liu.seSearch for publications in DiVA
Endre søk
Begrens søket
1 - 10 of 10
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik och mätteknik. Linköpings universitet, Tekniska högskolan.
    Boreal vegetation responses to forestry as reflected in field trial and survey data2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis had two objectives: the first objective was to evaluate the response of forest ground vegetation to selected forestry operations, i.e. cutting of different intensities and scarification; the second objective was to compare the use of survey data in vegetation research with that of more traditional research using field trials - i.e. can survey data be used and produce results that comply with those emerging from field trials? Here, the results from an analysis of survey data has been compared with results emerging from a field trial.

    Survey data was analysed from the National Forest Inventory (NFI), using 789 sample plots in central and northern Sweden visited twice at an interval of 10-11 years, 294 of which had been subjected to logging between inventories. This was compared with a field trial in central Sweden: a complete block design with four replicates - three treatments and conventional harvesting as the control.

    The cutting intensity was found to have an impact on the ground-layer flora, the change being mostly differences in abundance rather than change in species richness. Those increasing were early successional species, i.e. crustose lichens, Deschampsia flexuosa. In contrast, Vaccinium myrtillus was decreasing substantially in response to increased cutting intensity. A number of species appeared to be indifferent to cutting, i.e. Vaccinium vitisidaea, Trientalis europaea.

    Scarification had a different impact on the flora than cutting: only Polytrichum spp. increased substantially, while many decreased.

    For those effects that were possible to compare in both studies, the results from survey data comply with those from the field trial, indicating that survey data is possible to use in forest vegetation research.

  • 2.
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Boreal vegetation responses to forestry as reflected in field trial and survey data and the quality of cover estimates and presence/absence in vegetation inventory2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Den här avhandlingen belyser hur avverkning och markberedning påverkar markfloran i den svenska barrskogen. Dessutom utvärderas två inventeringsmetoder som används inom växtekologin. Vid arbetet har både rikstäckande inventeringsdata och fältförsök använts och de likartade resultaten tyder på att rikstäckande inventeringar är en underutnyttjad resurs i forskningen.

    Ju större andel av träden som avverkas desto större blir förändringen av markflorans sammansättning. Vissa arter, som lingon, ljung, etc., verkar dock inte påverkas i nämnvärd omfattning, medan andra, som blåbär, minskar i relation till hur mycket som avverkats. Gräs och mjölkört ökar efter avverkning, dock visar sig vissa gräs och mjölkört inte reagera om inte avverkningen överskrider ett tröskelvärde på ca 80 %. Avverkning har en liten, men signifikant, effekt på antalet arter, medan artomsättning, d.v.s. arters etablering på och/eller försvinnande från provytorna, framförallt påverkas av andel gran innan avverkning, markens produktionsförmåga och först därefter av hur stor andel av träden som avverkas. Det var också uppenbart att markberedning har en stark effekt som skiljer sig från avverkning. Framförallt gynnas björnmossor av markberedning men även vårfryle, kruståtel och mjölkört. Arter som missgynnas av markberedning var bl.a., en levermossa, lingon, väggmossa och kråkbär.

    I växtekologi är visuell täckningsbedömning, d.v.s. hur stor del av en provyta som täcks av en växtart, och registrering av förekomst/icke förekomst, d.v.s. finns en växtart på en provyta eller inte, de två vanligaste metoderna vid vegetationsinventering.

    Vid registrering av förekomst/icke förekomst missas upp till en tredjedel av förekomsterna, vanligaste orsaken till missade registreringar verkar vara att man inte upptäcker arten snarare än att den inte kan identifieras. Det var stora variationer mellan arter, där arter med få exemplar på provytan missas oftare.

    Både den visuella täckningsbedömningen och förekomst/icke förekomst visar sig ha personberoende fel, d.v.s. att olika personer genomgående ger högre eller lägre värden än andra. Trots det personberoende felet visar sig täckningsbedömningar ha ett större informationsvärde än registrering av förekomst/icke förekomst när det gäller att särskilja olika typer av vegetation. Erfarenhet har en förvånansvärt liten effekt på kvaliteten av täckningsbedömningar.

