The efficacy of soil ameliorants to improve early establishment in trees and shrubs in degraded Eucalyptus gomphocephala woodlands

Abstract

Many Mediterranean-type ecosystems (MTEs) are now vulnerable to climate change, with some regions predicted to undergo a shift towards much drier and hotter conditions. Although MTE woodlands are highly resilient to periods of drought and perturbations such as fire, this shift increases the already wide range of threatening processes they face. Without intervention, such as revegetation, many of these woodlands could degrade to the point where they support little of the original biota. However, in MTEs with hard to predict breaks in the season and nutrient poor soils; seedling establishment success is often very low. Using degraded Eucalyptus gomphocephala woodlands as a case study, we undertook two field trials with five commercially available plant treatments to evaluate their effectiveness in increasing early seedling establishment. We found that the mere addition of seedlings may not be enough to undertake successful revegetation in some degraded woodlands because a) survival rates in controls were, on average 53% at one of the study sites and b) the supplementation of nutrient resources beneath the rootball when planting increased early seedling growth and health compared with other treatments. We suggest that under emerging and well-recognized challenges to revegetation, supplementing abiotic resources, in particular nutrients applied exclusively beneath planted seedlings, may increase early establishment success.