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Resource-use efficiency explains grassy weed invasion in a low-resource savanna in north Australia

Ens, Emilie, Hutley, Lindsay B., Rossiter-Rachor, Natalie A., Douglas, Michael M. and Setterfield, Samantha A. (2015). Resource-use efficiency explains grassy weed invasion in a low-resource savanna in north Australia. Frontiers in Plant Science,6(Article No. 560).

Document type: Journal Article
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Title Resource-use efficiency explains grassy weed invasion in a low-resource savanna in north Australia
Author Ens, Emilie
Hutley, Lindsay B.
Rossiter-Rachor, Natalie A.
Douglas, Michael M.
Setterfield, Samantha A.
Journal Name Frontiers in Plant Science
Publication Date 2015
Volume Number 6
Issue Number Article No. 560
ISSN 1664-462X   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84938860307
Total Pages 10
Place of Publication Switzerland
Publisher Frontiers Research Foundation
HERDC Category C1 - Journal Article (DIISR)
Abstract Comparative studies of plant resource use and ecophysiological traits of invasive and native resident plant species can elucidate mechanisms of invasion success and ecosystem impacts. In the seasonal tropics of north Australia, the alien C4 perennial grass Andropogon gayanus (gamba grass) has transformed diverse, mixed tree-grass savanna ecosystems into dense monocultures. To better understand the mechanisms of invasion, we compared resource acquisition and usage efficiency using leaf-scale ecophysiological and stand-scale growth traits of A. gayanus with a co-habiting native C4 perennial grass Alloteropsis semialata. Under wet season conditions, A. gayanus had higher rates of stomatal conductance, assimilation, and water use, plus a longer daily assimilation period than the native species A. semialata. Growing season length was also ~2 months longer for the invader. Wet season measures of leaf scale water use efficiency (WUE) and light use efficiency (LUE) did not differ between the two species, although photosynthetic nitrogen use efficiency (PNUE) was significantly higher in A. gayanus. By May (dry season) the drought avoiding native species A. semialata had senesced. In contrast, rates of A. gayanus gas exchange was maintained into the dry season, albeit at lower rates that the wet season, but at higher WUE and PNUE, evidence of significant physiological plasticity. High PNUE and leaf 15N isotope values suggested that A. gayanus was also capable of preferential uptake of soil ammonium, with utilization occurring into the dry season. High PNUE and fire tolerance in an N-limited and highly flammable ecosystem confers a significant competitive advantage over native grass species and a broader niche width. As a result A. gayanus is rapidly spreading across north Australia with significant consequences for biodiversity and carbon and retention.
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Additional Notes This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Description for Link Link to CC Attribution 4.0 License

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