Swedish Polar Research Secretariat
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The potential disturbance of the 210Pb profile in peat cores by roots and the implications for 210Pb dating.
No full textAt this moment there is a gap in information regarding the affect roots might have on 210Pb distribution in peat cores and in turn the obtained chronologies by 210Pb dating. Therefore, four peat cores were collected from the snow manipulation study site within the mire complex Storflaket (68°20048″N, 18°58016″E). Two cores from snow fence plots, which has experienced root growth due to permafrost thaw, and 2 cores from control plots. 210Pb distribution and the provided 210Pb chronologies were then compared with root content within and between the cores. In two of the cores (C5 and SF2) did subsurface peaks in the 210Pb activity profile follow the distribution profile of the dwarf shrub roots. The same pattern was not seen with Eriophorum roots. This indicates that presence of dwarf root with their shallow and horizontally growth can affect the 210Pb profile by horizontal translocation of 210Pb. The chronologies obtained by the CF:CS and CRS dating models could not be validated for the C5 core which suggest that dwarf shrub roots also can affect the 21oPb dating
Global plant trait relationships extend to the climatic extremes of the tundra biome
No full textThe majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world
Secondary metabolites in Betula nana ssp. nana : Effects of browsing intensity and nutrient availability
No full textThe ongoing shrubification of the Arctic tundra may in the future have serious consequences for the ecosystem. More trees and shrubs will lead to changes in species composition and may alter diversity, carbon and nutrient balance, and result in a lower albedo. Reindeer can reduce the spread of shrubs, but plants have developed chemical defenses against herbivores made up of secondary metabolites. The concentration of these can be affected by several factors, including damages from herbivory and the availability of nutrients. In this study samples of the shrub B. nana ssp. nana (dwarf birch) and soil samples were collected from outside and inside herbivore exclosures in Fennoscandia. Then, concentrations of phenols and terpenes, the major defense component in birches, and soil nutrient availability were analyzed. A proxy was created for measuring the density of reindeer at each location. The aim was to evaluate this data and see if the exclusion of herbivores or the nutrient availability had any effect on the concentration of the defense components. Few differences between the exclosures and control plots could be found and only two out of 18 t-tests showed any difference that was deemed statistically significant. The density of herbivores was found to have no effect and the nutrient availability showed no clear results. This study concludes there are many factors influencing the concentration of defense components in dwarf birches, including the rising temperatures, that need to be considered in future studies. A better understanding of this subject would be essential in visualizing the future of the Arctic tundra
Invasive earthworms unlock arctic plant nitrogen limitation
No full textArctic plant growth is predominantly nitrogen (N) limited. This limitation is generally attributed to slow soil microbial processes due to low temperatures. Here, we show that arctic plant-soil N cycling is also substantially constrained by the lack of larger detritivores (earthworms) able to mineralize and physically translocate litter and soil organic matter. These new functions provided by earthworms increased shrub and grass N concentration in our common garden experiment. Earthworm activity also increased either the height or number of floral shoots, while enhancing fine root production and vegetation greenness in heath and meadow communities to a level that exceeded the inherent differences between these two common arctic plant communities. Moreover, these worming effects on plant N and greening exceeded reported effects of warming, herbivory and nutrient addition, suggesting that human spreading of earthworms may lead to substantial changes in the structure and function of arctic ecosystems. Arctic plant growth is predominantly nitrogen limited, where the slow nitrogen turnover in the soil is commonly attributed to the cold arctic climate. Here the authors show that the arctic plant-soil nitrogen cycling is also constrained by the lack of larger detritivores like earthworms
Decade of experimental permafrost thaw reduces turnover of young carbon and increases losses of old carbon, without affecting the net carbon balance
No full textThicker snowpacks and their insulation effects cause winter-warming and invoke thaw of permafrost ecosystems. Temperature-dependent decomposition of previously frozen carbon (C) is currently considered one of the strongest feedbacks between the Arctic and the climate system, but the direction and magnitude of the net C balance remains uncertain. This is because winter effects are rarely integrated with C fluxes during the snow-free season and because predicting the net C balance from both surface processes and thawing deep layers remains challenging. In this study, we quantified changes in the long-term net C balance (net ecosystem production) in a subarctic peat plateau subjected to 10 years of experimental winter-warming. By combining(210)Pb and(14)Cdating of peat cores with peat growth models, we investigated thawing effects on year-round primary production and C losses through respiration and leaching from both shallow and deep peat layers. Winter-warming and permafrost thaw had no effect on the net C balance, but strongly affected gross C fluxes. Carbon losses through decomposition from the upper peat were reduced as thawing of permafrost induced surface subsidence and subsequent waterlogging. However, primary production was also reduced likely due to a strong decline in bryophytes cover while losses from the old C pool almost tripled, caused by the deepened active layer. Our findings highlight the need to estimate long-term responses of whole-year production and decomposition processes to thawing, both in shallow and deep soil layers, as they may contrast and lead to unexpected net effects on permafrost C storage
