Holocene peatland carbon dynamics in Patagonia

Abstract

Patagonian peatland ecosystems have received very little attention in the scientific literature despite their widespread distribution in the regional landscape and the anthropogenic pressure they experience from the peat extraction industry. The functioning of these southern peatlands is strikingly similar to that of northern peatlands, but they have developed under very different climate boundary conditions. Therefore, studying these ecosystems provides a unique opportunity to test ideas and hypotheses about the sensitivity of carbon-rich peat accumulating ecosystems to climate change, in addition to filling significant data and knowledge gaps. Here we provide a synthesis of detailed peat accumulation records for southern Patagonia using a combination of new peat-core analysis (from 4 sites) and a data review from previously published studies (from 19 sites). We also present the modern climate space (temperature, precipitation, and seasonality ranges) of Patagonian peatlands on the basis of modern peatland distribution and gridded climate data to discuss climate controls of Patagonian peatlands at the present and in the past by inference. Results indicated that Patagonian peatlands occupy a distinct climatological niche that corresponds to an end-member of the northern peatland climate domain, with a mild mean annual temperature (from 3 to 9 °C) and very weak temperature seasonality. We also found that Patagonian peatlands have been efficient land carbon sinks since their initiation, with a mean soil carbon density of 168 kg C m−2 ± 10%. The total carbon pool for these ecosystems was estimated at 7.6 GtC. Modeled peat addition rates to the catotelm in Patagonian peatlands were significantly higher than what has been reported for northern peatlands, but decay coefficients were similar between these two high-latitude regions. These results support the idea that long, mild growing seasons promote peat formation in southern Patagonia. At the regional scale however, the lack of correlation between climatic parameters and peat accumulation indices suggests that autogenic controlling factors might be at play. Overall, southern peatlands provide a unique opportunity for studying peatland–carbon–climate linkages under a new set of climatic conditions.