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Tropics
Vol. 7 (1997) No. 1+2 P 21-33

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http://doi.org/10.3759/tropics.7.21

Regular papers

Dryobalanops aromatica and D. Ianceolata (hereafter denoted as Lin and Dl, respectively) are major Dipterocarp species constituting an emergent layer in the Bornean Rain Forest, and their distributions are in proximity, but never overlap. Thus, we examined the relationship between the distribution of these species and soils with reference to the soil physico-chemical, morphological, and microbiological properties,
Based on the topographical investigation, was located only on the upper slope, whereas Dl occupied on both upper and lower slopes. The soil solums examined around these two species were always deeper than 1,3 meter. Soil texture was always sandy for the soils around Da, on the other hand, ranging from sandy te clayey for these around Dl. Furthermore, the following differences were found; 1) organic layer was thicker {n the Da soils, 2) soil color of subsurface horizons was duller in the Dl soils, and 3) only the Dl soils contained coarse fragments. 4) the amounts of exchangeable cations such as Ca and/or Mg and total oxides’ content of K2O, MgO, and P2O5 were higher for the Dl soils, 5) the amounts of exchangeable At and H were higher in the Da soils, 6} proportion of air phase and volume of macropore, and the value of sand content were higher for the Da soils, showing that the Da soils easily attain to drier soil moisture condition after rainfall, which was proved by monitoring soil water potential, 7) ten times as much fungal colonies were detected in the Da soils as compared to the Dl soils.
These result$ suggest that Da emerges on a sandy soil with a dominance of drier soil moisture condition for some period and a low nutrient status with high acidity on the reflection of stable pedogenetic processes, while Dl stands on either clayey or sandy soil with a dominance of reductive condition for a certain period and relatively high nutrient status with low acidity, reflecting weak pedogenctic processes. It was well-known that shifting cultivators utilize a land where Dl dominates as a productive crop field, Their traditional way of land selection proves to be rational from the standpoint of soil science.

Copyright © 1997 The Japan Society of Tropical Ecology

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