Browsing by Author "Evers, Stephanie"

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    Immediate environmental impacts of transformation of an oil palm intercropping to a monocropping system in a tropical peatland
    (International Mire Conservation Group, International Peat Society, 2022-04-14) Dhandapani, Selva; Girkin, Nicholas T.; Evers, Stephanie; Ritz, Karl; Sjögersten, Sofie
    The expansion of oil palm plantations is one of the greatest threats to carbon-rich tropical peatlands in Southeast Asia. More than half of the oil palm plantations on tropical peatlands of Peninsular Malaysia are smallholder-based, which typically follow varied cropping systems, such as intercropping. In this case study, we compare the immediate biogeochemical impacts of conversion of an oil palm and pineapple intercropping to an oil palm monocropping system. We also assess how these changes affect the subsequent temperature sensitivity of greenhouse gas (GHG) production. We found that peat bulk density is unchanged, while organic matter content, pH and temperature is slightly yet significantly altered after conversion from oil palm intercropping to monocropping. Both in-situ and ex-situ CO2 emissions and temperature sensitivity of CO2 and CH4 production did not significantly vary between conversion stages; however, in-situ CO2 emissions in monocropping system exhibited a unique positive correlation with moisture. The findings show that some of the defining peat properties, such as bulk density and organic matter content, were mostly conserved immediately after conversion from intercropping to oil palm monocropping. However, there were signs of deterioration in other functional relationships, such as significantly greater CO2 emissions observed in the wet season to that of the dry season, showing moisture limitation to CO2 emissions in monocropping, postconversion. Nevertheless, there is a need for further research to identify the long-term impacts, and also the sustainability of intercropping practices in mature oil palm plantations for the benefit of these peat properties.
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    Spatial variability of surface peat properties and carbon emissions in a tropical peatland oil palm monoculture during a dry season
    (Wiley, 2021-06-22) Dhandapani, Selva; Girkin, Nicholas T.; Evers, Stephanie
    The expansion of oil palm monocultures into globally important Southeast Asian tropical peatlands has caused severe environmental damage. Despite much of the current focus of environmental impacts being directed at industrial scale plantations, over half of oil palm land-use cover in Southeast Asia is from smallholder plantations. We differentiated a first generation smallholder oil palm monoculture into 8 different sampling zones, and further divided the 8 sampling zones into oil palm root influenced (Proximal) and reduced root influence (Distal) areas, to assess how peat properties regulate in situ carbon dioxide (CO2) and methane (CH4) fluxes. We found that all the physico-chemical properties and nutrient concentrations except sulphur varied significantly among heterogeneous zones. All physico-chemical properties except electrical conductivity, and all nutrient content except nitrogen and potassium varied significantly between Proximal and Distal areas. Mean CO2 fluxes (ranged between 382 and 1191 mg m-2 hr-1) varied significantly among heterogeneous zones, and between Proximal and Distal areas, with notably high emissions in Dead Wood and Path zones, and consistently higher emissions in Proximal areas compared Distal areas within almost all the zones. CH4 fluxes (ranged between -32 and 243 µg m-2 hr-1) did not significantly vary between Proximal and Distal areas, however significantly varied amongst heterogenous zones. CH4 flux were notably high in Canal Edge and Understorey Ferns zones, and negative in Dead Wood zone. The results demonstrate the high heterogeneity of peat properties within oil palm monoculture, strengthening the need for intensive sampling to characterise a land-use in the tropical peatlands.