oa Organic Matter Differences and Similarities Across Diverse Peatland Types: Energy Limitation While Surrounded by Carbon

Tropical peatlands contain abundant but vulnerable organic carbon stocks. The stability and accumulation of the organic carbon stored in tropical peat systems, and its sensitivity to changing temperature and/or hydrology, is intrinsically linked to the organic matter (OM) character. Large surveys of OM composition suggest that it is more recalcitrant in tropical peatlands than temperate ones, because of the former’s relatively high aromatic content. However, the precursor aromatic-bearing macromolecules, such as lignin, are produced in different proportions by diverse plant communities, and are often not equally recalcitrant. To predict tropical peat organic matter stability in the 21st century, both on a global scale and in individual peatlands, we need to properly characterise the complexity of the ‘recalcitrant’ carbon pool and how it varies across diverse peatland types.

Here, we characterise bulk organic matter in plants, leaf litter, and peat depth profiles from a range of tropical (n = 7) and temperate (n = 1) peatland ecosystems. This characterisation is achieved primarily via Pyrolysis Gas Chromatography Mass Spectrometry, complemented by Fourier-Transform Infrared Spectroscopy. Our results show that each site exhibits distinct pools of putatively labile and recalcitrant (plant) organic matter, with both shared and distinct downcore degradation features.