Dynamics of soil mineral-associated carbon under nitrogen enrichment controlled by microbial activity and geochemistry
Abstract
Terrestrial ecosystems worldwide are receiving increasing amounts of biologically reactive nitrogen (N) as a consequence of anthropogenic activities. This intended or unintended fertilization can have a wide-range of impacts on the dynamics of soil organic carbon (C). Experimental results have shown that the effect of N enrichment on stable (mineral-associated) C pools appears highly variable among ecosystems, and the underlying mechanisms remain unclear. Results from our long-term (15-yr) N enrichment experiment in a Mongolian steppe demonstrated that N inputs significantly reduced soil pH, heavy fraction C (HFC) and calcium (Ca)-bound C but increased iron (Fe)-bound C. A complementary acid addition experiment also showed that high soil acidity concurred with reduced HFC and Ca-bound C and increased Fe-bound C. Also, N-induced soil acidification significantly reduced microbial biomass and activity. Together, these results provide convincing evidence from field experiments illustrating that total HFC decreased likely due to reduced microbial C transformations and/or disruption of polyvalent cation bridges in organic-mineral associations. Together, these findings suggest that the impacts of N-induced soil acidification on microbial activity and geochemical properties linked to C stabilization should be included as important factors in Earth system models that predict ecosystem C budgets under future N deposition/input scenarios.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B41K2858Y
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 0486 Soils/pedology;
- BIOGEOSCIENCES