The role of nutrients for stream ecosystem function in Arctic landscapes : drivers of productivity under environmental change
No full textArctic and sub-Arctic freshwaters are currently experiencing substantial ecosystem changes due to the effects of global warming. Global warming effects on these freshwaters include increasing water temperatures, altered hydrological patterns, shifts in riparian vegetation and changes in the export of nutrients and carbon from soils. How these alterations to the physical and chemical hab-itat will affect stream ecosystem functioning largely depends on the responses by autotrophic pro-ducers and heterotrophic primary consumers. In this thesis, I explore how key stream ecosystem processes such as metabolic rates and nutrient cycling vary as a function of climate and landscape drivers, particularly light, temperature, and nutrient and carbon availability. To do this I leveraged natural gradients in vegetation, altitude, disturbance, and precipitation throughout the year in northern Sweden, as well as long- and short-term manipulations of nutrient availability. I also synthesized nutrient limitation data from lakes and streams to more holistically assess the re-sponses of boreal to Arctic freshwaters to changes in nutrients and climate variables. I found that nutrient availability, and especially nitrogen (N), is a main driver of spatial and temporal patterns of biofilm productivity, whole system metabolic rates, and short term N uptake in Arctic and sub-Arctic streams. I also show the importance of light and temperature constraints during early spring and late autumn, which set the limit for the aquatic growing season and annual productivity pat-terns. I present a first comparison of combined drivers of lake and stream responses to nutrient addition, which points to a shared importance of N and phosphorus (P) rather than light or tem-perature in driving the magnitude of nutrient limitation across these systems. Ultimately, I pro-pose that across large ranges in habitat variables, widespread nutrient limitation of Arctic fresh-waters constrain other climate change effects on ecosystem functions. The results presented in this thesis will promote better predictions of climate change effects on Boreal to Arctic stream ecosystem functioning
Stream metabolism controls diel patterns and evasion of CO2 in Arctic streams
No full textStreams play an important role in the global carbon (C) cycle, accounting for a large portion of CO2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 production and evasion from streams remains poorly understood. In this study, we measured O-2 and CO2 continuously in streams draining tundra-dominated catchments in northern Sweden, during the summers of 2015 and 2016. From this, we estimated daily metabolic rates and CO2 evasion simultaneously and thus provide insight into the role of stream metabolism as a driver of C dynamics in Arctic streams. Our results show that aquatic biological processes regulate CO2 concentrations and evasion at multiple timescales. Photosynthesis caused CO2 concentrations to decrease by as much as 900 ppm during the day, with the magnitude of this diel variation being strongest at the low-turbulence streams. Diel patterns in CO2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO2 evasion was sustained by aquatic ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases, the contribution of stream respiration exceeded CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, thus creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO2 evasion in the Arctic and demonstrate that stream metabolic processes are key drivers of the transformation and fate of terrestrial organic matter exported from these landscapes.Originally included in thesis in manuscript form.</p
Marknadsanalys över tekniska lösningar för avsyning av lavinterräng samt ett analysverktyg för att förstå hur och var laviner har gått
No full textI Kiruna kommun mellan Abisko - Björkliden, på berget Nuoljas ostliga sluttning går det ett flertal laviner varje säsong. Sedan 2013 har Trafikverket installerat ett lavinbekämpningssystem bestående av Gazex kanoner som med en stor smäll startar kontrollerade laviner. Genom regelbunden sprängning motverkar man att större snömassor byggs upp och därmed tar man bort risken för stora laviner att gå. Stora laviner riskerar att nå fram till väg- och järnvägen och kan medföra längre stopp för malmtrafiken. Före varje sprängning vill man vara säker på att varken människor eller djur befinner sig i terrängen, idag gör man en visuell bedömning innan man inleder en sprängning. Genom ny teknik kan man säkerhetsställa att ingen befinner sig i riskzonen vilket gör att sprängningen kan ske med större säkerhet. Rapporten har belyst olika tekniker som radar, drönare och infraröda rörelsedetektorer och hur dessa kan implementeras på Nuolja. Drönare används mer och mer runt om i världen tack vare deras mångsidiga användningsområden. Att använda en drönare för att skanna lavinterräng är tideffektivt men inte optimalt i alla väderförhållanden. IR-rörelsedetektorer är ett annat alternativ som med stor precision känner av den minsta rörelsen från djur eller människor. Till följd av undersökningen av industrier och skidanläggningar runt om i världen (bland annat alperna och Nordamerika) kan man dra slutsatsen, att radar är det som används för att hitta människor och djur i lavinterräng. Rapporten behandlar även ett analysverktyg som efterfrågades av Trafikverket avseende hur man kan studera och analysera laviner som har gått. Med LiDAR-Laser kan man få fram samma underlag och information som lavintekniker får genom fältundersökningar. Med LiDAR får man aktuell information från ett säkert avstånd vilket minskar exponeringen av personal i riskzonen. Man kan även använda LiDAR för att studera snötäcket i förebyggande arbete mot laviner
