Soil carbon and nitrogen dynamics in a tropical peatland. In Soil Management and Climate Change

Abstract

Tropical peatlands are primarily formed in coastal areas, developing behind mangroves, where sulfides and anoxia in the mud and water restrict bacterial activities, leading to a re duced decomposition of plant debris and an accumulation of organic matter as peat (Mutert et al., 1999). Tropical soil is organic soil, sometimes referred to as peat soil, which, by defini tion, according to Couwenberg (2009), is soil with more than 20% of organic matter. Peat soil naturally accumulates under anaerobic conditions, which favor the incomplete decomposi tion of organic matters to form peats (Sabihan et al., 2012). The production of peat soils is also favored by a cool, wet climate with water logged poorly drained environment, which helps preserve the plant remains and prevent them from rapid decomposition. These conditions highlighted above, though favor the formation of peat soils, but make the peat soils unsuit able for agriculture. Among the major primary nutrients required by microorganisms present in the peat soil are carbon, nitrogen, phosphorus, and potassium (Wang and Moore, 2014). Of these, soil carbon, followed by nitrogen, has the highest percentage in composition depending on whether the soil is organic or inorganic (Hood-Nowotny et al., 2010). According to the definition of tropical peatland organic soil given earlier, the soil carbon content ranges from 40% to 65%, and it could be as low as 10%–11% in other areas if the peatlands have been in use for some time. The stored carbon is being lost due to anthropogenic and natural activities, which include deforestation, logging activities, and bush burning, that the peatlands are being subjected to in these areas (Davies et al., 2013; Ayeni et al., 2014; Englhart et al., 2014; Crutzen and Andreae, 2016). According to Batjes (1996), the world’s soil collectively stores nearly 2200Gt (billion tonnes) of carbon, about 80% of total C in the terrestrial biosphere. Two-thirds of this is in the form of organic matter, which is three times the amount of carbon held in the atmosphere (Lal, 2004). As a result of their high organic matter content, peatlands have large quantities of carbon and are known as carbon sinks (Ardo, 2015). Several studies have been carried out, varying from estimating the carbon stored within the peat soil (Wahyunto et al., 2004) to the factors controlling the carbon flux in the peatland (Kayranli et al., 2010). Maltby and Immirzi (1993) also concluded that peatlands can store up to 525Gt of carbon, despite the fact that they only occupy 3% of the earth’s total land area. The global tropical peat covers about 0.3 and 0.5 million km2 (Maltby and Proctor, 1996; Lappalainen, 1996). Peat soil with a high quantity of carbon locked up in the soil is mostly found in Southeast Asia. In Malaysia, a country with the highest amount of carbon stored in the soil after Indonesia, the quan tity of peat soil carbon content ranges from 44.6% to 47.8% of agricultural soil in Sarawak (Sajarwan et al., 2002; Melling et al., 2005); this was also supported by Lähteenoja et al. (2009) and Jaya (2007).