Photosynthetic Efficiency and Leaf Traits of Shorea leprosula Grown Under the Sun and Shade Conditions in Lentang Forest Reserve

Abstract

Rehabilitation of degraded forests can be a huge challenge as these areas usually face problems including weed invasion, nutrient-deficient soil, lack of seed source and inability of native tree species to colonise or regenerate naturally. Human intervention is thus needed to accelerate the process of rehabilitation. In this regard, using the right species is as important as providing the right environment to encourage the survival and establishment of seedlings. Therefore, the aim of this study was to compare the photosynthetic characteristics and leaf traits of Shorea leprosula trees grown under the sun and shaded environments in a degraded forest. Shade trees were found to have about 20% higher leaf dry weight and 5% higher leaf area as well as significantly (p < 0.05) more chlorophyll than leaves on sun trees. Leaves in shade trees attained maximum photosynthesis at lower photosynthetic photon flux density (PPFD) compared to sun trees. When comparing both sun and shade trees, fast chlorophyll induction curve showed no significant differences in maximum quantum yield of PSII photochemistry (F_v/F_m) and thus was almost unaffected by the leaf ambient light environment. This indicated that although shade trees received lower light intensity compared to sun trees, the physiological responses indicated that the former were capable of minimising light limitation through foliar morphological and physiological adaptations. Our results thus suggested that S. leprosula, being an economically valuable timber species, can be planted in areas with partial shade or in gaps for the purpose of rehabilitation.