    Delarbeid
    1. The impact of logging intensity on field-layer vegetation in Swedish boreal forests
    Åpne denne publikasjonen i ny fane eller vindu >>The impact of logging intensity on field-layer vegetation in Swedish boreal forests
    2001 (engelsk)Inngår i: Forest Ecology and Management, ISSN 0378-1127, Vol. 154, nr 1-2, s. 105-115Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The relationship between logging intensity and changes in ground cover vegetation was studied in 16 species and groups of species recorded at 10- or 11-year intervals in mature conifer-dominated forests. The 789 plots located in northern and central Sweden had been surveyed by the National Forest Inventory and the National Survey of Forest Soil and Vegetation. Thirty-seven percent of the plots had been subjected to a thinning or clear-cutting between the inventories. A principal components analysis showed that, of the variables considered, logging intensity had the highest explanatory power regarding change in ground cover vegetation between the inventories (the other variables were sum of temperatures, age of stand, timber volume, percentage Pinus sylvestris and site productivity). A multivariate direct gradient analysis technique (Redundancy analysis) showed that the logging intensity significantly affected the change in cover. This analysis also ranked the species in their responsiveness to logging. Epilobium angustifolium, narrow-leaved grasses and broad-leaved grasses, increased most with logging intensity. The response was not linear and only detectable at high logging intensities (>80%). In contrast, Vaccinium myrtillus seemed to decrease linearly with increased logging intensity. There was several years time-lag in the response to logging of E. angustifolium, V. myrtillus and narrow-leaved grasses. Several species and groups of species seemed unaffected by the logging. In sample plots unaffected by logging the cover of most species decreased.

    Emneord
    Clear cut, Community, Cutting, Multivariate analysis, Sweden, Thinning
    Identifikatorer
    urn:nbn:se:liu:diva-13278 (URN)10.1016/S0378-1127(00)00642-3 (DOI)
    Tilgjengelig fra: 2008-05-07 Laget: 2008-05-07 Sist oppdatert: 2018-07-03
    2. Composition of vegetation after a modified harvesting and propagation method compared with conventional clear-cutting, scarification and planting: evaluation 14 years after logging
    Åpne denne publikasjonen i ny fane eller vindu >>Composition of vegetation after a modified harvesting and propagation method compared with conventional clear-cutting, scarification and planting: evaluation 14 years after logging
    2008 (engelsk)Inngår i: Applied Vegetation Science, ISSN 1402-2001, Vol. 11, nr 2, s. 159-168Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Question: How does the vegetation of boreal forests respond to harvesting and scarification?

    Location: 650 m a.s.l., central Sweden (61°38' N).

    Methods: The response of boreal forest vegetation to cutting and scarification was studied in a field trial, which consisted of three treatments plus conventional harvesting as a control in a complete block design with four replicates. The cutting was done 14 years prior to vegetation inventory and scarification and planting were conducted the first or second years after cutting.

    Results: The species most abundant at higher cutting intensities were crustose lichens, Cladonia spp., Cladina arbuscula, Polytrichum spp. and pioneer mosses, the grass Deschampsia flexuosa, and the tree Betula pubescens, A few species had substantially lower abundance in treatments with higher cutting intensity, notably Hylocomium splendens and Vaccinium myrtillus. Scarification had a strong effect that was different from the one created by cutting. In scarification treatments, Polytrichum spp. were the only species with high abundance; most species had low abundance, i.e. Barbilophozia lycopodioides, Vaccinium vitis-idaea, Pleurozium schreberi, Carex globularis, Empetrum nigrum, Cladina arbuscula, Sphagnum spp.

    Conclusions: Our results elaborate on the details of the well-known effect of cutting on ground-layer flora, and also give support for the profound and long-lasting effect that soil scarification has on forest vegetation.

