Growth and nonstructural carbohydrate reserves inChionochloa rigidaandC. macra,and their short-term response to fire

Abstract

The relationships of growth and flowering to storage of nonstructural carbohydrate reserves and the influence of the pastoral management practice of burning on these relationships have been investigated in Chionochloa rigida and C. macra on the Old Man Range, Central Otago. Growth, as measured by elongation of the youngest exposed leaf, decreased significantly with increasing altitude. It was significantly greater in C. rigida than in C. macra. Leaf dieback did not show a significant species difference, but decreased significantly with increasing altitude in C. macra. Neither new leaf nor new tiller production was significantly affected by species. The production of new tillers did, however, decrease significantly with increasing altitude in C. macra. Spring burning increased leaf elongation, relative to unburnt plants during the first two seasons after fire, C. rigida > C. macra. Leaf dieback exceeded that of unburnt plants during the season after a spring burn, but was depressed next season. Sucrose is the major component of the nonstructural carbohydrate reserves in both species, occurring with small amounts of starch, glucose, and fructose. Reserve carbohydrates are stored in both leaf and stem tissue. Roots were consistently low in nonstructural carbohydrates. Carbohydrate reserves were lowest during the period of active growth, increasing towards the end of the growing season. Reserve carbohydrate storage (expressed as a percentage of plant dry weight) increased with altitude, with C. macra > C. rigida. Fire, which stimulated growth, reduced carbohydrate reserves to low levels, especially dunng the season of burning. Carbohydrate reserve levels were approaching those of adjacent unburnt plants by the end of the first season after fire.