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University of Western Australia

Restoration ecology of rare shallow-soil endemic flora from a semi-arid biodiversity hotspot

Ruoss, Sacha B.

Titre : Restoration ecology of rare shallow-soil endemic flora from a semi-arid biodiversity hotspot.

Auteur : Ruoss, Sacha B.

Université de soutenance : University of Western Australia

Grade : Doctor of Philosophy (PhD) 2013

Résumé
[Truncated abstract] Shallow-soil environments over rock present challenges for the establishment of plant species particularly in semi-arid or seasonally droughted sites. Amongst the species of these shallow-soil ecosystems are a wide variety of phylogenetically diverse plants including endemics that are restricted to these rocky environments. As these rocky environments, particularly in resource rich areas such as the southwest biodiversity hotspot in Western Australia are also prospective for mineral extraction, it is important to develop an understanding of the ecology of these species to enable their restoration after disturbance activities have ceased. However, surprisingly little is known of why many plant species are ’narrow range endemics’ of shallow-soil environments. This thesis is the first to investigate aspects of the ecology and ecophysiology of rare, narrow range endemic species of shallow soils associated with Banded Ironstone Formation (BIF) complexes in the southwest Australian biodiversity hotspot with special reference to their ecological restoration. The restoration of BIF shallow-soil endemic species (SSES) in Western Australia is crucial due to the high number of current and planned mining activities associated with this substrate. From the literature the largest areas that were identified for facilitating successful restoration can be simplified into three main categories that require research. The soil seed bank, often used as the primary method of plant establishment in ecological restoration, has not been assessed for its potential effectiveness. The planting of seedlings (greenstock), another method of supplementing plant establishment, is often difficult due to low and erratic rainfall. Manipulating soil/substrate factors should be investigated to increase water availability that may in turn increase survival and growth of these species.
Species should be investigated for specific ecophysiological mechanisms, to determine if they have adaptations to their environment restricting them to defined parts of the landscape. A study was undertaken to assess the soil seed bank as a means of plant establishment in the restoration of rare SSES from semi-arid Western Australia. It was aimed to measure the size and diversity of the germinable soil seed bank of the total plant community and also to assess the spatial variation of rare SSES restricted to the BIF ecosystem. The study also assessed the effect of time since fire on the soil seed bank, with long unburnt sites hypothesised to comprise a significantly higher density than recently burnt sites. The seedling emergence method was used to investigate 216 plots, each 225 cm2 (4.86 m2 total) soil samples collected from the top 5 cm across eight sites. A large and diverse germinable soil seed bank was found, with a total of 6604 emergents from 50 taxa recorded. Annuals dominated the soil seed bank accounting for 92% of total numbers, with an average density of 1359 seeds/m2 found across all sites. Three rare species Darwinia masonii (Myrtaceae), Lepidosperma gibsonii (Cyperaceae) and Acacia cerastes (Fabaceae) were investigated...

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Page publiée le 19 septembre 2013, mise à jour le 5 juillet 2017