Soil-landscape and soil-hydrological relationships in the Glendhu Experimental Catchments, East Otago Uplands, New Zealand

Abstract

Soil-landscape relationships were investigated in a first-order catchment and a fifth-order catchment of the Waipori River. The soils are formed mainly from loess and loess−colluvium derived fromschist, with limited inclusions of rock material from under lying schist bedrock. Five soil series are identified primarilyon the basis of differences in soil drainage. Occurrence of soil series within the landscape is related to a combination of aspect and slope angle while the depth of regolith is related to a combination of landform element and slope angle.

Five soil profiles within a first-order catchment were analysed for chemical, mineralogical, and hydrological properties. Allsoils are acidic, strongly leached, and moderately weathered. Pedogenesis and geomorphology are discussed in relation to glacial history, climate, and vegetation. Evidence is presented to indicate that the change from forest to tussock grassland vegetation, 700−1000 years ago, has had a major impact on the development of a perch-gley profile morphology.

Permeable conditions are largely confined to the upper 0·10−0·15 m depth and to underlying very stony horizons below 0·50 m depth. All profiles have one or more horizons with very slow permeability. Under high or prolonged rainfall conditions, water will perch above slowly permeable horizons and flow laterally within more permeable surface horizons. This conclusion is in agreement with previous water-flow measurements in the catchment.