Geographic Variation in Flowering Responses to Fire and Season of Clipping in a Fire-Adapted Plant

Abstract

Identifying optimal fire regimes for a given species requires monitoring its responses to different fire regimes. This study examined the effects of fire during the lightning season and clipping in different seasons on the induction of flowering in a fire-adapted species, Pityopsis graminifolia, in two different fire-dependent ecosystems (oak forest edges in north Mississippi and longleaf pine savannas in south Mississippi). The two ecosystems differed in the frequency of lightning (higher in south Mississippi) and the timing of peak drought conditions during the lightning season (earlier in south Mississippi). Flowering was induced by prescribed fires during the lightning season in both regions. Flowering was greater in unburned controls in north Mississippi than in south Mississippi. These differences persisted in a common grass-dominated environment in the greenhouse, suggesting a genetically-based bet-hedging strategy with respect to fire-induced flowering in north Mississippi. Flowering of both varieties responded better to clipping during peak drought periods during the lightning season than to clipping treatments at other times of the year, but the causes of such seasonal differences (be they genetic or environmental) remain unresolved at this time and require further investigation.