# Satellite-Based Estimation of Carbon Dioxide Budget in Tropical Peatland Ecosystems
## 3 Results
### Ecosystem Respiration  
The RMSE and bias of satellite-based \(R_{e}\) were 1.12 and 0.09 g C/m\({}^{2}\)/day, respectively, for the all three sites. In detail, the RMSEs of _UF_, _DF_, and _BF_ were 1.31, 1.22, and 0.82 g C/m\({}^{2}\)/day, respectively. The biases were \(-\)0.15, 0.45, and \(-\)0.02 g C/m\({}^{2}\)/day for _UF_, _DF_, and _BF_, respectively. The standard deviations were 1.14, 0.8, and 0.5, respectively. As shown in Figure 6, the variances of flux tower-based \(R_{e}\) were highest in _UF_ and lowest in _BF_, which was related to their vegetation coverages. _UF_ and _DF_ are relatively dense forests; however, _BF_ has lost its vegetation due to fires, resulting in a sparse vegetation area. _DF_ is a referested area that is covered by secondary forests for logging [25]. The GPP values of _DF_ and _BF_ were obviously lower than those of the intact site (_UF_). Natural forests usually have more dense vegetation coverages. Vegetation productivities are related to the amount of biomass, including leaves, foliage, branches, plant body, and litter. Consequently, \(R_{e}\) is also high in natural forests.  
The RMSE, bias and standard deviation of _UF_ were higher than the others. The NRMSEs for _UF_, _DF_, and _BF_ were 0.01, 0.01, and 0.02, respectively. From this result, _BF_ showed more uncertainties in \(R_{e}\), when considering original data distributions, than the other sites. For _DF_, a trend of a lower _GWT_ caused by drainage was already confirmed in Section 3.1. The lower _GWT_ of _DF_ than that of _UF_ had the effect of increasing \(R_{e}\), as well. The in situ \(R_{e}\) of _DF_ showed a high positive bias (0.45 g C/m\({}^{2}\)/day) due to drier conditions that promoted the decomposition of peat soil. Note the KBDI-based  
Figure 6: Daily ecosystem respirations (\(R_{e}\)) from the satellite-based approach in this study (gray solid line) and tower measurements (black dashed line) in three cases of flux tower sites: (**a**) undrained forest (_UF_), (**b**) drained forest (_DF_), and (**c**) burned forest (_BF_).  
_GWT_ for \(R_{e}\) calculation in _DF_ did not consider the effects of drainage canals. Hence, we concluded that _UF_ provided the most suitable model to extrapolate \(R_{e}\) flux observations to spatial estimations. From the annual average maps of \(R_{e}\) from 2002 to 2018, the carbon (C) emissions by \(R_{e}\) were high (814.63 Mt C/year), middle (754.76 Mt C/year), and low (404.70 Mt C/year), in the _UF_, _DF_, and _BF_ sites, respectively (Figure 7). Pixels with values larger than 1000 g C/m\({}^{2}\)/year were not confirmed in the \(R_{e}\) maps. This means that the method proposed in this study to estimate \(R_{e}\) only depends on a formula that represents the groundwater condition in peatlands. Choosing appropriate ground conditions is necessary and affects spatial distribution of \(R_{e}\). However, we only considered a baseline of \(R_{e}\) when using the data at the _UF_ site, assuming that all peatlands were intact and the \(R_{e}\) was high due to the forest productivity and autotrophic respiration being high, since those are related to vegetation growth rate [56].  
Figure 7: Spatial distributions of annual average ecosystem respiration (\(R_{e}\)) from 2002 to 2018 in three cases created using (**a**) undrained forest (_UF_), (**b**) drained forest (_DF_), and (**c**) burned forest (_BF_) equations.