    Emneord
    Boreal forest, Cutting intensity, Field trial, Forest understorey, Logging, Propagation, Sweden
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13279 (URN)10.3170/2007-7-18343 (DOI)
    Tilgjengelig fra: 2008-05-07 Laget: 2008-05-07 Sist oppdatert: 2014-10-08
    3. Turnover of ground layer species in Swedish boreal forests and its response to logging
    Åpne denne publikasjonen i ny fane eller vindu >>Turnover of ground layer species in Swedish boreal forests and its response to logging
    Manuskript (Annet vitenskapelig)
    Identifikatorer
    urn:nbn:se:liu:diva-13280 (URN)
    Tilgjengelig fra: 2008-05-07 Laget: 2008-05-07 Sist oppdatert: 2010-01-13
    4. Systematic and random variation in vegetation monitoring data
    Åpne denne publikasjonen i ny fane eller vindu >>Systematic and random variation in vegetation monitoring data
    Vise andre…
    2008 (engelsk)Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 19, s. 633-644Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Question: Detecting species presence in vegetation and making visual assessment of abundances involve a certain amount of skill, and therefore subjectivity. We evaluated the magnitude of the error in data, and its consequences for evaluating temporal trends.

    Location: Swedish forest vegetation.

    Methods: Vegetation data were collected independently by two observers in 342 permanent 100-m2 plots in mature boreal forests. Each plot was visited by one observer from a group of 36 and one of two quality assessment observers. The cover class of 29 taxa was recorded, and presence/absence for an additional 50.

    Results: Overall, one third of each occurrence was missed by one of the two observers, but with large differences among species. There were more missed occurrences at low abundances. Species occurring at low abundance when present tended to be frequently overlooked. Variance component analyses indicated that cover data on 5 of 17 species had a significant observer bias. Observer-explained variance was < 10% in 15 of 17 species.

    Conclusion: The substantial number of missed occurrences suggests poor power in detecting changes based on presence/absence data. The magnitude of observer bias in cover estimates was relatively small, compared with random error, and therefore potentially analytically tractable. Data in this monitoring system could be improved by a more structured working model during field work.

    sted, utgiver, år, opplag, sider
    Institutionen för fysik, kemi och biologi, 2008
    Emneord
    Forest, Observer error, Permanent plot, Statistical power, Sweden
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-11872 (URN)10.3170/2008-8-18423 (DOI)
    Merknad
    Original publication: Milberg, P., Bergstedt, J., Fridman, J., Odell, G & Westerberg, L., Systematic and random variation in vegetation monitoring data, 2008, Journal of Vegetation Science, (19), 633-644. http://dx.doi.org/10.3170/2008-8-18423. Copyright: Opulus Press, http://www.opuluspress.se/index.phpTilgjengelig fra: 2008-05-22 Laget: 2008-05-22 Sist oppdatert: 2017-12-13
    5. In the eye of the beholder: bias and stochastic variation in cover estimates
    Åpne denne publikasjonen i ny fane eller vindu >>In the eye of the beholder: bias and stochastic variation in cover estimates
    Manuskript (Annet vitenskapelig)
    Identifikatorer
    urn:nbn:se:liu:diva-13282 (URN)
    Tilgjengelig fra: 2008-05-07 Laget: 2008-05-07 Sist oppdatert: 2010-01-13
  • 3.
    Bergstedt, Johan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Hagner, M.
    Milberg, P.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Composition of vegetation after a modified harvesting and propagation method compared with conventional clear-cutting, scarification and planting: evaluation 14 years after logging2008Inngår i: Applied Vegetation Science, ISSN 1402-2001, Vol. 11, nr 2, s. 159-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Question: How does the vegetation of boreal forests respond to harvesting and scarification?

    Location: 650 m a.s.l., central Sweden (61°38' N).

