Peatland Formation and Carbon Accumulation : A Pantropical Synthesis

<p>Tropical peatlands account for a small portion of global peatland area but hold over 100 Gt of carbon (C), equivalent to approximately 13% of the C stored in the atmosphere. At this point, a comprehensive synthesis on the timing and behavior of peatland formation and peat accumulation does not exist for the tropics, where long-term accumulation rates could be higher than other regions due to the high productivity and water availability characteristic of tropical regions. In this work, we synthesize data collected from tropical peatlands around the world, to identify dominant external drivers (such as climate or tectonics) that influence patterns of peat depth and accumulation. We use radiocarbon measurements compiled in the International Soil Radiocarbon Database (ISRaD) to calculate peat and C accumulation rates of peat profiles across the tropics. Currently 44 individual studies make up this synthesis that together cover 12 countries and 62 tropical peat sites. This analysis focuses on comparisons between tropical peatlands from different continents and geographic locations and with different site characteristics. We identify three geographically distinct types of peatlands across the tropics: a) inland b) coastal c) montane that differ in terms of underlying substrate, timing of initiation, and accumulation rate. Four regions have been recognized in this analysis with differences in the range of peatland ages and depth: Africa (4000-10,600 cal yr BP) with 1-3m low elevation peatlands, the Neotropics (1400-13,000 cal yr BP) with higher variability in elevation and 1-8m peat deposits, Southeast Asia (4000-47,000 cal yr BP) with 1-18m deep peat deposits, and Hawaii (115-45,000 cal yr BP) with 1-4m peat deposits. We explore possible drivers of these differences in peatland age and accumulation across the tropics. This study complements the recent progress that has been made in mapping tropical peats, identifying their specific characteristics, assessing their potential uses, and calling attention to their potential vulnerability, restoration, and conservation.</p>