Oil palm modelling in the global land surface model ORCHIDEE-MICT

Yidi Xu,Philippe Ciais,Peng Gong,Wei Li,Le Yu,Arthur P Cracknell,Kasturi Kanniah,Haicheng Zhang,Chao Yue,Xiuzhi Chen

doi:10.5194/gmd-14-4573-2021

Abstract

Abstract. Oil palm is the most productive oil crop that provides ∼ 40 % of the global vegetable oil supply, with 7 % of the cultivated land devoted to oil plants. The rapid expansion of oil palm cultivation is seen as one of the major causes for deforestation emissions and threatens the conservation of rain forest and swamp areas and their associated ecosystem services in tropical areas. Given the importance of oil palm in oil production and its adverse environmental consequences, it is important to understand the physiological and phenological processes of oil palm and its impacts on the carbon, water and energy cycles. In most global vegetation models, oil palm is represented by generic plant functional types (PFTs) without specific representation of its morphological, physical and physiological traits. This would cause biases in the subsequent simulations. In this study, we introduced a new specific PFT for oil palm in the global land surface model ORCHIDEE-MICT (v8.4.2, Organising Carbon and Hydrology in Dynamic Ecosystems–aMeliorated Interactions between Carbon and Temperature). The specific morphology, phenology and harvest process of oil palm were implemented, and the plant carbon allocation scheme was modified to support the growth of the branch and fruit component of each phytomer. A new age-specific parameterization scheme for photosynthesis, autotrophic respiration and carbon allocation was also developed for the oil palm PFT, based on observed physiology, and was calibrated by observations. The improved model generally reproduces the leaf area index, biomass density and fruit yield during the life cycle at 14 observation sites. Photosynthesis, carbon allocation and biomass components for oil palm also agree well with observations. This explicit representation of oil palm in a global land surface model offers a useful tool for understanding the ecological processes of oil palm growth and assessing the environmental impacts of oil palm plantations.

Highlights

Oil palm is one of the most important vegetative oil crops in the world
We aimed to model oil palm growth from young to mature plants and the specific morphology, phenology and management characteristics in the ORCHIDEE land surface models (LSMs)
Only branches and fruit bunches were simulated at each phytomer while leaf was simulated as the entirety of all phytomers at the plant functional types (PFTs) level to remain consistent with the four leaf age cohorts of the modelled phenological equations

Summary

Introduction

Oil palm is one of the most important vegetative oil crops in the world. It provides 39 % of the global supply of vegetable oil and occupies 7 % of the agricultural land devoted to oilproducing plants (Caliman, 2011; Rival and Levang, 2014). With the increasing demand for palm oil as a biofuel and a feedstock for industrial products, oil palm plantation continuously expanded from 5.59 to 19.50 × 106 ha during 2001– 2016 in the world’s top two palm oil producers, Malaysia and Indonesia (Xu et al, 2020). This rapid expansion brought about high ecological and social costs. Each phytomer has its own sequence of initiation, allocation, fruit production and pruning, they share the same stem and root biomass and the same carbon assimilation process. The the number of fruit and branch components was set corresponding to phytomer number but the leaf linked with the leaf biomass pool was divided into four age classes without duplication in each phytomers (Fig. 2)

Objectives

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Discussion

Conclusion