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Restoration thinning has minor and temporary effects on understorey fuels in a regrowth eucalypt floodplain forest under conservation management.

Laura White , Samantha Travers , Danielle McAllister, Kristy Lawrie, Emma Gorrod

Abstract

Context: Forest conservation reserves with logging histories typically have dense woody regrowth, which has potential implications for fuel hazard management. Thinning has been used to reduce fuel hazards in some forest restoration programs, but there is limited and conflicting evidence for its effectiveness in Australian eucalypt forests. Aims: To determine how tree density and restoration thinning affect understorey fuel attributes and fuel hazards in a recently reserved river red gum (Eucalyptus camaldulensis Dehnh.) floodplain forest with dense regrowth following historical logging. Methods: Twenty-two sites were established, within which a control (no thinning) and two thinning treatments (removing varying proportions of trees <40 cm diameter) were applied to 9-hectare plots. Fuel attributes including surface litter, near-surface vegetation, and elevated understorey vegetation were monitored for five years. Fuel hazard ratings were determined using widely-used assessment methods. Key results: In control plots, tree density had minimal effects on fuel attributes or fuel hazard. Thinning caused a small (<5%) decrease in cover of near-surface and elevated understorey vegetation and slightly increased the proportion that was dead (by ≤0.07) compared with control plots. These trends disappeared or reversed by five years after thinning. Thinning reduced the mean height of elevated vegetation (by ≤1.6 m). Thinning did not have any effect on fuel hazard ratings. Conclusions: Thinning did not substantially change understorey fuels or reduce fuel hazards in a dense river red gum forest. Implications: Thinning is not warranted as a routine fuel management method when previously logged forests transition into conservation tenure.

PC24081  Accepted 19 May 2025

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