Effect of groundwater level fluctuation on soil respiration rate of tropical peatland in Central Kalimantan, Indonesia

Abstract

Soil respiration (SR) rate was measured at the burned land (BL), the cropland (CL), the forest land (FL) and the grassland (GL) of a tropical peatland in Central Kalimantan, Indonesia from 2002 to 2011 for the purpose of analysis with a relation to the drying and rewetting. The SR rate was fitted with groundwater level (GWL) to the equation of log(SR) = α-β × GWL using hierarchical Bayesian analysis where α and β were regression coefficients classified by GWL changing directions (drying, rewetting and fluctuating), water-filled pore space (WFPS) ranges in topsoil (low 0-0.54, intermediate 0.54-0.75 and high 0.75-1 m 3 m −3), and land uses (BL, CL, FL and GL). SR rate (Mean ± SD, mg C m −2 h −1) was the significantly largest in the CL (333 ± 178) followed by GL (259 ± 151), FL (127 ± 69) and lastly BL (100 ± 90). In the CL, the significantly larger SR rate was found in the rewetting period than in the drying period in the high WFPS range. Also, the significantly steeper slope (β) in the rewetting period was obtained in the high WFPS range than in the drying period. These results suggested that the rewetting of peatland enhanced the SR rate rapidly in the CL, and that the further rise of GWL decreased the SR rate. In contrast, the SR rate in the rewetting period was significantly smaller than in the drying period in the BL in the high WFPS range, because the BL in the high WFPS range was flooded in most cases. The SR rate in the rewetting period was not significantly different from the drying period in the FL and GL. All of β were significant in the high WFPS range in all land uses, but not in the lowintermediate WFPS ranges, suggesting that GWL was not controlling factor of the SR rate when the GWL was deep due to the disconnection of capillary force under dry conditions. According to the results of correlation analysis of the α and β, the α was significantly correlated with relative humidity, soil temperature and soil pH, suggesting that the α was enhanced by dry condition, high soil temperature and neutralization of soil acidity, respectively. The β was significantly correlated with exchangeable Na + and Mg 2+ in the soil, but the reason was not clear. In conclusion, SR rate was enhanced by rising GWL with rewetting in the CL in the high WFPS ranges as well as by deepening GWL.

Factors affecting oxidative peat decomposition due to land use in tropical peat swamp forests in Indonesia

“…Higher soil temperatures have been reported to enhance SR in tropical peatland (e.g., Melling et al, 2005;Ali et al, 2006;Ishikura et al, 2017); however, our results showed only a weak positive correlation between PD and soil temperature (p < 0.05) at DB, which lacked a canopy. Moreover, our results suggest that PD could predominantly be explained by variation in GWL.…”

“…3a and b). A large CO2 efflux in November 2014 at DF was removed from the correlation analysis, because rewetting can temporarily enhance decomposition or respiration during a dry period (as detailed in Ishikura et al, 2017). At DB, PD peaked at the beginning of the dry period and decreased with decreasing GWL until GWL reached a depth of -1.4 m. By contrast, PD increased with decreasing GWL in the wet season, when there was a relatively high GWL (Fig.…”

“…4c), implying that other factors besides GWL enhanced PD after the dry period in 2014. Ishikura et al (2017) examined the larger SR rate during the rewetting period in cropland on tropical peatland. They considered that the decomposition of labile organic matter derived from dead microbes and that the modification of organic matter during dry periods (Birch 1958;Marumoto et al, 1977;van Gestel et al, 1993) contributed to the enhanced CO2 emissions.…”

CO2 fluxes from drained tropical peatland used for oil palm plantation in relation to peat characteristics and crop age after planting

“…Draining the excess of water to provide aerobic layer can lower the groundwater table and increase air and soil temperature. The tendency of higher soil temperature at deeper groundwater level was reported by Ishikura et al (2017) and Wakhid et al (2018). As a result, microbial activities in peat decomposition process increase and release a significant amount of carbon to the atmosphere.…”

Soil carbon dioxide emissions due to oxidative peat decomposition in an oil palm plantation on tropical peat

“…Due to the limitations of field studies, the controlling factors of soil CO 2 efflux are not well understood at the process level. For example, it was reported that no significant relationship exists between R S and groundwater level (GWL) (Jauhiainen et al, 2008), probably due to the disconnection of capillary force under dry conditions, resulting in soil moisture in the topsoil becoming decoupled from the GWL (Ishikura et al, 2017). Soil moisture in the topsoil can be a better predictor than GWL for soil CO 2 efflux (Melling et al, 2005(Melling et al, , 2013a, because soil moisture is affected more by capillary rise than GWL when a peat soil is compacted (Price, 1997;Michel et al, 2001).…”