Abstract

Elevated and chronic nitrogen (N) deposition to N-limited terrestrial ecosystems can lead to 'N saturation', with resultant ecosystem damage and leaching of nitrate (NO3 (-)) to surface waters. Present-day N deposition, however, is often a poor predictor of NO3 (-) leaching, and the pathway of the ecosystem transition from N-limited to N-saturated remains incompletely understood. The dynamics of N cycling are intimately linked to the associated carbon (C) and sulphur (S) cycles. We hypothesize that N saturation is associated with shifts in the microbial community, manifest by a decrease in the fungi-to-bacteria ratio and a transition from N to C limitation. Three mechanisms could lead to lower amount of bioavailable dissolved organic C (DOC) for the microbial community and to C limitation of N-rich systems: (1) Increased abundance of N for plant uptake, causing lower C allocation to plant roots; (2) chemical suppression of DOC solubility by soil acidification; and (3) enhanced mineralisation of DOC due to increased abundance of electron acceptors in the form of and NO3 (-) in anoxic soil micro-sites. Here we consider each of these mechanisms, the extent to which their hypothesised impacts are consistent with observations from intensively-monitored sites, and the potential to improve biogeochemical models by incorporating mechanistic links to the C and S cycles.

Keywords

Nitrogen; Carbon; Sulphur; Acidification; Forest soil; Modelling

Published in

Biogeochemistry
2013, Volume: 115, number: 1-3, pages: 33-51
Publisher: SPRINGER

UKÄ Subject classification

Geosciences, Multidisciplinary


Publication identifier

DOI: https://doi.org/10.1007/s10533-013-9892-7

Permanent link to this page (URI)

https://res.slu.se/id/publ/89036