Does artificial compaction affect carbon emission on tropical peat land?

Efforts to address the issue of carbon emissions of oil palm plantations have become a major topic of discussion. As a result, ideas to apply artificial compaction on peat with the aim of lowering CO₂ have been introduced. However, information on the artificial compaction effect to carbon emission of tropical peat is limited. This study is the first to experimentally investigate the in-situ artificial compaction on two ecosystems: a secondary peat swamp forest (SF) and an oil palm plantation (OP). Treatment was based on peat depth vertical compression using a fabricated hybrid compaction apparatus, which also served as a static closed-chamber for gas entrapment purposes. The mixed gas was analysed using a portable automated gas analyser for gas sampling purposes. Peat samples were collected at the end of the experiment to determine their physicochemical properties. Water table level (WTL) was also monitored. The results reveal that the physicochemical properties of peat in both ecosystems were not affected by artificial compaction due to their interaction with WTL fluctuation. Nevertheless, CO₂ and CH₄ emission changes were observed in SF, and showed inverse patterns of reduction and enhancement at a percentage ratio of 1:2 (CO₂:CH₄) based on the different treatments, suggesting that peat depth decreases as a result of compression and thus becomes closer to the WTL. Although the significantly peat decomposition proxies influenced less than 28% of carbon emissions, WTL was also a key factor that caused CO₂ and CH₄ to exhibit inversely emissions by 61% and 70% from total variation, respectively. However, this was only observed for SF, owing to substrate availability in the former. Most importantly, this study suggests that artificial compaction should be carefully defined, as compaction effectiveness will decline due to WTL fluctuation. Consideration of the confounding factor between decomposition degree and WTL fluctuation is important to further understand the effect of artificial compaction on tropical peat.