Pasoh Forest Reserve (PFR), which is located in Malaysia at 2° N and 102° E, is far from any industrialized or urbanized areas, suitable for providing background information on tropical forest soil properties. Hence, the objective of the study was to determine the physicochemical properties of the PFR soils. Three plots of 9 x 9 m were established and divided into 1 ´ 1 m subplots. Two subplots of dimension 1 x 1 m were sampled in each plot resulting in a total of six subplots selected for soil analysis. A pit of 1 m deep was dug out and soil samples were taken from every 10 cm layer until 1 m depth. Soil acidity (pH), moisture content, bulk density, electrical conductivity, available phosphate (PO₄^2_), available sulphate (SO₄^2_), exchangeable acidity, exchangeable Al and H, exchangeable base cations, Effective Cation Exchangeable Capacity (ECEC) and base saturation were determined. The results indicated that the soil profile was characterized by A, E, EB, and B horizon with respective characteristics. Mean base saturation values of the PFR soils were 78.77 ± 3.78% and strongly correlated with the exchangeable Ca. The physicochemical properties of the PFR soil is similar to the previous studies and presumably unaffected by anthropogenic and natural activities.

Pasoh Forest Reserve (PFR) is a very important research area for evaluating the effects of long-range transport and deposition of acidic substance on soils in areas of removed anthropogenic activities from sources. Major setbacks in the advancement research into acid deposition in Malaysia are due to lack of studies on changes of soil chemistry. Soil sensitivity to acidic deposition is based upon the chemical properties such as soil's effective cation exchangeable capacity, base saturation, exchangeable base and pH, while the physical properties such as moisture content, bulk density, electrical conductivity and soil profile are as essential as the chemical properties in influencing the buffering capacity of a soil. This study is important because it provides the current soil status throughout 100 cm, which is a comparative study to Allbrook (1973) and Yoda (1978). The objective of the study was to determine the physicochemical properties of soils at PFR for evaluating the extent of anthropogenic and natural activities. This study contributes significantly to the establishment of baseline information on tropical forest soil properties and level of soil acidification due to air pollution in Malaysia. Hence, the results provide fundamental information integration of soil data, which can be further correlated with the acid deposition impact on forest decline.

There are a few different soil series in PFR derived from acidic granites, shales and inter-bedded shales and sandstones (Allbrook, 1973). However, only three different soil series in PFR were selected for physicochemical properties determination. The shales derived soils (Malacca, Durian and Batu Anam Series) form a topographical sequence ranging from reddish brown laterites at the top of low hills (hummocks) to pale brown soil at the valley bottom. The soils are clayey and compact in texture. The granite-derived soils (Tampin series) are pale in color and contain a considerable amount of angular quartz in their profiles. The interbedded shale and sandstone-derived soils (Serdang, Munchong and Bungor Series) are of variable color and texture.

Soil And Water Sciences Journal, Physicochemical Properties, Tropical Forest Soil, Pasoh Forest Reserve, Electrical Conductivity, Laboratory Analysis, Acid Deposition Monitoring Network, Chemical Soil Composition, Effective Cation Exchangeable Cation, Organic Acid Production, Soil Acidification, Remote Forest Ecosystem.