Comparison of soil groups in North and South Westland, and the implications for land use

Abstract

Abstract The soils of North and South Westland have similar properties. The main soil groups present in both regions are gleyed recent soils, gley soils, organic soils, yellow-brown earths, podzols and gley podzols. However, the proportions and distribution of these soil groups within the landscape are not the same in the two regions. Differences in time for soil formation, landform variation and climate are chiefly responsible for the differences in proportions and distribution. The generally higher rainfall in the south compared with the north is a major influence. The parent materials and vegetation types in the two regions are broadly similar. In the north, more yellow-brown earths have formed on the widespread, low and intermediate glacial outwash terraces than on the low outwash surfaces in the south. In the south, soils of the outwash surfaces are mainly gley soils, organic soils and gley podzols. More podzols are found with yellow-brown earths in hill country associations in the north than in the south. In the south, organic soils are more widely distributed and are linked with wetter, cooler conditions. Relatively young piedmont till deposits separated by outwash surfaces, flood plains, and blocks of strongly dissected hill country dominate the South Westland landscape. In contrast, till deposits are localised in the north, with extensive outwash deposits in the form of flights of terraces located between blocks of dissected hill country. The areas and types of land that are capable of sustained use differ considerably between the two regions, because of the major differences in proportions of soil groups, landscape types and amounts of rainfall. As the soil-landscape-climate system is so dynamic in South Westland, extreme care must be exercised if the indigenous vegetation cover is to be changed. Proportions of soils with greater land use versatility are higher in the north, and this is reflected by current patterns of land use.