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Igniting river health? Testing the effectiveness of low intensity burns to improve riparian vegetation quality in modified ecosystems

Elisha Duxbury, Kirstie Fryirs , Michelle Leishman, Thunghutti Natural Regeneration Team

Abstract

Background: Fire is a largely untested method for controlling invasive exotic plant species in highly-modified riparian systems. Aims: This study aimed to test low intensity burn effectiveness as a method in combination with business-as-usual herbicide application for reducing cover of three common riparian woody weeds and increasing the presence of native plant species. Methods: We surveyed native and exotic riparian vegetation and three target woody weeds over one year at a river reach that underwent herbicide treatment followed by a low intensity burn. Temperatures were recorded during the fire at the soil surface and 10cm depth. Key results: Maximum temperatures in burned areas exceeded 399 °C at the soil surface and reached 47.1 °C at 10 cm soil depth. In the first three months after burning, exotic midstorey cover and species richness and cover for three common woody riparian weeds was considerably less after burning and herbicide treatment compared with herbicide treatment alone, then subsequently increased. Conclusions: A combination of herbicide treatment with follow-up low intensity burning may be effective in reducing woody weed cover in the short term. However, fire temperatures recorded during the burn may not be hot enough to trigger germination for fire-promoted native species. Implications: The use of low intensity burns in riparian systems to promote native plant regeneration has promise, however, integrated weed management utilising fire in highly modified riparian systems will require follow-up interventions within a relatively short timeframe.

WF24140  Accepted 26 March 2025

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