Holocene patterns of peat accumulation in Peruvian Amazonia

Abstract

Peatlands accumulate and store carbon over centuries to tens of millennia. Analysing the age structure of peatlands helps us to understand their genesis, development, and stability as carbon stores, and informs peatland management. Here we analyse new and previously published radiocarbon dates from peatlands in the Pastaza-Marañón Basin in Peru, the largest known peatland complex in Amazonia. We show that peatlands here are younger (< c. 8900 and frequently <2500 years old) than in many other parts of the tropics. Basal peat ages in extant peatlands vary depending on the geomorphological stability of the landscape, with younger basal dates typically occurring close to active river floodplains and older basal dates in more stable contexts. The data indicate that within individual peatlands, peat initiation may occur synchronously across a basin, or peat may spread laterally from one or more nucleation sites. Only two out of seven well-dated records show clear hiatuses in past peat accumulation, suggesting that carbon sequestration in some, but not all peatlands has been vulnerable to landscape hydrological change or climate change. Peatland ecosystems in the region are economically important sources of non-timber forest products, which it may be possible to harvest sustainably without biomass loss or drainage, but our analysis indicates that the peat itself accumulates too slowly to be considered as a renewable resource on economically meaningful timescales.