US EPA

2043308 

Journal Article 

The effect of nitrogen deposition on forest carbon sequestration: A model-based analysis 

Dezi, S; Medlyn, BE; Tonon, G; Magnani, F 

2010 

Yes 

Global Change Biology
ISSN: 1354-1013
EISSN: 1365-2486 

WILEY 

HOBOKEN 

16 

5 

1470-1486 

10.1111/j.1365-2486.2009.02102.x 

WOS:000276696100005 

http://doi.wiley.com/10.1111/j.1365-2486.2009.02102.x
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The perturbation of the global nitrogen (N) cycle due to the increase in N deposition over the
last 150 years will likely have important effects on carbon (C) cycling, particularly via impacts
on forest C sequestration. To investigate this effect, and the relative importance of different
mechanisms involved, we used the Generic Decomposition And Yield (G’DAY) forest C–N
cycling model, introducing some new assumptions which focus on N deposition. Specifically,
we (i) considered the effect of forest management, (ii) assumed that belowground C allocation
was a function of net primary production, (iii) assumed that foliar litterfall and specific leaf
area were functions of leaf N concentration, (iv) assumed that forest canopies can directly take
up N, and (v) modified the model such that leaching occurred only for nitrate N. We applied
the model with and without each of these modifications to estimate forest C sequestration for
different N deposition levels. Our analysis showed that N deposition can have a large effect
on forest C storage at ecosystem level. Assumptions (i), (ii) and (iv) were the most important,
each giving rise to a markedly higher level of forest C sequestration than in their absence. On
the contrary assumptions (iii) and (v) had a negligible effect on simulated net ecosystem
production (NEP). With all five model modifications in place, we estimated that the C storage
capacity of a generic European forest ecosystem was at most 121 kgCkg 1N deposited. This
estimate is four times higher than that obtained with the original version of G’DAY
(27.8 kgCkg 1 N). Thus, depending on model assumptions, the G’DAY ecosystem model
can reproduce the range of dC : dNdep values found in the literature. We conclude that effects
of historic N deposition must be taken into account when estimating the C storage capacity of
a forest ecosystem. 

allocation; canopy nitrogen uptake; carbon and nitrogen cycles; leaf nitrogen concentration; models; specific leaf area