Hakea decurrens subsp. physocarpa increases the risk of fire
Hakea decurrens subsp. physocarpa (Proteaceae: EPPO A2 List) is an invasive shrub species native to Australia. In invaded areas, the increased biomass of H. decurrens subsp. physocarpa may increase fire intensity. Fire can benefit the plant as it can trigger the release of the seeds from the hard seed pods, and in the aftermath of the fire, nutrient enriched soil and reduced competition from other plant species can promote the establishment of the shrub. Models were developed based on experimental data and included different factors: (1) the development stage: early (plants height ≤ 1m) intermediate (> 1m ≤2.5m), mature (>2.5m) and (2) type: standing fuel (plants were uncut) and slashed fuel (vegetation was cut and left on the ground). These combinations were used for three different scenarios: 25 % cover, 50 % cover and 75 % cover under different plant moisture conditions. The models predict that standing plants are more hazardous than slashed plants and fire can increase and spread more with the maturity of the plant. In areas of Portugal at risk of wild fires, early detection and rapid response remains the most cost effective method to manage the invasion of H. decurrens subsp. physocarpa. Where established populations occur, the priority should be to reduce the presence of mature plants with the application of slash treatments.
Sources
Gerber D, Azevedo JC, Mereu M, Silva de Oliveira A, Marchante E, Jacobson TKB, Silva JS (2024) Hakea decurrens invasion increases fire hazard at the landscape scale. Biological Invasions 26, 3779-3793. https://doi.org/10.1007/s10530-024-03410-6