Landform affects the distribution of mineral nutrients in the tropical peats: a case study in a peatland of Siak, Indonesia

Abstract

ABSTRACT Most peatlands in Indonesia border mineral upland, yet research reporting the effects of the presence of mineral upland on the distribution of mineral nutrients are limited. We collected multiple samples in surface layers from a peatland located between the Siak River and a mineral upland in Riau Province, Indonesia and measured electrical conductivity, pH, and exchangeable Ca2+, Mg2+, K+, and Na+. Transects were investigated for ash content and chemical composition of its profiles. Although electrical conductivity (183 ± 79 μS cm–1) and pH values (3.7 ± 0.3) were similar at surface layers, exchangeable Ca2+ (especially near the mineral upland) and Mg2+ were high at 0–15 cm deep (8.3 ± 5.1 cmolc kg–1 and 2.7 ± 1.1 cmolc kg–1, respectively) and tended to decline in the lower layers. Exchangeable K+ and Na+ did not show a clear trend, probably because of weaker bonding with peat material. High ash content (>10%) was found more frequently alongside the mineral upland than by the riverbank. In the profiles near the mineral upland, total Ca, Mg, Al, and Fe levels in the surface layer were higher (4.5 ± 0.3 g kg–1, 0.9 ± 0.0 g kg–1, 3.0 ± 0.5 g kg–1, and 1.6 ± 0.5 g kg–1, respectively), than those near the riverbank, which were 1.7 ± 0.7 g kg–1, 0.5 ± 0.2 g kg–1, 1.4 ± 0.3 g kg–1, and 0.6 ± 0.3 g kg–1, respectively. Based on the distribution of ash, exchangeable Ca2+ and Mg2+, and total Ca, Mg, Al, and Fe content, the present study suggests that the presence of the mineral upland nutritionally enriches the peat with Ca, Mg, and Fe. The influence of landform should be considered for a comprehensive understanding of nutrients sources in peatlands.