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Articles by Pekka Vakkari

Category: Research article

article id 1510, category Research article
Tähti Pohjanmies, Sakina Elshibli, Pertti Pulkkinen, Mari Rusanen, Pekka Vakkari, Helena Korpelainen, Tomas Roslin. (2016). Fragmentation-related patterns of genetic differentiation in pedunculate oak (Quercus robur) at two hierarchical scales. Silva Fennica vol. 50 no. 2 article id 1510. https://doi.org/10.14214/sf.1510
Highlights: While long-lived, widespread tree species should be resistant to genetic impoverishment, we detected high differentiation among populations and pronounced genetic structure within populations of Quercus robur in Finland; These patterns seem indicative of population processes active at range margins, and of disequilibrium following historic habitat change; Preservation of remaining genetic variation is thus important in the conservation of Q. robur.

Populations at species’ range margins are expected to show lower genetic diversity than populations at the core of the range. Yet, long-lived, widespread tree species are expected to be resistant to genetic impoverishment, thus showing comparatively high genetic diversity within populations and low differentiation among populations. Here, we study the distribution of genetic variation in the pedunculate oak (Quercus robur L.) at its range margin in Finland at two hierarchical scales using 15 microsatellite loci. At a regional scale, we compared variation within versus among three oak populations. At a landscape scale, we examined genetic structuring within one of these populations, growing on an island of ca 5 km2. As expected, we found the majority of genetic variation in Q. robur to occur within populations. Nonetheless, differentiation among populations was markedly high (FST = 0.12) compared with values reported for populations of Q. robur closer to the core of its range. At the landscape level, some spatial and temporal sub-structuring was observed, likely explained by the history of land-use on the island. Overall, Q. robur fulfils the expectation of the central-marginal hypothesis of high differentiation among marginal populations, but the notable population differentiation has most likely been influenced also by the long, ongoing fragmentation of populations. Finnish oak populations may still be adjusting to the drastic habitat changes of the past centuries. Preservation of genetic variation within the remaining stands is thus an important factor in the conservation of Q. robur at its range margin.

