Annabel Green

Year

2022

Degree Name

Bachelor of Environmental Science (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Jeffrey Kelleway

Abstract

The Black Summer Bushfires of 2019-2020, was the worst bushfire season on record for New South Wales, with 5.5 million hectares of land burnt. These fires were so extreme that many areas never before affected by fires were impacted. This included mangrove communities, previously believed to be too moist to catch fire. Little is known about the response of mangroves to bushfires and very few studies have been undertaken to investigate this topic. This event provided a rare opportunity to study fire-affected mangroves and how they respond to fire events in the short-term. This study assessed the recovery and regeneration of Avicennia marina and Aegiceras corniculatum at Chinamans Point, Batemans Bay, 27-30 months post-fire disturbance. A combination of field-based mangrove and soil sampling approaches, as well as laboratory and geospatial analysis was undertaken of the four bays of fire-affected mangroves. Vegetation and Real-Time Kinematic (RTK) GPS surveys showed that epicormic regrowth of existing mangroves is highly pronounced in the center and at the seaward extent of the bays, where elevation is lower, and mangroves were further away from the fire front. Seedling establishment of A. marina was found to favour the landward side of the bays, with a mean seedling elevation of 0.47 m AHD in which seedlings were able to establish and grow up to 1 m in height. Soil core analysis to compare the root volume and biomass of fire and non-fire affected sites, showed that significant root losses occurred at the seaward side of fireaffected bays, especially with roots ≥ 2 mm in diameter. This is likely due to minimal input of new roots to replace decaying roots, which will have possible future implications regarding the elevation of these sites. Analysis of remotely piloted aircraft (RPA) imagery has shown potential as a tool for quantifying post-fire regeneration for management of fire-affected areas, however, on ground field assessments are still recommended. High-resolution aerial imagery (NearMap) was shown to be less affective and was not recommended for this use. Overall, this study suggests that the modes of postfire recovery of mangroves are spatially varied. This study has shown that the state of mangrove recovery 27-30 months post-fire is still reasonably low, however, is making a lot of progress compared to recovery 18 months post-fire. Epicormic regrowth is significantly higher than nine months prior and the presence of hundreds of seedlings shows promise for the future recovery of the site. Little is still known about the timeframe required for mangrove communities to recover to pre-fire disturbance levels, or whether sites with severe mangrove mortality have the ability to return to their pre-fire state. Therefore further research in this area is essential for informing future management decisions related to the recovery and protection of these communities, especially as fire severity continues to increase into the future.

FoR codes (2020)

410102 Ecological impacts of climate change and ecological adaptation, 410205 Fire ecology, 410402 Environmental assessment and monitoring

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.