Morphological Responses of a Light-Demanding Alstonia scholaris and a Shade-Tolerant Eusideroxylon zwageri to the Air Humidity and Light Intensity

B Irawan,R A Hardiyanti,R P Tamin

doi:10.7226/jtfm.27.3.193

Abstract

The response of tropical trees to the change of light intensity has been reported to be varied among different species. Some reports argued that the growth was increasing parallel to the increasing of light intensity, but other reports mentioned that the sensitivity to the light intensity was depending on the species. Another environmental factor that has been scientifically proven to affect tree growth is humidity. While humidity itself also directly affected by the light intensity in the forest ecosystems. Therefore, it is possible that the growth pattern of trees under different light intensities is also affected by air humidity under the canopy. This research aimed to study the growth response of a light-demanding Alstonia scholaris and a shade-tolerant Eusideroxylon zwageri to the different levels of air humidity and light intensity. The experiment was conducted in Jambi, Indonesia from April to November 2019. The experiment was carried out using split plot design with factorial treatments. The main plot was the air humidity with three levels and the sub plots was light intensity with five levels. Four replicates were applied. In general, the A. scholaris tends to be more sensitive to the humidity and light intensity compared to E. zwageri. In particular, A. scholaris tends to be more sensitive to the light intensity while, E, zwageri is more sensitive to the humidity. However, there is also strong indication that the effects of light intensity to the growth, especially for A. scholaris, was affected by the humidity level.

Highlights

The tree growth is influenced by genetic factors and by the environmental factors
Shade-tolerant old-forest species The F-values of six different parameters of E. zwageri and A, scholaris seedlings that treated by different levels of air humidity and light intensity at eight months after treatment was presented on Table 1
A. scholaris tend to be more sensitive to the light intensity, while E, zwageri is more sensitive to the humidity as shown in Table 1, Table 2, and Table 3

Summary

Introduction

The tree growth is influenced by genetic factors and by the environmental factors. Many studies have been conducted in recent years to study the causal relationships between trees and local environmental factors in tropical forests (Rao & Rajput, 1999; Ogata et al, 2001; Schongart et al, (2002); Yanez-Espinosa et al, 2006). Yanez-Espinosa et al (2006) reported that each tropical species adapts to the different environmental conditions especially to the microclimatic factors. Whitmore (1996) classified the tree species of rain forest into two main functional groups according to their growth and light requirements. Similar classification was proposed that forest tree species have been divided into two: (1) pioneers, which regenerate only in open conditions, and (2) non-pioneers, which can germinate and establish under the shade of forest canopy (Swaine & Whitmore, 1988)

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