[en] Western Siberia contains the world's most extensive wetlands. Despite its recognition as a significant global carbon reservoir, the spatial structure and composition of micro-topographical elements in patterned wetlands have never been analyzed in detail. To address this uncertainty, we applied a multi-scale approach to make a general and realistic estimation of land cover in Western Siberia. Our approach was based on using a regional wetland typology map (1:2500 000 scale), further refined by satellite image classifications (LANDSAT TM, ETM+ in 1:200 000 scale) on test areas designated in the boreal region of Western Siberia. In addition, QuickBird imagery was used for evaluation the fraction of area occupied by micro-topographical elements within patterned wetlands. Finally, we estimated the areal fractions of these micro-landscapes composing the vegetation mosaic of 20 classes on the wetland typology map for each climatic region of the study area. The total area of peatlands was calculated at 68.5 x 10⁶ ha, which is higher than earlier estimates. We found almost equal areal extents of ridge-hollow and ridge-hollow-pool patterned wetlands in almost all climatic regions of Western Siberia; in the northern boreal region, however, the ridge-hollow-pool wetland type became dominant and exceeded the areal extent of ridge-hollow wetlands in a proportion of 80-20%. Also, the open water fraction increased dramatically in the northern boreal region. The results of this survey can be used in models of ecosystem carbon dynamics and inventory of trace gas fluxes in wetlands.

[en] We examined the effects of ultraviolet radiation (UVR) on net phosphorus (P) flux into phytoplankton communities in two boreal lakes at the Experimental Lakes Area (ELA), Canada. We manipulated P available to and irradiance received by phytoplankton during four different three-day incubations of dilution bioassays. Net P flux was estimated by measuring the accumulation of particulate P (that retained on glass fiber filters) over the incubation period. No effects of UVR on net P flux were found at ambient P levels in any of the experiments. At the highest levels of P addition, less particulate phosphorus (PP) accumulated in both the minus-UVB (∼15-40%; photosynthetically active radiation (PAR) + UVA) and full-sunlight (∼25-45%; PAR + UVA + UVB) exposed phytoplankton compared with those that received PAR only. Neither chlorophyll- nor carbon-specific net P flux was affected by UVR exposure at ambient P levels. However, at the highest levels of P enrichment, chlorophyll-specific net P flux increased in response to UVR in both lakes, whereas carbon-specific net P flux declined in one of the lakes and was unaffected by UV exposure in the second lake. Our results indicate that UVR can affect total PP accumulation in enriched systems, but not at ambient P levels, and that UVR has a weak and variable effect on biomass-specific P uptake in phytoplankton under enriched conditions. (author)

[en] This study focused on investigating the soil-to-plant transfers of natural uranium and its distribution in the vegetative parts of four plant species representing different plant types common in boreal forest: May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and spruce (Picea abies). The results were also used to assess concentration ratios between soil and different plant parts. (LN)

[en] The effects of a crude oil spill on three distinct sub-arctic environments were examined. One of these was an undisturbed black spruce forest, another a moderately disturbed simulated transport corridor right-of-way, and the third a severely disturbed simulated buried pipeline trench. Trees, shrubs, ground cover and organic layers were removed and the area excavated and refilled to simulate the construction of of a buried small-diameter pipeline. Extensive work was also completed on permafrost degradation and ground subsidence related to the creation of right-of-ways and trenches. The experiment was carried on for three years. By the third year the active layer in the oiled forest increased by about 150 per cent, and in the oiled right-of-way by about 80 per cent. There was no change in the oiled trench. By the third year, the active layers in all oiled environments were significantly deeper than their unoiled counterparts and the active layer in the oiled trench was significantly deeper than in the oiled forest. It was found that this oil spill has caused the greatest increase in thaw depths ever recorded for a crude-oil spill in a sub-arctic forest. The increase in thaw depth was attributed to high oil concentration, especially in the areas where the oil had pooled on the ground. 31 refs., 4 figs

[en] Atmospheric deposition of chemical substances may influence the behaviour of radionuclides in soil and their uptake in plants. This is a fact that has so far received limited attention in radioecological studies. This paper presents briefly two cases where differences in atmospheric deposition of heavy metals from a strong pollution source and marine aerosols, respectively, influence the turnover of radionuclides in natural boreal ecosystems. (au)

[en] Full text: Carbon stocks in boreal forests soils alone are estimated at 470 Gigatons. Boreal forests are expected to face large temperature increases in the next century, as compared to other ecosystems. This will have a significant impact on forest composition and its carbon balance. Northward migration of the entire boreal biome is predicted and, within the main boreal forest, deciduous trees will replace evergreens. The main objective of our research is to assess how this vegetation shift may affect the overall storage and stability of boreal soil carbon. Our work focuses on the boreal mixed wood landscape of western Canada, which consists of a mosaic of deciduous (mostly aspen)- and coniferous (mostly white spruce)-dominated stands. A series of laboratory and field incubations is being conducted using a range of ¹³C-labelled substrates to follow the fate of plant litter as it is processed by the soil microbial communities. Specifically, incubation of ¹³C-labelled aspen litter (leaves, roots, twigs) in spruce soils allows us to quantify effects of vegetation shifts. Carbon assimilation by microbes is tracked by isotope probing of phospholipid fatty acids, and evolved ¹³C-CO₂ and total CO₂ measurements are used to quantify carbon utilization efficiency and overall carbon stability. Results to date indicate that soils under aspen and spruce harbor functionally distinct microbial communities that diverge in their carbon utilization pathways, even for simple labile (i.e.; ¹³C-glucose) compounds. Furthermore, it appears that the community under spruce is less diverse but more active in assimilating ¹³C-labelled aspen litter. Results from this research will help enhance the global soil carbon projections of earth system models, which are singularly lacking in their simulation of microbial processes. (author)

