## 1 Introduction  
Around 44 Mha out of all worldwide peatlands (400 Mha) lies in tropical nations, of which about 15 to 21 Mha are in Indonesia [1]. A recent study updated the estimate of the total peatlands in Indonesia that is 13.4 Mha [2]. Tropical peatland ecosystems are among the largest ecosystem carbon (C) stocks on earth, with about 82-92 PgC [3, 4]. The largest peatland area is on the island of Borneo (\(\approx\)6.8 Mha) [5]. Tropical peatland forests have significantly been affected by deforestation, forest degradation, and land conversion [6, 7]. Carbon stocks of tropical peatlands have been estimated to range from 81.7 to 91.9 Pg or about 15-19% of all global peat C stocks (610 Pg) [8]. Peat forests in Indonesia store about 57 Pg C [9]. The degradation is widespread in Indonesia; intact peat swamp forest now only comprises <7% of all peatland areas in Indonesia [7]. Land-use change has shifted carbon dynamics such that the converted peatland landscapes are now net sources of carbon [10]. Factors that govern peat accumulation in the tropical peat swamp forest ecosystem are the diverse vegetation peat-forming communities, the continued supplies of woody organic matters, the inundated environment [11], and the absence of fires. When the conversion of tropical peatlands occurs, these first three factors disappear and cause the rate of peat decomposition to become higher than the rate of organic matter supply. A rapid rate of peat oxidation occurs because of sufficient oxygen availability in the aerobic peat layer due to drainage and shortage of organic matter supply due to deforestation and the change of land cover, from the forest into serial grasses and monoculture oil palm estate. Agriculture and tree estate development and management in peatlands include draining saturated soils necessary to provide suitable growing conditions [12]. Drainage canals decrease the water levels of peatlands, thus increasing aerobic decomposition rates and, therefore, carbon emissions [9]. An increase of drainage depth by 10 cm may increase emissions of about 9 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)[13]. Another consequence of drainage includes the increased occurrence of peat fires, resulting in the release of significant amounts of CO\({}_{2}\), as much as 1400 Mg CO\({}_{2}\) ha\({}^{-1}\)[14; 15]. Changes in carbon sequestration and emissions affected by peat forest deforestation and LUC can be quantified by comparing the net ecosystem production (NEP) of different land cover types in the same ecosystem [16; 17]. Net ecosystem production (NEP) is defined as the difference between gross primary production (GPP) and ecosystem respiration (ER) [16]. GPP is defined as the gross vegetation uptake of CO\({}_{2}\) utilized for the photosynthesis process [16]. Ecosystem respiration is the total CO\({}_{2}\) that is released from the ecosystem to the atmosphere through autotrophic (vegetation) and heterotrophic (microbial) respiration processes [16; 18; 19]. Net primary production (NPP) is defined as the difference between GPP and autotrophic respiration [20]. NEP is determined by subtracting heterotrophic respiration from NPP. Few studies have determined NEP in tropical peat forests [15; 21]. However, [22; 23] reported that the NPP of tropical peat forests was 11.2 Mg C ha\({}^{-1}\) yr\({}^{-1}\) and 13.2 Mg C ha\({}^{-1}\) yr\({}^{-1}\), respectively. Many studies have reported differences in soil respiration due to land use. Soil respiration was higher in intact peat forests (21 Mg C ha\({}^{-1}\) yr\({}^{-1}\)) than oil palm and sago estates (15 Mg C ha\({}^{-1}\) yr\({}^{-1}\) and 11 Mg C ha\({}^{-1}\) yr\({}^{-1}\), respectively) in Sarawak, Malaysia [24]. In contrast, it was found that soil respiration of Indonesian oil palm estates was higher (28.4 Mg C ha\({}^{-1}\) yr\({}^{-1}\)) than those in both intact and logged peat forests (16.0 Mg C ha\({}^{-1}\) yr\({}^{-1}\) and 18.5 Mg C ha\({}^{-1}\) yr\({}^{-1}\), respectively) [25].