Impact of early and late dry-season fires on plant mortality and seed banks within riparian and subriparian infestations of rubber vine (Cryptostegia grandiflora)

Abstract

This study compared the efficacy of first and second fires applied during the early (August–September) and late dry season (October–November) on mortality of riparian (climbing) and subriparian (freestanding) infestations of rubber vine (Cryptostegia grandiflora R. Br.). The impact of fire treatments on germinable seed banks of monocotyledonous and dicotyledonous species was also determined. Individually, fire season, habitat type and number of fires significantly affected mortality of rubber vine plants. Late-season fires promoted higher mortality of rubber vine (96%) than early season fires (77%), with rubber vine in subriparian habitats more susceptible (90% mortality) than that growing in riparian areas (68% mortality). On average, fire mortality increased from 32% after the first fire up to 86% following 2 fires. Sensitivity of juvenile, mature, and old rubber vine plants to fire was in the order of mature>juvenile>old. Early fires significantly reduced seed banks of monocotyledonous plants, particularly in riparian habitats. Late fires significantly reduced seed banks of both dicotyledonous and monocotyledonous plants. No rubber vine seeds were detected in the germinable seed bank of either burnt or unburnt plots.