Insights from stable isotopes for evaluating weed invasion in urban bushland
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Date
2015-07-08
Authors
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Publisher
University of New South Wales and Australian Nuclear Science and Technology Organisation
Abstract
Why is Pittosporum undulatum taking over in Sydney’s urban bushland? Bush regeneration manuals recommend removing the native shrub Pittosporum undulatum because it creates shady conditions suppressing regeneration of other native plants. We used stable isotope analysis to compare the water use efciency and nutrient cycling processes of Pittosporum with other plant species to determine why it has a competitive edge in urban bushland. We collected plant, litter and soil samples from eight sites along Wolli Creek in southern Sydney. Four sites were dominated by exotic weeds and Pittosporum undulatum (‘weedy' sites), while the other four sites were dominated by native vegetation species (‘native' sites). Plant, litter and soil samples were analysed for %C, %N, δ13C and δ15N.
Plant material and litter at ‘native’ sites had a higher carbon content and lower nitrogen content compared to ‘weedy‘ sites. Soil and Pittosporum undulatum had similar %C and %N values regardless of whether they were collected from ‘native’ or ‘weedy’ sites. Initial results indicate that native species and exotic species had distinct
δ13C values in their mature leaf tissue, suggesting higher water use efficiency of native plants. Pittosporum undulatum had a similar isotopic signature to other native species. Nitrogen isotope results show plant species have unique δ15N values reecting unique N capture strategies. Soil δ15N signatures were variable.
Pittosporum undulatum was expected to be similar to the exotic plants in terms of isotopic signature, assuming that this native species is utilising resources in a similar way to invasive exotic species. Our pilot study indicates this is not the case, and thus nativespecies may be becoming dominant in urban bushland through other mechanisms. Further research is required to understand how nutrients are captured and cycled in urban bushland.
Description
Physical copy held by ANSTO Library at DDC: 551/7
Keywords
Isotopes, Weeds, Urban areas, Stable isotopes, Plants
Citation
Beer, J., Chagué-Goff, C., & Barry, L. 2015. Insights from stable isotopes for evaluating weed invasion in urban bushland. Presentation to the 13th Australasian Environmental Isotope Conference, Sydney, Australia, 8-10th July 2015. In 13th Australasian Environmental Isotope Conference, Sydney, Australia, 8-10th July 2015, Programme and Abstracts, (pp. 26.)