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Peatlands contain a disproportionate share of global carbon stocks, such that their biogeochemistry plays an outsized role in carbon balance and climate regulation. The precise mechanisms underpinning peat formation and stabilisation are not yet clear, with several hypotheses co-existing. Further opacity stems from a strong historical bias in research efforts towards boreal and temperate peatlands in the Northern Hemisphere, leaving the tropical case relatively under-studied. On the basis of the economics of oxidative decomposition and juxtaposition of chemical compositional data from tropical peatlands and northern peatlands, we make the case that a rapid, globally-consequential but as yet unidentified endergonic oxidation process must be occurring in tropical but not cold-climate peatlands. We suggest that low temperature limits this process in northern peatlands and, therefore, that a significant quantity of carbon in these systems is more vulnerable to warming than previously thought. We conclude that the existence of tropical peatlands - and their role in regulating global climate - may be partially underwritten by a mechanism largely unmapped by our current knowledge of soil carbon turnover.

The tropical peatland degradation crisis in Southeast Asia has triggered a surge in peatland restoration activity to reduce carbon emissions caused by biological oxidation of dry peat and recurrent peat fires. Monitoring the effects of restoration activities on carbon cycling is essential. We conducted a systematic literature review to determine where, how and by whom field-based carbon monitoring of tropical peatland restoration is being conducted. Our search focused on rewetting, revegetation of native plant communities, and interventions to reduce fire. Despite tropical peatland restoration activities occurring since the early 2000s, published studies monitoring their carbon effects are extremely limited, both temporally and geographically; only nine studies met the criteria of our systematic search. Concentrated in Kalimantan and Sumatra (Indonesia) and Selangor (Malaysia), all except one of these studies were published in the last six years. Southeast Asian academic institutions, nonprofit organisations, government and the private sector are interconnected in generating this research through authorship and the provision and/or management of land. Monitoring activities are heavily focused on flux chamber measurements of peat surface carbon fluxes. Monitoring of revegetation and fire reduction is very limited, and establishment of pre-restoration baseline conditions is lacking. In the detected studies, reported monitoring periods extended to a maximum of two years. Standardised reporting of the spatial extent of restoration activities would assist comparisons of restoration outcomes. There is an urgent need for longer term, continuous studies investigating the carbon outcomes of tropical peatland restoration that transcend existing funding and political time constraints.

Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg-1 and 13.9 ± 7.4 g kg-1, with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg-1) and lowest in intermediate and extremely rich fens (375–414 g kg-1). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.

Acidity negatively impacts upon soil capability and conditions across approximately 50% of the world's arable land. Plant growth and nutrient cycling are known to respond positively to the addition of lime to decrease soil acidity. However, the interactions between liming and soil carbon dynamics remain incompletely understood. The nexus of soils, food security and climate change make this topic an urgent concern for investigation. This study utilised soils (Cambisols) from three long-term lime field trials (13-39 years) on farms. Soils (0-10 cm) were incubated in the laboratory for 3 months with and without 13C-labelled wheat crop residue. This approach enabled direct quantification of the CO2-C originating from three different processes; decomposition of extant soil organic carbon (SOC), decomposition of the added crop residue, and SOC priming i.e. the additional decomposition of SOC stimulated by addition of plant material. Biological and chemical soil properties were also quantified, with a novel application of measurement of the abundance of the functional genes involved in SOC decomposition. Priming was significantly increased in limed soils (P