Significant sedge-mediated methane emissions from degraded tropical peatlands

Abstract

Sedge-mediated gas transport to the atmosphere has been recognized as a significant CH4 pathway in northern peatlands; however, in the Tropics, this pathway remains unquantified. In Southeast Asia, degraded tropical peatlands covered with sedges and ferns have increased to approximately 10% of the total peatland area due to an increased drainage and fires. In view of this, we investigated the role of sedge, Scleria sumatrensis, in CH4 emissions from a fire-degraded tropical peatland in Brunei. At our site, we found that this sedge-mediated transport contributed >70% of the total CH4 emission, making it a significant CH4 emission pathway. We also observed significant seasonal and spatial variation with values ranging from 0.78 ± 0.14 to 4.86 ± 0.66 mgCH4 m−2 h−1. This variation was mainly attributed to water table level along with changes in sedge cover and pore-water properties (pH, salinity, cations, and anions). More importantly, these numbers are three times higher when compared to intact peat-swamp forests and 17 times higher when compared to similar degraded tropical peatland covered with shrubs.