Studies on a chronosequence of terrace soils near Reefton

Abstract

One method of studying the effects of time on soil development is the recognition and investigation of a chronosequence, wherein all the soil-forming factors, except Time, are kept constant or ineffectively varying. Hence, observed differences between soils of different ages in a sequence are regarded as the result of the influence of Time since the onset of soil formation. Three late Pleistocene glaciations have deposited morainic and alluvial debris at various times in the Reefton district. These glacial outwash surfaces were eroded and downcut by rivers during the warm interglacial periods giving rise to a series of terraces of different heights. These terraces from the lowest to the highest, correspond to a time-sequence from the youngest to the oldest in terms of soil development. Such a situation offers a good opportunity to study the effectiveness of time as a soil-forming factor. The present investigation attempts to measure the changes in some of the soil properties such as soil reaction, bulk density, amounts of C, N and P in the soil with respect to soil development.