Soil genesis and plant succession in the Subalpine and Alpine :Zones of Torlesse Range, Canterbury, New Zealand

Abstract

The high-country steepland yellow-brown earths of Foggy Peak Ridge are examined from the following aspects: parent material, distribution and morphology, physical and chemical properties, vegetatic.i and formation. Two distinct soils are recognised within two previously described altitudinal zones, and variants within each soil are discussed. Most soils carry a strong impress of past as well as present environments and hence are polygenetic (sensu lato). The evidence gleaned from profiles proves that a mor-forming subalpine beech forest (Nothofagus solandri var. cliffortiordes) and alpine tall-tussock grassland (Chionochloa spp.) were the principal communities prior to the arrival of man in New Zealand about 1,000 years ago. Since then the vegetation has altered and soils have been rejuvenated by erosion, deposition, and dust accretion. Solifluction detritus forms a discontinuous mantle over most slopes and is the parent material of the solum. The formation of this material is correlated with late-glacial deposits nearby and, by applying the chronology established elsewhere for these deposits, it is concluded that soil formation commenced at least 8,000 years ago, achieving maximum profile stability around the post-glacial climatic optimum. Throughout the late post-glacial the region has experienced at least two and probably three phases of vegetation and soil modification of varying degrees of intensity which together are responsible for the present soil-vegetation complex. The classification of these soils is discussed and attention is drawn to other parts of the South Island with a similar soil history.