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Soil seed bank dynamics in Mediterranean urban vegetation fragments

Davis, Jessica (2012) Soil seed bank dynamics in Mediterranean urban vegetation fragments. Masters by Coursework thesis, Murdoch University.

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Abstract

Conservation of biodiversity in urban vegetation fragments is of increasingly high importance with growing urbanisation globally, particularly so in the biodiversity hotspot of the Mediterranean southwest of Western Australia. Relationships between fragmentation (connectivity, fragment size, time since isolation) and urban disturbances (weed invasion, human disturbance, rubbish) relative to the soil seed bank of a representative sample of Perth’s urban woodland fragments (N=36) were examined. In total, 182 seedling types comprising 57 invasive, 105 native and 20 unknowns were identified. Approximately 65% of the 21,770 seedlings counted were native, 33% invasive and 2% unidentified. The average soil seed bank seedling density was 2,787 germinates per m2. Community analysis (ordination) showed that the soil seed bank composition correlated with fragment age. Subsequent quantitative analysis (linear regression) did not find evidence for species or functional trait groups being vulnerable to decline due to isolation or fragment age, indicating that species extinction is not evident within Perth’s urban fragments. More invasive annual herbs were found within older fragments and the soil seed banks of smaller fragments were found to have lower native species abundance compared to larger fragments. A positive relationship was found between the number of footpaths within a fragment and the abundance of annual invasive herbs within the soil seed bank. High weed cover in a fragment resulted in high weed presence within the soil seed bank. It was also found that high weed cover did not necessarily indicate low native species diversity or abundance within the soil seed bank, suggesting caution in using weed cover to classify sites as suitable/unsuitable for topsoil transfer in restoration activities. The soil seed bank of the study sites contained a diverse range of native species, indicating that topsoil from these areas may be useful in restoration of degraded sites.

Publication Type: Thesis (Masters by Coursework)
Murdoch Affiliation: School of Environmental Science
Supervisor: Enright, Neal and Fontaine, Joe
URI: http://researchrepository.murdoch.edu.au/id/eprint/12926
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