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 × 106ha, 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.
Although recent studies have recognized Northern Eurasian ecosystems as an important carbon reservoir, little is known about the forest–peatland interactions in a boreal environment induced by ...ongoing climatic changes. This study focuses on the evaluation of both the long-term and contemporary trends of land-cover changes and rates of lateral extension of peat-accumulating wetlands toward the adjacent forests, estimated at the southern climatic range of the Sphagnum-dominated mires in Western Siberia. We used the radiocarbon dates and stratigraphy of peat sediments from seven peat cores, analyzed at two types of forest–peatland ecotones, which are located close to each other but differ by topography and composition of their plant communities. The rate of lateral extension was found in a wide range varying from 2.3 to 791.7cmyr−1. It was observed to be rapid during the initial stage of mire development, but to have slowed down over the last 2000–3000yr. Our results, therefore, strongly contradict the concept of progressive peat accumulation throughout the late Holocene and contribute to our knowledge about ongoing land-cover change in the natural ecosystems of the Northern hemisphere.
Simulation of vegetation–climate feedbacks in high latitudes in the ORCHIDEE land surface model was improved by the addition of three new circumpolar plant functional types (PFTs), namely ...non-vascular plants representing bryophytes and lichens, Arctic shrubs and Arctic C3 grasses. Non-vascular plants are assigned no stomatal conductance, very shallow roots, and can desiccate during dry episodes and become active again during wet periods, which gives them a larger phenological plasticity (i.e. adaptability and resilience to severe climatic constraints) compared to grasses and shrubs. Shrubs have a specific carbon allocation scheme, and differ from trees by their larger survival rates in winter, due to protection by snow. Arctic C3 grasses have the same equations as in the original ORCHIDEE version, but different parameter values, optimised from in situ observations of biomass and net primary productivity (NPP) in Siberia. In situ observations of living biomass and productivity from Siberia were used to calibrate the parameters of the new PFTs using a Bayesian optimisation procedure. With the new PFTs, we obtain a lower NPP by 31 % (from 55° N), as well as a lower roughness length (−41 %), transpiration (−33 %) and a higher winter albedo (by +3.6 %) due to increased snow cover. A simulation of the water balance and runoff and drainage in the high northern latitudes using the new PFTs results in an increase of fresh water discharge in the Arctic ocean by 11 % (+140 km3 yr−1), owing to less evapotranspiration. Future developments should focus on the competition between these three PFTs and boreal tree PFTs, in order to simulate their area changes in response to climate change, and the effect of carbon–nitrogen interactions.
A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to ...verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The paper is addressed to scientists, policymakers, and funding agencies who need to have a global picture of the current state of the (diverse) carbon observations. We identify the current state of carbon observations, and the needs and notional requirements for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion of the ground-based observation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for addressing policy-relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over areas such as the southern oceans, tropical forests, and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote-sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground-based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants), as well as the inclusion of fossil fuel CO2 proxy measurements such as radiocarbon in CO2 and carbon-fuel combustion tracers. Additionally, a policy-relevant carbon monitoring system should also provide mechanisms for reconciling regional top-down (atmosphere-based) and bottom-up (surface-based) flux estimates across the range of spatial and temporal scales relevant to mitigation policies. In addition, uncertainties for each observation data-stream should be assessed. The success of the system will rely on long-term commitments to monitoring, on improved international collaboration to fill gaps in the current observations, on sustained efforts to improve access to the different data streams and make databases interoperable, and on the calibration of each component of the system to agreed-upon international scales.
Grassland management type (grazed or mown) and intensity (intensive or extensive) play a crucial role in the greenhouse gas balance and surface energy budget of this biome, both at field scale and at ...large spatial scale. However, global gridded historical information on grassland management intensity is not available. Combining modelled grass-biomass productivity with statistics of the grass-biomass demand by livestock, we reconstruct gridded maps of grassland management intensity from 1901 to 2012. These maps include the minimum area of managed vs. maximum area of unmanaged grasslands and the fraction of mown vs. grazed area at a resolution of 0.5deg by 0.5deg. The grass-biomass demand is derived from a livestock dataset for 2000, extended to cover the period 19012012. The grass-biomass supply (i.e. forage grass from mown grassland and biomass grazed) is simulated by the process-based model ORCHIDEE-GM driven by historical climate change, risingCO2 concentration, and changes in nitrogen fertilization. The global area of managed grassland obtained in this study increases from 6.1 x 10(exp 6) km(exp 2) in 1901 to 12.3 x 10(exp 6) kmI(exp 2) in 2000, although the expansion pathway varies between different regions. ORCHIDEE-GM also simulated augmentation in global mean productivity and herbage-use efficiency over managed grassland during the 20th century, indicating a general intensification of grassland management at global scale but with regional differences. The gridded grassland management intensity maps are model dependent because they depend on modelled productivity. Thus specific attention was given to the evaluation of modelled productivity against a series of observations from site-level net primary productivity (NPP) measurements to two global satellite products of gross primary productivity (GPP) (MODIS-GPP and SIF data). Generally, ORCHIDEE-GM captures the spatial pattern, seasonal cycle, and inter-annual variability of grassland productivity at global scale well and thus is appropriate for global applications presented here.
The peat-forming process of the southern margin of the taiga zone in West Siberia depends on climatic fluctuations, which have an effect on the peat stratigraphy and chemical composition of peat. It ...is shown that the contemporary warming does not interrupt the bog formation, which is due to the lateral flooding by water came from adjoining peatlands and periodical waterlogging of floodplain depressions during the years of excessive water supply.
New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga subzone over the past five years are presented. The relationship between ...net primary production and the stock of live phytomass is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass and net primary production decrease.
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.
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