Morphological and physical properties of 35 Typic Paleudults and Typic Hapludults, the major soils of the "Lowland Dipterocarp Forest" in East Kalimantan were investigated. The soil morphology was related to the texture, and occasionally to the geomorphology. The coarse soils were distinguished from the fine ones by the more frequent occurrence of gray and rusty mottles in the epipedons, thicker albic horizons, thinner cutan development in the argillic horizons, weaker mottling in the subsoils, and weaker structure development throughout the solum. Clay migration was more pronounced in the fine soils than in the coarse ones. Silt translocation was detected in the fine soils, but not in the coarse soils. Physical properties were controlled by the texture and depth. Bulk density increased with depth, and was inversely correlated with the clay and carbon contents in each horizon. Fine pore space increased with depth, and was directly correlated with the clay content. Meanwhile the coarse pore space decreased downward, and was inversely correlated with the clay content. Hydraulic conductivity was high in the topsoils and decreased with depth. The soil shrinkage pattern was assumed to be associated with the difference in morphology, and clay and silt migration.

No abstract

Status of C, N, and P including available N and P was studied in 35 Typic Paleudults and Typic Hapludults under a "Lowland Dipterocarp Forest" in East Kalimantan, Indonesia. The total C, N, and P contents decreased abruptly within the top 15-20 em layers. The contents were directly correlated with the clay content in each horizon group. The higher C, N, and P contents in the finer soils were considered to be associated with the stabilization of organic matter by clay particles and with the higher mobility of organic matter in the finer soils. The content of available N which was directly correlated with the total N content. The N availability was the highest when the C : N ratio ranged between 10 and 15. Nitrification was not as pronounced as ammonification. The available P content was well correlated with the total C content. Although the absolute level of available P did not differ remarkably among the texture types, the availability decreased with the increase of the contents of exchangeable A1, dithionite citrate soluble Fe, and clay. The amount of C, and total and available N and P stored in soils (0-150 cm depth) varied widely depending on the texture. The finer soils stored larger amounts of these elements which were distributed more largely in the subsoils (30-150 cm) than it has been believed.