Role of cation exchange in preventing the decay of anoxic deep bog peat

Abstract

The major bog systems in northern areas are dominated by Sphagnum species, the partially decomposed remains of which form the bulk of deep peat. By adding mono- and di-valent cations to deep peat cores (2.0–2.5 m) and measuring CH 4 and CO 2 concentrations in the manipulated peat cores using quadrupole mass spectrometry (QMS) we demonstrate that the lack of availability to microorganisms of essential cations is limiting decay in deep peat. The cations with the highest binding strength displaced the most cations and stimulated decay. Decay in deep peat cores was also stimulated by a C source (acetate), but not by NH 4 +. The addition of cations and acetate resulted in a less than additive stimulation of decay. The stimulatory effect of acetate and copper decreased in the presence of ammonium. The addition of EDTA to surface bog peat (where cations are conserved) decreased decay rates in surface peat (0.0–0.5 m) to that of the untreated deep peat (2.0–2.5 m). Deep peat was unaffected by treatment with EDTA. The effect of adding Cu 2+differed with the depth from which the peat was collected. Cu 2+ did not stimulate decay in surface bog peat (0.0–1.5 m) but stimulated decay in peat from 1.5–3.5 m. Below 3.5 m to the bottom of the profile (5.0 m) no positive effect was observed. By comparing deep peat with surface peat we have shown that cation limitation because of high cation exchange capacity is specific to the main mass of deep bog peat and may explain differences in decay rates between anoxic surface peat and deep peat.