Gwydir Selected Area 2021-22 Annual Summary Report – Appendix J – The effects of fire on microinvertebrate eggbanks in three vegetation communities in the Gwydir Wetlands, NSW

Fire is a common phenomenon in Australia and overseas and is known to affect many ecological processes. We examined the effects of wildfire on the eggbank of invertebrates and bioavailable nutrients in the Gwydir Wetlands, northern NSW. Fire reduced the density and richness of hatching invertebrates but did not destroy the entire biota, suggesting some level of resilience in the invertebrate eggbank. Nutrients did not behave as predicted as less bioavailable nitrogen oxides were available from burnt soils while there were no overall differences in either soluble reactive phosphorus or dissolved organic carbon between burnt and unburnt wetland soils. Abundance and richness of microinvertebrates hatching from the eggbank varied in different vegetation types, reflecting an inundation gradient. The greatest number and richness of hatching invertebrates were found in the most frequently inundated typha reedbed community, followed by water couch marshlands and coolibah woodlands, the least frequently inundated community. Ongoing monitoring may indicate if fire and the current environmental watering regime has affected aquatic invertebrates into the future.