Studies of the tall-tussock (Chionochloa) vegetation/soil systems of the southern Tararua Range, New Zealand

Abstract

The vegetation/soil relationships of Chionochloa flavescens Zotov and C. pallens Zotov are described for the high-rainfall, low-alpine environment of the southern Tararua Range near Wellington. C. pallens is the dominant species on the younger soils which are better drained, as indicated by the soil air space percentages and oxygen diffusion rates. C. pallens is significantly positively correlated with soil stoniness, and negatively with percentage organic carbon, total nitrogen, and C/N ratio, whereas C. flavescens is significantly negatively correlated with the same factors. The levels of inorganic phosphorus are higher under C. pallens- than under C. flavescens-dominBited stands. The relative importance of the two species on an established time sequence of sites suggests that C. flavescens succeeds C. pallens during the process of system maturation, although C. flavescens is able to grow well on sites dominated by C. pallens once it has become established. Iron pans occur significantly more frequently beneath C. flavescens than beneath C. pallens. The relative importance of the two species at higher altitudes in the alpine zone appears to be governed as much by the stability of the soil conditions as by temperature alone. The floristics of respective communities are described and several species show a marked preference for sites dominated by one or other of the tall-tussocks. A modified height-frequency method was used as an estimate of the mass of vegetation and litter in a stand, and to show its spacial distribution. Variability in these parameters is described relative to species composition and soil factors.