Effect of Light Intensity on Growth and Photosynthesis Related Variables of Forest Tree Seedlings

Abstract

 Growth and related photosynthetic parameters were studies in three forest tree seedlings; Hopea odorata Roxb., Dalbergia cochinchinensis Pierre and Tectona grandis L.f.. Seedlings were transferred to 25 cm diameter pots filled with soil media and placed under different light intensities including 100% (light on canopy), 40% (light under canopy) and 10% (light above the ground forest) at the nursery in the Faculty of Forestry, Kasetsart University, Bangkok for 1 year. The objectives of the study were 1) to study growth, chlorophyll content, chlorophyll efficiency, and specific leaf area in different species and light intensities and 2) to manage the areas of plantation, degraded lands, or natural forest for increasing biodiversity based on this study.

All 3 species had the greatest growth rate under full light intensity (100%) and T. grandis also performed best under medium light intensity (40%). Growth in all species decreased at the low light intensity (10%). Chlorophyll, which is the essential element in photosynthesis, tended to decrease when light intensity increased while chlorophyll efficiency varied within species. Chlorophyll contents in H. odorata was higher than both of D. cochinchinensis and T. grandis. Moreover, low light intensity resulted in reduction in leaf thickness in order to acclimate to capture more light. Although, growth rate of all species was low under the low light intensity, D. cochinchinensis showed the highest growth followed by H. odorata and T. grandis. Overall, D. cochinchinensis was recommended for planting under limited-light condition such as the natural forest covered with plant canopy. H. odorata was recommended to establish in the open area for restoration propose while T. grandis can be planted after H. odorata because the medium light is in favor for Teak growth.