Forest soils derived from granite in northern Tasmania: an overview of properties, distribution and management requirements

Granitic rocks cover a large area in northern Tasmania, occurring as a number of discrete blocks from Trial Harbour in the west to Freycinet Peninsula in the east. The granitic rocks are mainly of Devonian age and include adamellite, granite and granodiorite. They occur in association with granite-derived alluvial sediments of Tertiary and Quaternary age. Climate varies widely over the granitic rocks resulting in a diverse range of vegetation and soil types. On a broad scale, the properties and distribution of the soils show close links to the distribution of major native forest types. Texture-contrast soils, characterised by coarse sandy and gravelly surface layers overlying clayey subsoils, predominate under dry forest types whereas gradational soils, characterised by loamy topsoils overlying clayey subsoils, are generally associated with wet forests. Texturecontrast soils have low levels of nutrients and high or moderate to high erodibility. In contrast, gradational soils under wet forest types have medium to high levels of nutrients and low to moderate erodibility.