Presence-absence of plant habitat specialists in 15 patches

Sampling event
Latest version published by University of Oslo on Oct 10, 2022 University of Oslo

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We present three years of presence-absence data of 49 vascular plant species in 15 patches of dry, calcareous grassland habitat. The species are considered to be habitat specialists, and thus unlikely to occur in between the patches. The data set combines three years of surveys, the last of which are re-surveys of a subset described in previous publications (Bakkestuen et al., 2014; Evju et al., 2015, 2016; Evju & Sverdrup-Thygeson, 2016; Wollan et al., 2011). Absences can be inferred for the 49 species included.

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Researchers should cite this work as follows:

Lieungh E, Wollan A K, Stabbetorp O E, Bjureke K (2022): Presence-absence of plant habitat specialists in 15 patches. v1.14. University of Oslo. Dataset/Samplingevent.


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The publisher and rights holder of this work is University of Oslo. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

GBIF Registration

This resource has been registered with GBIF, and assigned the following GBIF UUID: a99cf6c0-4eb2-476b-8414-a513f0925d86.  University of Oslo publishes this resource, and is itself registered in GBIF as a data publisher endorsed by GBIF Norway.


Samplingevent; checklist; vascular plants; specialist species; presence-absence data; calcareous grassland; habitat patch; metapopulation


Eva Lieungh
  • Metadata Provider
  • Originator
  • Point Of Contact
PhD student
Natural History Museum, University of Oslo
Anders Kvalvåg Wollan
  • Metadata Provider
  • Originator
Head Engineer
Natural History Museum, University of Oslo
Odd Egil Stabbetorp
  • Metadata Provider
  • Originator
Senior Research Scientist
Norwegian Institute for Nature Research
Kristina Bjureke
  • Metadata Provider
Assistant professor
Natural History Museum, University of Oslo
Olav Skarpaas
  • Metadata Provider
Natural History Museum, University of Oslo
Siri Lie Olsen
  • Metadata Provider
Associate professor
Norwegian University of Life Sciences
Marianne Evju
  • Metadata Provider
Senior Research Scientist
Norwegian Institute for Nature Research
Kristina Bjureke
  • Metadata Provider
Assistand professor
Natural history museum, University of Oslo
Vegar Bakkestuen
  • Point Of Contact
Senior Research Scientist
Norwegian Institute for Nature Research
Rukaya Johaadien
  • User
Natural History Museum, University of Oslo

Geographic Coverage

The species were recorded in 15 polygons of dry, calcareous grassland on Gressholmen island, situated in the inner Oslo fjord. These calcareous grasslands occur naturally fragmented on shallow soils by the Oslo fjord, mainly on exposed and/or grazed Cambrian–Silurian marine sedimentary rock. The climate is relatively warm, with an annual temperature of 5.7 °C (Aune 1993) and annual precipitation of 763 mm (Førland 1993). The area is among the most species-rich in Norway, as this combination of calcareous bedrock and warm summers is rare, and hosts species mostly found further south in Europe. Dry, calcareous grasslands are characterised by drought-tolerant grasses, forbs, shrubs and occasionally trees. Interannual variability plays an important role; intense droughts keep competitive vegetation away from the driest patches. The summer of 2018 was exceptionally dry and hot, visibly impacting the vegetation the following years. Many drought-intolerant plants and young trees died, and some of our habitat specialists came back in full vigour the next season. Though originally defined as naturally tree-less, the borders are transient between naturally tree-less and potentially forested semi-natural habitats kept open by grazing. The habitat patches surveyed also include semi-natural vegetation where dry pine forest could grow. Humans have shaped and impacted the habitats on Gressholmen, probably as long as the Oslo fjord has been settled. Today, the island is artificially connected to two other islands, Heggholmen and Rambergøya. Most of this island trio is protected as nature reserves, but has previously housed a shooting range, Norway’s first main airport, a soap factory with connected houses, and a paint factory. It has likely been grazed by domestic animals while the island was inhabited. From the 1970’s until its eradication in 2007, a large rabbit population occupied the islands and grazed the vegetation heavily. Several summerhouses and a restaurant are still in use, and the islands are a popular destination for day-trips in the summer.

Bounding Coordinates South West [59.882, 10.717], North East [59.887, 10.727]

Taxonomic Coverage

The data set encompasses 49 specialist vascular plant species. The list of habitat specialist species was developed based on flora information of habitat requirements and distributional range, expert opinion and field observations from a large number of polygons. More vascular plant species were recorded in the first two years, and are available upon request. Field surveyors used Lid’s Flora (2005) and Mossberg & Stenberg (2012). Species names were checked and updated using the Species Nomenclature Database, along with common names in Norwegian.

