| 1. |
- Audet, J., et al.
(författare)
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Forest streams are important sources for nitrous oxide emissions
- 2020
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26:2, s. 629-641
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Tidskriftsartikel (refereegranskat)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6±2.1 and 1.3±1.8µgN/L, respectively (mean±SD) despite higher total N (TN) concentrations in agricultural streams (1,520±1,640 vs. 780±600µgN/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8×109g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800×109gCO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. © 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd
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| 2. |
- Campeau, Audrey, et al.
(författare)
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Current forest carbon fixation fuels stream CO 2 emissions
- 2019
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Stream CO 2 emissions contribute significantly to atmospheric climate forcing. While there are strong indications that groundwater inputs sustain these emissions, the specific biogeochemical pathways and timescales involved in this lateral CO 2 export are still obscure. Here, via an extensive radiocarbon ( 14 C) characterisation of CO 2 and DOC in stream water and its groundwater sources in an old-growth boreal forest, we demonstrate that the 14 C-CO 2 is consistently in tune with the current atmospheric 14 C-CO 2 level and shows little association with the 14 C-DOC in the same waters. Our findings thus indicate that stream CO 2 emissions act as a shortcut that returns CO 2 recently fixed by the forest vegetation to the atmosphere. Our results expose a positive feedback mechanism within the C budget of forested catchments, where stream CO 2 emissions will be highly sensitive to changes in forest C allocation patterns associated with climate and land-use changes. © 2019, The Author(s).
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| 3. |
- Hurry, V.M., et al.
(författare)
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Effects of growth at cold hardening temperatures and temperature shifts on resistance to photoinhibition
- 1993
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Ingår i: Advances in plant cold hardiness. - Boca Raton : CRC Press. - 9781351069526 - 0849349508 ; , s. 103-112
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Bokkapitel (refereegranskat)abstract
- This chapter presents a summary of results that illustrate the photosynthetic responses of cold-tolerant cereals, spinach, and pine to low temperature-induced photoinhibition. Pre Exposure to a low temperature regime induces a cold-hardened state that imparts a certain level of freezing resistance and enhances the winter survival of the seedlings under natural conditions. Photosynthesis provides the energy for this cold hardening process. The phenomenon of resistance to photoinhibition was examined at several levels of cellular organization in winter rye: isolated thylakoids; isolated, intact mesophyll cells; and leaf segments. In contrast to the herbaceous cold-tolerant plants, Scots pine exposed to cold hardening conditions exhibited the same susceptibility to low temperature-induced photoinhibition as nonhardened Scots pine. To attain maximum cold hardiness, the herbaceous plants grow and develop at low temperatures and, as a consequence, develop a resistance to low temperature photoinhibition. The capacity to down-regulate PSII through photoinhibition may be an important characteristic that separates cold-tolerant from chilling-sensitive plant species.
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| 4. |
- Johansson, Elisabeth, et al.
(författare)
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Methane emissions from a constructed wetland treating wastewater : Seasonal and spatial distribution and dependence on edaphic factors
- 2004
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 38:18, s. 3960-3970
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Tidskriftsartikel (refereegranskat)abstract
- Constructed wetlands for wastewater treatment have many advantages. They can be used for several purposes, for example, to reduce levels of organic matter and nutrients, and to retain toxic metals. However, most wetlands are inherently net sources of gaseous compounds like methane and nitrous oxide, which are of environmental concern due to their rapid current accumulation in the atmosphere and their potent global warming capacity. In order to determine the flux of methane from a constructed wetland a study was conducted over two growth seasons on a pilot scale wetland constructed to reduce nutrient levels in secondary treated wastewater. The emissions for the spring to autumn period averaged 141 mg CH4 m-2 d-1 (S.D.=187), ranging from consumption of 375 mg CH4 m-2 d-1 to emissions of 1739 mg CH4 m-2 d-1. The spatial and temporal variations were large, but could be accounted for by measured environmental factors. Among these factors, sediment and water temperatures were significant in all cases and independent of the scale of analysis (r2 up to 0.88).
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| 5. |
- Björkman, G., et al.
(författare)
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Att genomföra och avrapportera projektarbetsuppgifter på delkurs PK:1
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta är en rapport om hur man bedriver och avrapporterar projektarbete på kurs PK:1 i informationsbehandling. Rapporten beskriver de olika momenten i projektarbetet och innehåller dessutom regler och anvisningar för detta arbete. Rapporten försöker även förmedla tips och erfarenheter från tidigare terminer beträffande kurs PK:1
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| 6. |
- Chow, Wah Soon, et al.
