Performance of late successional rainforest species following sudden exposure to shade and sun

Abstract Sudden changes in the light environment are common both for seedlings in the understory of natural forests, and for plants transplanted from nurseries to restoration areas. Yet, how seedlings react to these changes is poorly understood. The present study investigates responses of 23 late successional rainforest tree species to sudden exposure to shade and light. The experiment was conducted in a nursery near Jambi, Indonesia. After an initial acclimation of two months where seedlings were acclimatised to shade (30% light) and sun conditions (100% light), ten plants of each species were moved from shade to sun and from sun to shade, while the remaining plants stayed as controls in shade and sun, resulting in four treatments. Reactions were assessed by measuring height, diameter and chlorophyll fluorescence from nine weeks before moving and until 36 weeks after moving. Compared to species with simple leaves, compound-leaved species showed faster growth rates in all treatments. Assessed by chlorophyll fluorescence, plants moved from shade to sun suffered from sudden light stress, while plants moved from sun to shade immediately recovered from light stress. Height growth was faster in shade than in sun, whereas diameter growth was less sensitive to the environment. However, reactions were species-dependent, and some species were highly sensitive to changes whereas others were quite robust. Our findings suggest that the growth of late successional species is favored by moderate shade but that it is possible to find species that thrive well under high light.