Estimation of Aboveground Oil Palm Biomass in a Mature Plantation in the Congo Basin

Abstract

Agro-industrial oil palm plantations are becoming increasingly established in the Congo Basin (West Equatorial Africa) for mainly economic reasons. Knowledge of oil palm capacity to sequester carbon requires biomass estimates. This study implemented local and regional methods for estimating palm biomass in a mature plantation, using destructive sampling. Eighteen 35-year-old oil palms with breast height diameters (DBH) between 48 and 58 cm were felled and sectioned in a plantation located in Makouké, central Gabon. Field and laboratory measurements determined the biomasses of different tree compartments (fruits, leaflets, petioles, rachises, stems). Fruits and leaflets contributed an average of 6% to total aboveground palm biomass, which petioles accounted for 8%, rachises for 13% and the stem, 73%. The best allometric equation for estimating stem biomass was obtained with a composite variable, formulated as DBH2 × stem height, weighted by tissue infra-density. For leaf biomass (fruits + leaflets + petioles + rachises), the equation was of a similar form, but included the leaf number instead of infra-density. The allometric model combining the stem and leaf biomass yielded the best estimates of the total aboveground oil palm biomass (coefficient of determination (r2) = 0.972, p < 0.0001, relative root mean square error (RMSE) = 5%). Yet, the model was difficult to implement in practice, given the limited availability of variables such as the leaf number. The total aboveground biomass could be estimated with comparable results using DBH2 × stem height, weighted by the infra-density (r2 = 0.961, p < 0.0001, relative RMSE (%RMSE) = 5.7%). A simpler model excluding infra-density did not severely compromise results (R2 = 0.939, p < 0.0003, %RMSE = 8.2%). We also examined existing allometric models, established elsewhere in the world, for estimating aboveground oil palm biomass in our study area. These models exhibited performances inferior to the best local allometric equations that were developed.

Allometric equation for the commonest palm in the Central Congo Peatlands,Raphia laurentiiDe Wild

“…The distribution of biomass between sheath, petiole, rachis and leaflets also varies from one palm species to another. In this study, the biomass of the petioles and leaflets were greater than that of the rachis, which is contrary to the findings of [34] for Elaeis guineensis , where the biomass of the rachis (13.53%) was greater than that of the petioles (7.95%) and leaflets (6.02%). This difference can be attributed to the length and diameter of the petioles and also the consistency and number of pairs of leaflets which differ between palm species.…”

“…(81 % in the stem) in the Amazonian Basin [10] and Elaeis guineensis Jacq. (73 % in the stem) in the Congo Basin [34]. This difference in biomass allocation can be linked to the architecture which differs from one type of palm to another [8,10].…”

Carbon stock estimation of mixed-age date palm (Phoenix dactylifera L.) farms in northeastern Ethiopia

“…Many studies has been undertaken and published on the estimation of palm biomass at various ages [4,11,12,13,14,15,16]. Similar approach was used to estimate date palm biomass in the current investigation.…”

Evaluation of FORMOSAT-2 and PlanetScope Imagery for Aboveground Oil Palm Biomass Estimation in a Mature Plantation in the Congo Basin

“…This equation was derived from a previous study that had been conducted in the same area [36], which proposed different allometric models that were based upon in situ measurements that were collected during destructive sampling. For the rest of the present study, in situ AGB is expressed in tons ha −1 ( Table 1).…”