(författare)
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Quantifying and monitoring functional photosystem II and the stoichiometry of the two photosystems in leaf segments : approaches and approximations
- 2012
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Ingår i: Photosynthesis Research. - Dordrecht : Springer. - 0166-8595 .- 1573-5079. ; 113:1-3, s. 63-74
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Forskningsöversikt (refereegranskat)abstract
- Given its unique function in light-induced water oxidation and its susceptibility to photoinactivation during photosynthesis, photosystem II (PS II) is often the focus of studies of photosynthetic structure and function, particularly in environmental stress conditions. Here we review four approaches for quantifying or monitoring PS II functionality or the stoichiometry of the two photosystems in leaf segments, scrutinizing the approximations in each approach. (1) Chlorophyll fluorescence parameters are convenient to derive, but the information-rich signal suffers from the localized nature of its detection in leaf tissue. (2) The gross O-2 yield per single-turnover flash in CO2-enriched air is a more direct measurement of the functional content, assuming that each functional PS II evolves one O-2 molecule after four flashes. However, the gross O-2 yield per single-turnover flash (multiplied by four) could over-estimate the content of functional PS II if mitochondrial respiration is lower in flash illumination than in darkness. (3) The cumulative delivery of electrons from PS II to P700(+) (oxidized primary donor in PS I) after a flash is added to steady background far-red light is a whole-tissue measurement, such that a single linear correlation with functional PS II applies to leaves of all plant species investigated so far. However, the magnitude obtained in a simple analysis (with the signal normalized to the maximum photo-oxidizable P700 signal), which should equal the ratio of PS II to PS I centers, was too small to match the independently-obtained photosystem stoichiometry. Further, an under-estimation of functional PS II content could occur if some electrons were intercepted before reaching PS I. (4) The electrochromic signal from leaf segments appears to reliably quantify the photosystem stoichiometry, either by progressively photoinactivating PS II or suppressing PS I via photo-oxidation of a known fraction of the P700 with steady far-red light. Together, these approaches have the potential for quantitatively probing PS II in vivo in leaf segments, with prospects for application of the latter two approaches in the field.
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| 7. |
- Ehnvall, Betty, et al.
(författare)
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Catchment characteristics control boreal mire nutrient regime and vegetation patterns over ~5000 years of landscape development
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 895
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Tidskriftsartikel (refereegranskat)abstract
- Vegetation holds the key to many properties that make natural mires unique, such as surface microtopography, high biodiversity values, effective carbon sequestration and regulation of water and nutrient fluxes across the landscape. Despite this, landscape controls behind mire vegetation patterns have previously been poorly described at large spatial scales, which limits the understanding of basic drivers underpinning mire ecosystem services. We studied catchment controls on mire nutrient regimes and vegetation patterns using a geographically constrained natural mire chronosequence along the isostatically rising coastline in Northern Sweden. By comparing mires of different ages, we can partition vegetation patterns caused by long-term mire succession (<5000 years) and present-day vegetation responses to catchment eco-hydrological settings. We used the remote sensing based normalized difference vegetation index (NDVI) to describe mire vegetation and combined peat physicochemical measures with catchment properties to identify the most important factors that determine mire NDVI. We found strong evidence that mire NDVI depends on nutrient inputs from the catchment area or underlying mineral soil, especially concerning phosphorus and potassium concentrations. Steep mire and catchment slopes, dry conditions and large catchment areas relative to mire areas were associated with higher NDVI. We also found long-term successional patterns, with lower NDVI in older mires. Importantly, the NDVI should be used to describe mire vegetation patterns in open mires if the focus is on surface vegetation, since the canopy cover in tree-covered mires completely dominated the NDVI signal. With our study approach, we can quantitatively describe the connection between landscape properties and mire nutrient regime. Our results confirm that mire vegetation responds to the upslope catchment area, but importantly, also suggest that mire and catchment aging can override the role of catchment influence. This effect was clear across mires of all ages, but was strongest in younger mires.
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| 8. |
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| 9. |
- Hurry, Vaughan M., 1960-, et al.
