Weather and growth performance of young rubber trees (Hevea brasiliensis)

Abstract

In order to study the growth and its dynamics, influence of weather variables and to model the growth of Hevea trees without including and with including climatic variables in growth functions during the immature phase, data were collected from two contrasting locations, L1 and L2. Monthly girth data collected for six to eleven years were used for comparative evaluation and performance of Hevea clones in monthly, seasonal and annual girth, girth increments and their rates. Daily weather data was used for studying the influence of weather elements on growth. Growth was modelled using three more commonly used growth models, namely Chapman-Richards (CR), Weibull and Schumacher. Seasonal and weather components were introduced into the growth functions. The study revealed that under the drought prone dry subhumid climatic conditions prevailing at L1, active growth period of Hevea trees would be about four months from July to October. At L2, which has a tropical humid climate, active growth period of Hevea trees was about seven months from May to November with a grand period of growth from July to September. Results from correlation, multiple regression and stepwise multiple regression indicated that RF was more important than other variables. In growth modelling, CR-model proved superior with RF as a very promising modifier function for inclusion in growth functions. It was concluded that if studies of this type come forth from different environmental conditions they would be of great value in future studies of growth modelling. It is hoped that the analytical treatment provided in this study will offer a suitable approach to the investigators who wish to examine the effect of various treatments or factors on growth for furthering our knowledge on growth of Hevea trees and its modelling.