| 41. |
- Hugelius, Gustaf, 1980-
(författare)
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Quantity and quality of soil organic matter in permafrost terrain
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High latitude terrestrial ecosystems are considered key components in the global carbon (C) cycle and hold large reservoirs of soil organic carbon (SOC). Much of this is stored as soil organic matter (SOM) in permafrost soils and peat deposits and is vulnerable to remobilization under future global warming. While the large size and potential vulnerability of arctic SOM reservoirs is recognized, detailed knowledge on its landscape partitioning and quality is poor. This thesis describes total storage, landscape partitioning and lability of SOM stored in permafrost areas of Canada and Russia. Detailed studies of SOC partitioning highlight the importance of especially permafrost peatlands, but also of O-horizons in moist tundra soils and cryoturbated soil horizons. A general characterization of SOM in an area of discontinuous permafrost shows that >70% of the SOC in the landscape is stored in SOM with a low degree of decomposition. Projections of permafrost thaw predict that the amount of SOC stored in the active layer of permafrost soils in this area could double by the end of this century. A lateral expansion of current thermokarst lakes by 30 m would expose comparable amounts of SOC to degradation. The results from this thesis have demonstrated the value of high-resolution studies of SOC storage. It is found that peat plateaus, common in the sporadic and discontinuous permafrost zones, store large quantities of labile SOM and may be highly susceptible to permafrost degradation, especially thermokarst, under future climate warming. Large quantities of labile SOM is also stored in cryoturbated soil horizons which may be affected by active layer warming and deepening. The current upscaling methodology is statistically evaluated and recommendations are given for the design of future studies. To accurately predict responses of periglacial C pools to a warming climate detailed studies of SOC storage and partitioning in different periglacial landscapes are needed.
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| 42. |
- Hugelius, Gustaf, 1980-
(författare)
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Soil organic carbon in permafrost terrain : Total storage, landscape distribution and environmental controls
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High latitude terrestrial ecosystems are considered key components in the global carbon (C) cycle and hold large reservoirs of soil organic carbon (SOC). To a large degree, this SOC is stored in permafrost soils and peatlands and is vulnerable to remobilization under future global warming and permafrost thawing. Recent studies estimate that soils in permafrost regions store SOC equivalent to ~ 1.5 times the global atmospheric C pool. Ecosystems and soils interact with the atmospheric C pool; photosynthesis sequesters CO2 into SOC whereas microbial decomposition releases C based trace gases (mainly CO2 and CH4). Because of the radiative greenhouse properties of these gases, soil processes also feedback on the global climate system. Recent studies report increases in permafrost temperatures and under future climate change scenarios permafrost environments stand to undergo further changes. As permafrost thaws and surface hydrology changes, there is concern that periglacial tundra and peatland ecosystems will switch from being sinks for atmospheric C into sources, creating a potential for positive feedbacks on global warming. The magnitude of change in C fluxes resulting from climate warming and permafrost thawing depends on the remobilization processes affecting SOC stores, the size of SOC stores that become available for remobilization and the lability of the SOM compounds in these stores. While the large size and potential vulnerability of arctic SOC reservoirs is recognized, detailed knowledge on the landscape partitioning and quality of this SOC is poor. Paper I of this thesis assesses landscape allocation and environmental gradients in SOC storage in the Usa River Basin lowlands of northeastern European Russia. The Russian study area ranges from taiga region with isolated permafrost patches to tundra region with nearly continuous permafrost. Paper II of this thesis investigates total storage, landscape partitioning and quality of soil organic carbon (SOC) in the tundra and continuous permafrost terrain of the Tulemalu Lake area in the Central Canadian Arctic. Databases on soil properties, permafrost, vegetation and modeled climate are compiled and analyzed. Mean SOC storage in the two study regions is 38.3 kg C m-2 for the Usa River Basin and 33.8 kg C m-2 for Tulemalu Lake (for 1m depth in mineral soils and total depth of peat deposits). Both estimates are higher than previous estimates for the same study areas. Multivariate gradient analyses from the Usa Basin show that local vegetation and permafrost are strong predictors of soil chemical properties, overshadowing the effect of climate variables. The results highlight the importance of peatlands, particularly bogs, in bulk SOC storage in all types of permafrost terrain. In the Tulemalu Lake area significant amounts of SOC is stored in cryoturbated soil horizons with C/N ratios indicating a relatively low degree of decomposition. As this pool of cryoturbated SOC is mainly stored in the active layer, no dramatic increases in remobilization are expected following a deepening of the active layer. However, recent studies have demonstrated the importance of SOC storage in deep (>1m) cryoturbated horizons. Perennially frozen peat deposits in permafrost bogs constitute the main vulnerable SOC pool in the investigated regions. Remobilization of this frozen C can occur through gradual but widespread deepening of the active layer with subsequent talik formation, or through more rapid but localized thermokarst erosion.