(författare)
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Cold hardening of spring and winter-wheat and rape results in differential-effects on growth, carbon metabolism, and carbohydrate content
- 1995
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 109:2, s. 697-706
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Tidskriftsartikel (refereegranskat)abstract
- The effect of long-term (months) exposure to low temperature (5 degrees C) on growth, photosynthesis, and carbon metabolism was studied in spring and winter cultivars of wheat (Triticum aestivum) and rape (Brassica napus). Cold-grown winter rape and winter wheat maintained higher net assimilation rates and higher in situ CO2 exchange rates than the respective cold-grown spring cultivars. In particular, the relative growth rate of spring rape declined over time at low temperature, and this was associated with a 92% loss in in situ CO2 exchange rates. Associated with the high photosynthetic rates of cold-grown winter cultivars was a P-fold increase per unit of protein in both stromal and cytosolic fructose-1,6-bisphosphatase activity and a 1.5- to 2-fold increase in sucrose-phosphate synthase activity. Neither spring cultivar increased enzyme activity on a per unit of protein basis. We suggest that the recovery of photosynthetic capacity at low temperature and the regulation of enzymatic activity represent acclimation in winter cultivars. This allows these overwintering herbaceous annuals to maximize the production of sugars with possible cryoprotective function and to accumulate sufficient carbohydrate storage reserves to support basal metabolism and regrowth in the spring.
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| 10. |
- Hurry, Vaughan, 1960-, et al.
(författare)
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Mitochondria contribute to increased photosynthetic capacity of leaves of winter rye (Secale-Cereale L) following cold-hardening
- 1995
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Ingår i: Plant, Cell and Environment. - 0140-7791 .- 1365-3040. ; 18:1, s. 69-76
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Tidskriftsartikel (refereegranskat)abstract
- Cold-hardening of winter rye (Secale cereale L. cv. Musketeer) increased dark respiration from -2.2 to -3.9 mu mol O-2 m(-2)s(-1) and doubled light- and CO2-saturated photosynthesis at 20 degrees C from 18.1 to 37.0 mu mol O-2 m(-2) s(-1). We added oligomycin at a concentration that specifically inhibits oxidative phosphorylation to see whether the observed increase in dark respiration reflected an increase in respiration in the light, and whether this contributed to the enhanced photosynthesis of cold-hardened leaves, Oligomycin inhibited light- and CO2-saturated rates of photosynthesis in non-hardened and cold-hardened leaves by 14 and 25%, respectively, and decreased photochemical quenching of chlorophyll a fluorescence to a greater degree in cold-hardened than in non-hardened leaves, These data indicate an increase both in the rate of respiration in the light, and in the importance of respiration to photosynthesis following cold-hardening, Analysis of metabolite pools indicated that oligomycin inhibited photosynthesis by limiting regeneration of ribulose-1,5-bisphosphate, This limitation was particularly severe in cold-hardened leaves, and the resulting low 3-phosphoglycerate pools led to a feed-forward inhibition of sucrose-phosphate synthase activity, Thus, it does not appear that oxidative phosphorylation supports the increase in photosynthetic O-2 evolution following cold-hardening by increasing the availability of cytosolic ATP, The data instead support the hypothesis that the mitochondria function in the light by using the reducing equivalents generated by nan-cyclic photosynthetic electron transport.
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| 11. |
- Ivanov, A. G., et al.
(författare)
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Implications of alternative electron sinks in increased resistance of PSII and PSI photochemistry to high light stress in cold-acclimated Arabidopsis thaliana
- 2012
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Ingår i: Photosynthesis Research. - Dordrecht : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 113:1-3, s. 191-206
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Tidskriftsartikel (refereegranskat)abstract
- Exposure of control (non-hardened) Arabidopsis leaves to high light stress at 5 A degrees C resulted in a decrease of both photosystem II (PSII) (45 %) and Photosystem I (PSI) (35 %) photochemical efficiencies compared to non-treated plants. In contrast, cold-acclimated (CA) leaves exhibited only 35 and 22 % decrease of PSII and PSI photochemistry, respectively, under the same conditions. This was accompanied by an accelerated rate of P700(+) re-reduction, indicating an up-regulation of PSI-dependent cyclic electron transport (CET). Interestingly, the expression of the NDH-H gene and the relative abundance of the Ndh-H polypeptide, representing the NDH-complex, decreased as a result of exposure to low temperatures. This indicates that the NDH-dependent CET pathway cannot be involved and the overall stimulation of CET in CA plants is due to up-regulation of the ferredoxin-plastoquinone reductase, antimycin A-sensitive CET pathway. The lower abundance of NDH complex also implies lower activity of the chlororespiratory pathway in CA plants, although the expression level and overall abundance of the other well-characterized component involved in chlororespiration, the plastid terminal oxidase (PTOX), was up-regulated at low temperatures. This suggests increased PTOX-mediated alternative electron flow to oxygen in plants exposed to low temperatures. Indeed, the estimated proportion of O-2-dependent linear electron transport not utilized in carbon assimilation and not directed to photorespiration was twofold higher in CA Arabidopsis. The possible involvement of alternative electron transport pathways in inducing greater resistance of both PSII and PSI to high light stress in CA plants is discussed.
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| 12. |
- Ivanov, Alexander G., et al.
