Ultisols of “lowland Dipterocarp forest” in East Kalimantan, Indonesia

Abstract

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.

Key Words:

• Dipterocarp forest
• morphology
• physical properties
• Ultisols