Swedish Polar Research Secretariat
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Recent Glacier Recession – a New Source of Postglacial Treeline and Climate History in the Swedish Scandes
No full textClimate warming during the past century has imposed recession of glaciers and perennial snow/ice patches along the entire Swedish Scandes. On the newly exposed forefields, subfossil wood remnants are being outwashed from beneath ice and snow bodies. In Scandinavia, this kind of detrital wood is a previously unused source of postglacial vegetation and climate history. The present study reports radiocarbon dates of a set of 78 wood samples, retrieved from three main sites, high above modern treelines and stretching along the Swedish Scandes. In accord with previous studies, pine (Pinus sylvestris) colonized early emerging nunataks already during the Late Glacial. Around 9600-9500 cal. yr BP a first massive wave of tree establishment, birch and pine, took place in "empty" glacier cirques. Both species grew 400-600 m above their present-ay treeline position and the summer temperatures may have been 3.5 °C warmer than present. In respons to Neoglacial cooling, treelines of both birch and pine descended until their final disappearance from the record 4400 and 5900 cal. yr BP, respectively. During the entire interval 9600 to 4400 cal. yr BP, birch prospered in a 100-150 broad belt above the uppermost pines. The recent emergence of tree remnants in the current habitats relates to the contemporary episode of climate warming, possibly unprecedented for several past millennia. It is inferred, by an anology with the past, that in a future scenario with summers 3.5 ° warmer than present, the birch treeline may rise by 600 m or so.Treeline dynamics in short and long term perspectives – observational and historical evidence from the southern Swedish Scande
Observation of a tropopause fold by MARA VHF wind-profiler radar and ozonesonde at Wasa, Antarctica : comparison with ECMWF analysis and a WRF model simulation
No full textTropopause folds are one of the mechanisms of stratosphere-troposphere exchange, which can bring ozone rich stratospheric air to low altitudes in the extra-tropical regions. They have been widely studied at northern mid- or high latitudes, but so far almost no studies have been made at mid- or high southern latitudes. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has operated at the Swedish summer station Wasa, Antarctica (73A degrees S, 13.5A degrees W) during austral summer seasons from 2007 to 2011 and has observed on several occasions signatures similar to those caused by tropopause folds at comparable Arctic latitudes. Here a case study is presented of one of these events when an ozonesonde successfully sampled the fold. Analysis from European Center for Medium Range Weather Forecasting (ECMWF) is used to study the circumstances surrounding the event, and as boundary conditions for a mesoscale simulation using the Weather Research and Forecasting (WRF) model. The fold is well resolved by the WRF simulation, and occurs on the poleward side of the polar jet stream. However, MARA resolves fine-scale layering associated with the fold better than the WRF simulation
Fågelinventeringar i Norrbottens län 1981-1996 inom Naturvårdsverketsmiljökvalitetsprogram (PMK)