(författare)
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The decreased PG content of pgp1 inhibits PSI photochemistry and limits reaction center and light-harvesting polypeptide accumulation in response to cold acclimation
- 2022
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Ingår i: Planta. - : Springer. - 0032-0935 .- 1432-2048. ; 255:2
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Tidskriftsartikel (refereegranskat)abstract
- Main conclusion: Decreased PG constrains PSI activity due to inhibition of transcript and polypeptide abundance of light-harvesting and reaction center polypeptides generating a reversible, yellow phenotype during cold acclimation of pgp1.Cold acclimation of the Arabidopsis pgp1 mutant at 5 °C resulted in a pale-yellow phenotype with abnormal chloroplast ultrastructure compared to its green phenotype upon growth at 20 °C despite a normal cold-acclimation response at the transcript level. In contrast, wild type maintained its normal green phenotype and chloroplast ultrastructure irrespective of growth temperature. In contrast to cold acclimation of WT, growth of pgp1 at 5 °C limited the accumulation of Lhcbs and Lhcas assessed by immunoblotting. However, a novel 43 kD polypeptide of Lhcb1 as well as a 29 kD polypeptide of Lhcb3 accumulated in the soluble fraction which was absent in the thylakoid membrane fraction of cold-acclimated pgp1 which was not observed in WT. Cold acclimation of pgp1 destabilized the Chl–protein complexes associated with PSI and predisposed energy distribution in favor of PSII rather than PSI compared to the WT. Functionally, in vivo PSI versus PSII photochemistry was inhibited in cold-acclimated pgp1 to a greater extent than in WT relative to controls. Greening of the pale-yellow pgp1 was induced when cold-acclimated pgp1 was shifted from 5 to 20 °C which resulted in a marked decrease in excitation pressure to a level comparable to WT. Concomitantly, Lhcbs and Lhcas accumulated with a simultaneous decrease in the novel 43 and 29kD polypeptides. We conclude that the reduced levels of phosphatidyldiacylglycerol in the pgp1 limit the capacity of the mutant to maintain the structure and function of its photosynthetic apparatus during cold acclimation. Thus, maintenance of normal thylakoid phosphatidyldiacylglycerol levels is essential to stabilize the photosynthetic apparatus during cold acclimation.
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| 13. |
- Maljanen, M, et al.
(författare)
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Nitrous oxide production in boreal soils with variable organic matter content at low temperature – snow manipulation experiment
- 2009
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Ingår i: Biogeosciences. - : Copernicus Publications on behalf of the European Geosciences Union. - 1726-4170 .- 1726-4189. ; 6:11, s. 2461-73
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural soils are the most important sources for the greenhouse gas nitrous oxide (N2O), which is produced and emitted from soils also at low temperatures. The processes behind emissions at low temperatures are still poorly known. Snow is a good insulator and it keeps soil temperature rather constant. To simulate the effects of a reduction in snow depth on N2O emission in warming climate, snow pack was removed from experimental plots on three different agricultural soils (sand, mull, peat). Removal of snow lowered soil temperature and increased the extent and duration of soil frost in sand and mull soils. This led to enhanced N2O emissions during freezing and thawing events. The cumulative emissions during the first year when snow was removed over the whole winter were 0.25, 0.66 and 3.0 g N2O-N m−2 yr−1 in control plots of sand, mull and peat soils, respectively. In the treatment plots, without snow cover, the respective cumulative emissions were 0.37, 1.3 and 3.3 g N2O-N m−2 yr−1. Shorter snow manipulation during the second year did not increase the annual emissions. Only 20% of the N2O emission occurred during the growing season. Thus, these results highlight the importance of the winter season for this exchange and that the year-round measurements of annual N2O emissions from boreal soils are integral for estimating their N2O source strength. N2O accumulated in the frozen soil during winter and the soil N2O concentration correlated with the depth of frost but not with the winter N2O emission rates per se. Also laboratory incubations of soil samples showed high production rates of N2O at temperatures below 0°C, especially in the sand and peat soils.
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| 14. |
- Noumonvi, Koffi Dodji, et al.