  • Pohjanmies, University of Helsinki, Department of Agricultural Sciences, Spatial Foodweb Ecology Group, P.O. Box 27, FI-00014 University of Helsinki, Finland; University of Jyväskylä, Department of Biological and Environmental Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Finland ORCID ID:E-mail: tahti.t.pohjanmies@jyu.fi (email)
  • Elshibli, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland; University of Helsinki, Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: sakina.elshibli@helsinki.fi
  • Pulkkinen, Natural Resources Institute Finland (Luke), Green technology, Haapastensyrjäntie 34, FI-12600 Läyliäinen, Finland ORCID ID:E-mail: pertti.pulkkinen@luke.fi
  • Rusanen, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: mari.rusanen@luke.fi
  • Vakkari, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: pekka.vakkari@luke.fi
  • Korpelainen, University of Helsinki, Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: helena.korpelainen@helsinki.fi
  • Roslin, University of Helsinki, Department of Agricultural Sciences, Spatial Foodweb Ecology Group, P.O. Box 27, FI-00014 University of Helsinki, Finland; Swedish University of Agricultural Sciences, Department of Ecology, P.O. Box 7044, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: tomas.roslin@helsinki.fi
article id 1274, category Research article
Juho Hautsalo, Paul Mathieu, Sakina Elshibli, Pekka Vakkari, Juha Raisio, Pertti Pulkkinen. (2015). Variation in height and survival among northern populations of pedunculate oak (Quercus robur L.): results of a 13-year field study. Silva Fennica vol. 49 no. 2 article id 1274. https://doi.org/10.14214/sf.1274
Highlights: A height-sum function allowed us to compare the combined growth and survival of northernmost stands of pedunculate oak; Individuals from Turku-Katariinanlaakso performed the best, although other families performed more consistently across trials, which should be considered in future conservation and breeding. Surprisingly, trees planted in a trial location beyond the natural northern limit of pedunculate oak showed the best performance.
We analysed the adaptive potential of pedunculate oak (Quercus robur L.) in terms of variation in height and survival in five field trials located in southern and central Finland. The trials were established with Finnish native material from six different seed origins. Thirteen years after planting, the number of living trees was counted and measured for height. Analysis of height and survival revealed a significant effect of origin, i.e., a genetic basis to individual tree performance. Two origins from the Turku region (Ruissalo and Katariinanlaakso) performed the best while trees originating from Parainen (Lenholmen) performed the worst. In order to study the effects due to tree origin, a comparison of families (half-sibling trees, i.e. those sharing the same ‘mother’ tree) was made by combining height and survival through a height-sum equation (i.e., the product of mean survival and height of each family in each trial) and used to calculate family- and origin-level ecovalences. Ecovalence is a metric for performance consistency, and indicates how much each variable contributes to the total variation; the higher the value, the lower the consistency of trees across the trials based on their origin or family. Analysis of consistency showed similar results to growth and survival, with Turku families performing the best and families from Parainen performing the worst. Families in the Katariinanlaakso stand (Turku) generally had more stable ecovalence values and more dispersed height-sums, while Ruissalo (Turku) families had higher mean height-sum but higher variability in ecovalence values. These results suggest that seed origins (i.e., genotypes) can be optimized in terms of their suitability for commercial or ecological forest management.
  • Hautsalo,  Natural Resources Institute Finland (Luke), Green technology, Antinniementie 1, FI-41330 Vihtavuori, Finland ORCID ID:E-mail: juho.hautsalo@luke.fi (email)
  • Mathieu, Agrocampus Ouest, 35000 Rennes, France ORCID ID:E-mail:
  • Elshibli, University of Helsinki, Helsinki, Finland ORCID ID:E-mail:
  • Vakkari, Natural Resources Institute Finland (Luke), Vantaa, Finland ORCID ID:E-mail: pekka.vakkari@luke.fi
  • Raisio, City of Helsinki, Helsinki, Finland ORCID ID:E-mail:
  • Pulkkinen, Natural Resources Institute Finland (Luke), Vantaa, Finland ORCID ID:E-mail: pertti.pulkkinen@luke.fi
article id 205, category Research article
Pekka Vakkari, Mari Rusanen, Katri Kärkkäinen. (2009). High genetic differentiation in marginal populations of European white elm (Ulmus laevis). Silva Fennica vol. 43 no. 2 article id 205. https://doi.org/10.14214/sf.205
Studies on the amount of genetic variation in marginal populations and differentiation between them are essential for assessment of best gene conservation strategies and sampling schemes. Thirteen marginal populations of Ulmus laevis in southern Finland and one in Estonia were investigated for genetic variation in 20 allozyme loci. Population differentiation among Finnish stands was high, Fst = 0.290, and mean genetic diversity low, He = 0.088. The differentiation follows the isolation-by-distance structure within the core of the distribution area (lake Vanajavesi). Fairly high frequency of recurrent genotypes was observed, but this did not have an influence on the genetic parameters. The observed genetic structure is consistent with the central-marginal hypothesis. In the light of the results, the Finnish gene conservation strategy for U. laevis seems to be on a sound basis.
  • Vakkari, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: pekka.vakkari@metla.fi (email)
  • Rusanen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Kärkkäinen, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:

Category: Article

article id 5537, category Article
Anu Mattila, Anne Pakkanen, Juha Raisio, Pekka Vakkari. (1994). Genetic variation in English oak (Quercus robur) in Finland. Silva Fennica vol. 28 no. 4 article id 5537. https://doi.org/10.14214/sf.a9177

Genetic variation in 5 natural stands of Quercus robur L. in Finland was analysed electrophoretically for 13 isozyme loci. Stands were on average polymorphic at 49.2% of the loci, with 2.1 alleles per locus. Observed heterozygosities, ranging from 13.6% to 16.9%, were slightly lower than estimates reported for German stands. The majority of the species’ genetic variation was found within each studied stand, and only 5.5% was between stands. Mean genetic differentiation (∂) was the same as that found in the primary range of the species, but the differentiation estimates (D) for single Finnish population were more variable.

  • Mattila, ORCID ID:E-mail:
  • Pakkanen, ORCID ID:E-mail:
  • Raisio, ORCID ID:E-mail:
  • Vakkari, ORCID ID:E-mail:

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