J. For. Sci., 2026, 72(2):82-92 | DOI: 10.17221/8/2026-JFS

Boulders as functional microrefugia: Quantifying a continental-like microclimate supporting Pinus cembra at its oceanic range marginOriginal Paper

Yann Fragnière ORCID...1, Stéphanie Morelon ORCID...1, Alain Müller1, Gregor Kozlowski ORCID...1,2
1 Department of Biology and Botanical Garden, University of Fribourg, Fribourg, Switzerland
2 Natural History Museum Fribourg, Fribourg, Switzerland

Climatic microrefugia allow some forest tree species to persist outside their main distribution range by locally decoupling site conditions from the regional climate. At its western, oceanic range margin in the Swiss Prealps, the Swiss stone pine (Pinus cembra L.) occurs on large boulders embedded within subalpine forests dominated by Norway spruce [Picea abies (L.) H. Karst.]. We hypothesised that these landforms generate a continental-like microclimate enabling P. cembra persistence under otherwise sub-oceanic conditions, and we aimed to quantify this phenomenon. Using high-resolution data loggers, we measured air and soil temperature, thermal amplitudes, and soil moisture on the summits and at the bases of ten limestone boulders over a two-year period. Linear mixed-effects models revealed a pronounced microclimatic decoupling between positions. Boulder summits were consistently warmer and drier during the growing season. In contrast, during winter, summits were significantly colder, while boulder bases remained thermally stable due to persistent snow insulation. The strongest microclimatic divergence occurred in spring, when temperatures at the bases remained stable near 0 °C, whereas summit temperatures were markedly warmer and more variable. This continental-like microclimate likely promotes P. cembra persistence. Our results highlight the importance of topographic heterogeneity for maintaining marginal tree populations.

Keywords: climatic microrefugia; microclimate measurements; relict species; subalpine forests; Swiss stone pine; thermal decoupling; topographic heterogeneity

Received: January 23, 2026; Revised: February 6, 2026; Accepted: February 9, 2026; Prepublished online: February 26, 2026; Published: February 27, 2026  Show citation

ACS AIP APA ASA Harvard Chicago Chicago Notes IEEE ISO690 MLA NLM Turabian Vancouver
Fragnière Y, Morelon S, Müller A, Kozlowski G. Boulders as functional microrefugia: Quantifying a continental-like microclimate supporting Pinus cembra at its oceanic range margin. Journal of Forest Science. 2026;72(2):82-92. doi: 10.17221/8/2026-JFS.
Share...
Download citation
  • BibTeX (.bib)
  • Bookends (.ris)
  • EasyBib (.ris)
  • EndNote (.enw)
  • EndNote 8 (.xml)
  • ISI WoS (.isi)
  • Medlars (.medlars)
  • Mendeley (.ris)
  • MODS (.xml)
  • Papers (.ris)
  • RefWorks (.txt)
  • RefManager (.ris)
  • RIS (.ris)
  • MS Word (.xml)
  • Zotero (.ris)
    • Open full article