[en] The literature study reported here forms part of an overall objective to review the methods for estimating the greenhouse gas emissions from the agricultural sector. In this report the focus is on the CH₄ and N₂O emissions arising from animal manure management. The IPCC methodology and default parameters are critically reviewed in order to establish their appropriateness under Swedish climatic and agricultural conditions. There are few reported studies which consider the emissions of CH₄ and N₂O from animal manure storage under climatic conditions corresponding to those in Sweden. Studies based on comprehensive, long-term field measurements are even scarcer. This gives a limited basis for recommending new emissions factors or other parameters. There is, however, support for updating some of the parameter values. Recommended changes are summarised in the report. Recommendations are offered on the principle that the IPCC defaults are to be kept unless there is reasonable support for deviation from these. This is done despite the observation that, in some cases, the IPCC defaults are themselves not well supported by published literature. The IPCC methodology consists of a relatively simple model, which aggregates several complex and dynamic influences. An alternate modelling approach has been identified for quantifying methane emissions from slurry systems. This model has a fundamental basis and, with appropriate input information could be employed for estimating Swedish emissions. Another factor, arising in this review, is the importance of the distribution of animals among the management systems. According to the IPCC criteria a portion of the systems which are currently viewed, in the Swedish Inventory, as 'Solid' systems should in fact fall under 'Liquid/Slurry' systems. This may have a significant effect on the overall balance of CH₄ and N₂O emissions. Potentials for improving the accuracy of Swedish emission estimates are identified. The need for studies and field measurements under Swedish conditions is emphasised. Particularly critical areas are: the characterisation of fresh cattle and swine manures, updated estimates for the distribution of manure management systems among so-called 'solid' and 'slurry' systems, measurements of methane from stored cattle and swine solid manure, and, measurement of nitrous oxide emissions from slurry systems with straw or natural-crust covers

[en] The spring sensible heating (SH) over the Tibetan Plateau (TP) serves as a huge ‘air pump’, significantly influencing the Asian summer monsoon, has experienced a decreasing trend. However, it remains unclear whether this decline will continue. Therefore, we here examine the long-term trends of spring SH over the central and eastern TP (CETP) based on a meteorological station-based calculated SH dataset, and CMIP6 multi-model simulations. These two sources confirmed the previous finding that the SH peaks in May. Further, we find that the declining SH was replaced by a fast recovery after approximate 2000 in the station-based SH. This is to some extent verified by the historical simulations of CMIP6 models. Importantly, CMIP6 future projections suggest that this increasing trend will continue, and get stronger with higher radiative forcing from SSP126 to SSP585. Mechanism analysis indicates that the previous decreasing trend in SH was mainly caused by the decline of 10 m wind speed, while the recent and future increasing trend results from the rising ground-air temperature difference. We suggest that this increasing trend of spring SH over the CETP may serve as an alternative driver for the enhancement of the East Asian summer monsoon in the future. (letter)

[en] The issue of bioremediation of heavy oil contaminated soils in cold climates was discussed. No model of the bioremediation system for cold climates exists. Environmental groups use three environmental concepts as the basis to evaluate petroleum activities: (1) cradle to grave responsibility, (2) the precautionary principle, and (3) sustainable development. The reclamation of an abandoned petroleum production facility must meet stringent standards. Most sites are contaminated with weathered hydrocarbons, brine and other chemicals that have been used at the location. Bioremediation, either in-situ or ex-situ, is one of the lowest cost remediation techniques available and has been used extensively by the downstream petroleum industry in warm climates. However, there are many unresolved issues with the use of bioremediation in cold climates, for heavy or weathered crude oil products and in areas of clay or other low permeability. Some of these unresolved issues are highlighted

[en] Estimating global carbon fluxes by inverting atmospheric CO₂ through the use of atmospheric transport models has shown the importance of the covariance between biospheric fluxes and atmospheric transport on the carbon budget. This covariance or coupling occurs on many time scales. This study examines the coupling of the biosphere and the atmosphere on the meso- and synoptic scales using a coupled atmosphere-biosphere regional model covering Canada. The results are compared with surface and light aircraft measurement campaigns at two boreal forest sites in Canada. Associated with cold and warm frontal features, the model results showed that the biospheric fluxes are strongly coupled to the atmosphere through radiative forcing. The presence of cloud near frontal regions usually results in reduced photosynthetic uptake, producing CO₂ concentration gradients across the frontal regions on the order of 10 parts per million (ppm). Away from the frontal region, the biosphere is coupled to the mesoscale variations in similar ways, resulting in mesoscale variations in CO₂ concentrations of about 5 ppm. The CO₂ field is also coupled strongly to the atmospheric dynamics. In the presence of frontal circulation, the CO₂ near the surface can be transported to the mid to upper troposphere. Mesoscale circulation also plays a significant part in transporting the CO₂ from the planetary boundary layer (PBL) to the mid-troposphere. In the absence of significant mesoscale or synoptic scale circulation, the CO₂ in the PBL has minimal exchange with the free troposphere, leading to strong gradients across the top of the PBL. We speculate that the ubiquity of the common synoptic and mesoscale processes in the atmosphere may contribute significantly to the rectifier effect and hence CO₂ inversion calculations