    Methods: The response of boreal forest vegetation to cutting and scarification was studied in a field trial, which consisted of three treatments plus conventional harvesting as a control in a complete block design with four replicates. The cutting was done 14 years prior to vegetation inventory and scarification and planting were conducted the first or second years after cutting.

    Results: The species most abundant at higher cutting intensities were crustose lichens, Cladonia spp., Cladina arbuscula, Polytrichum spp. and pioneer mosses, the grass Deschampsia flexuosa, and the tree Betula pubescens, A few species had substantially lower abundance in treatments with higher cutting intensity, notably Hylocomium splendens and Vaccinium myrtillus. Scarification had a strong effect that was different from the one created by cutting. In scarification treatments, Polytrichum spp. were the only species with high abundance; most species had low abundance, i.e. Barbilophozia lycopodioides, Vaccinium vitis-idaea, Pleurozium schreberi, Carex globularis, Empetrum nigrum, Cladina arbuscula, Sphagnum spp.

    Conclusions: Our results elaborate on the details of the well-known effect of cutting on ground-layer flora, and also give support for the profound and long-lasting effect that soil scarification has on forest vegetation.

  • 4.
    Bergstedt, Johan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Milberg, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    The impact of logging intensity on field-layer vegetation in Swedish boreal forests2001Inngår i: Forest Ecology and Management, ISSN 0378-1127, Vol. 154, nr 1-2, s. 105-115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between logging intensity and changes in ground cover vegetation was studied in 16 species and groups of species recorded at 10- or 11-year intervals in mature conifer-dominated forests. The 789 plots located in northern and central Sweden had been surveyed by the National Forest Inventory and the National Survey of Forest Soil and Vegetation. Thirty-seven percent of the plots had been subjected to a thinning or clear-cutting between the inventories. A principal components analysis showed that, of the variables considered, logging intensity had the highest explanatory power regarding change in ground cover vegetation between the inventories (the other variables were sum of temperatures, age of stand, timber volume, percentage Pinus sylvestris and site productivity). A multivariate direct gradient analysis technique (Redundancy analysis) showed that the logging intensity significantly affected the change in cover. This analysis also ranked the species in their responsiveness to logging. Epilobium angustifolium, narrow-leaved grasses and broad-leaved grasses, increased most with logging intensity. The response was not linear and only detectable at high logging intensities (>80%). In contrast, Vaccinium myrtillus seemed to decrease linearly with increased logging intensity. There was several years time-lag in the response to logging of E. angustifolium, V. myrtillus and narrow-leaved grasses. Several species and groups of species seemed unaffected by the logging. In sample plots unaffected by logging the cover of most species decreased.

  • 5.
    Bergstedt, Johan
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi.
    Milberg, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi.
    The impact of logging on species richness and turnover of field layer species in Swedish boreal forests2008Inngår i: Open environmental & biological monitoring journal, ISSN 1875-0400, Vol. 1, s. 48-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     On two occasions, with a 10- or 11-year interval, species occurring in 650 plots (100 m2) in boreal production forests in Sweden were recorded within a monitoring program. During this interval, many of the plots had been subjected to varying degrees of timber extraction. The presence of 49 vascular plant species or species groups was recorded and we evaluated how species number varied over time. There was an overall increase in species number, probably partly reflecting changing attitudes and strategies for fieldwork. Logging had a modest, but significant positive effect on the change in species number per plot. When analysing individual species, three of 18 showed a differential response along the logging gradient: Linnea borealis was more likely to appear at low logging intensities while the opposite pattern was present in Epilobium angustifolium and Calluna vulgaris. A species turnover index was calculated per plot and used as the dependent variable in a multiple regression with six independent variables. Three of these contributed significantly to the model: turnover increased (i) with decreasing amounts of Pinus sylvestris in the tree canopy; (ii) with increasing site productivity; and (iii) with increasing logging intensity. Hence, greatest changes over time occurred in stands lacking P. sylvestris (consequently dominated by Picea abies) that occurred on fertile soil, and was amplified by logging.

