| 1. |
- Pärn, J., et al.
(author)
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Nitrogen-rich organic soils under warm well-drained conditions are global nitrous oxide emission hotspots
- 2018
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1, s. 1-8
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Journal article (peer-reviewed)abstract
- Nitrous oxide (N2O) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of N2O, predicting soil response to changes in climate or land use is central to understanding and managing N2O. Here we find that N2O flux can be predicted by models incorporating soil nitrate concentration (NO3 -), water content and temperature using a global field survey of N2O emissions and potential driving factors across a wide range of organic soils. N2O emissions increase with NO3 - and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of N2O emission from all organic soils. Above 5 mg NO3 --N kg-1, either draining wet soils or irrigating well-drained soils increases N2O emission by orders of magnitude. As soil temperature together with NO3 - explains 69% of N2O emission, tropical wetlands should be a priority for N2O management.
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| 2. |
- Fowler, D., et al.
(author)
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Atmospheric composition change : Ecosystems-Atmosphere interactions
- 2009
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:33, s. 5193-5267
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Research review (peer-reviewed)abstract
- Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O-3, CH4, N2O and particles in the size range 1 nm-10 mu m including organic and inorganic chemical species. The main focus of the review is on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean-atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent. New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere-surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O-3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.
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| 3. |
- Arneth, Almut, et al.
(author)
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From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere
- 2010
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In: Biogeosciences. - 1726-4189. ; 7:1, s. 121-149
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Research review (peer-reviewed)abstract
- Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation.
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| 4. |
- Gharahi Ghehi, N., et al.
(author)
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N2O and NO emission from the Nyungwe tropical highland rainforest in Rwanda
- 2014
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In: Geoderma Regional. - 2352-0094. ; 2-3, s. 41-49
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Journal article (peer-reviewed)abstract
- Tropical forest soils are a significant source for N2O and NO. Current estimates of N2O and NO emissions are uncertain due to the limited number of fieldmeasurements and model input data. Furthermore, considerable spatial and temporal variability exists due to variation of soil properties, vegetation characteristics and meteorology.We used a process-based model (ForestDNDC-tropica) to estimate N2O and NO emissions from the entire (970 km2) tropical highland forest (Nyungwe) in southwestern Rwanda. Scaling these results to that regional level using legacy soil, meteorological and simulated vegetation data we found in most cases agreement between N2O and NO measurements and model predictions. Limited agreement was found for acid soils with high clay content and reduced metals, indicating that abiotic N2O and NO forming processes in acidic soils might be under-represented in the current ForestDNDC-tropica model. The Nyungwe forest was estimated to emit 439 t N2O-N year−1 (2.8– 5.5 kg N2O-N ha−1 year−1) and 244 t NO-N year−1 (0.8–5.1 kg N ha−1 year−1), corroborating previous studies in tropical forests and highlighting that also tropical highland rainforest soils are a major source of atmospheric N2O and NO. The uncertainty for the N2O and NO emission estimates was 153 and 50 t N2O-N year−1 and 36 and 16 t NO-N year−1 considering uncertainty in model input data and annual variability, respectively. The results showed that soil bulk density and pH were the most influential factors driving spatial variation and model uncertainty. To improve global model-based estimates of N2O and NO emission from tropical forest focus should therefore also be oriented in delivering more detailed soil and vegetation data.
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| 5. |
- Herrero, M., et al.
(author)
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Greenhouse gas mitigation potentials in the livestock sector
- 2016
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In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-6798 .- 1758-678X. ; 6:5, s. 452-461
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Research review (peer-reviewed)abstract
- The livestock sector supports about 1.3 billion producers and retailers, and contributes 40-50% of agricultural GDP. We estimated that between 1995 and 2005, the livestock sector was responsible for greenhouse gas emissions of 5.6-7.5GtCO(2)e yr(-1). Livestock accounts for up to half of the technical mitigation potential of the agriculture, forestry and land-use sectors, through management options that sustainably intensify livestock production, promote carbon sequestration in rangelands and reduce emissions from manures, and through reductions in the demand for livestock products. The economic potential of these management alternatives is less than 10% of what is technically possible because of adoption constraints, costs and numerous trade-offs. The mitigation potential of reductions in livestock product consumption is large, but their economic potential is unknown at present. More research and investment are needed to increase the affordability and adoption of mitigation practices, to moderate consumption of livestock products where appropriate, and to avoid negative impacts on livelihoods, economic activities and the environment.
