Recovery of Chionochloa rigida tussocks from fires in South Island, New Zealand

Abstract

Tussock and tiller characteristics of snow tussock ( Chionochloa rigida ) were sampled at 13 tussock grassland sites in eastern Otago, New Zealand. The sites were located at 500 m to 1100 m altitude in areas with minimal grazing by introduced mammals. They were last burnt 1 to 26 years prior to sampling. Collective tiller area per m2 and maximum lamina length per tussock were significantly correlated with time since last fire. Using these parameters and a jack-knifing procedure, the time since the last fire for four of the 13 sites (30%) could be predicted within 3 years. The predictions were not improved by adding altitude as a factor. The time since the last fire for the most recently burnt sites or those burnt more than 25 years previously could not be predicted by any of the tussock or tiller characteristics. In montane and subalpine tussock grassland in eastern Otago, burnt tussocks, under low intensity pastoralism, are estimated to take 15–20 years to reach a state similar to that of tussocks which had not been burnt for at least 25 years. Grazing of recently burnt tussocks severely retards their recovery from fire.