Expedition report: SWEDARCTIC Ryder 2019
No full textAboard the Swedish Icebreaker (IB) Oden, the Ryder 2019 Expedition, which the ExplorersClub officially designated as “Flag Expedition #51,” we successfully achieved our ambitious goals of scientifically investigating northern Greenland and creating the first ever maps of water depths in the ice-infested seas of the usually inaccessible and essentially unexplored Sherard Osborn Fjord, which connects the southern Lincoln Sea and the northern Nares Strait to the Ryder Glacier, one of the primary outlet glaciers draining the Greenland Ice Sheet.The expedition departed from the harbor of US Air Force Base Thule on August 5, 2019, and returned there on September 10th. During those 37 days, the international scientific party of 39 scientists, assisted by seven representatives from the Swedish Polar Research Secretariat, and 26 crew members, travelled 3369 nautical miles achieving all of their high-priority research goals on land and sea. One of the primary accomplishments was creating the first-ever, high-quality bathymetric map of large areas of previously uncharted waters. IB Oden was the first vessel (after Greenlandic Inuit in kayaks, of course) to enter these waters, and to reveal the fascinating and complicated shape of the seafloor that shows geological structuresand evidence of the powerful forces of the Greenland Ice Sheet and its marine outlet glaciers as they advanced and retreated during past glaciations. The map shows that the near vertical fjord walls, roughly 1 km high, continue downward, below sea level, with equal steepness, and nearly equal depths, as great as 900 meters in Sherard Osborn Fjord. The new map also shows the specific pathways by which warmer subsurface waters of Atlantic origin reach into the fjords of northern Greenland, where they come into contact with the floating glacial ice tongues and impact the rate at which the ice melts. The warmer waters have first circulated through the Arctic Ocean and into the Lincoln Sea, before reaching the fjord mouths. Another major achievement of the expedition was collecting many types of data that reveal dramatic environmental changes, over a variety of timescales, of the frozen world (cryosphere, which consists of ice sheets, marine outlet glaciers, and their floating icetongues, and sea ice) and how it waxes and wanes, in response to climate change, and, conversely, also contributing to it. Revealing the history of the cryosphere, and the mechanismsby which it changes, provides information that is essential to understanding Greenland’s modern cryosphere, which has global significance with respect to climate, because the ice sheet holds water equivalent to a global sea-level rise by over 7 meters. The broad scientific program included marine geology, geophysics and marine chemistry, biology, ecology, glaciology, oceanography, climatology, air chemistry, and archeology. Data processing began immediately onboard IB Oden in the permanent and temporary laboratories setup specifically for the expedition in portable containers. As opportunities to explore remote, generally inaccessible regions are rare, teams of scientists who conduct research on land joined the expedition, making it truly multidisciplinary. They journeyed back and forth to the ship by two helicopters on IB Oden’s helipad either on day trips, or for a week at a time, by camping on lands nearby the fjord. By taking samples of driftwood from the shoreline, clam shells from elevated terraces, and by studying modern and ancient remains of plant and animals, and artifacts left behind by ancient peoples, these teams will reconstruct sea-level history, ice sheet thickness, climate change, and the colonization history of Greenland, after the last ice age, by humans, animals and plants, and how they have shaped the environment of what we now find in Greenland.Meteorologiska och oceanografiska data, samt skeppsdata, insamlade ombord på isbrytaren Oden. Svensk nationell datatjänst. Version 1. https://doi.org/10.48515/4s61-7520</p
Spatial patterns of zooplankton communities In Swedish mountain and boreal lakes.
No full text Zooplankton is crucial for lake ecosystems as it is an important component in most of the food webs of these ecosystems. However, environmental changes have caused reductions in ecosystems nutrients and stoichiometry, which directly affects phytoplankton’s development and quality. Studies were carried out in 33 different lakes throughout Sweden, divided into 4 regions (Abisko, Jämtland, Västerbotten and Värmland) to assess whether differences in environmental characteristics induced differences in phytoplankton abundance and zooplankton communities. Using data from 3 different seasons of the year, I found that zooplankton composition differed between northern and southern regions, and greater differences were found between the mountain regions than between the boreal regions. Dissolved inorganic N (DIN) and dissolved inorganic N to total P ratio (DIN:TP) concentrations were lower in northern regions than in southern regions. Phytoplankton biomass increased with dissolved organic carbon (DOC), likely through the positive effects of DOC on overall nutrient availability. DOC concentrations were higher in boreal regions than in mountain regions, as also happens with chlorophyll-a. Positive correlations between DOC and 3 different zooplankton genera were proven, whereas 3 different zooplankton taxa were correlated with DIN:TP (two negatively and one positively). Lakes with lower DIN:TP ratios had higher abundances of calanoids, which were the major contributor of the dissimilarity in zooplankton composition among the regions. Therefore, the DIN:TP ratio possibly has stronger effects than DOC on zooplankton composition in Swedish oligotrophic lakes. But further increases in DOC concentrations will likely reduce the differences in zooplankton composition caused by the declines in lake DIN:TP observed in this study