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| 6. |
- van Oijen, M., et al.
(author)
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A Bayesian framework for model calibration, comparison and analysis : Application to four models for the biogeochemistry of a Norway spruce forest
- 2011
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In: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923 .- 1873-2240. ; 151:12, s. 1609-1621
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Journal article (peer-reviewed)abstract
- Four different parameter-rich process-based models of forest biogeochemistry were analysed in a Bayesian framework consisting of three operations: (1) Model calibration, (2) Model comparison, (3) Analysis of model-data mismatch. Data were available for four output variables common to the models: soil water content and emissions of N(2)O, NO and CO(2). All datasets consisted of time series of daily measurements. Monthly averages and quantiles of the annual frequency distributions of daily emission rates were calculated for comparison with equivalent model outputs. This use of the data at model-appropriate temporal scale, together with the choice of heavy-tailed likelihood functions that accounted for data uncertainty through random and systematic errors, helped prevent asymptotic collapse of the parameter distributions in the calibration. Model behaviour and how it was affected by calibration was analysed by quantifying the normalised RMSE and r(2) for the different output variables, and by decomposition of the MSE into contributions from bias, phase shift and variance error. The simplest model, BASFOR, seemed to underestimate the temporal variance of nitrogenous emissions even after calibration. The model of intermediate complexity. DAYCENT, simulated the time series well but with large phase shift. COUP and MoBiLE-DNDC were able to remove most bias through calibration. The Bayesian framework was shown to be effective in improving the parameterisation of the models, quantifying the uncertainties in parameters and outputs, and evaluating the different models. The analysis showed that there remain patterns in the data - in particular infrequent events of very high nitrogenous emission rate - that are unexplained by any of the selected forest models and that this is unlikely to be due to incorrect model parameterisation.
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| 7. |
- Fowler, D., et al.
(author)
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Effects of global change during the 21st century on the nitrogen cycle
- 2015
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 15:24, s. 13849-13893
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Research review (peer-reviewed)abstract
- The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (N-r) from human activities, including combustion-related NOx, industrial and agricultural N fixation, estimated to be 220 TgNyr(-1) in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 TgNyr(-1) by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented. Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of Nr is the emission to the atmosphere of NH3, which is estimated to increase from 65 TgNyr(-1) in 2008 to 93 TgNyr(-1) in 2100 assuming a change in global surface temperature of 5 degrees C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH3 emissions to 135 TgNyr(-1). Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH4NO3 close to the ground to form HNO3 and NH3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH4)(2)SO4 in the 1970s to 1980s, and large reductions in emissions of SO2 have removed most of the SO42- from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH4NO3, a volatile aerosol which contributes substantially to PM10 and human health effects globally as well as eutrophication and climate effects. The volatility of NH4NO3 and rapid dry deposition of the vapour phase dissociation products, HNO3 and NH3, is estimated to be reducing the transport distances, deposition footprints and inter-country exchange of N-r in these regions. There have been important policy initiatives on components of the global N cycle. These have been regional or country-based and have delivered substantial reductions of inputs of Nr to sensitive soils, waters and the atmosphere. To date there have been no attempts to develop a global strategy to regulate human inputs to the nitrogen cycle. However, considering the magnitude of global Nr use, potential future increases, and the very large leakage of Nr in many forms to soils, waters and the atmosphere, international action is required. Current legislation will not deliver the scale of reductions globally for recovery from the effects of Nr deposition on sensitive ecosystems, or a decline in N2O emissions to the global atmosphere. Such changes would require substantial improvements in nitrogen use efficiency across the global economy combined with optimization of transport and food consumption patterns. This would allow reductions in Nr use, inputs to the atmosphere and deposition to sensitive ecosystems. Such changes would offer substantial economic and environmental co-benefits which could help motivate the necessary actions.
