Characteristics of soil and productivity of Pinus radiata (D Don) in New South Wales .II. Pedogenesis on a range of parent materials

Abstract

Soil profile descriptions were made at a series of 11-year-old unfertilized Pinus radiata stands in the Lithgow district of New South Wales. Catenas within three soil parent materials were selected to compare variation in soil physical and morphological properties with growth of P. radiata. These parent materials were a Silurian siltstone, a Permian conglomerate and a Silurian-Devonian rhyolite. Basal area growth of the P. radiata stands increased down catenas on the Silurian siltstone as soil depth to a root impeding layer increased. Plateau soils on the Permian conglomerate had hardsetting surfaces and high gravel contents, and were associated with very poor pine growth. By way of contrast, lower slope, colluvial gradational earths were deep, fine-textured soils and supported more productive pine stands. The Silurian-Devonian rhyolite parent material produced highly leached soils, commonly with conspicuously bleached A2 horizons and poor sandy textures of surface soil. Both physical and chemical features of the rhyolite interacted with pedological processes to affect adversely soil physical conditions and trace element availability, in particular boron. The poorer P. radiata growth on lower or concave slope in comparison with upper slope position was a result of increased soil leaching and horizon differentiation. This pattern contrasted with improved pine growth on the deeper soils on lower slopes on the two sedimentary parent materials. These case studies emphasize the importance of geology and pedological processes when evaluating the applicability of specific soil physical factors to site classification for P. radiata plantations.