  • 6.
    Bergstedt, Johan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Westerberg, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Milberg, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    In the eye of the beholder: bias and stochastic variation in cover estimates2009Inngår i: PLANT ECOLOGY, ISSN 1385-0237, Vol. 204, nr 2, s. 271-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cover estimates by eye is a prevailing method to assess abundance. We examined cover estimates with regard to bias and random variation. Ten observers working with a national forest vegetation survey estimated sixteen 100 m(2)-plots, placed in two different vegetation types. These had similar species composition but were clearly distinguishable in the field. In species-wise analyses, observer bias varied greatly, with Dicranum spp., Vaccinium vitis-idaea and Vaccinium myrtillus having the largest bias. Experience had a surprisingly small impact on variation. Power analysis revealed only small differences between observers in the ability to distinguish the two vegetation types, and little value in averaging the assessments from two, three or four observers. Cover estimates did better than presence/absence data in separating the two vegetation types and multivariate analyses were more powerful than univariate ones.

  • 7.
    Callaghan, Terry V.
    et al.
    Royal Swedish Academy of Sciences, Stockholm, Sweden .
    Tweedie, Craig E.
    University of Texas at El Paso, USA .
    Åkerman, Jonas
    Royal Swedish Academy of Sciences, Stockholm, Sweden .
    Andrews, Christopher
    Centre for Ecology & Hydrology, Penicuik, UK .
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Butler, Malcolm G.
    North Dakota State University, Fargo, ND, USA .
    Christensen, Torben R.
    Lund University, Sweden.
    Cooley, Dorothy
    Department of Environment, Yukon Territorial Government, Dawson City, YT, Canada.
    Dahlberg, Ulrika
    Lantmäteriet, Gävle, Sweden .
    Danby, Ryan K.
    Queen’s University, Kingston, ON, Canada.
    Daniëls, Fred J. A.
    Institute of Biology and Biotechnology of Plants, Münster, Germany .
    de Molenaar, Johannes G.
    Maurik, The Netherlands .
    Dick, Jan
    Centre for Ecology & Hydrology, Penicuik, UK .
    Mortensen, Ebbe
    Alterra, Wageningen University, The Netherlands .
    Ebert-May, Diane
    Michigan State University, East Lansing, MI, USA .
    Emanuelsson, Urban
    Swedish Biodiversity Centre, Uppsala, Sweden.
    Eriksson, Håkan
    Umeå University, Sweden .
    Hedenås, Henrik
    Abisko Scientific Research Station, Sweden.
    Henry, Greg. H. R.
    University of Alberta, Edmonton, Canada .
    Hik, David S.
    University of Alberta, Edmonton, Canada .
    Hobbie, John E.
    Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA.
    Jantze, Elin J.
    Stockholm University, Sweden.
    Jaspers, Cornelia
    DTU Aqua, Charlottenlund, Denmark .
    Johansson, Cecilia
    Uppsala University, Sweden .
    Johansson, Margareta
    Lund University, Sweden.
    Johnson, David R.
    University of Texas at El Paso, USA .
    Johnstone, Jill F.
    University of Saskatchewan, Canada.
    Jonasson, Christer
    Abisko Scientific Research Station, Sweden.
    Kennedy,, Catherine
    Department of Environment, Yukon Territorial Government, Whitehorse, YT, Canada .