Species Acinos arvensis (Lam.) Dandy (Bakkemynte), Androsace septentrionalis L. (Smånøkkel), Arabis hirsuta (L.) Scop. (Bergskrinneblom), Asplenium ruta-muraria L. (Murburkne), Avenula pratensis (L.) Dumort. (Enghavre), Carex caryophyllea Latourr. (Vårstarr), Carlina vulgaris L. (Stjernetistel), Centaurea scabiosa L. (Fagerknoppurt), Cerastium semidecandrum L. (Vårarve), Cotoneaster scandinavicus B.Hylmö (Dvergmispel), Cotoneaster niger (Wahlb.) Fr. (Svartmispel), Cynoglossum officinale L. (Hundetunge), Draba verna L. (Vårrublom), Dracocephalum ruyschiana L. (Dragehode), Echium vulgare L. (Ormehode), Epipactis atrorubens (Hoffm.) Besser (Rødflangre), Erysimum virgatum Roth (Berggull), Filipendula vulgaris Moench (Knollmjødurt), Fragaria viridis Weston (Nakkebær), Geranium sanguineum L. (Blodstorkenebb), Hypochaeris maculata L. (Flekkgrisøre), Inula salicina L. (Krattalant), Lappula squarrosa (Retz.) Dumort. (Sprikepiggfrø), Lepidium campestre (L.) W.T.Aiton (Markkarse), Ligustrum vulgare L. (Liguster), Linum catharticum L. (Vill-lin), Lithospermum officinale L. (Legesteinfrø), Myosotis ramosissima Rochel (Bakkeforglemmegei), Myosotis stricta Link ex Roem. & Schult. (Dvergforglemmegei), Myosurus minimus L. (Muserumpe), Odontites litoralis Fr. (Strandrødtopp), Phleum phleoides (L.) H.Karst. (Smaltimotei), Poa compressa L. (Flatrapp), Polygonatum odoratum (Mill.) Druce (Kantkonvall), Potentilla crantzii (Crantz) Beck ex Fritsch (Flekkmure), Rhamnus cathartica L. (Geitved), Rosa majalis Herrm. (Kanelrose), Saxifraga granulata L. (Nyresildre), Saxifraga osloënsis Knaben (Oslosildre), Saxifraga tridactylites L. (Trefingersildre), Scleranthus perennis L. (Flerårsknavel), Seseli libanotis (L.) W.D.J.Koch (Hjorterot), Silene nutans L. (Nikkesmelle), Aria edulis (Willd.) M.Roem. (Sølvasal), Thymus pulegioides L. (Bakketimian), Veronica arvensis L. (Bakkeveronika), Veronica spicata L. (Aksveronika), Woodsia alpina (Bolton) Gray (Fjell-lodnebregne)
Variety Poa alpina alpina (frøfjellrapp)

Temporal Coverage

Start Date / End Date 2009-07-07 / 2009-07-10
Start Date / End Date 2019-07-01 / 2019-08-16
Start Date / End Date 2020-06-04 / 2020-06-22

Project Data

The PhD project of Eva Lieungh

Title Dynamic Distribution Modelling
Funding Natural History Museum, University of Oslo, and the Norwegian Ministry of Education and Research

The personnel involved in the project:

Sampling Methods

Field work in 2009 was carried out by KB, OES, and AKW, all experienced botanists. Potential locations of dry, calcareous grassland had been identified by aerial photos and distribution modelling. The locations were then visited by the field work team (KB, OES, and AKW) and either discarded or confirmed and delimited. Polygon coordinate points were recorded using a handheld GPS with an estimated accuracy of 1-10 m. All three in the team looked for species in the same polygon, one being in charge of writing down occurrences. When no new species were found, all three tried to find one more species each before declaring the list complete. Species lists per polygon were noted in a weatherproof notebook. Field work in 2019 and 2020 surveys was carried out by EL alone. Polygons were found using a map with semi-transparent polygons over a recent aerial photo. Species presences were recorded in a spreadsheet on a smartphone with daily backups. Polygons were inventoried by carefully walking back and forth across the polygon to cover the entire area. EL took pictures of each polygon, and of uncertain species using the iNaturalist app.

Study Extent Field surveys were carried out in 2009, 2019, and 2020. All vascular plant species inside the 15 habitat polygons were recorded in 2009 and 2019, but only the habitat specialists’ occurrences are reported in this data set. In 2020, only the 49 habitat specialists were looked for.
Quality Control We took several steps to quality check the data. Each occurrence was evaluated manually to ensure the highest possible quality of data. After data collection was complete in 2019 and 2020, each observation was checked against the data from the previous year(s), occurrences in GBIF, and pictures taken during field work. Some uncertainty was resolved using iNaturalist, where image recognition and other users can aid identification, and where pictures were stored for individual plants along with their coordinates and other metadata. Some pictures were also sent to OS, SLO and other experts to confirm uncertain species identifications. An additional trip to Gressholmen by EL along with SLO was carried out in september 2019, and alone in June 2020, to check uncertain presences and suspected false absences.

