## 4 Discussion  
### How Land Use Change Affects Soil Respiration in Tropical Peatland Ecosystems  
Total soil respiration in the different peatland cover types ranged from 40 to 50 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\), and heterotrophic respiration ranged from 31 to 41 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\) (Table 1). Similar total soil and heterotrophic respiration were measured in the intact forests, logged forests, and oil palm estates (\(p>0.05\)). However, significantly lower total soil and heterotrophic respiration were found in early seal than intact forests (\(p<0.05\)). We suspect that the lower heterotrophic respiration in early seal sites may be due to the loss of significant soil microbial populations and the decline of labile - non-recalcitrant forms of organic carbon as a result of repeated fires and losses of dissolved organic carbon in early seal ecosystems [42]. Soil respiration (48.5 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) of the intact forests in this study was similar to that reported in a review of South East Asia peatlands [43] but slightly lower than studies from Sumatera, Indonesia (59 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [25]), South Kalimantan, Indonesia (55 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [21]) and Sarawak, Malaysia (77 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [24]). The total soil respiration of logged forest (50.2 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) in our study area was much lower than those reported from a logged forest in Sumatera (68 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [25]). The differences in soil respiration in these logged forests may vary in the definition of logged forests. In this study, logged forests were only partially logged by local communities (often for domestic uses) and impacted by a 3-m wide and 2-m deep canal to the north (>0.5 km in the distance) and an 8-m wide and 1-m deep canal to the east (4.5 km in the distance). In contrast, other studies measured respiration where drainage canals are denser, and the entire large overstory had been removed. Soil respiration in our early seal sites (30 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) was also lower than bare land sites in Sumatera (60 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [44]). Similarly, our soil respiration in the sampled oil palm estates (47.5 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) was lower than studies in Sarawak, Malaysia (55 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [24]) and Sumatera, Indonesia (104 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [25]). However, the value was similar to a study in Kalimantan, Indonesia (44 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\); [21]). Those differences may have been affected by the use of different methodologies in measur  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Site**} & \multicolumn{3}{c}{**Water Table Depth Level (cm)**} & \multicolumn{3}{c}{**Soil Temperature (\({}^{\circ}\)C)**} \\ \cline{2-7}  & **Dry Months** & **Wet Months** & **Annual** & **Dry Months** & **Wet Months** & **Annual** \\ \hline Peat swamp forest & 81 \(\pm\) 13 & 21 \(\pm\) 8 & 46 \(\pm\) 6 \({}^{\mathrm{a}}\) & 27.3 \(\pm\) 0.5 & 27.1 \(\pm\) 0.3 & 27.2 \(\pm\) 0.1 \({}^{\mathrm{a}}\) \\ Logged peat swamp forest & 74 \(\pm\) 13 & 15 \(\pm\) 9 & 40 \(\pm\) 6 \({}^{\mathrm{a}}\) & 27.0 \(\pm\) 0.5 & 27.1 \(\pm\) 0.6 & 27.0 \(\pm\) 0.1 \({}^{\mathrm{a}}\) \\ Early seal & 84 \(\pm\) 21 & 26 \(\pm\) 13 & 50 \(\pm\) 7 \({}^{\mathrm{a}}\) & 30.0 \(\pm\) 0.8 ing the soil respiration (portable EGM vs. gas sampling), as well as the inherent differences in land use, peat-soil characteristics [45; 46] latitude, and groundwater table [47]. These results suggest that soil respiration of tropical peat forests is highly variable, site-specific, and likely high in annual variation [48].