THE UNIQUE DEVELOPMENTAL HISTORY OF PATAGONIAN PEATLANDS

Patagonian peatland ecosystems have received very little attention in the scientific literature despite their widespread distribution in the regional landscape and the growing 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 hypotheses about the sensitivity of carbon-rich peat accumulating ecosystems to past and ongoing changes in climate, in addition to fill significant data and knowledge gaps at the regional scale. Here we present the Patagonian peatland climate space to discuss differences in peatland distribution between the northern and southern high latitudes, as well as to assess the control of climate on long-term rates of peat-carbon sequestration. We also provide detailed peat accumulation records for southern Patagonia using a combination of new peat-core analysis (4 sites) and a data synthesis from published studies (19 sites). Results indicate 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 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 ± 17 kg C m^-2. The total carbon pool for these ecosystems was estimated at 7.6 ± 0.8 Gt C. Our plant macrofossil analysis indicates that the fen-to-bog transition has occurred around 4.2ka BP throughout the study region. Site-specific periodic variations between wet- and dry-adapted plant communities were also found along all 4 cores. In terms of carbon sequestration, we found that peat addition rates to the catotelm are significantly higher than what has been reported for northern sites, but decay coefficients are similar between these regions. These results support the idea that long, mild growing seasons promote peat formation in southern Patagonia. Overall, southern peatlands provide a unique opportunity for studying peatland-carbon-climate linkages under a new set of climatic conditions.