EFFECTS OF LIGHT ON SEED GERMINATION AND SEEDLING ESTABLISHMENT OF A TROPICAL RAINFOREST CANOPY TREE,POMETIA TOMENTOSA

Aims Pometia tomentosa is the major dominant species in the tropical seasonal rain forests of Xishuangbanna,Southwest China.It is listed in the rare and endangered species in China.Research on seed and seedling ecology of P.tomentosa may provide information for rare and endangered species conservation and forest restoration.Methods Shade house and forest experiments were designed to investigate light effects on seed germination and seedling establishment of P.tomentosa.Seedling growth,biomass allocation and physiological properties of P.tomentosa were examined in neutral-density shade houses,which were used to mirror different light levels in centers of forest gaps,at edges of forest gaps and forest understory.Important findings Results showed that final seed germinations in all treatments were greater than 95% and occurred within six days.Seedlings in 30% light treatment had the highest root mass ratio(RMR)and stem mass ratio(SMR).However,seedlings in 10% and 3.5% light treatments had the highest leaf mass ratio(LMR).Seedlings grown in low light environments(such as 10% and 3.5% light treatments)had a higher leaf area ratio(LAR)than those in high light(30% light treatment).Seedlings in 30% light treatment had the highest maximum photosynthetic rate(Pnmax),dark respiration(Rd)and light saturation point(Isat),but the compensation point(Icomp)was not significantly different among the three light treatments.Seedlings of P.tomentosa were able to grow slowly and survive for a long time;therefore,it is a shade tolerant species.Also,seedlings of shade houses showed increased RGRM and RGRH in high light comparing with low light.It is concluded that gaps in the forest canopy are probably necessary for successful regeneration of P.tomentosa.Soil moisture also may affect the habitat selection of P.tomentosa seedlings.