Arctic wildfires a burning hot topic by Lena Hermesdorf, PhD Student, CENPER M, University of Copenhagen In recent years, wildfires in arctic tundra landscapes have increased in frequency, and models project them to increase in the future due to warmer and drier summers. To date, little is known about the impact such events may have on the net greenhouse gas (GHG) balance in arctic ecosystems. To test this, we conducted an experimental burn of a well-drained tundra site in West Greenland. Fire is a destructive force on aboveground vegetation, thus, significantly affects the carbon dioxide balance. Despite this, the underlying soils and soil processes linked to the carbon and nitrogen cycles seem to be surprisingly resistant to moderate wildfires. Most people associate the Arctic with landscapes of endless ice and snow, making it almost impossible to believe that this region may face large wildfires. However, every year when the sun rises above the horizon and temperatures increase, the snow melts and ice-free parts of the Arctic become green and alive. Despite the short growing season, this is a crucial time for the Arctics total carbon (C) and the nitrogen (N) budgets. A delicate balance between uptake and production in both soils and plants controls the proportions of greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Changes in net GHG budgets are dependent on various factors, especially climatic factors such as temperature and precipitation. Therefore, climate-driven changes in temperature and precipitation patterns will lead to warmer and drier summers. This in turn may lead to an increase in wildfire frequency in tundra ecosystems. Unprecedented wildfires of greater extent and intensity have already been observed in the Arctic in recent years, devastating large areas in Greenland, Siberia and Alaska. To date, few studies have investigated the GHG budgets of all three gasses in Arctic ecosystems. Even fewer studies link changing GHG budgets to shifts in climatic conditions or event-driven changes such as wildfires. Of these studies, most have focused on boreal forest and peat tundra fires. There is a lack of data from tundra ecosystems that are characterized by dwarf shrubs and shallow organic layers that overlay mineral soils. Such landscapes dominate the tundra - especially in Greenland. 10 CENPERM Annual Report 2020 In summer 2017, we set up an experimental burn site in a well-drained heath tundra landscape in Blæsedalen on Disko Island, West Greenland. The aim of this study was to investigate the potential effects of event-driven fire on net GHG exchanges. In the same year, Western Greenland experienced one of its largest ever recorded fire events, where nearly 24 km2 of tundra was burnt. Prior to this, there have been no known large fire events recorded in Greenland. This fire was coincidental and was independent of our fire experiment. The experimental design consists of three different treatments and control plots in a total area of approx. 530 m2 . To simulate vegetation destruction, in one plot, all vegetation taller than 5 cm was cut, and vegetation shorter than 5 cm left intact. In the second plot, all vegetation was completely burned. In the third treatment, passive warming was achieved by open top chambers (OTCs) to simulate increasing air temperatures predicted in a warming climate. In a pre-burning test, we determined the amount of time it takes for the vegetation to burn off completely, in an area similar in size to our plots. Based on these preliminary tests, we exposed the vegetation to fire for seven minutes using a weed-burner. In contrast to other studies on natural tundra fires, our experimental fire was fast burning and limited to the surface. According to our temperature observations from the burning process, extreme high temperatures (>400 C) only occurred in the surfaces litter layer and did not penetrate deeper into the soil than the top two centimetres. ANNUAL REPORT 2020 CENPERM Center for Permafrost Field sites Brønlundhus Qaanaaq Svalbard Longyearbyen Greenland Zackenberg Disko Qajaa Sweden Kangerlussuaq Nuuk Narsarsuaq Abisko Sermilik Directors welcome Visions and aims Highlights 2020 Højdepunk ter 2020 Arctic wildf ires a burning hot topic Publications & conferences