Long-term effects of burning on growth, flowering, and carbohydrate reserves in narrow-leaved snow tussock (Chionochloa rigida)

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Abstract
Previously published results on certain short-term physiological responses to the spring burning of narrow-leaved snow tussock, Chionochloa rigida, have been confirmed and extended to include nonstructural carbohydrate reserves and to cover a greatly extended response period of 14 years. Vegetative growth, measured as leaf elongation, increased significantly during the first two post-fire seasons, but then declined relative to that of adjacent unburnt plants. Production of new leaves and tillers, which both increased significantly in the two seasons after fire, was not subsequently significantly depressed. Although narrow-leaved snow tussock is characterised by capricious flowering, flowering was invariably prolific in the first season after burning. Flowering then declined relative to that of unburnt plants, over the next 13 seasons. Mean seasonal levels of nonstructural carbohydrate reserves, in both leaf and stem tissue, were significantly depressed in the year after spring burning. Thereafter, the small increase in mean seasonal carbohydrate levels, over those in unburnt plants, appeared to reflect rather than determine growth patterns. Reburning produced a response similar to that of the initial fire, but the magnitude of the response increased with the interval between fires. Above-ground biomass of tussock recovered slowly after burning and required about 14 years to approach that of nearby unburnt plants. Application of the results to the management and conservation of the grasslands dominated by C. rigida is discussed and suggestions offered to account for some of the responses this species shows to burning that have yet to be adequately explained.