    Kenney, Alice J.
    University of British Columbia, Vancouver, Canada .
    Keuper, Frida
    VU University Amsterdam, The Netherlands.
    Koh, Saewan
    University of Alberta, Edmonton, Canada .
    Krebs, Charles J.
    University of British Columbia, Vancouver, Canada .
    Lantuit, Hugues
    Alfred Wegener Institute, Potsdam, Germany .
    Lara, Mark J.
    University of Texas at El Paso, USA .
    Lin, David
    University of Texas at El Paso, USA .
    Lougheed, Vanessa L.
    University of Texas at El Paso, USA .
    Madsen, Jesper
    Aarhus University, Roskilde, Denmark .
    Matveyeva, Nadya
    Department of Vegetation of the Far North, Komarov Botanical Institute, St. Petersburg, Russia .
    McEwen, Daniel C.
    Minnesota State University, Moorhead, MN, USA .
    Myers-Smith, Isla H.
    University of Alberta, Edmonton, Canada .
    Narozhniy, Yuriy K.
    Tomsk State University, Russia .
    Olsson, Håkan
    Swedish university of Agricultural Sciences, Umeå, Sweden .
    Pohjola, Veijo A.
    Uppsala University, Sweden .
    Price, Larry W.
    Portland State University, OR, USA .
    Rigét, Frank
    Minnesota State University, Moorhead, MN, USA .
    Rundqvist, Sara
    Umeå Univerity, Sweden .
    Sandström, Anneli
    Gävle, Sweden .
    Tamstorf, Mikkel
    Minnesota State University, Moorhead, MN, USA .
    Van Bogaert, Rik
    Flanders Research Foundation, Brussels, Belgium .
    Villarreal, Sandra
    University of Texas at El Paso, USA .
    Webber, Patrick J.
    Michigan State University, East Lansing, MI, USA .
    Zemtsov, Valeriy A.
    Tomsk State University, Russia.
    Multi-Decadal Changes in Tundra Environments and Ecosystems: Synthesis of the International Polar Year-Back to the FutureProject (IPY-BTF)2011Inngår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, nr 6, s. 705-716Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the responses of tundra systemsto global change has global implications. Most tundraregions lack sustained environmental monitoring and oneof the only ways to document multi-decadal change is toresample historic research sites. The International PolarYear (IPY) provided a unique opportunity for such researchthrough the Back to the Future (BTF) project (IPY project#512). This article synthesizes the results from 13 paperswithin this Ambio Special Issue. Abiotic changes includeglacial recession in the Altai Mountains, Russia; increasedsnow depth and hardness, permafrost warming, andincreased growing season length in sub-arctic Sweden;drying of ponds in Greenland; increased nutrient availabilityin Alaskan tundra ponds, and warming at mostlocations studied. Biotic changes ranged from relativelyminor plant community change at two sites in Greenland tomoderate change in the Yukon, and to dramatic increasesin shrub and tree density on Herschel Island, and in subarcticSweden. The population of geese tripled at one sitein northeast Greenland where biomass in non-grazed plotsdoubled. A model parameterized using results from a BTFstudy forecasts substantial declines in all snowbeds andincreases in shrub tundra on Niwot Ridge, Colorado overthe next century. In general, results support and provideimproved capacities for validating experimental manipulation,remote sensing, and modeling studies.