    References

    1. Baig M., Tranquillini W. (1980): The effects of wind and temperature on cuticular transpiration of Picea abies and Pinus cembra and their significance in dessication damage at the alpine treeline. Oecologia, 47: 252-256. Go to original source...
    2. Barbeito I., Dawes M.A., Rixen C., Senn J., Bebi P. (2012): Factors driving mortality and growth at treeline: A 30-year experiment of 92 000 conifers. Ecology, 93: 389-401. Go to original source... Go to PubMed...
    3. Barbeito I., Brücker R.L., Rixen C., Bebi P. (2013): Snow fungi-induced mortality of Pinus cembra at the alpine treeline: Evidence from plantations. Arctic, Antarctic, and Alpine Research, 45: 455-470. Go to original source...
    4. Bates D., Mächler M., Bolker B., Walker S. (2015): Fitting linear mixed-effects models using lme4. Journal of Statistical Software, 67: 1-48. Go to original source...
    5. Casalegno S., Amatulli G., Camia A., Nelson A., Pekkarinen A. (2010): Vulnerability of Pinus cembra L. in the Alps and the Carpathian mountains under present and future climates. Forest Ecology and Management, 259: 750-761. Go to original source...
    6. Caudullo G., De Rigo D. (2016): Pinus cembra in Europe: Distribution, habitat, usage, and threats. In: San-Miguel-Ayanz J., De Rigo D., Caudullo G., Houston Durrant T., Mauri A. (eds): European Atlas of Forest Tree Species. Luxembourg, Publication Office of the European Union: 120-121.
    7. Dobrowski S.Z. (2011): A climatic basis for microrefugia: The influence of terrain on climate. Global Change Biology, 17: 1022-1035. Go to original source...
    8. Doutaz J., Bugmann H., Frey H.U. (2006): Swiss stone pine and oceanic climate: The importance of microsites. Schweizerische Zeitschrift fur Forstwesen, 157: 196-207. (in French) Go to original source...
    9. Ducci F., Donnelly K. (2018): Forest tree marginal populations in Europe - Report on the state of knowledge on forest tree marginal and peripheral populations in Europe. Annals of Silvicultural Research, 41: 1-12.
    10. Ellenberg H. (1988): Vegetation Ecology of Central Europe. Cambridge, Cambridge University Press: 731.
    11. Federal Office of Topography swisstopo (2022): swissALTI3D, the High Precision Digital Elevation Model of Switzerland. Available at: https://www.swisstopo.admin.ch/en/height-model-swissalti3d
    12. Fragnière Y., Sonnenwyl V., Clément B., Kozlowski G. (2022): Large-scale historical afforestation failure with Pinus cembra in the Swiss Prealps. New Forests, 53: 533-553. Go to original source...
    13. Fragnière Y., Champoud L., Küffer N., Braillard L., Jutzi M., Wohlgemuth T., Kozlowski G. (2024): Cliff-edge forests: Xerothermic hotspots of local biodiversity and models for future climate change. Global Change Biology, 30: e17196. Go to original source... Go to PubMed...
    14. Gernandt D.S., López G.G., García S.O., Liston A. (2018): Phylogeny and classification of Pinus. Taxon, 54: 29-42. Go to original source...
    15. Gugerli F., Rüegg M., Vendramin G. (2009): Gradual decline in genetic diversity in Swiss stone pine populations (Pinus cembra) across Switzerland suggests postglacial re-colonization into the Alps from a common eastern glacial refugium. Botanica Helvetica, 119: 13-22. Go to original source...
    16. Gugerli F., Brodbeck S., Bebi P., Bollmann K., Dauphin B., Gossner M., Krumm F., Peter M., Queloz V., Reiss G., Rellstab C., Stofer S., von Arx G., Wasem U., Zweifel R. (2022): L'arole - portrait d'un montagnard. Notice pour le praticien, 72: 1-16. (in French) Go to original source...
    17. Gugerli F., Brodbeck S., Lendvay B., Dauphin B., Bagnoli F., van der Knaap W.O., Tinner W., Höhn M., Vendramin G.G., Morales-Molino C., Schwörer C. (2023): A range-wide postglacial history of Swiss stone pine based on molecular markers and palaeoecological evidence. Journal of Biogeography, 50: 1049-1062. Go to original source...
    18. Hao Z.Z., Liu Y.Y., Nazaire M., Wei X.X., Wang X.Q. (2015): Molecular phylogenetics and evolutionary history of sect. Quinquefoliae (Pinus): Implications for Northern Hemisphere biogeography. Molecular Phylogenetics and Evolution, 87: 65-79. Go to original source... Go to PubMed...
    19. Höhn M., Gugerli F., Abran P., Bisztray G., Buonamici A., Cseke K., Hufnagel L., Quintela-Sabarís C., Sebastiani F., Vendramin G.G. (2009): Variation in the chloroplast DNA of Swiss stone pine (Pinus cembra L.) reflects contrasting post-glacial history of populations from the Carpathians and the Alps. Journal of Biogeography, 36: 1798-1806. Go to original source...
    20. Jönsson A.M., Linderson M.L., Stjernquist I., Schlyter P., Bärring L. (2004): Climate change and the effect of temperature backlashes causing frost damage in Picea abies. Global and Planetary Change, 44: 195-207. Go to original source...
