Nitrogen leaching from natural ecosystems under global change : a modelling study

Maarten C. Braakhekke, Karin T. Rebel, Stefan C. Dekker, Benjamin Smith, Arthur H. W. Beusen, Martin J. Wassen

Research output: Contribution to journalArticlepeer-review

Abstract

To study global nitrogen (N) leaching from natural ecosystems under changing N deposition, climate, and atmospheric CO2, we performed a factorial model experiment for the period 1901–2006 with the N-enabled global terrestrial ecosystem model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator). In eight global simulations, we used either the true transient time series of N deposition, climate, and atmospheric CO2 as input or kept combinations of these drivers constant at initial values. The results show that N deposition is globally the strongest driver of simulated N leaching, individually causing an increase of 88% by 1997–2006 relative to pre-industrial conditions. Climate change led globally to a 31% increase in N leaching, but the size and direction of change varied among global regions: leaching generally increased in regions with high soil organic carbon storage and high initial N status, and decreased in regions with a positive trend in vegetation productivity or decreasing precipitation. Rising atmospheric CO2 generally caused decreased N leaching (33% globally), with strongest effects in regions with high productivity and N availability. All drivers combined resulted in a rise of N leaching by 73% with strongest increases in Europe, eastern North America and South-East Asia, where N deposition rates are highest. Decreases in N leaching were predicted for the Amazon and northern India. We further found that N loss by fire regionally is a large term in the N budget, associated with lower N leaching, particularly in semi-arid biomes. Predicted global N leaching from natural lands rose from 13.6 TgNyrˉ1 in 1901–1911 to 18.5 TgNyrˉ1 in 1997–2006, accounting for reductions of natural land cover. Ecosystem N status (quantified as the reduction of vegetation productivity due to N limitation) shows a similar positive temporal trend but large spatial variability. Interestingly, this variability is more strongly related to vegetation type than N input. Similarly, the relationship between N status and (relative) N leaching is highly variable due to confounding factors such as soil water fluxes, fire occurrence, and growing season length. Nevertheless, our results suggest that regions with very high N deposition rates are approaching a state of N saturation.
Original languageEnglish
Pages (from-to)1121-1139
Number of pages19
JournalEarth System Dynamics
Volume8
Issue number4
DOIs
Publication statusPublished - 2017

Open Access - Access Right Statement

© Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License.

Keywords

  • atmospheric deposition
  • climatic changes
  • ecosystems
  • leaching
  • nitrogen

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