River Red Gum Ecological Thinning Trial Monitoring Report 2020

Abstract

This report presents results from the third year of post-thinning monitoring of an ecological thinning trial in River Red Gum forests within Murray Valley National Park, NSW. The trial aims to evaluate whether ecological thinning can improve biodiversity, canopy condition and forest resilience across stands with varying stem densities and water availability. Key findings from 2019-20 monitoring showed that thinned plots had faster tree growth rates (by 0.7-2.8 mm per year) but higher tree mortality compared to control plots. Canopy condition improved in thinned plots on drier sites, with 10-15% fewer trees showing recent crown decline. While moderately thinned plots supported higher bird species richness and bat activity, no significant effects were detected on overall fuel hazard, native plant species richness, or threatened species occurrence. The magnitude of canopy cover decline was less in thinned plots compared to controls during drought conditions. These preliminary results suggest ecological thinning may provide some benefits for forest health and habitat values, particularly on drier sites, though longer-term monitoring through to 2022 will be needed to fully evaluate treatment effectiveness. The trial's findings will inform future conservation management of River Red Gum forests in NSW.