| 1. |
- Flechard, Chris R., et al.
(författare)
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Carbon-nitrogen interactions in European forests and semi-natural vegetation - Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17:6, s. 1583-1620
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Tidskriftsartikel (refereegranskat)abstract
- The impact of atmospheric reactive nitrogen (N-r) deposition on carbon (C) sequestration in soils and biomass of unfertilized, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC/dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates of N-r deposition obtained from large-scale chemical transport models. This study and a companion paper (Flechard et al., 2020) strive to reduce uncertainties of N effects on C sequestration by linking multi-annual gross and net ecosystem productivity estimates from 40 eddy covariance flux towers across Europe to local measurement-based estimates of dry and wet N-r deposition from a dedicated collocated monitoring network. To identify possible ecological drivers and processes affecting the interplay between C and N-r inputs and losses, these data were also combined with in situ flux measurements of NO, N2O and CH4 fluxes; soil NO3- leaching sampling; and results of soil incubation experiments for N and greenhouse gas (GHG) emissions, as well as surveys of available data from online databases and from the literature, together with forest ecosystem (BAS-FOR) modelling. Multi-year averages of net ecosystem productivity (NEP) in forests ranged from -70 to 826 gCm(-2) yr(-1) at total wet + dry inorganic N-r deposition rates (N-dep) of 0.3 to 4.3 gNm(-2) yr(-1) and from -4 to 361 g Cm-2 yr(-1) at N-dep rates of 0.1 to 3.1 gNm(-2) yr(-1) in short semi-natural vegetation (moorlands, wetlands and unfertilized extensively managed grasslands). The GHG budgets of the forests were strongly dominated by CO2 exchange, while CH4 and N2O exchange comprised a larger proportion of the GHG balance in short semi-natural vegetation. Uncertainties in elemental budgets were much larger for nitrogen than carbon, especially at sites with elevated N-dep where N-r leaching losses were also very large, and compounded by the lack of reliable data on organic nitrogen and N-2 losses by denitrification. Nitrogen losses in the form of NO, N2O and especially NO3- were on average 27%(range 6 %-54 %) of N-dep at sites with N-dep < 1 gNm(-2) yr(-1) versus 65% (range 35 %-85 %) for N-dep > 3 gNm(-2) yr(-1). Such large levels of N-r loss likely indicate that different stages of N saturation occurred at a number of sites. The joint analysis of the C and N budgets provided further hints that N saturation could be detected in altered patterns of forest growth. Net ecosystem productivity increased with N-r deposition up to 2-2.5 gNm(-2) yr(-1), with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP/GPP ratio). At elevated N-dep levels (> 2.5 gNm(-2) yr(-1)), where inorganic N-r losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate N-dep levels was partly the result of geographical cross-correlations between N-dep and climate, indicating that the actual mean dC/dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. N-dep.
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| 2. |
- Nilsson, K., et al.
(författare)
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Comparative life cycle assessment of margarine and butter consumed in the UK, Germany and France
- 2010
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Ingår i: The International Journal of Life Cycle Assessment. - : Springer Science and Business Media LLC. - 0948-3349 .- 1614-7502. ; 15:9, s. 916-926
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The goal of the study was to compare the environmental impact of butter and margarine. Altogether, seven products were studied in three European markets: UK, Germany and France. Methods: The approach used for the analysis is descriptive (attributional) LCA. The SimaPro software PRé 2007 was used to perform the calculations. Data for the production chain of the margarine products (production of raw materials, processing, packaging and logistics) were compiled from Unilever manufacturing sites, suppliers and from literature. The edible oil data inventories have been compared with those in proprietary databases (ecoinvent and SIK food database) and they show a high degree of similarity. For the butter products, data on milk production and butter processing were taken from various published studies for the countries of interest. Sensitivity analyses were conducted for a number of parameters (functional unit, allocation method, impact of using different oil, milk and dairy data, impact of estimating GHG emissions from land use change for certain oils) in order to evaluate their influence on the comparison between margarine and butter. The sensitivity analyses demonstrate that the initial results and conclusions are robust. Results: The results show that margarine has significantly lower environmental impact (less than half) compared to butter for three impact categories global warming potential, eutrophication potential and acidification potential. For primary energy demand, the margarines have a lower impact than butter, but the difference is not as significant. Margarines use approximately half of the land required used for producing the butter products. For POCP, the impact is higher for the margarines due to the use of hexane in the oil extraction (no similar process occurs for butter). Conclusions: The margarine products analysed here are more environmentally favourable than the butter products. In all three markets (UK, DE and FR) the margarine products are significantly better than the butter products for the categories global warming potential, eutrophication potential and acidification potential. These findings are also valid when comparing margarines and butters between the markets; for this reason they are likely to be of general relevance for other Western European countries where similar margarine and butter production systems are found. © 2010 Springer-Verlag.
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