Comparison of soil physical properties in evergreen and deciduous forests in central Cambodia

Abstract

We investigated soil physical properties in three forest types in tropical lowland monsoon forests in central Cambodia under the same climatic conditions, i.e., Kanhaplic Haplustults in dry evergreen forest (KH-E), Arenic Haplustults in dry deciduous forest (AH-D), and Arenic Ultic Alorthods in mixed evergreen–deciduous forest (AA-M), to clarify the relationship between forest types and soil physical properties. The clay content was correlated with water content at ψ = −9.8 and −1500 kPa (WC10 and WC1500), available water capacity (AWC), and the van Genuchten (vG) parameter N (P < 0.01). vG parameter N was in the order AH-D > AA-M > KH-E whereas vG parameter α had a high value in KH-E soil at 0–100 cm in depth. The cumulative AWC (AWCcl, mm) at a soil depth of 0–200 cm was higher in the AH-D than in the KH-E, and was not considered a major factor affecting the distribution of different forest types under the same climatic conditions. The unsaturated hydraulic conductivity (K) at 0–100 cm in depth, estimated by use of models, was higher in AH-D than in KH-E mostly at matric potential ψ > −10 kPa. The low K in KH-E at ψ > −10 kPa was considered favorable for evergreen trees to retain the soil water for the transpiration in the dry season, and the matric potential in KH-E showed more gentle decreases in the early dry seasons than AH-D. Thus the differences in K among generally sandy soil types could possibly affect the establishment of different forest types in the study area with the same climate.