Dipterocarpaceae: tree-mycorrhizae-seedling connections.

Research on natural regeneration of Dipterocarpaceae is described. Work in greenhouse experiments, in planting experiments in natural forests and from monitoring of natural regeneration in undisturbed natural forest are discussed. In addition work on photosynthesis measurements is discussed. The findings show that survival of dipterocarp seedlings under closed forest canopies is not related to any chemical soil properties or to light intensities. Best growth takes place nearest to the fine roots of the mother tree. The photosynthesis measurements show that 89% of the time light intensity is not high enough for photosynthesis in the dipterocarp seedlings and that these seedlings survive despite a negative carbon balance from photosynthesis. Sugar analyses of roots and stems show that available carbohydrate is relatively higher in the roots and also higher during the night time than in daytime, while also being higher closest to the roots of the mother tree, indicating a transport of sugars from the mother tree to the seedlings through the ectomycorrhizal connections. It is concluded that in practical forest management this nursing role should be taken in consideration when formulating silvicultural management options, particularly in forest regeneration