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| 43. |
- Hugelius, Gustaf, et al.
(författare)
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Soil Organic Carbon Pools in a Periglacial Landscape; a Case Study from the Central Canadian Arctic
- 2010
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Ingår i: Permafrost and Periglacial Processes. - : Wiley. - 1045-6740 .- 1099-1530. ; 21:1, s. 16-29
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Tidskriftsartikel (refereegranskat)abstract
- We investigated total storage and landscape partitioning of soil organic carbon (SOC) in continuous permafrost terrain, central Canadian Arctic. The study is based on soil chemical analyses of pedons sampled to 1-m depth at 35 individual sites along three transects. Radiocarbon dating of cryoturbated soil pockets, basal peat and fossil wood shows that cryoturbation processes have been occurring since the Middle Holocene and that peat deposits started to accumulate in a forest-tundra environment where spruce was present (∼6000 cal yrs BP). Detailed partitioning of SOC into surface organic horizons, cryoturbated soil pockets and non-cryoturbated mineral soil horizons is calculated (with storage in active layer and permafrost calculated separately) and explored using principal component analysis. The detailed partitioning and mean storage of SOC in the landscape are estimated from transect vegetation inventories and a land cover classification based on a Landsat satellite image. Mean SOC storage in the 0–100-cm depth interval is 33.8 kg C m−2, of which 11.8 kg C m−2 is in permafrost. Fifty-six per cent of the total SOC mass is stored in peatlands (mainly bogs), but cryoturbated soil pockets in Turbic Cryosols also contribute significantly (17%). Elemental C/N ratios indicate that this cryoturbated soil organic matter (SOM) decomposes more slowly than SOM in surface O-horizons.
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| 44. |
- Hugelius, Gustaf
(författare)
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Spatial upscaling using thematic maps : an analysis of uncertainties in permafrost soil carbon estimates
- 2012
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 26, s. GB2026-
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Tidskriftsartikel (refereegranskat)abstract
- Studies of periglacial regions confirm their importance in the global carbon (C) cycle, but estimates of ecosystem C storage or green-house gas fluxes from these remote areas are generally poorly constrained and quantitative estimates of upscaling uncertainties are lacking. In this study, a regional database describing soil organic carbon (SOC) storage in periglacial terrain (European Russian Arctic) was used to evaluate spatial upscaling from point measurements using thematic maps. The selection of classes for upscaling and the need for replication in soil sampling were statistically evaluated. Upscaling using a land cover classification and a soil map estimated SOC storage to 48.5 and 47.0 kg C m(-2), respectively with 95% confidence intervals (CI) within +/- 8%. When corrected for spatial errors in the LCC upscaling proxy, SOC was estimated to 46.5 kg C m(-2) with a 95% CI reflecting propagated variance from both natural variability and spatial errors of +/- 11%. Artificially decreasing the size of the database used for upscaling showed that relatively stable results could be achieved with lower replication in some upscaling classes. Decreased spatial resolution for upscaling from 30 m to 1 km had little impact on SOC estimates in this region, but classification accuracy was dramatically reduced and land cover classes show different, sometimes nonlinear, responses to scale. The methods and recommendations presented here can provide guidelines for any future study where point observations of a variable are upscaled using remotely sensed thematic maps or classifications and potential applications for circum-arctic studies are discussed. For future upscaling studies at large geographic scales, a priori determination of sample sizes and tests to insure unimodal and statistically independent samples are recommended. If these prerequisites are not fulfilled, classes may be merged or subdivided prior to upscaling.
