|Title||Low historical nitrogen deposition effect on carbon sequestration in the boreal zone|
|Author(s)||Fleischer, K.; Wårlind, D.; Molen, M.K. Van Der; Rebel, K.T.; Arneth, A.; Erisman, J.W.; Wassen, M.J.; Smith, B.; Gough, C.M.; Margolis, H.A.; Cescatti, A.; Montagnani, L.; Arain, A.; Dolman, A.J.|
|Source||Journal of Geophysical Research: Biogeosciences 120 (2015)12. - ISSN 2169-8953 - p. 2542 - 2561.|
Meteorology and Air Quality
|Publication type||Refereed Article in a scientific journal|
|Keyword(s)||carbon sequestration - FLUXNET - forests - global dynamic vegetation models - nitrogen deposition|
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 kg N-1 when modeled at site scale and were reduced to 12-22 kg C kg N-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.