Method step description:

  1. For 2009 and 2019, there is more data available than was described here. These data include all vascular plant species, not just the specialists, and some additional descriptive variables for each polygon.
  2. In spite of quality control, some uncertainty remains. Delineating polygons inevitably involves uncertainties, and GPS polygon boundaries were not physically delimited in the field. In addition, changes in patch size may have occurred between 2009 and 2019, due to regrowth or other factors. To a smaller degree this is also an issue between the 2019 and 2020 data. False absences may occur in the data set, which is common in field surveys (Morrison 2016), either from incomplete survey effort, or because the species was not detectable at the time of field work. As flowering phenology varies, early-flowering species (e.g. Veronica arvensis, Draba verna) are especially susceptible to being omitted, even though special care was taken to look for them. Misidentification could also occur, though the availability of previous data and use of trained botanists with expert knowledge of the local flora should minimise this risk.

Bibliographic Citations

  1. Lid, J., and D. T. Lid. Norsk Flora. Edited by R. Elven. 7th edition. Oslo, NO: Samlaget, 2005. ISBN: 9788252160291
  2. Aune, B. (1993). Temperaturnormaler normalperiode 1961-1990 (No. 02/93; Klima, Vol. 2, pp. 1–63). Norwegian Meteorological Institute.
  3. Bakkestuen, V., Stabbetorp, O., Molia, A., & M., E. (2014). Hotspot åpen grunnlendt kalkmark i Oslofjordområdet. Beskrivelse av habitatet og forslag til overvåkingsopplegg fra ARKO-prosjektet [Hotspot open clacareos vegetation on shallow soils in the Oslo fjord. Habitat description and suggested monitoring scheme from the ARKO project] (No. 1102; NINA Rapport, Vol. 1102, p. 46). ISBN: 978-82-426-2722-3
  4. Evju, M., Blumentrath, S., Skarpaas, O., Stabbetorp, O. E., & Sverdrup-Thygeson, A. (2015). Plant species occurrence in a fragmented grassland landscape: The importance of species traits. Biodiversity and Conservation, 24, 547–561. DOI 10.1007/s10531-014-0835-y
  5. Evju, M., Stange, E., Berger, A. L., Blumentrath, S., Endrestøl, A., Olsen, S. L., Skarpaas, O., Stabbetorp, O. E., Stöckmann, F., & Sverdrup-Thygeson. (2016). Når artenes leveområder splittes opp – eksempler fra øyene i indre Oslofjord. Sluttrapport fra strategisk instituttsatsing (SIS) [When species’ habitats are fragmented – examples from the inner Oslo fjord islands.] 2011-2015 (No. 065; p. 54). Norwegian Institute for Nature Research. ISBN: 978-82-426-2885-5
  6. Evju, M., & Sverdrup-Thygeson, A. (2016). Spatial configuration matters: A test of the habitat amount hypothesis for plants in calcareous grasslands. Landscape Ecology, 31(9), 1891–1902.
  7. Førland, E. J. (1993). Nedbørnormaler normalperiode 1961-1990 (No. 39/93; Klima, pp. 1–63). Norwegian Meteorological Institute.
  8. Wollan, A. K., Bakkestuen, V., Bjureke, K., Bratli, H., Endrestøl, A., Stabbetorp, O. E., Sverdrup-Thygeson, A., & Halvorsen, R. (2011). Åpen grunnlendt kalkmark i Oslofjordområdet – et hotspot-habitat. Sluttrapport under ARKO-prosjektets periode II [Dry, calcareous grasslands in the Oslo fjord area—A hotspot habitat. End report for the ARKO project phase II]. NINA-rapport 713. NINA. ISBN: 978-82-426-2300-3
  9. Morrison, L. W. (2016). Observer error in vegetation surveys: A review. Journal of Plant Ecology, 9(4), 367–379. doi:10.1093/jpe/rtv077
  10. Halvorsen, R., Skarpaas, O., Bryn, A., Bratli, H., Erikstad, L., Simensen, T., & Lieungh, E. (2020). Towards a systematics of ecodiversity: The EcoSyst framework. Global Ecology and Biogeography, 29(11), 1887–1906.
  11. iNaturalist. Available from Accessed 22.02.2022.
  12. Mossberg, B., & Stenberg, L. (2012). Gyldendals store nordiske flora (2nd ed.). Gyldendal Norsk Forlag. ISBN: 978-82-05-42485-2

Additional Metadata

Purpose The data set was collected for use in a manuscript in EL's PhD project.
Maintenance Description We do not plan to update or add to the data set regularly.
Alternative Identifiers a99cf6c0-4eb2-476b-8414-a513f0925d86