Tropical peat deposits undergoing land-use change: the case of Buhandanda and Lushala peatlands (Democratic Republic of Congo)

Abstract

Discovery of the world’s largest known peat deposit in the Central African Basin creates a need for the Democratic Republic of Congo (DRC) to undertake a realistic national assessment of peat carbon. In the study described here we determined physicochemical properties of the Buhandanda and Lushala peat deposits, located in Sud-Kivu Province, to gain insights about their structure and functioning and provide a first estimate of C stocks. A change of land use (to seasonal subsistence agriculture) operating in the last few decades has dramatically modified the vegetation, which was originally dominated by mesophilic forest species. Several peat properties (pH, organic matter content, porosity, dry matter, ash and fibre contents) increased with depth in the peat profile, although some (nitrogen, nitrate, phosphate content and air-filled porosity) decreased and others (bulk density, solids density, C/N) showed no trend. The C densities of peat at the two sites were 68.60 and 60.64 kg m-3, our estimates of mean (± SD) peat thickness were 324 ± 139 and 212 ± 109 cm, and total C storage was 0.136 and 0.023 Mt, for Buhandanda and Lushala, respectively. The range of calibrated radiocarbon dates for a 200 cm deep core collected from Lushala was 648–2005 cal. AD, with a high modern carbon fraction (F14C) near the surface (at depths of 15 cm and 80 cm). Overall, our results indicated that carbon accumulation has declined at these two sites owing to the reduction in litter flux associated with land use change. Using the average C densities and peat thicknesses measured at Lushala and Buhandanda, we estimated that the total C storage in Sud-Kivu peatlands is approximately 1.23 Mt.

Keywords

• carbon stocks
• greenhouse gas
• mountain peatland
• peat soil
• subsistence agriculture