Browsing by Subject "LONG-TERM IMPACTS"

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  • Flechard, Chris R.; Ibrom, Andreas; Skiba, Ute M.; de Vries, Wim; van Oijen, Marcel; Cameron, David R.; Dise, Nancy B.; Korhonen, Janne F. J.; Buchmann, Nina; Legout, Arnaud; Simpson, David; Sanz, Maria J.; Aubinet, Marc; Loustau, Denis; Montagnani, Leonardo; Neirynck, Johan; Janssens, Ivan A.; Pihlatie, Mari; Kiese, Ralf; Siemens, Jan; Francez, Andre-Jean; Augustin, Juergen; Varlagin, Andrej; Olejnik, Janusz; Juszczak, Radoslaw; Aurela, Mika; Berveiller, Daniel; Chojnicki, Bogdan H.; Dammgen, Ulrich; Delpierre, Nicolas; Djuricic, Vesna; Drewer, Julia; Dufrene, Eric; Eugster, Werner; Fauvel, Yannick; Fowler, David; Frumau, Arnoud; Granier, Andre; Gross, Patrick; Hamon, Yannick; Helfter, Carole; Hensen, Arjan; Horvath, Laszlo; Kitzler, Barbara; Kruijt, Bart; Kutsch, Werner L.; Lobo-do-Vale, Raquel; Lohila, Annalea; Longdoz, Bernard; Marek, Michal; Matteucci, Giorgio; Mitosinkova, Marta; Moreaux, Virginie; Neftel, Albrecht; Ourcival, Jean-Marc; Pilegaard, Kim; Pita, Gabriel; Sanz, Francisco; Schjoerring, Jan K.; Sebastia, Maria-Teresa; Tang, Y. Sim; Uggerud, Hilde; Urbaniak, Marek; van Dijk, Netty; Vesala, Timo; Vidic, Sonja; Vincke, Caroline; Weidinger, Tamas; Zechmeister-Boltenstern, Sophie; Butterbach-Bah, Klaus; Nemitz, Eiko; Sutton, Mark A. (2020)
    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.
  • Korpela, Katri; Salonen, Anne; Virta, Lauri J.; Kumpu, Minna; Kekkonen, Riina A.; de Vos, Willem M. (2016)
    Antibiotic use is considered among the most severe causes of disturbance to children's developing intestinal microbiota, and frequently causes adverse gastrointestinal effects ranging from mild and transient diarrhoea to life-threatening infections. Probiotics are commonly advocated to help in preventing antibiotic-associated gastrointestinal symptoms. However, it is currently unknown whether probiotics alleviate the antibiotic-associated changes in children's microbiota. Furthermore, it is not known how long-term probiotic consumption influences the developing microbiota of children. We analysed the influence of long-term Lactobacillus rhamnosus GG intake on preschool children's antibiotic use, and antibiotic-associated gastrointestinal complaints in a double blind, randomized placebo-controlled trial with 231 children aged 2-7. In addition, we analysed the effect of L. rhanmosus GG on the intestinal microbiota in a subset of 88 children. The results show that long-term L. rhamnosus GG supplementation has an influence on the composition of the intestinal microbiota in children, causing an increase in the abundance of Prevotella, Lactococcus, and Ruminococcus, and a decrease in Escherichia. The treatment appeared to prevent some of the changes in the microbiota associated with penicillin use, but not those associated with macrolide use. The treatment, however, did reduce the frequency of gastrointestinal complaints after a macrolide course. Finally, the treatment appeared to prevent certain bacterial infections for up to 3 years after the trial, as indicated by reduced antibiotic use.