Prescribed burning in a mediterranean-climate region mitigates the disturbance by bushfire to a critical food resource for an endangered bird, the Carnaby\u2019s cockatoo

Valerie S Densmore,Emma S Clingan

doi:10.1186/s42408-019-0054-8

Abstract

BackgroundPrescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia. The 2016 census recorded well over 1.9 million people living on the SCP, which also encompasses Perth, the fourth largest city in Australia. Banksia woodland is prone to frequent ignitions that can cause extensive bushfires that consume canopy-stored banksia seeds, a critical food resource for an endangered bird, the Carnaby’s cockatoo (Calyptorynchus latirostris, Carnaby 1948). The time needed for banksias to reach maturity and maximum seed production is several years longer than the typical interval between prescribed burns. We compared prescribed burns to bushfires and unburned sites at three locations in banksia woodland to determine whether low-intensity prescribed burns affect the number of adult banksias and their seed production. Study sites were matched to the same vegetation complex, fire regime, and time-since-fire to isolate fire intensity as a variable.ResultsHeadfire rates of spread and differenced normalized burn ratios indicated that prescribed burning was generally of a much lower intensity than bushfire. The percentage survival of adult banksias and their production of cones and follicles (seeds) did not decrease during the first three years following a prescribed burn. However, survival and seed production were significantly diminished followed high-intensity bushfire. Thus, carrying capacity for Carnaby’s cockatoo was unchanged by prescribed burning but decreased markedly following bushfire in banksia woodland.ConclusionsThese results suggest that prescribed burning is markedly different from bushfire when considering appropriate fire intervals to conserve canopy habitats in fire-resilient vegetation communities. Therefore, low-intensity prescribed burning represents a viable management tool to reduce the frequency and extent of bushfire impacts on banksia woodland and Carnaby’s cockatoo.

Highlights

Prescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia
Prescribed burning did not decrease the percentage of banksias that survived compared to unburned sites
A trend was apparent for more dead adult banksias following a bushfire, the effect was only significant compared to unburned sites

Summary

Introduction

Prescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia. The characteristic MCR climate includes cool wet winters and warm dry summers This cyclical pattern promotes vegetation growth followed by an extended drying period and facilitates the regular occurrence of bushfires or wildfires (Keeley 1986; McCaw and Hanstrum 2003; Syphard et al 2009; Van Wilgen et al 2010). Given the inevitability of fire in MCRs, most plant species exhibit traits that promote their persistence, including resprouting from heat-shielded buds and germinating from seed stored in the soil or canopy Both resprouter and seeder strategies facilitate resilience, but the relative benefit provided by either response depends on the fire regime (Gill 1978; Keeley 1986)

Objectives

Methods

Results

Discussion

Conclusion