Modelling the Effects of Physiological and Morphological Characters on Oil Palm Growth and Productivity

摘要

The model OPRODSIM is a mechanistic simulation model of oil palm growth and yield, the output of which depends crucially on the values assigned to various physiological and morphological characters. In this article, the effects of manipulating these values are explored and related to what is known concerning the magnitude of their natural variation. The main physiological and morphological variables in crop growth simulation models include leaf photosynthetic characteristics such as the initial light-use (quantum) efficiency (a) and the photo-synthetic rate at light saturation (AMAX), the canopy structural features affecting the capture of radiation, summarized in terms of the radiation extinction coefficient (k), the partitioning of assimilates between the various organs, and morphological attributes, which either influence or are the outcome of, underlying physiological processes. In relation to its morphology, the specific leaf area (m2 kg-1 dry weight) of the fronds of oil palm is of interest as this may affect the efficiency of light capture in relation to dry matter allocation. Other aspects of palm growth considered in the model are frond expansion rate, frond production rate (determined as the emergence rate which influences not only the allocation of dry matter to fronds but also the production of inflorescences that are located in the frond axils), the rate of increase in height of the trunk (which has practical implications in terms of ease of harvesting of bunches), the rate of root biomass turnover (possibly a source of wasteful assimilate use) and the bunch development time (time from anthesis to ripening), which affects standing biomass and maintenance respiration requirements. Assimilate storage and frond turnover are also briefly discussed. The effects of varying each of these parameters is examined and a sensitivity analysis undertaken where appropriate, to determine the relative importance of each. The results are compared with those of previous studies.