Preliminary investigation of the formation age and chemical characterization of the tropical peat in the middle Sepik Plain, northern Papua New Guinea

Chisato Takenaka,Mitsutoshi Umemura,Eisuke Ono,Takuya Ishida

doi:10.1186/s40562-015-0021-4

Abstract

Seven gouge cores in the middle Sepik Plain (northern Papua New Guinea) were bored to clarify the depositional age and the chemical characteristics of the tropical peat. The weakly-acidic peat layer (3–4 m thick) is distributed around the south bank of the Blackwater Lakes. The peat layer consists mainly of sago palm and grass remains within a mineral matrix of very fine sand and clay. Radiocarbon dating indicates that the peat’s formation had commenced by 3,710–3,560 cal BP. Nitrogen and exchangeable potassium reach their highest values in the upper 60 cm of the peat column. Conversely, exchangeable sodium, calcium and magnesium, as well as carbon, increase their values with depth in the peat. These differences in the exchangeable cations’ contribution suggest changes in the plant species, which were decomposed during the peat’s formation.

Highlights

Carbon dioxide storage in tropical peatlands has recently attracted significant international attention
The peat layers consist of partially-decomposed organic matter and contain sago palm and grass remains in a mineral matrix of very fine sand and clay
Inorganic silty clay and fine sand have been carried by rivers, accumulating sago palm and grass remains in the shallow swamp waters

Summary

Introduction

Carbon dioxide storage in tropical peatlands has recently attracted significant international attention. Carbon dioxide emission from deforested tropical peatlands is a very important and controversial issue, in the context of global warming [1,2]. Tropical peatlands are widely distributed in south-east Asia and Oceania, but only a limited area has been studied, with regard to carbon dioxide storage and emission problems. The detailed distribution, formation process and chemical properties of tropical peats have been clarified in Indonesia and Malaysia There have been relatively few studies of tropical peatlands in Oceania. Oceania’s largest peatland area, estimated at 290,000– 500,000 ha [7,8], is situated in Papua New Guinea

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