Repeated disturbance through chaining and burning differentially affects recruitment among plant functional types in fire-prone heathlands

Abstract

Managing fire regimes is increasingly recognised as important for biodiversity conservation in fragmented agricultural landscapes in fire-prone regions. In the global biodiversity hotspot of south-west Western Australia, chaining and burning is a novel technique for facilitating fire management. Vegetation is first dislodged using a chain, then after a period of curing, burnt. The effects on plant communities are largely unstudied, despite the potential consequences of combining two disturbance events. We hypothesised that outcomes would vary depending on plant functional types defined by disturbance response. We compared plant community composition and recruitment and resprouting of plant functional types in mallee-heath subject to chaining and burning, burning only and neither of these. The effects of chaining and burning did not differ from only burning at the community level. Importantly, however, we recorded 90% fewer recruits of serotinous, obligate seeders in chained and burnt compared with only burnt plots, and a 44% decrease in their species richness. By contrast, recruits of obligate seeding shrubs and fire-ephemeral herbs with persistent soil-stored seed banks increased by 166% in chained and burnt plots. Sprouters showed little difference. We conclude that chaining and burning is likely to significantly alter vegetation composition, and potentially poses a significant threat to serotinous, obligate seeders. These impacts require consideration in fire management planning.