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Accueil du site → Doctorat → Australie → 2012 → Restoration in a postmine environment : using ecophysiological techniques to improve the establishment of framework Banksia woodland seedlings

University of Western Australia (2012)

Restoration in a postmine environment : using ecophysiological techniques to improve the establishment of framework Banksia woodland seedlings

Benigno, Stephen M

Titre : Restoration in a postmine environment : using ecophysiological techniques to improve the establishment of framework Banksia woodland seedlings

Auteur : Benigno, Stephen M

Université de soutenance : University of Western Australia

Grade : Doctor of Philosophy (PhD 2012

Résumé
Restoration of the diminished Banksia woodland community is necessary to maintain one of the world’s biodiversity hotspots. In postmine environments, extreme soil compaction prevents framework overstorey species of this ecosystem from accessing essential groundwater. Coupled with extreme summer drought, the stresses posed by postmine environments have prevented the restoration of the Banksia woodland community to its historic trajectory. This thesis investigates the ecophysiological responses of seedlings to the abiotic barriers of drought and increased soil compaction to aid restoration in postmine conditions. In addition, methods to manipulate both the seedling and the postmine environment are examined, focusing on improving seedling establishment of framework overstorey species to postmine sites through the use of ecophysiological techniques. Seedlings of three phreatophytic trees, Banksia attenuata, B. menziesii, and Eucalyptus todtiana, were subjected to drought, increased soil compaction, and a combination of the two stresses under a controlled glasshouse study to identify species-specific ecophysiological adaptations to these commonly encountered stresses. Increased soil compaction alone did not cause seedling mortality or alter physiological function, but negatively affected root structure by decreasing root elongation by 70%. Under drought stress, the two Banksia species exhibited isohydric characteristics, with a “water-saving” strategy, whereas E. todtiana can be classified as an anisohydric species and has a more “drought-tolerant” strategy. The physiology of all species was more severely and promptly damaged by a second round of water deficit, causing mortality in all seedlings within 48 days of the second drought. Simultaneous drought and soil compaction represented an environment which severely damaged seedling morphology and physiology.
Despite the discrepancies in physiological mechanisms to cope with drought and/or soil compaction stresses, no differences in mortality between species were observed. To alleviate soil compaction and increase soil water retention in situ, an organic and inorganic soil amendment were incorporated into the top 50 cm of the soil profile in a fresh restoration site within a sand quarry. The organic amendment increased seedling establishment of B. attenuata and B. menziesii 24 and 42%, respectively, over two years. This benefit most likely resulted from a significant increase in moisture within the rooting zone. From ecophysiological monitoring, seedlings of B. attenuata and B. menziesii grown in the organic amendment plots functioned at a significantly higher rate over the dry summers than seedlings grown in inorganic amendment soil or soil containing no amendment. Neither the organic nor inorganic amendments displayed an ability to alleviate the soil compaction associated with reconstructed postmine soils. The belowground morphology of seedlings in restoration sites was significantly altered from seedlings grown in native remnant bushland, most notably a restriction of root depth to the top 40 cm of the soil in restoration sites compared to depths deeper than 100 cm in native bushland...

Mots clés : Banksia woodlands ; Drought ; Ecological restoration ; Soil amendment ; Ecophysiology ; Soil compaction ; Postmine restoration ; Eucalyptus todtiana

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Page publiée le 30 mai 2017