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Role of nitrogen fixing bacteria in the invasion success of weedy Australian Acacias

Birnbaum, C., Thrall, P.H. and Leishman, M.R. (2010) Role of nitrogen fixing bacteria in the invasion success of weedy Australian Acacias. In: Ecological Society of Australia 2010 Annual Conference Sustaining biodiversity – the next 50 years (book of abstracts), 4 - 10 December, Canberra, ACT, Australia.


Several Australian Acacias have become invasive when introduced into new areas within Australia. These invasive Acacias may have a detrimental effect on native flora and induce changes to below-ground microbial composition. Previous studies have shown that the invasive success of Acacias can be at least partly attributed to their ability to associate with N-fixing rhizobial bacteria. This study assessed the role of rhizobia in the invasion success of four Acacia species (A. cyclops, A. longifolia, A. melanoxylon, A. saligna) and closely related species Paraserianthes lophantha in their nonnative environment within Australia. Presence or absence of rhizobia in soils in both the native and introduced ranges of each species, as well as infectivity and efficacy, were estimated using the Most Probable Number (MPN) method to determine numbers of rhizobial cells/g-1 of soil. A glasshouse experiment had shown that there are significant differences in aboveground biomass between plants grown in soils from their native compared with non-native environment.

The outcome of this study will enhance our understanding of the role of plant-soil interactions in Acacia invasion into novel ranges in Australia and also contribute towards a larger global framework of studies on the invasion ecology of non-native Acacias.

Item Type: Conference Item
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