The Effects of Light Quality and Quantity on the Developmental Ecology of Malaysian Rainforest Trees

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The earth's remaining tropical rainforests are threatened with destruction in the next 10 years. The mechanisms are shifting agriculture, conversion to pasture, global climate changes, industrial agriculture and logging, and the reasons are over-population and short-sightedness. Knowledge which would assist in the regeneration and restoration of these forests is mostly lacking. In particular detailed knowledge of the environmental factors that determine the growth of the individual tree species in these forests is needed. Different trees vary in their tolerance to shade conditions in the forest, controlling the patterns of regeneration of these trees. Trees growing in the natural shade of forests are subjected to a reduction in light intensity and a change in the spectral quality of the light. Virtually all of the shade responses of tree have been studied at varying light levels without regard to these shifts in light quality. Thus, previous studies on shade responses of trees probably underestimate responses of trees to shade conditions. The purpose of this proposal is to study the effects of shifts in light quality independently of the reduced light intensity to which plants are exposed in the forest shade. The responses of seedlings of ten Malaysian rainforest trees to light quantity and quality will be studied in specially constructed shadehouses at the Forestry Research Institute in Kuala Lumpur, Malaysia. These trees will include pioneer species, shade-tolerant emergent and shade-intolerant emergent. The seedlings will be grown for twelve months and then be analysed for their architecture, leaf morphology and anatomy, and photosynthetic properties. The results will be compared to those from seedlings grown under natural canopy shade, and will help in understanding how these trees respond to natural light climates in the forest. Such information can also be used to help grow them in nurseries for later transplanting into regenerating forests.