  • 8.
    Hedenas, Henrik
    et al.
    Abisko Science Research Stn.
    Olsson, Hakan
    Swedish University of Agriculture Science.
    Jonasson, Christer
    Abisko Science Research Stn.
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Dahlberg, Ulrika
    Royal Swedish Academic Science.
    Changes in Tree Growth, Biomass and Vegetation Over a 13-Year Period in the Swedish Sub-Arctic2011Inngår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, nr 6, s. 672-682Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was conducted in the Swedish sub-Arctic, near Abisko, in order to assess the direction and scale of possible vegetation changes in the alpine-birch forest ecotone. We have re-surveyed shrub, tree and vegetation data at 549 plots grouped into 61 clusters. The plots were originally surveyed in 1997 and re-surveyed in 2010. Our study is unique for the area as we have quantitatively estimated a 19% increase in tree biomass mainly within the existing birch forest. We also found significant increases in the cover of two vegetation types-"birch forest-heath with mosses and "meadow with low herbs, while the cover of snowbed vegetation decreased significantly. The vegetation changes might be caused by climate, herbivory and past human impact but irrespective of the causes, the observed transition of the vegetation will have substantial effects on the mountain ecosystems.

  • 9.
    Milberg, Per
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Fridman, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Odell, Gunnar
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Westerberg, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ekologi. Linköpings universitet, Tekniska högskolan.
    Systematic and random variation in vegetation monitoring data2008Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 19, s. 633-644Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Question: Detecting species presence in vegetation and making visual assessment of abundances involve a certain amount of skill, and therefore subjectivity. We evaluated the magnitude of the error in data, and its consequences for evaluating temporal trends.

    Location: Swedish forest vegetation.

    Methods: Vegetation data were collected independently by two observers in 342 permanent 100-m2 plots in mature boreal forests. Each plot was visited by one observer from a group of 36 and one of two quality assessment observers. The cover class of 29 taxa was recorded, and presence/absence for an additional 50.

    Results: Overall, one third of each occurrence was missed by one of the two observers, but with large differences among species. There were more missed occurrences at low abundances. Species occurring at low abundance when present tended to be frequently overlooked. Variance component analyses indicated that cover data on 5 of 17 species had a significant observer bias. Observer-explained variance was < 10% in 15 of 17 species.

    Conclusion: The substantial number of missed occurrences suggests poor power in detecting changes based on presence/absence data. The magnitude of observer bias in cover estimates was relatively small, compared with random error, and therefore potentially analytically tractable. Data in this monitoring system could be improved by a more structured working model during field work.

  • 10.
    Petersson, Linda K.
    et al.
    Swedish Univ Agr Sci, Sweden.
    Milberg, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Bergstedt, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Dahlgren, Jonas
    Swedish Univ Agr Sci, Sweden.
    Felton, Annika M.
    Swedish Univ Agr Sci, Sweden.
    Gotmark, Frank
    Univ Gothenburg, Sweden.
    Salk, Carl
    Swedish Univ Agr Sci, Sweden.
    Lof, Magnus
    Swedish Univ Agr Sci, Sweden.
    Changing land use and increasing abundance of deer cause natural regeneration failure of oaks: Six decades of landscape-scale evidence2019Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 444, s. 299-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many tree species worldwide are suffering from slow or failed natural regeneration with dramatic consequences for biodiversity and ecosystem services. However, it is difficult to disentangle the complex effects of factors influencing regeneration processes on long-lived tree species at large scales. In this study, we use long-term data from the Swedish National Forest Inventory (1953-2015) combined with deer hunting data (1960-2015) to reveal experimentally-intractable processes impeding oak (Quercus spp.) regeneration in southern Sweden. Oak-dominated ecosystems are widespread in northern temperate regions, where oaks are foundation species with disproportionate importance for biodiversity and ecosystem functions. Our study reveals that during the last six decades, oak tree numbers and standing volume have continuously increased, while natural regeneration of oak declined steeply after the early 1980s. We connect this decline to denser and darker forests, combined with increased abundance of deer. Land use changes during the six decades, such as abandonment of traditional practices and large-scale introduction of forest management oriented towards high volume production, led to continuously denser forests and thereby reduced the oak regeneration niche. In addition, the impact of changed game management was evident. This was particularly clear from a natural experiment on Gotland, a large island free of deer until roe deer were introduced in the late 20th century, at which point oak regeneration began a steep decline. At the stand level, natural oak regeneration could be expected to mainly occur in pulses after disturbance events, followed by a period of low regeneration success as the cohort ages. However, at a landscape scale one would expect a mix of successional stages that would even out such demographic patterns. A prolonged period of low regeneration at a landscape scale will eventually lead to a large gap in the oak size distribution as was observed in this study. This could eventually hurt the many species dependent on old and large oak trees. Active management to restore the oak regeneration niche, i.e. forest habitats with more light and less browsing pressure, therefore seems essential. The latter includes developing strategies that manage both deer populations and their available food across landscapes. Our study is the first to link oak regeneration failure to long-term changes in land use and increased deer populations at a landscape scale in this region. Furthermore, our study show how historical data can clarify confounded processes impacting long-lived forest species.

1 - 10 of 10
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf