Organic matter composition and thermal stability influence greenhouse gases production in subtropical peatland under different vegetation types

Abstract

Peatlands are a major carbon (C) sink globally. Organic matter quality influence greenhouse gases production. However, little is known about how organic matter from different vegetation types, influences C composition and resultant greenhouse gases production in subtropical peatland. Anoxic incubation experiments were conducted using two types of peats with different botanical origin to assess C composition, CO₂ and CH₄ production. First peat had cypress dominance and the second knotted spikerush and water lily (spike + lily). Solid-state CPMAS ¹³C NMR determined C chemical stability, MESTA determined C thermal stability, stable isotopes for C source and gas chromatograph for carbon dioxide (CO₂) and methane (CH₄). The results indicated dominance of autochthonous C as indicated by δ¹³C signatures. Low thermal stable C (LTSC) dominated in litter, FL (fermentation layer) and spike + lily sediment, high thermal stable C was dominant in cypress peat. O-alkyl C strongly correlated with LTSC whereas aromatic C correlated negatively with R400 (LTSC:total C ratio). Generally, O-alkyl decreased and alkyl increased along litter-FL-peat continuum. Spike + lily peat exhibited initial stage of decomposition. Indicated by increased alkyl C, aromatic C and aromatic:O-alkyl ratio with increasing peat depth. Also, exhibited 3 times more CH₄ and CO₂ production compared to cypress peat that dominantly exhibited second stage of decomposition. O-alkyl C exhibited positive relationship with CH₄ (P = 0.012, r² = 0.57) and CO₂ (P = 0.047, r² = 0.41) production whereas R400 related positively with CH₄ (P = 0.05, r² = 0.40). Organic matter thermal and chemical composition varied between the peat types and thermally and chemically labile C influenced CO₂ and CH₄ production.

Citation

Akinbi, G.O.; Ngatia, L.W.; Grace, J.M.; Fu, R.; Tan, C.; Olaborode, S.O.; Abichou, T.; Taylor, R.W. 2022. Organic matter composition and thermal stability influence greenhouse gases production in subtropical peatland under different vegetation types. Heliyon. 8(11): e11547-. https://doi.org/10.1016/j.heliyon.2022.e11547.