Environmental archives and carbon storage from Inland Tropical Peat in West Kalimantan, Indonesia

Abstract:

Tropical peat in inland areas of Kalimantan (Indonesia) formed before the Last Glacial Maximum and persist until the present day. We obtained 14 cores along an 12-km transect across a large peat dome in the Upper Kapuas basin, measured carbon, humification, and charcoal content, and obtained radiocarbon dates. A synthesis of our results with other dated cores show that while a peat-accumulation hiatus possibly occurred during a cool and dry period 30-20 ka, the glacial-maximum climate was not sufficiently dry to cause significant loss to existing peat. These areas likely functioned as an important carbon sink during the last glacial period and present potential environmental archives for this region. The peat reached a maximum depth of 18 m, and we estimate a regional average carbon density of 2,790 ± 1,440 Mg C/ha, which put this inland peat as one of the most carbon-dense ecosystems in the world. Our basal radiocarbon dates across the core transect date from 18 to 48 cal ka BP, with the oldest date reaching a radiocarbon-dead age of >50 ka. Preliminary analyses of charcoal counts show three distinct periods: zero to little from 1200-250 cm (xx to 13.3 ka), moderate amounts of charcoal at 250-50 cm (13.3 to ca. 0.6 ka), and an extremely high amount of charcoal at 30-0 cm which indicates very recent fire. Humification, a proxy with an inverted relationship with precipitation and water availability, shows a lower level of humification (suggesting a higher water table) during the glacial period from 750-500 cm (ca. 26.5 to 18.2 ka), that agrees with low charcoal counts during that depth. In ongoing work, additional down-core radiocarbon dates, assessment of potential depositional hiatuses, and analyses from additional cores will aid interpretation of these results.