Communication & outreach Educational activities Ongoing research projects & graduate students International collaborators & funding CENPERM staff 3 4 6 8 10 12 16 2 CENPERM Annual Report 2020 Directors welcome The year 2020 has been a special year in many ways; a year with changes for almost everyone and difficult in different ways for most due to Covid-19. We have been able to complete most of the planned field work by continuously making changes according to regulations. Unfortunately, Visions and aims Center for Permafrost Microbial activity Plant ecology CENPERM Permafrost soil & landscape dynamics CENPERM integrates multidisciplinary research of biogeochemical and physical processes in a climate-vegetation-soil-microorganismpermafrost approach in transects across the major c CENPERM Annual Report 2020 5 Highlights 2020 Highlights 2020 is dedicated to the PhDstudents of CENPERM. The students, despite Covid-19 and continued difficulties, have kept their motivation levels high and been able to continue their research, working intensively on specific projects, and for some defended online. Three multid present the first Arctic multi-threat assessment focusing on the Nuuk region of Greenland. In this region, more than 300 archaeological sites are already threatened by exposure to impacts from microbial degradation, permafrost thaw, vegetation growth and erosion driven by climate change. Within the Højdepunkter 2020 Højdepunkter 2020 er dedikeret til vores ph.d.-studerende ved CENPERM. På trods udfordringerne som følge af Covid-19 restriktionerne, har de ph.d.-studerende bevaret motivationen på et højt niveau, fortsat deres forskning, afsluttet diverse delprojekter, og nogle har måtte forsvare 3. Klimaforandringer truer de velbevarede arkæologiske områder i Arktis. I Archaeometry præsenterer Fenger-Nielsen et al. (2020) det første forsøg på i en arktisk sammenhæng, at sammenholde de mange trusler i en samlet trusselvurdering med fokus på Nuuk-regionen i Grønland. I denne region er der mer Arctic wildfires a burning hot topic by Lena Hermesdorf, PhD Student, CENPER M, University of Copenhagen In recent years, wildfires in arctic tundra landscapes have increased in frequency, and models project them to increase in the future due to warmer and drier summers. To date, little is known a In order to analyse whether the fire and destruction of vegetation led to changes in soil processes, and hence in GHG fluxes, we measured the exchange rates of all three GHGs and took several soil samples during three growing seasons (2017-2019). In this way we can differentiate between effects that Publications & conferences International journals Andersen, E. A. S., Michelsen, A., Fenger-Nielsen, R., Hollesen, J., Ambus, P. L., Elberling, B. (2020). Nitrogen isotopes reveal high N retention in plants and soil of old Norse and Inuit deposits along a wet-dry arctic fjord transect in Greenland. birch forest via effects on soil thermal regime and sequestration of deposited nitrogen. Journal of Ecology 13567. Kristensen, J. A., Michelsen, A., Metcalfe, D. B. (2020). Background insect herbivory increases with local elevation but makes minor contribution to element cycling along natural gradie Rasmussen, L. H., Michelsen, A., LadegaardPedersen, P., Nielsen, C. S., Elberling, B. (2020). Arctic soil water chemistry in dry and wet tundra subject to snow addition, summer warming and herbivory simulation. Soil Biology and Biochemistry 141, 107676. Ravn, N. R., Elberling, B., Michelsen, A. (202 Westergaard-Nielsen, A., Balstrøm, T., Treier, U., Normand, S., Elberling, B. (2020). Estimating meltwater retention and associated nitrate redistribution during snowmelt in an Arctic tundra landscape. Environmental Research Letters 15, 034025. Wester-Larsen, L., Kramshøj, M., Albers, C. N., Rinnan, Communication & outreach CENPERM continued its series of regular talks in spite of the Covid-19 situation; however, most talks during the year have been via zoom. By meeting regularly, it was possible to keep in touch and share problems and solutions within the Center. Unfortunately, a planned write Elberling, B.: Four Citizen Science talks onboard Antarctic Cruise: Climate and environmental changes: trends and variations, Penguin colonies: a hotspot for greenhouse