Interpreting the ash trend within ombrotrophic bog profiles: atmospheric dust depositions vs. mineralization processes. The Etang de la Gruère case study
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Ash peaks along ombrotrophic bog profiles may arise from several different processes. In a recent paper, Leifeld and co-authors (Plant Soil 341:349–361, 2011) argued that ash peaks along the Etang de la Gruère (EGr) peat bog profiles are signs of previous periods of higher peat decomposition rather that an indication of periods of elevated dust inputs.
Aims and methods
Here we question the approach and scrutinize results using published data on several peat cores from EGr, demonstrating that peaks in ash content at EGr are very reproducible when cores are carefully collected (e.g., using the Wardenaar corer), and age dated (using 210Pb and 14C).
Data clearly show that variations in ash content along bog profiles cannot be attributed simply, or exclusively, to differences in organic matter mineralization rate, and that averaging the ash contents and normalizing to a single ash peak leads to losses in valuable information and defeats the purpose of detailed paleoenvironmental reconstructions.
Comparing results obtained using sensitive spectroscopic and isotopic tools with the ash content profiles at EGr shows clearly that the distribution of ash and/or acid-insoluble ash cannot be used as a surrogate for the intensity of processes including organic matter mineralization, decomposition and/or humification.
KeywordsAsh residue method Ombrotrophic bog Organic matter loss Mineral matter Age dating Humification
C. Zaccone thanks the Italian Society of Soil Science for the “Training Award” that allowed the present research, and Prof. Moore for his useful suggestions.
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