(författare)
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The Kulbäcksliden research infrastructure : a unique setting for northern peatland studies
- 2023
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Ingår i: Frontiers in Earth Science. - : Frontiers Media S.A.. - 2296-6463. ; 11
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Forskningsöversikt (refereegranskat)abstract
- Boreal peatlands represent a biogeochemically unique and diverse environment in high-latitude landscape. They represent a long-term globally significant sink for carbon dioxide and a source of methane, hence playing an important role in regulating the global climate. There is an increasing interest in deciphering peatland biogeochemical processes to improve our understanding of how anthropogenic and climate change effects regulate the peatland biogeochemistry and greenhouse gas balances. At present, most studies investigating land-atmosphere exchanges of peatland ecosystems are commonly based on single-tower setups, which require the assumption of homogeneous conditions during upscaling to the landscape. However, the spatial organization of peatland complexes might feature large heterogeneity due to its varying underlying topography and vegetation composition. Little is known about how well single site studies represent the spatial variations of biogeochemical processes across entire peatland complexes. The recently established Kulbäcksliden Research Infrastructure (KRI) includes five peatland study sites located less than 3 km apart, thus providing a unique opportunity to explore the spatial variation in ecosystem-scale processes across a typical boreal peatland complex. All KRI sites are equipped with eddy covariance flux towers combined with installations for detailed monitoring of biotic and abiotic variables, as well as catchment-scale hydrology and hydrochemistry. Here, we review studies that were conducted in the Kulbäcksliden area and provide a description of the site characteristics as well as the instrumentation available at the KRI. We highlight the value of long-term infrastructures with ecosystem-scale and replicated experimental sites to advance our understanding of peatland biogeochemistry, hydrology, ecology, and its feedbacks on the environment and climate system.
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| 15. |
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| 16. |
- Öquist, Gunnar, et al.
(författare)
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Why Are Some Nations More Successful Than Others in Research Impact? A Comparison Between Denmark and Sweden
- 2015
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Ingår i: Incentives and Performance: Governance of Research Organizations. - Cham : Springer International Publishing. - 9783319097855 - 9783319097848 ; , s. 241-257
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Bokkapitel (refereegranskat)abstract
- Bibliometric impact analyses show that Swedish research has less international visibility than Danish research. When taking a global view on all subject fields and selecting publications cited higher than the 90th percentile, i.e., the Top 10 %—publications, the Swedish Research Council shows that although Sweden ranks 15 % above world average, Denmark, the Netherlands and Switzerland rank 35–40 % above. To explain these different performances, The Royal Swedish Academy of Sciences asked us to compare the national research systems on three levels: priority setting at national level, governance of universities and direction and funding of research. There are of course many similarities between the Danish and Swedish research systems but there are still subtle differences that have developed over time, which may explain the different international visibility. First of all, it does not depend on different levels of public spending on research and development. However, the core funding of universities relative external funding is higher in Denmark than in Sweden. The academic leadership of Danish universities in terms of board, vice-chancellor, faculty dean and department chair is also more coherent and focused on priority setting, recruitment, organization and deployment of resources to establish research environments that operate at the forefront of international research. On all these points we see a weaker leadership in Sweden. Furthermore, over the last 20 years, public funding of research in Sweden has become more and more unpredictable and program oriented with many new actors, while the Danish funding system, although it also has developed over time, shows more consistency with strong actors to fund individuals with novel ideas. The research policy in Sweden has also developed multiple, sometimes even conflicting goals, which have undermined conditions for high-impact research, while in Denmark a policy to support excellence in research has been more coherent.
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| 17. |
- Öquist, M.G., et al.
(författare)
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Winter soil frost conditions in boreal forests control growing season soil CO2 concentration and its atmospheric exchange
- 2008
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 14:12, s. 2839-2847
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Tidskriftsartikel (refereegranskat)abstract
- The impact of changes in winter soil frost regime on soil CO2 concentration and its atmospheric exchange in a boreal Norway spruce forest was investigated using a field-scale soil frost manipulation experiment. The experiment comprised three treatments: deep soil frost, shallow soil frost and control plots (n = 3). Winter soil temperatures and soil frost distribution were significantly altered by the different treatments. The average soil CO2 concentrations during the growing season were significantly lower in plots with deep soil frost than in plots with shallow soil frost. The average CO2 soil-atmosphere exchange rate exhibited the same pattern, and differences in soil respiration rates among the treatments were statistically significant. Both the variation in soil CO2 concentration and the CO2 soil-atmosphere exchange rate could statistically be explained by the differences in the maximum soil frost depth during the previous winter. A response model for growing season soil respiration rates suggests that every 1 cm change in winter soil frost depth will change the emission rates by ca. 0.01 g CO2 m(-2) day(-1), corresponding to 0.2-0.5% of the estimated net ecosystem productivity (NEP). This suggests that the soil frost regime has a significant influence on the C balance of the system, because interannual variations in soil frost up to 60 cm have been recorded at the site. We conclude that winter climate conditions can be important in controlling C balances in northern terrestrial ecosystems, and also that indirect effects of the winter season must be taken into account, because these can affect the prevailing conditions during the growing season.
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