgående 2x3 m. På 20 år producerade björken ca 100, granen ca 150 och poppeln ca 225 m3sk per ha. Björken har drabbats av allehanda skador och utbildat få vackra stammar. Svenska björken har vuxit något bättre än den finska men skillnaden är inte signifikant. Granen har vuxit bra och övre höjden vid 23 års ålder indikerar G34. Poppelklonernas utveckling skiljer sig signifikant. Den som var grövst vid den första gallringen hade samtidigt klenast grenar. Därefter växte den klart sämre. Flertalet popplar drabbades av kambiedöd mot sydväst på stammens nederdel våren 2003. Klonerna drabbades ungefär lika. Skadorna har delvis övervallat och tycks inte ha haft någon större inverkan på tillväxten. Etablering av poppel med rotade sticklingar (plantor) i stället för direkt utsättning av sticklingspinnar medförde högre överlevnad och en tidsvinst i höjd på ca 0,5 år. En sammanfattning ges av de erfarenheter av åkerplantering som vunnits i försöket.
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