Low historical nitrogen deposition effect on carbon sequestration in the boreal zone

K. Fleischer, D. Wårlind, M.K. van der Molen, K.T. Rebel, A. Arneth, J. W. Erisman, M. J. Wassen, B. Smith, C.M. Gough, H. A. Margolis, A. Cescatti, L. Montagnani, A. Arain, A.J. Dolman. 2015. Low historical nitrogen deposition effect on carbon sequestration in the boreal zone. Journal of Geophysical Research: Biogeosciences. 12. 120
Aantal pagina's: 20
Soort document: Wetenschappelijk artikel
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Taal van het document: Engels
Abstract / summary in English:

Nitrogen (N) cycle dynamics and N deposition play an important role in determining the terrestrial biosphere’s carbon (C) balance. We assess global and biome-specific N deposition effects on C sequestration rates with the dynamic global vegetation model LPJ-GUESS. Modeled CN interactions are evaluated by comparing predictions of the C and CN version of the model with direct observations of C fluxes from 68 forest FLUXNET sites. N limitation on C uptake reduced overestimation of gross primary productivity for boreal evergreen needleleaf forests from 56% to 18%, presenting the greatest improvement among forest types. Relative N deposition effects on C sequestration (dC/dN) in boreal, temperate, and tropical sites ranged from 17 to 26 kg C kgN-1 whenmodeled at site scale andwere reduced to 12–22 kg C kgN-1 at global scale. We find that 19% of the recent (1990–2007) and 24% of the historical global C sink (1900–2006) was driven by N deposition effects. While boreal forests exhibit highest dC/dN, their N deposition-induced C sink was relatively low and is suspected to stay low in the future as no major changes in N deposition rates are expected in the boreal zone. N deposition induced a greater C sink in temperate and tropical forests, while predicted C fluxes and N-induced C sink response in tropical forests were associated with greatest uncertainties. Future work should be directed at improving the ability of LPJ-GUESS and other process-based ecosystem models to reproduce C cycle dynamics in the tropics, facilitated by more benchmarking data sets. Furthermore, efforts should aim to improve understanding and model representations of N availability (e.g., N fixation and organic N uptake), N limitation, P cycle dynamics, and effects of anthropogenic land use and land cover changes.

Keywords in English: Nitrogen, biosphere, carbon, forests, ecosystem, global vegetation