Evaluation on the decomposability of tropical forest peat soils after conversion to an oil palm plantation

Faustina E Sangok; Nagamitsu Maie; Lulie Melling; Akira Watanabe

doi:10.1016/j.scitotenv.2017.02.165

Evaluation on the decomposability of tropical forest peat soils after conversion to an oil palm plantation

Sci Total Environ. 2017 Jun 1:587-588:381-388. doi: 10.1016/j.scitotenv.2017.02.165. Epub 2017 Feb 24.

Authors

Faustina E Sangok¹, Nagamitsu Maie², Lulie Melling³, Akira Watanabe⁴

Affiliations

¹ Graduate School of Bioagricultural Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan; Sarawak Tropical Peat Research Institute, Lot 6035, Kota Samarahan Expressway, 94300 Kota Samarahan, Sarawak, Malaysia. Electronic address: fausties@sarawak.gov.my.
² School of Veterinary Medicine, Kitasato University, Towada, Aomori 034-8628, Japan.
³ Sarawak Tropical Peat Research Institute, Lot 6035, Kota Samarahan Expressway, 94300 Kota Samarahan, Sarawak, Malaysia.
⁴ Graduate School of Bioagricultural Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.

PMID: 28242223
DOI: 10.1016/j.scitotenv.2017.02.165

Abstract

To understand the variations in the decomposability of tropical peat soil following deforestation for an oil palm plantation, a field incubation experiment was conducted in Sarawak, Malaysia. Peat soils collected from three types of primary forest, namely Mixed Peat Swamp (MPS; Gonystylus-Dactylocladus-Neoscrotechinia association), Alan Batu (ABt; Shorea albida-Gonstylus-Strenonurus association), and Alan Bunga (ABg; Shorea albida association), were packed in polyvinyl chloride pipes and installed in an oil palm plantation. Carbon dioxide (CO₂) and methane (CH₄) fluxes from soil were monthly measured for 3years. Environmental variables including soil temperature, soil moisture content, and groundwater table were also monitored. The pH, loss on ignition, and total carbon (C) content were similar among the three soils, while total N content was larger in the MPS than in the ABg soils. Based on ¹³C nuclear magnetic resonance (NMR) spectroscopy, C composition of the MPS and ABg soils was characterized by the largest proportion of C present as alkyl C and O-alkyl C, respectively. The C composition of the ABt soil was intermediate between the MPS and ABg soils. The CO₂ fluxes from the three soils ranged from 78 to 625mgCm^-2h^-1 with a negative correlation to groundwater level. The CH₄ fluxes ranged from -67 to 653μgCm^-2h^-1. Both total CO₂ and CH₄ fluxes were larger in the order ABg>ABt>MPS (P<0.05). Annual rate of peat decomposition as was estimated from cumulative C loss differed up to 2 times, and the rate constant in exponential decay model was 0.033y^-1 for the MPS soil and 0.066y^-1 for the ABg soil. The field incubation results of the three forest peat soils seem to reflect the difference in the labile organic matter content, represented by polysaccharides.

Keywords: (13)C NMR; Decomposition; Greenhouse gas flux; Oil palm plantation; Tropical peat swamp forest.