Process-Based Modelling of Growth and Carbon Sequestration of Young Teak (Tectona grandis L.f.)

Abstract

The objectives of the research are : 1 ) To understand the processes in phenology, growth, and water balance of teak and its interaction with environmental factors, as the basis for designing quantitative relationships in modelling activity, 2) To caiibrate a process-based model that can describe the relationship between teak growth and soil water availability, 3) To predict the carbon sequestration of teak. The research consists of a modelling project and a field experiment to obtain model parameters. The model consists of three sub-models, 1.e. development, growth, and soil water balance. The objective of the mdel is to simulate teak growth, development and carbon sequestration as affected by soil moisture regime and weather variables. The model predicts individual teak growth, development and carbon sequestration on a daily time step. The field experiment was conducted for two years in Jakarta, with three levels of irrigation: control (0) , 7 and 14 mm day-' to reflect varymg seasonal water regime. The measurements included pheno fogy,i. e. : leaf emergence and drop, growth, i. e. : biomass production, arbon content, w d density, stem height diameter and volume, leaf number and leaf area index, climate variabies, i.e. : rainfall and solar radiation, and soil water content. The climatological data to run the model was obtained from the Climatological Station at Pondok Betung, Tangerang, Province of Banten, Indonesia. The results show that soil water availability affected teak development and growth. Leaf emerged regularly after reaching a thermal unit of 265 dd in the nonwater deficit condition. Leaf dropped regularly in wet and dry seasons after reaching a thermal unit of 460 dd. Water deficit inhibited leaf emergence and fasten leaf drop for the plants that always received excessive water input. Water deficit reduced biomass production, stem diameter and height, stem volume, light use efficiency. leaf number and leaf area index. Water availability did not affect carbon sequestration by teak. The excessive of water tended to reduce wood density. As water deficit affected growth and development, biomass prduction in the model was corrected by a water availability factor. The water availability factor used in this model is the ratio of actual and maximum transpiration. The process-based model built in this research can describe the dynamics of early growth stage of teak especially for leaf emergence, stem diameter, height, wood volume and soil moisture content. The model is sensitive to water availability but still cannot describe adequately the dynamics of biomass and carbon content, leaf area index and number. The water availability factor is not enough to describe it. The mdel needs to be improved and validated with a different data set.