gas emissions, Dry Valleys: the cold desert but surprisingly alive, The Antarctic continent in a global context. Jan. Talks Elber Jun. 11. Emily Pickering Pedersen. PhD student, CENPERN, BIO. Foraging deeply: Depth-specific plant nitrogen uptake in a high arctic permafrost ecosystem. Sep. 3. Welcome back from the field. Short reports on fieldwork. Sep. 17. Jesper Riis Christiansen, IGN/ Christian Juncher Jørgensen, AU. Methane Educational activities CENPERMs activities in 2020 include a number of educational efforts, which this year mainly classic university courses at the basic and advanced levels at the University of Copenhagen. In addition to course taught, a number of M.Sc. meant theses have been supervised (see: Ongo Climate change and biogeochemical cycles. Dept. of Biology, University of Copenhagen, autumn, R. Rinnan, K. Rousk, P. Ambus, G. Schurgers. Climate change - an interdisciplinary challenge. Dept. of Geosciences and Natural Resource Management, University of Copenhagen, autumn, R. Rinnan, G. Schurgers, Ongoing research projects & graduate students Postdoc and Assistant Professor projects Alvarenga, Danillo: Interactions between cyanobacteria and moss-hosts. DImperio, Ludovica. Postdoc: Soil-plant interactions and greenhouse gas dynamics in permafrost-affected ecosystems. Kramshøj, Magnus. Postdoc Defended PhD thesis 2020 Fenger-Nielsen, Rasmus: Archaeological sites threatened by climate change: a regional perspective from Greenland. Supervisors: Bo Elberling, Jørgen Hollesen and Aart Kroon. Defended: May 2020. Ongoing PhD projects 2020 Baggesen, Nanna: Emissions of biogenic volatile organ Xu, Wenyi: Fire in Arctic tundra - impacts on bio-geochemical cycles. Supervisor: Per Ambus. Yun, Hanbo: Quantifying and modelling methane dynamics in contrasting landscapes of the Qinghai-Tibetan Plateau. Supervisor: Bo Elberling, co-supervisor: Ludovica D Imperio and Wenxin Zhang. Zastruzny, Sebas Ongoing M.Sc. projects: 7 Christensen, Maj Paornak Sofie: The effects of enhanced precipitation and phosphorus addition on carbon dioxide and methane fluxes in heath tundra in Greenland. Supervisor: Anders Michelsen. Jacobsen, Cathrine Kallestrup: Plant ecophysiology, carbon cycling and vegetation International collaborators & funding Research activities at CENPERM are linked to a number of well-established international arctic networks. These cooperation agreements are supplemented by a strong affiliation to internationally recognized researchers. CENPERM has continuously extended the intern Los Alamos National Laboratory, USA: C. Andresen, permafrost impacts on hydrology. Michigan State University, USA: Tiedje J.; microbial studies, scientific publications. The Netherlands Central Organisation for Radioactive Waste (COVRA). NOAA (National Oceanic and Atmospheric Administration) Global University of Bergen, Norway: L. Øverås. University of Boulder, Institute for Arctic and Alpine Research (INSTAAR), Colorado, USA: I. Overeem, K. Barnhart. Coastal changes in Greenland. University of Eastern Finland, Department of Environmental Science, Finland: M. Kivimäenpää. Sample treatment, lig Danish Ministry for Research: Integrated Carbon Observation System, Research Infrastructure (ICOS-RI). Grant holder: Thomas Friborg (2016-2021): 6.5 mio. Independent Research Fund Denmark, Sapere Aude DFF-Research leader: Climatic, ecological and molecular controls of nitrogen fixation in pristine s CENPERM staff Researchers Ambus Per Lennart Professor Andersen Thorbjørn J. Professor Christiansen Casper Tai Postdoc Elberling Bo Professor, Director Friborg Thomas Associate professor Hansen Birger Ulf Associate professor Hollesen Jørgen Senior Researcher Kroon Aart Associat CENPERM staff PhD students Baggesen Nana PhD student Danielsen Birgitte Kortegaard PhD student Fenger-Nielsen Rasmus PhD student Hermesdorf Lena PhD student Hornum Mikkel Toft PhD student Kylborg Sarah Estela PhD student Liu Yijing PhD student Pedersen Emily Pickering PhD student P ANNUAL REPORT 2020 The Danish National Research Foundation (DNRF) is an independent organization established by the Danish Parliament in 1991 with the objective to promote and stimulate basic research at the highest international level at the frontiers of all scientific fields. The Center of Excell