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Mitchell, Edward
Nom
Mitchell, Edward
Affiliation principale
Fonction
Professeur ordinaire
Email
edward.mitchell@unine.ch
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Résultat de la recherche
Voici les éléments 1 - 2 sur 2
- PublicationAccès libreGlasshouse vs field experiments: do they yield ecologically similar results for assessing N impacts on peat mosses?(2012)
;Limpens, J. ;Granath, G. ;Aerts, R. ;Heijmans, M. M. P. D. ;Sheppard, L. J. ;Bragazza, L. ;Williams, B. L. ;Rydin, H. ;Bubier, J. ;Moore, T. ;Rochefort, L.; ;Buttler, A. ;van den Berg, L. J. L. ;Gunnarsson, U. ;Francez, A. -J. ;Gerdol, R. ;Thormann, M. ;Grosvernier, P. ;Wiedermann, M. M. ;Nilsson, M. B. ;Hoosbeek, M. R. ;Bayley, S. ;Nordbakken, J. -F. ;Paulissen, M. P. C. P. ;Hotes, S. ;Breeuwer, A. ;Ilomets, M. ;Tomassen, H. B. M. ;Leith, I.Xu, B.
• Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss (Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments.
• We investigated whether glasshouse experiments are reliable proxies for field experiments for assessing interactions between N deposition and environment as controls on Sphagnum N concentration and production. We performed a meta-analysis over 115 glasshouse experiments and 107 field experiments.
• We found that glasshouse and field experiments gave similar qualitative and quantitative estimates of changes in Sphagnum N concentration in response to N application. However, glasshouse-based estimates of changes in production – even qualitative assessments – diverged from field experiments owing to a stronger N effect on production response in absence of vascular plants in the glasshouse, and a weaker N effect on production response in presence of vascular plants compared to field experiments.
• Thus, although we need glasshouse experiments to study how interacting environmental factors affect the response of Sphagnum to increased N deposition, we need field experiments to properly quantify these effects. - PublicationMétadonnées seulementClimatic modifiers of the response to nitrogen deposition in peat-forming Sphagnum mosses: a meta-analysis(2011)
;Limpens, J. ;Granath, G. ;Gunnarsson, U. ;Aerts, R. ;Bayley, S. ;Bragazza, Luca ;Bubier, J. ;Buttler, Alexandre ;van den Berg, L. J. L. ;Francez, Andre-Jean ;Gerdol, R. ;Grosvernier, Philippe ;Heijmans, M. M. P. D. ;Hoosbeek, M. R. ;Hotes, S. ;Ilomets, M. ;Leith, I.; ;Moore, T. ;Nilsson, Mats B. ;Nordbakken, J. F. ;Rochefort, L. ;Rydin, H. ;Sheppard, L. J. ;Thormann, M. ;Wiedermann, M. M. ;Williams, B. L.Xu, B.Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain. Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data. We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased annual precipitation intensified the negative effects of N. The temperature effect was comparable to an experimental application of almost 4 g N m(-2) yr(-1) for each 1 degrees C increase. Our results indicate that current rates of N deposition in a warmer environment will strongly inhibit C sequestration by Sphagnum-dominated vegetation.