No full textInom ramen för naturvårdsverkets program för miljökvalitetsövervakning (PMK) genomfördes fågelinventeringar i Norrbottens län åren 1981–1996. Tre s.k. referensområden låg helt inom (Abisko, Muddus och Reivo) och ett fjärde (Sorsele) berörde delvis länet. Inventeringarna bedrevs dels med punkt- och linjetaxeringar (s.k. milrutter) över större områden, dels med revirkartering i mindre provytor. Antalet milrutter var femton i Abisko, nitton i Muddus, åtta i Reivo och sexton i Sorsele. Milrutter inventerades i Abisko 1981–1995, i Muddus 1983–1984 och 1994–1995, i Reivo 1987–1994 och i Sorsele 1982–1984. Det sammanlagda antalet inventerade mil var 129 i Abisko, 55 i Muddus, 54 i Reivo och 45 i Sorsele. Antalet provytor var tre i Abisko, två i Muddus samt en vardera i Reivo och Sorsele. De inventerades ungefär samma år som milrutterna. Materialet från Abisko, som omfattar björkskog, kalfjäll och myrmark, är stort och av hög kvalitet och utgör en utmärkt bas för jämförelse vid en eventuell återinventering. Materialen från Muddus, Reivo och Sorsele, områden som domineras av barrskog och myrmark, är mindre bra eftersom antalet rutter och år med inventeringar är färre. Tillsammans representerar emellertid dessa tre områden ett stort stickprov om 43 olika rutter, en period om fjorton år och totalt 154 inventerade mil. Såväl tätheter som artsammansättning var inbördes lika i de tre områdena i skogslandet och de kan tillsammans betraktas som ett homogent stickprov i Norrlands inre skogsland. Vid en återinventering bör därför de tre områdena tillsammans utgöra jämförelsematerialet. Förändringar i fågelfaunan kunde med tillförsikt endast analyseras med det mångåriga materialet från Abisko. Där skedde en svag men signifikant nedgång av både artantal och antalet fåglar. I Muddus och Reivo var också negativa förändringar fler än positiva. Totalbilden för länet verkar således ha varit negativ under perioden, vilket innebär att fågelfaunans utveckling Norrland liknade den i södra Sverige under samma period. I Muddus gjordes en jämförelse mellan ruttsträckor som löpte innanför och utanför nationalparkens gräns. Den totala fågeltätheten var densamma innanför och utanför och de skillnader som fanns på artnivå var inte entydiga. En jämförelse mellan milrutterna och angränsande standardrutter, inventerade på 2000-talet, gjordes. De skillnader i fågeltätheter som observerades kan ge vissa antydningar om förändringar i fågelfaunan, men tolkningen är mycket osäker eftersom mil- och standardrutter inte är identiska utan har olika biotopsammansättning. Rekommendationen inför återinventering är att i första hand välja milrutterna i Abisko och i andra hand milrutterna i de tre barrskogsomårdena. Provytorna har lägre prioritet. Abisko ges prioritet både för att materialet är så gediget och för att fågelarterna i björk- och lågfjällszonerna länge varit betydligt sämre övervakade än arterna i skogslandet
Bevakning av häckningsframgången hos staren. Årsrapport för 2009
No full text(1) Antal starar som skrider till häckning i bevakningsområdena och som således ligger till grund för analys av häckningens förlopp och produktionen av ungar samt möjliggör provtagning för miljögiftsanalyser är efter uppsättning av kompletteringsholkar i vissa av områdena nu helt tillfredsställande i Grimsö, Kvismaren, Tiveden, Svartedalen, Fleringe, Ottenby och Revinge. I Berg har antal häckningar minskat och om trenden inte vänder kan en kompletterande holkgrupp komma att behövas. För Tyresta behövs ett kompletterings- eller ersättningsområde. (2) Den genomsnittliga äggkullstorleken var hög 2009, men andelen flygga ungar var däremot låg i förhållande till vad som gällt under senare delen av 1990-talet och 2000-talet. Den var dock högre än många år under 1980-talet och första delen av 1990-talet. Långsiktigt över hela bevakningsperioden sedan början av 1980-talet finns inga övergripande negativa trender. (3) Äggläggningen startade 2009 tidigare än någonsin i flera av områdena och nytt tidighetsrekord slogs i en holk i Fleringe där första ägget lades 16 april. Starens häckningsstart och häckningsframgång är känsliga för vårens väder och därför indikatorer på effekter av klimatförändringar
The Effect of Snow on Plants and Their Interactions with Herbivores.
