Postfire Flowering Patterns in Blandfordia nobilis (Liliaceae)

Abstract

Blandfordia nobilis Smith (Liliaceae) is a small herbaceous monocotyledon that resprouts from a rhizomatous corm after fire. The complex pattern of flowering shown in the five years following a fire in January 1987 was investigated for five populations near Sydney. This pattern was then related to concurrent changes in soil chemistry.

Most (60%) plants flowered in the first post-fire flowering season (November-January), but this dropped to fewer than 20% of the plants flowering by the third or fourth season. Most plants flowered only once, but almost all plants did flower. Consequently, 35% of the flowering events were by plants that flowered only within the first year. Flowering in the first season produced more flowers per plant in that season, and was also correlated with increased chance that a plant would flower again. Repeat flowering produced fewer flowers per plant in the subsequent seasons, but multiple flowering did increase the total number of flowers produced per plant. This form of pulse flowering and short secondary juvenile period after fire seems to be typical of resprouting monocotyledons in Australia, but is much less common among resprouting dicotyledons.

The pulse of flowering appears to be closely associated with changes in the soil chemistry during the post-fire period. Many of the soil attributes measured show either a characteristic decrease or increase during the 3-4 years following the fire, with a subsequent reversal in the trend. The plants thus flower prolifically during these changing soil conditions, but almost cease flowering when these changes are reversed, thereby taking advantage of soil conditions that are not available throughout most of the inter-fire period.