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Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes

Author:
Kopáček, Jiří, Cosby, Bernard J., Evans, Christopher D., Hruška, Jakub, Moldan, Filip, Oulehle, Filip, Šantrůčková, Hana, Tahovská, Karolina, Wright, Richard F.
Source:
Biogeochemistry 2013 v.115 no.1-3 pp. 33-51
ISSN:
0168-2563
Subject:
carbon, dissolved organic carbon, leaching, microbial communities, mineralization, models, nitrates, nitrogen, roots, soil, soil acidification, solubility, sulfur, surface water, terrestrial ecosystems
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 Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes 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.
Agid:
231295