No full textThe ongoing climate changes are predicted to accelerate fast in arctic regions with increases in both temperatures and precipitation. Although the duration of snow cover is generally expected to decrease in the future, snow depth may paradoxically increase in those areas where a large amount of the elevated precipitation will fall as snow. The annual distribution and duration of snow are important features in arctic ecosystems, influencing plant traits and species interactions in various ways. In this thesis, I investigated the effect of snow on plants and their interactions with herbivores by experimentally increasing the snow cover by snow fences in three different habitats along an environmental gradient in Abisko, northern Sweden. I found that the snow cover mattered for plant quality as food for herbivores and herbivore performance. An enhanced and prolonged snow cover increased the level of insect herbivory on dwarf birch leaves under field conditions. Autumnal moth larvae feeding on leaves that had experienced increased snow-lie grew faster and pupated earlier than larvae fed with leaves from control plots. These findings indicated that plants from snow-rich plots produced higher-quality food for herbivores. My studies showed that differences in snow-lie explained parts of the within-year spatial and seasonal variation in plant chemistry and patterns of herbivory in this arctic landscape. The relationship between leaf nitrogen concentration and plant phenology was consistent between treatments and habitats, indicating that snow per se, via a delayed phenology, was controlling the nitrogen concentration. The relationship between leaf age and level of herbivory was positive in the beginning of the growing season, but negative in the end of the growing season, indicating an increasing importance of plant palatability and a decreasing importance of exposure time in determining the level of herbivory throughout the growing season. The concentrations of phenolics varied among habitats, treatments and sampling occasions, suggesting that these plants were able to retain a mosaic of secondary chemical quality despite altered snow conditions. Furthermore, the nutrient limiting plant growth, according to N:P ratio thresholds, appeared to shift from nitrogen to phosphorus along the topographic gradient from snow-poor ridges to more snow-rich heathlands and fens. Snow addition had, however, no significant effect on other nutrient concentrations than nitrogen and no significant effect on the leaf N:P ratio, indicating that differences in snow cover could not explain the variation in plant nutrient concentrations among habitats. In a five-year study, I found opposing inter-annual effects of increased snow on plant chemistry. In contrast to earlier results, the effect of snow-lie on plant nitrogen concentration was predominantly negative. However, the effect of increased snow cover on the level of herbivory remained predominantly positive. The strong within-year relationship between snow-melt date (via plant phenology) and plant nitrogen concentration and level of herbivory could not predict inter-annual variation in the effect of snow manipulation. I did not find any conclusive evidence for a single factor causing the inter-annual opposing effect of snow addition, but the results indicated that interactions with summer and winter temperatures might be important. In conclusion, this thesis showed that climate-induced changes in snow conditions will have strong effects on plant traits and plant-herbivore interactions. However, alterations in snow cover do not influence all plant traits and the effect may vary in time and space
Phosphorus availability and microbial respiration across biomes : from plantation forest to tundra
No full textPhosphorus is the main limiting nutrient for plant growth in large areas of the world and the availability of phosphorus to plants and microbes can be strongly affected by soil properties. Even though the phosphorus cycle has been studied extensively, much remains unknown about the key processes governing phosphorus availability in different environments. In this thesis the complex dynamics of soil phosphorus and its availability were studied by relating various phosphorus fractions and soil characteristics to microbial respiration kinetics. The soils used represent a range of aluminium, iron, carbon and total phosphorus content, and were located in four different biomes: subtropical forest, warm temperate forest, boreal forest and tundra. The results showed that NaOH extractable phosphorus, a fraction previously considered to be available to plants only over long time scales, can be accessed by microbes in days or weeks. Microbial phosphorus availability was not related to aluminium or iron content in any of the studied systems, not even in highly weathered soils with high aluminium and iron content. This is in contrast with other studies of soils with high sorption capacity and shows the variability of factors that govern phosphorus availability in different environments. In the boreal forest chronosequence, no difference could be seen with age in total phosphorus content or concentrations of occluded phosphorus forms. However, there were lower concentrations of labile phosphorus forms in older systems, which were correlated with a decrease in microbial respiration. This was most likely related to organic matter quality in the system, and not to geochemical factors. Phosphorus availability was linked to differences in topography (water regime) and vegetation in the tundra ecosystems. The results suggest that the availability of phosphorus, both for microbes and plants, was lower on the meadow vegetation sites compared to the two types of heath vegetation. Many factors are important for phosphorus availability in soils, but these results suggest that microbes can access less available phosphorus if not restricted by carbon, and this may be important in regard to forest management practices as well as effects of environmental change
