Impact of forest plantation on methane emissions from tropical peatland

Abstract

Tropical peatlands are a known source of methane (CH4) to the atmosphere, but their contribution to atmospheric CH4 is poorly constrained. Since the 1980s, extensive areas of the peatlands in Southeast Asia have experienced land‐cover change to smallholder agriculture and forest plantations. This land‐cover change generally involves lowering of groundwater level (GWL), as well as modification of vegetation type, both of which potentially influence CH4 emissions. We measured CH4 exchanges at the landscape scale using eddy covariance towers over two land‐cover types in tropical peatland in Sumatra, Indonesia: (a) a natural forest and (b) an Acacia crassicarpa plantation. Annual CH4 exchanges over the natural forest (9.1 ± 0.9 g CH4 m−2 year−1) were around twice as high as those of the Acacia plantation (4.7 ± 1.5 g CH4 m−2 year−1). Results highlight that tropical peatlands are significant CH4 sources, and probably have a greater impact on global atmospheric CH4 concentrations than previously thought. Observations showed a clear diurnal variation in CH4 exchange over the natural forest where the GWL was higher than 40 cm below the ground surface. The diurnal variation in CH4 exchanges was strongly correlated with associated changes in the canopy conductance to water vapor, photosynthetic photon flux density, vapor pressure deficit, and air temperature. The absence of a comparable diurnal pattern in CH4 exchange over the Acacia plantation may be the result of the GWL being consistently below the root zone. Our results, which are among the first eddy covariance CH4 exchange data reported for any tropical peatland, should help to reduce the uncertainty in the estimation of CH4 emissions from a globally important ecosystem, provide a more complete estimate of the impact of land‐cover change on tropical peat, and develop science‐based peatland management practices that help to minimize greenhouse gas emissions.

Spatio-Temporal Variability of Peat CH4 and N2O Fluxes and Their Contribution to Peat GHG Budgets in Indonesian Forests and Oil Palm Plantations

“…Annual soil CH 4 emission in forest plots (14.0 ± 2.8 kg CH 4 ha −1 year −1 ) was comparable to fluxes measured in undrained peat swamp forest of Kalimantan in Indonesia (Inubushi et al, 2003;Jauhiainen et al, 2005) but under the 38 ± 13 kg CH 4 ha −1 year −1 average for Southeast Asian peat swamp forests (Hergoualc'h and . It was also lower than CH 4 emission in peat swamp forest from eddy covariance studies (e.g., Wong et al, 2018;Deshmukh et al, 2020) which account for peat surface flux as well as vegetation-mediated flux from tree stems and pneumatophores (Pangala et al, 2013;Van Lent et al, 2019).…”

Multiple processes contribute to methane emission in a riparian cottonwood forest ecosystem

“…6) and showed a strong linear relationship with evapotranspiration rate. These data suggest that methane may be emitted from cottonwood tree leaves, in association with uptake and transpiration of alluvial groundwater that had methane dissolved in it (Nesbit et al ., 2009; Long et al ., 2010; Deshmukh et al ., 2020). Further research is required to test this suggestion that cottonwood tree leaves emit methane during daytime periods.…”

“…Growing season (May–September) cumulative net methane emission to the atmosphere was very small (17.4 mmol CH 4 m −2 per period) in the cottonwood forest compared to peatland, wetland or tundra ecosystems (Knox et al ., 2015, 2016; Morin et al ., 2017; Raz‐Yaseef et al ., 2017; Deshmukh et al ., 2020). For example, cumulative net methane emission during the main growing season (late May to late September) was 254 mmol CH 4 m −2 per period for a northern peatland, typical of the most abundant peatland type in northern Alberta, Canada (Long et al ., 2010).…”

Asymmetric response of soil methane uptake rate to land degradation and restoration: Data synthesis

“…A great number of studies have attempted to explore the effect of land degradation and restoration on soil CH 4 uptake, as well as their associated driving factors in various terrestrial ecosystems (Deshmukh et al, 2020;Gütlein, Gerschlauer, Kikoti, & Kiese, 2018;Han & Zhu, 2020;Lang et al, 2020;Tan et al, 2020). In this study, Figure S1).…”

“…A great number of studies have attempted to explore the effect of land degradation and restoration on soil CH 4 uptake, as well as their associated driving factors in various terrestrial ecosystems (Deshmukh et al., 2020; Gütlein, Gerschlauer, Kikoti, & Kiese, 2018; Han & Zhu, 2020; Lang et al, 2020; Tan et al., 2020). In this study, our meta‐analysis based on more than 200 cases provided the first global assessment of the response of soil CH 4 uptake to both land degradation and restoration, to improve our comprehensive understanding of how global change can affect the CH 4 sink strength of upland soils.…”