Responses of three dipterocarp species to light regime

Adaptability to light conditions was examined for seedlings of three specie s of Dipterocarpaceae, Shorea leprosula, S. ovalis and Dryobalanops lanceol ata, possessing different ecological and silvicultural properties. S. lepro sula and S. ovalis showed significant morphological adaptations to weak lig ht conditions by changing leaf weight ratio, root weight ratio and leaf are al weight, as compared with D. lanceolata which is the most shade tolerant among the three species. When the shade-adapted leaves of each species were released from shading, they showed depression in photosynthetic activity, though the extent of depression differed with species. Only S. leprosula sh owed a recovery in photosynthetic rate 18 days after the release from shadi ng. This result indicates that S. leprosula was more adaptable to increase in light intensity than the other two species. S. leprosula could be regard ed as one of the adaptable species for reforestation in degraded open land.