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| 8. |
- Meyer, Astrid, et al.
(author)
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Integrating mycorrhiza in a complex model system: effects on ecosystem C and N fluxes
- 2012
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In: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 131:6, s. 1809-1831
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Journal article (peer-reviewed)abstract
- During the last decades, ectomycorrhiza has been identified to be of major importance for ecosystem carbon (C) and nitrogen (N) cycling and tree growth. Despite this importance, mycorrhiza has largely been neglected in ecosystem models or regarded only implicitly by a static mycorrhiza term. In order to overcome this limitation, we integrated the dynamic mycorrhiza model MYCOFON (Meyer et al. in Plant Soil 327:493-517, 2010a, Plant Soil 327:519, 2010b) into the ecosystem modelling framework MoBiLE (Modular Biosphere simuLation Environment) and coupled it to available forest growth and development process models. Model testing was done for different beech and spruce forest sites in Germany. Simulation results were compared to a standard model set-up, that is, without explicit consideration of mycorrhiza. Parameters were set in order not to violate previous findings about C partitioning into aboveground and belowground biomasses. Nevertheless, the explicit consideration of mycorrhiza let to considerable differences between sites and deposition scenarios with respect to simulated root biomass, plant nitrogen supply, and gaseous soil C and N emissions. The latter was mainly a result of differences in soil N concentration and dynamics. Our simulation results also show that the C supply to mycorrhizal fungi by plants as well as the importance of mycorrhizal fungi for plant N uptake, that is, the allocation of C and N between plants and fungi, depends on the magnitude of N deposition. This effect is neglected by standard model approaches so far. Therefore, explicit consideration of mycorrhiza in ecosystem models has a high potential to improve model simulations of ecosystem C and N cycling and associated biosphere-hydrosphere-atmosphere exchange processes and consequently simulation of soil CO2 and N trace gas emissions from forest sites.
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| 9. |
- Werner, C., et al.
(author)
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A global inventory of N2O emissions from tropical rainforest soils using a detailed biogeochemical model
- 2007
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In: Global Biogeochemical Cycles. - 0886-6236. ; 21:3, s. 3010-3010
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Journal article (peer-reviewed)abstract
- Beside agricultural soils, tropical rainforest soils are the main source of atmospheric N2O. Current estimates of the global N2O source strength of tropical rainforest soils are still based on rather simplistic upscaling approaches and do have a large range of uncertainty. In this study, the biogeochemical ForestDNDC-tropica model was recalibrated and intensively tested on the site scale prior to inventory calculations. For this, the model was coupled to a newly developed global GIS database holding relevant information on model initialization and driving parameters in 0.25 degrees x 0.25 degrees resolution. On average, the mean annual N2O emission source strength of rainforests ecosystems worldwide for the 10-year-period 1991-2000 was calculated to be 1.2 kg N2O-N ha(-1) yr(-1). Using a total rainforest area of 10.9 x 10(6) km(2), this amounts to a total source strength of 1.34 Tg N yr(-1). The result of an initialization parameter uncertainty assessment using Latin Hypercube sampling revealed that the global source strength of N2O emissions from tropical rainforests may range from 0.88 to 2.37 Tg N yr(-1). Our calculations also show that N2O emissions do vary substantially on spatial and temporal scales. Regional differences were mainly caused by differences in soil properties, whereas the pronounced seasonal and interannual variability was driven by climate variability. Our work shows that detailed biogeochemical models are a valuable tool for assessing biosphere-atmosphere exchange even on a global scale. However, further progress and a narrowing of the uncertainty range do crucially depend on the availability of more detailed field measurements for model testing and an improvement of the quality of spatial data sets on soil and vegetation properties.
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