Relationships between mature trees and fire fuel hazard in Australian forest
Nicholas Wilson A B C , Geoffrey J. Cary A and Philip Gibbons AA Fenner School of the Environment and Society, The Australian National University, Building 141, Linnaeus Way, Canberra, ACT 2601, Australia.
B Centre for Environmental Risk Management of Bushfires, University of Wollongong, Building 35, Northfields Avenue, Wollongong, NSW 2522, Australia.
C Corresponding author. Email: n.wilson091@gmail.com
International Journal of Wildland Fire 27(5) 353-362 https://doi.org/10.1071/WF17112
Submitted: 28 July 2017 Accepted: 20 February 2018 Published: 23 April 2018
Abstract
Increasing density of mid-storey vegetation since European settlement has been observed in forests and woodlands in several parts of the world and may result in greater fire fuel hazard. This phenomenon is often attributed to a longer interval between fires since European settlement, but may also be influenced by tree removal during the same period. We hypothesised that the number of mature trees in a stand reduces mid-storey vegetation cover and the associated fire fuel hazard through competition. To test this hypothesis, we examined associations between mid-storey cover and fire fuel hazard and the mean diameter of trees within stands of open forest and woodland in south-eastern Australia, a region prone to wildfires. We found that vegetation cover between 2 and 4 m and 4 and 6 m above the ground and two measures of fire fuel hazard were negatively associated with the quadratic mean tree diameter. Our results suggested that the removal of mature trees since European settlement may have triggered tree and shrub regeneration, resulting in higher mid-storey cover and fire fuel hazard. Thus, managing stands for the persistence and replacement of mature trees may contribute to long-term fuel reduction in Australian forests and woodlands.
Additional keywords: Australia, Eucalyptus, prescribed burning, tree loss, vegetation thickening.
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