Ecophysiology of two tropical species in an abandoned eucalypt plantation: effect of plant litter removal and seasonality

Abstract

The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a fluorescence, and content of photosynthetic pigments) of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalypt (Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae)). The study was conducted at the União Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after five years of litter removal. The removal of plant litter did not influence the ecophysiological responses of the species. There was however significant seasonal variation. During the dry period, intercellular CO2 concentration (Ci), transpiration (E), and stomatal conductance (gs) were decreased, while intrinsic efficiency of water use (IWUE), non-photochemical quenching (NPQ), and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for Fv/Fm (maximum quantum efficiency) and Fm/Fo (ratio of fluorescence yields for open and closed states) indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A) during the dry period. The data indicated that X. sericea was photosynthetically more efficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed.

Keywords

• Atlantic forest
• Corymbia citriodora
• Photosynthesis
• Siparuna guianensis
• Xylopia sericea