    21. Kemppinen J., Lembrechts J.J., Van Meerbeek K., Carnicer J., Chardon N.I., Kardol P., Lenoir J., Liu D., Maclean I., Pergl J. et al. (2024): Microclimate, an important part of ecology and biogeography. Global Ecology and Biogeography, 33: e13834. Go to original source...
    22. Körner C. (2012): Alpine Treelines: Functional Ecology of the Global High Elevation Tree Limits. Basel, Springer Science Business Media: 220. Go to original source...
    23. Körner C., Spehn E.M. (2019): Mountain Biodiversity: A Global Assessment. London, Routledge: 350. Go to original source...
    24. Lenoir J., Hattab T., Pierre G. (2017): Climatic microrefugia under anthropogenic climate change: Implications for species redistribution. Ecography, 40: 253-266. Go to original source...
    25. Lenth R.V., Piaskowski J. (2025): emmeans: Estimated marginal means, aka least-squares means. Available at: https://rvlenth.github.io/emmeans/
    26. Leuschner C., Ellenberg H. (2017): Ecology of Central European Forests: Vegetation Ecology of Central Europe. Cham, Springer International Publishing: 972. Go to original source...
    27. Li M.H., Yang J. (2004): Effects of microsite on growth of Pinus cembra in the subalpine zone of the Austrian Alps. Annals of Forest Science, 61: 319-325. Go to original source...
    28. Lotter A.F., Birks H.J.B. (2003): The Holocene palaeolimnology of Sägistalsee and its environmental history - A synthesis. Journal of Paleolimnology, 30: 333-342. Go to original source...
    29. MeteoSwiss (2023): Climate Normals. Zurich, Federal Office for Meteorology and Climatology. Available at: https://www.meteoswiss.admin.ch/climate/the-climate-of-switzerland/climate-normals.html (accessed Jan 7, 2026)
    30. Millar C.I., Charlet D.A., Westfall R.D., King J.C., Delany D.L., Flint A.L., Flint L.E. (2018): Do low-elevation ravines provide climate refugia for subalpine limber pine (Pinus flexilis) in the Great Basin, USA? Canadian Journal of Forest Research, 48: 663-671. Go to original source...
    31. Oberhuber W. (2004): Influence of climate on radial growth of Pinus cembra within the alpine timberline ecotone. Tree Physiology, 24: 291-301. Go to original source... Go to PubMed...
    32. Pinheiro J., Bates D., R Core Team (2025): nlme: Linear and nonlinear mixed effects models. Available at: https://cran.r-project.org/web/packages/nlme/index.html
    33. R Core Team (2023): R: A Language and Environment for Statistical Computing. Vienna, R Foundation for Statistical Computing. Available at: http://www.R-project.org
    34. Rikli M. (1909): Die Arve in der Schweiz. Basel, Georg Cie: 455. (in German)
    35. Schönenberger W. (1975): Standortseinflusse auf Versuchsaufforstungen an der alpinen Waldgrenze (Stillberg, Davos). Zürich, Beer Co.: 71. (in German)
    36. Sonnenwyl V., Dauphin B., Fragnière Y., Clément B., Grünig S., Brodbeck S., Parisod C., Kozlowski G., Gugerli F. (2024): Genetic underpinning of historical afforestation with allochthonous Pinus cembra in the northwestern Swiss Alps. Alpine Botany, 134: 1-13. Go to original source...
    37. Tranquillini W. (2012): Physiological Ecology of the Alpine Timberline: Tree Existence at High Altitudes with Special Reference to the European Alps. Berlin, Springer Science Business Media: 140.
    38. Ulber M., Gugerli F., Bozic G. (2004): EUFORGEN Technical Guidelines for Genetic Conservation and Use for Swiss Stone Pine (Pinus cembra). Rome, International Plant Genetic Resources Institute: 6.
    39. Vittoz P., Rulence B., Largey T., Freléchoux F. (2008): Effects of climate and land-use change on the establishment and growth of cembran pine (Pinus cembra L.) over the altitudinal treeline ecotone in the Central Swiss Alps. Arctic, Antarctic, and Alpine Research, 40: 225-232. Go to original source...
    40. Wild J., Kopecký M., Macek M., ©anda M., Jankovec J., Haase T. (2019): Climate at ecologically relevant scales: A new temperature and soil moisture logger for long-term microclimate measurement. Agricultural and Forest Meteorology, 268: 40-47. Go to original source...
    41. Zieba A., Rozanski W., Bukowski M., Ciesielska B., Szwagrzyk J. (2019): Distribution and habitat conditions of Pinus cembra forests in the Tatra Mountains. Dendrobiology, 81: 86-96. Go to original source...
    42. Zuur A.F., Ieno E.N., Walker N.J., Saveliev A.A., Smith G.M. (2009): Mixed Effects Models and Extensions in Ecology with R. New York, Springer: 574. Go to original source...

    This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits use, distribution, and reproduction in any medium, provided the original publication is properly cited. No use, distribution or reproduction is permitted which does not comply with these terms.


    Return to the content