EFFECT OF LEAF LITTER ON SEED DORMANCY, GERMINATION AND SEEDLING SURVIVAL OF THREE TROPICAL FOREST TREE SPECIES IN GHANA

Abstract

The exact role of leaf litter and its interaction with irradiance in tree species regeneration is still poorly understood. We conducted a three – factor full factorial plant house experiment to determine the effect of leaf litter and irradiance (with particular interest in their interaction) on germination and seedling survival of three tropical tree species, namely; Khaya anthotheca (Welw.) C.DC., Terminalia superba Engl.& Diels and Cedrela odorata L. We made three predictions: 1. Seeds of tropical tree species take a longer period to germinate and also have lower germination percentage at full irradiance, 2. seedling survival is lower at full irradiance, 3. presence of litter at full irradiance reduces length of seed dormancy and increases seed germination and seedling survival. Our results indeed showed higher mean lengths of seed dormancy and lower germination percentages at full irradiance for all three species tested. Also, seedling survival was lowest at full irradiance and highest at intermediate irradiance. Germination percentages of all three species were higher with litter present than when litter was absent. The positive effect of litter on seed germination was higher at higher levels of irradiance. Presence of litter reduced length of seed dormancy only for seeds of C. odorata, but litter had no effect on seedling survival of any of the tested species, contrary to prediction. We suggest that very high irradiances may have adverse effects on regeneration of studied species, but presence of leaf litter may ameliorate adverse effects of high irradiance