Can the impacts of invasive African Olive on native Cumberland Plain Woodland plants be mitigated through bioinoculation?

Abstract

Invasive plants often impact the abiotic and biotic conditions of the ecosystems they invade. These impacts can persist after the removal of the invader as legacy effects that may hamper restoration. We assessed whether the invasion of Cumberland Plain Woodland in Australia by African Olive impacts the performance of native species through legacy effects. We also tested whether the addition of soil inocula from uninvaded Cumberland Plain Woodland and rhizosphere soils can mitigate the effects of invaded soils on native plant performance. To do this, we grew four native Cumberland Plain Woodland species (Australian Indigo, Climbing Saltbush, Hickory Wattle, Wedge-leaf Hop-bush) in mesocosms containing either uninvaded Cumberland Plain Woodland soil, African Olive-invaded Cumberland Plain Woodland soil or invaded Cumberland Plain Woodland soil inoculated with uninvaded or native rhizosphere soil. We found invaded soils to not consistently impact the growth of the Cumberland Plain Woodland species studied. In invaded soil, Hickory Wattle produced lower above and belowground biomass, Climbing Saltbush produced lower belowground biomass and Australian Indigo had a lower root to shoot ratio compared to plants grown in Cumberland Plain Woodland soil. The nodulation of Australian Indigo did not differ between soil treatments, while that of Hickory Wattle responded positively to inoculation. Our results suggest that the addition of native soil biota may improve the outcomes of ecological restoration projects on a species-specific basis.