Carbon metabolism in clear-water and brown-water lakes
No full textThe trophic state of lakes is commonly defined by the concentration of nutrients in the water column. High nutrient concentrations generate high phytoplankton production, and lakes with low nutrient concentrations are considered low-productive. This simplified view of lake productivity ignores the fact that benthic primary producers and heterotrophic bacteria can be important basal producers in lake ecosystems. In this thesis I have studied clear-water and brown-water lakes with respect to primary production, respiration and bacterial production based on allochthonous organic carbon. These processes were quantified in pelagic and benthic habitats on temporal and spatial scales. I also calculated the net ecosystem production of the lakes, defined as the difference between gross primary production (GPP) and respiration (R). The net ecosystem production indicates whether a lake is net heterotrophic (GPP < R), net autotrophic (GPP > R) or in metabolic balance (GPP = R). Net heterotrophic lakes are sources of carbon dioxide (CO2) to the atmosphere since respiration in these lakes, by definition, is subsidized by an external organic carbon source. External organic carbon is transported to lakes from the terrestrial environment via inlets, and can serve as a carbon source for bacteria but it also limits light availability for primary producers by absorbing light. On a seasonal scale, four of the clear-water lakes studied in this thesis were dominated by primary production in the soft-bottom benthic habitat and by respiration in the pelagic habitat. Concentrations of dissolved organic carbon (DOC) were low in the lakes, but still high enough to cause the lakes to be net heterotrophic. However, the lakes were not low-productive due to the high production in the benthic habitat. One of the clear-water lakes was studied also during the winter and much of the respiration under ice was supported by the benthic primary production from the previous summer. This is in contrast to brown-water lakes where winter respiration is suggested to be supported by allochthonous organic carbon. By studying lakes in a DOC gradient (i.e. from clear-water to brown-water lakes) I could draw two major conclusions. The lakes became less productive since benthic primary production decreased with increasing light extinction, and the lakes became larger sources of CO2 to the atmosphere since pelagic respiration was subsidized by allochthonous organic carbon. Thus, lake carbon metabolism can have an important role in the global carbon cycle due to their processing of terrestrial organic carbon and to their possible feedback effects on the climate system
Population Differentiation in Solidago virgaurea along Altitudinal Gradients
No full textAltitudinal gradients offer attractive opportunities for studies of population differentiation in response to environmental heterogeneity. In this thesis, I examined population differentiation along altitudinal gradients by combining common-garden experiments with field studies and experiments in alpine, subalpine and boreal populations of the perennial herb Solidago virgaurea. More specifically, I determined whether leaf physiology in terms of nitrogen concentration and resorption, flowering phenology, flower production and reproductive effort vary along altitudinal gradients. Nitrogen concentration in green leaves were higher in alpine than in subalpine and boreal populations. These differences persisted when plants were grown from seeds in a common-garden experiment at two sites, suggesting that the differences have a genetic component. There was mixed support for a trade-off between maximized carbon gain through the maintenance of high nitrogen concentration, and minimized nitrogen loss through high resorption. In their natural habitats alpine populations began flowering later than subalpine populations, but this difference was reversed when plants were grown in a common environment. This suggests that genetic differences among populations counteract environmental effects and reduce phenotypic variation in flowering time among populations. Flowering time thus shows countergradient genetic variation in S. virgaurea. In a common-garden experiment, boreal populations produced more flowers and had a higher reproductive effort than subalpine and alpine populations indicating habitat-specific genetic differences in reproductive allocation. In a field study, which included three populations, seed set was close to zero in the alpine population, intermediate in the subalpine population, and high in the boreal population. Experimental flower removal showed that seed production was associated with a considerable cost in terms of reduced flowering propensity the following year, but did not support the hypothesis that a large floral display is important for pollination success
Survey of waste water disposal practices at Antarctic research stations
No full textSource: Polardok by Swedish Polar Research Secretariat</p
Holocene climate and atmospheric circulation changes in northern Fennoscandia : Interpretations from lacustrine oxygen isotope records
No full textThis thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.</p