Abstract:
Much of the structural, floristic and dynamic variation in the hyperdiverse dipterocarp forest on the 52 ha long term ecological research plot at Lambir, Sarawak, is associated with soil differences, as indicated by topography, labile topsoil nutrients, and humus. This review expands the edaphic characterisation of the plot by collation of published and unpublished data on soil morphology, physical properties and non-labile nutrients. Topographically the plot consists of two dipslopes at different elevations with a steep and unstable intervening scarp. Sandstone underlies the main upper dipslope and shale the lower, and the scarp has mixed clastic sedimentary lithology. Most of the dipslope soils are moderately developed Red Yellow Podzolics (Acrisols/Udults). They are of medium depth, with thin topsoils and reddish yellow blocky subsoils that become redder, finer textured, firmer and blockier with depth. Textures vary with lithology, and range from loamy sand over sandy loam on sandstone to silty clay over clay on shale. The scarp has shallower, stonier and less horizonated Skeletal soils (Cambisols/Inceptisols). All of the soils are very acid, and have low contents of all labile nutrients. Contents of non-labile forms of P are low and those of Ca extremely low, but K and Mg are moderate. All nutrients are significantly lower in sandstone soils than on shale. The differences are more pronounced for non-labile than labile forms and in subsoils than topsoils. Ratios of mineral nutrient are stoichiometrically typical for Red Yellow Podzolics on clastic sediments, and differ from morphologically similar soils on other parent materials. The ecologically significant reserves of K and Mg are attributed to small but sustained replenishments by mica weathering.