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| 45. |
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| 46. |
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| 47. |
- Hugelius, Gustaf, 1980-
(författare)
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Uncertainty analysis for estimates of soil organic carbon storage in permafrost terrain, a regionalstudy from the western Russian Arctic
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Studies of periglacial regions confirm their importance in the global carbon (C) cycle,but estimates of e.g. soil organic carbon (SOC) storage are poorly constrained and lack quantitativeestimates of errors following upscaling. In this study, a comprehensive regional SOC database from thenorthern Usa River Basin (European Russian Arctic, 55 000 km2) is used to evaluate the currentmethodology of SOC upscaling in periglacial terrain. The selection of classes for upscaling and the need forreplication in soil sampling are statistically evaluated. Upscaling using a land cover classification and a soilmap estimates SOC storage at 48.5 and 47.0 kg C m-2, respectively with 95% confidence intervals (CI)within ±8%. When corrected for spatial errors in the upscaling proxy, SOC is estimated to 46.5 kg C m-2with a 95% CI reflecting propagated variance from both natural variability and spatial errors of ±11%.Artificially decreasing the size of the database used for upscaling shows that relatively stable results can beachieved with lower replication in some upscaling classes. For future upscaling studies at large geographicscales, a priori determination of sample sizes and tests to insure unimodal and statistically independentsamples are recommended. If these prerequisites are not fulfilled, classes may be merged or subdividedprior to upscaling. Decreased spatial resolution for upscaling from 30 m to 1 km has little impact on SOCestimates in this region, but classification accuracy is dramatically reduced and land cover classes show different, sometimes non-linear, responses to scale.
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| 48. |
- Humborg, Christoph, et al.
(författare)
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Environmental Impacts - Freshwater Biogeochemistry
- 2015
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Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 307-336
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Bokkapitel (refereegranskat)abstract
- Climate change effects on freshwater biogeochemistry and riverine loads of biogenic elements to the Baltic Sea are not straight forward and are difficult to distinguish from other human drivers such as atmospheric deposition, forest and wetland management, eutrophication and hydrological alterations. Eutrophication is by far the most well-known factor affecting the biogeochemistry of the receiving waters in the various sub-basins of the Baltic Sea. However, the present literature review reveals that climate change is a compounding factor for all major drivers of freshwater biogeochemistry discussed here, although evidence is still often based on short-term and/or small-scale studies.
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| 49. |
- Humborg, Christoph, et al.
(författare)
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Environmental Impacts—Freshwater Biogeochemistry
- 2015
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Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 307-336
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 50. |
- Jackson, Robert B., et al.
(författare)
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Human well-being and per capita energy use
- 2022
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Ingår i: Ecosphere. - : Wiley. - 2150-8925 .- 2150-8925. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Increased wealth and per capita energy use have transformed lives and shaped societies, but energy poverty remains a global challenge. Previous research has shown positive relationships among metrics of health and happiness and economic indices such as income and gross domestic product and between energy use and human development. To our knowledge, however, no comprehensive assessment has examined to what extent energy use may limit national-level trends in such metrics. We analyze the maximum global performance of nine health, economic, and environmental metrics by country, determining which metrics increase with per capita energy use and which show thresholds or plateaus in maximum performance. Across the dataset, eight of nine metrics, including life expectancy, infant mortality, happiness, food supply, and access to basic sanitation services, improve steeply and then plateau at levels of average primary annual energy consumption between 10 and 75 GJ person−1 computed nationally (five metrics plateau between 10 and 30 GJ person−1). One notable exception is air quality (energy threshold of 125 GJ person−1 across 133 countries). Averaged across metrics, the 10 countries (with at least seven metrics) showing the best performance given their per capita primary energy use are Malta, Sri Lanka, Cuba, Albania, Iceland, Finland, Bangladesh, Norway, Morocco, and Denmark. If distributed equitably, today's average global energy consumption of 79 GJ person−1 could, in principle, allow everyone on Earth to realize 95% or more of maximum performance across all metrics (and assuming no other limiting factors). Dozens of countries have average per capita energy use below this 79 GJ energy sufficiency threshold, highlighting the need to combat energy poverty. Surprisingly, our analysis also suggests that reduced per capita primary energy consumption could in principle occur in many higher energy-consuming countries with little or no loss in health, happiness, or other outcomes, reducing the need for global energy infrastructure and increasing global equity.
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