Research ArticleECOLOGY

Carbon neutral expansion of oil palm plantations in the Neotropics

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Science Advances  20 Nov 2019:
Vol. 5, no. 11, eaaw4418
DOI: 10.1126/sciadv.aaw4418
  • Fig. 1 Soil carbon stocks after pasture conversion into OP plantations at 0- to 50cm depth.

    The dashed line represents the fitted segmented regression equation. Significance of the slope coefficients from each side of the breaking point is indicated (***P < 0.001).

  • Fig. 2 Dynamics of pasture C4-derived C and OP C3-derived C following pasture conversion into OP plantations.

    (A) 0- to 10-cm soil layer, (B) 10- to 20-cm soil layer, (C) 20- to 30-cm soil layer, and (D) 30- to 50-cm soil layer. Inset graphs show bulk SOC stocks for each layer. See Table 1 for the used functions and their kinetic parameters.

  • Fig. 3 TEC stocks.

    TEC in OP plantations and pastures includes above- and belowground biomass and SOC stocks down to 50 cm (but not dead trees after replanted). The orange diamond and its vertical SE bars correspond to the time-averaged TEC stocks in pastures. Purple circle and its vertical SE bars correspond to time-averaged TEC stocks in OP, and purple band indicates the time-averaged TEC stocks during the 56 years of OP cultivation.

  • Fig. 4 Soil chemical fertility dynamics.

    (A) Soil C content as a function of time after pasture conversion into OP plantations at the soil surface (0- to 10-cm). The yellow line represents the fitted segmented regression equation. Significance of the slope coefficients from each side of the breaking point is indicated (***P < 0.001). (B) Sum of cations as a function of time after pasture conversion into OP plantations at two soil depths: close circles, 0- to 10-cm; open circles, 30- to 50-cm. The lines represent the linear regression equations. (C) Available phosphorus (Bray P) as a function of time after pasture conversion into OP plantations at the soil surface (0- to 10-cm). The red line represents the fitted segmented regression equation. Significance of the slope coefficients from each side of the breaking point is indicated (***P < 0.001).

  • Fig. 5 PCA of soil properties in pastures and OP plantations derived from pastures.

    (A) The soil surface (0- to 10-cm) and (B) the subsoil (30- to 50-cm). BD, bulk density; C:N, C and N ratio; 13C, δ13C; N, nitrogen; EA, exchangeable acidity; Na, sodium; K, potassium; Mg, magnesium; 15N, δ15N; Ca, calcium; BS, base saturation and P, available phosphorus (Bray P). The OP plots are indicated with time after conversion in years (yrs).

  • Table 1 List of functions and kinetic parameters.

    Parameters describe changes in bulk SOC stocks and C3- and C4-derived C stocks in the four sampled soil layers. R2, coefficient of determination; slopes 1 and 2, significance of the two slopes for segmented regression analysis; K, rate constant; A, annual input of C3-C; C0, SOC stocks before pasture change to OP. **P < 0.01; ***P < 0.001.

    Soil layerModel typeFunctionR2Slope 1Slope 2AICk (year−1)Half-lifeAC0
    Bulk soil, 0- to 10-cmSegmentedF(t) = 31.87 − 0.42*t0.75***NS88.26
    OP-derived C, 0- to 10-cmExponential rise to equilibriumF(t) = −0.62*exp(−0.038*t) + 0.62/0.0380.9166.0**18.1***
    Pasture-derived C, 0- to 10-cmSingle exponential decayF(t) = 31.4*exp(t* − 0.037)0.9186.2***18.7***
    Bulk soil, 10- to 20-cmSegmentedF(t) = 24.49 − 0.36*t0.83***NS75.52
    OP-derived C, 10- to 20-cmLinearF(t) = −0.27 + 0.10*t0.8546.4
    Pasture-derived C, 10- to 20-cmSingle exponential decayF(t) = 24.1*exp(t* − 0.02)0.8480.7***34.7***
    Bulk soil, 20- to 30-cmSegmentedF(t) = 19.91 − 0.23*t0.75***NS75.08
    OP-derived C, 20- to 30-cmLinearF(t) = −0.20 + 0.07*t0.745.56
    Pasture-derived C, 20- to 30-cmSingle exponential decayF(t) = 19.8*exp(t* − 0.02)0.7977.7***40.8***
    Bulk soil, 30- to 50-cmLinearF(t) = 29.42 − 0.25*t0.7187.73
    OP-derived C, 30- to 50-cmLinearF(t) = 0.02 + 0.10*t0.6066.39
    Pasture-derived C, 30- to 50-cmSingle exponential decayF(t) = 29.8*exp(t* − 0.016)0.6999***43.3***

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaaw4418/DC1

    Fig. S1. Map of study sites and the potential area for the expansion of OP in pasture lands in the Neotropics.

    Table S1. Set of models tested for the bulk soil and pasture- and OP-derived carbon.

    Table S2. Soil chemical, physical, and isotopic properties.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Map of study sites and the potential area for the expansion of OP in pasture lands in the Neotropics.
    • Table S1. Set of models tested for the bulk soil and pasture- and OP-derived carbon.
    • Table S2. Soil chemical, physical, and isotopic properties.

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