PhD Candidate: Paola Pisetta Raupp

PhD Supervisors: Dr Yolima Carillo (WSU), Associate Professor Paul Rymer (WSU), Associate Professor Uffe Nielsen (WSU), Dr Ian Oliver (DCCEEW)

Project Summary: Cumberland Plain Woodlands have been reduced to less than 9% of their original extent due to continuous degradation from agriculture, livestock grazing, and urbanisation. These areas are now dominated by a few grazing-tolerant native grasses, naturalised pasture species, and invasive exotics. The seed banks in these degraded landscapes are largely composed of exotic species, which thrive in nutrient-enriched soils, presenting a significant challenge for restoration efforts. Conventional restoration methods, such as herbicide use and planting native species, have proven inadequate in fully addressing the issue. One promising technique for reducing soil fertility and weed seed banks is topsoil removal, which has been shown to promote native plant recovery by reducing exotic dominance. However, topsoil removal can also deplete the native seed bank, and its effectiveness may vary depending on local soil conditions. The removal of approximately 10 to 15 cm of topsoil is commonly applied, yet the depth of soil layers can differ, making pre-removal soil assessment critical. Variations in soil depth affect chemical concentrations, physical structure, moisture content, seed bank density, and microbial communities, all of which play essential roles in successful revegetation efforts. Despite its potential, few studies have explored the impact of topsoil removal depth on restoration, particularly in non-mining degraded ecosystems. This research aims to fill this gap by examining seed bank emergence and characteristics across different soil layers and degradation conditions in Cumberland Plain Woodland ecosystems. Soil samples collected from multiple sites were transferred to pots in a glasshouse and regularly watered to stimulate seed bank emergence.

Seedlings were monitored weekly to identify species and assess the effects of soil removal depth on native plant germination and establishment. This study will provide critical insights for guiding restoration practices and determining the most appropriate soil removal depth for successful revegetation across varying soil conditions.

Collaborators: Local Land Services (NSW Government), National Parks, Botanic Garden Mount Annan, Western Sydney Parklands