Variation in flower production of nine grassland species with time since fire, and implications for grassland management and restoration

Abstract

The impact of time since fire on flower production was examined in a temperate Themeda triandra grassland in Gippsland, Victoria. Flower production by nine species (Arthropodium strictum, Bulbine bulbosa, Burchardia umbellata, Chrysocephalum apiculatum, Craspedia variabilis, Diuris punctata, Helichrysum scorpioides, Leptorhynchos squamatus and Pimelea humilis) was compared between areas burnt six months and two years previously. Thick grass in the area burnt two years previously inhibited flowering by most species. All species except C. apiculatum and D. punctata flowered most abundantly in the area burnt six months earlier, and flower production by B. bulbosa, A. strictum and C. variabilis was largely restricted to that area. There were over 100 times as many flowering plants of B. bulbosa in the most recently burnt area. C. apiculatum produced similar quantities of flowers in both zones, but D. punctata countered the general pattern for greater flower production in the most recently burnt area by flowering most abundantly in the area burnt two years previously. Some of the species studied form transient seed banks, so maximum recruitment may be attained by burning sites the year immediately after a season of high flower production, rather than delaying burning until later years, when little flowering occurs and few seeds are present for recruitment. Annual autumn burning could eliminate the threatened orchid, D. punctata.