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41,467,000 Yen (FY 1995 13,621,000 Yen)
(1) The process of fruit production
Morphological characteristics of fruits of Durio zibethinus Murray were investigated at an experimental field of Universiti Pertanian Malaysia(UPM) in Kuala Lumpur. Proportionality was observed in the allometries of lateral fruit diameter to longitudinal fruit diameter and of fruit volume to the 3/2nd power of the product of lateral and longitudinal fruit diameters. The allometry of fruit weight to the product of lateral and longitudinal fruit diameters was derived from the allometry of fruit volume to the product of lateral and longitudinal fruit diameters. The relation of fruit weight to the sectional area of peduncle satisfied a generalized power function whose exponent was ca. 2. Namely, the fruit weight dropped abruptly when the sectional area approached the minimum. The gradient of the generalized power function on log-log coordinates was hyperbolically related to the sectional area of peduncle.
(2) The growth of seedlings under different light conditions
To know the regeneration processes of tropical rain forest, growth of seedlings under the natural and artificial light conditions was surveyed. Seedlings of Shorea leprosula were cultivated under the various sizes of gaps and heights and basal diameters were measured. Both height- and diameter-growths were influenced by the gap-sizes and were high under the big gap. The effect of shading on the growth and photosynthesis of 1.5 year old seedlings of Shorea maximum was also determined. Seedlings grown under low-shaded (45% of full sunlight) condition were 1.7 times larger in height, 2.1 times larger in phytomass and 1.2 times larger in leaf area ratio than seedlings grown under high-shaded condition(15%). Results suggested that photosynthetic products should be more effectively allocated to leaves in low-shaded seedlings than in high-shaded seedlings.
(3) CO2 profile in soil at the secondary forest and grassland
The CO2 profile in soil was determined in a secondary forest and a grassland. The CO2 concentration increased with increasing depth and exceeded 100 times at 50cm deep as compared with the concentration at the soil surface. In a grassland, the CO2 concentration was higher than that in a secondary forest at any depth and was approximately double of the concentration observed in a secondary forest. These differences in CO2 concentration between the secondary forest and the grassland were considered to be caused by the carbon supplied from the buried wood. However, the profile of the CO2 concentration and the amount of carbon in soil was quite different in both sites, another factor should be considered to make clear the cause of higher CO2 concentration in the grassland.
Disturbance of Tropical forest, Regeneration, Seedling Establishment, Soil Respiration