Overstorey tree density and understorey regrowth effects on plant composition, stand structure and floristic richness in grazed temperate woodlands in eastern Australia

Le Brocque, Andrew F. and Goodhew, Kellie A. and Zammit, Charlie A. (2009) Overstorey tree density and understorey regrowth effects on plant composition, stand structure and floristic richness in grazed temperate woodlands in eastern Australia. Agriculture, Ecosystems and Environment, 129 (1-3). pp. 17-27. ISSN 0167-8809

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As natural woodlands decline in both extent and quality worldwide, there is an increasing recognition of the biodiversity conservation value of production landscapes. In low-input, low-productivity grazing systems in Australia, the modification of natural woodlands through overstorey tree and woody regrowth removal are vegetation management options used by landholders to increase native grass production for livestock grazing; however, there is little empirical evidence to indicate at what tree densities biodiversity attributes are compromised. We examined the effects of overstorey tree density and understorey regowth on the floristic composition, stand structure and species richness of Eucalyptus woodlands in a grazing landscape in the Traprock region of southern Queensland, Australia. We sampled 47 sites stratified according to vegetation type (Eucalyptus crebra/E. dealbata woodland; E. melliodora/E. microcarpa grassy woodland), density of mature trees (<6 trees /ha; 6-20 trees/ha; >20 trees/ha), and presence/absence of regrowth. Distinct patterns in composition were detected using Indicator Species Analysis and Non-Metric Multidimensional Scaling, with low density areas compositionally indistinguishable, although distinct from other land management units. Within vegetation type, medium tree density woodlands were compositionally similar to high density and reference woodlands. Species richness ranged from 18 to 67 species per 500m2 across all sites. No differences in total or native species richness were detected across management units; however, some differences in exotic species richness were detected. Differences in grass cover existed between low and high density management units, yet no difference in grass cover was evident between low and medium density management units. Our results suggest that medium tree densities may provide biodiversity benefits concordant with more natural areas, yet not adversely impact on pasture production. Retaining trees in grazing landscapes provides significant landscape heterogeneity and important refuges for species that may be largely excluded from open grassland habitats. Maintaining a medium density of overstorey trees in grazed paddocks can provide both production and biodiversity benefits.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Author's version deposited in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 29 Mar 2009 11:29
Last Modified: 02 Jul 2013 23:10
Uncontrolled Keywords: tree density; woody regrowth; production landscapes; paddock trees; biodiversity benefits; eucalypt woodlands
Fields of Research : 05 Environmental Sciences > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity
07 Agricultural and Veterinary Sciences > 0705 Forestry Sciences > 070501 Agroforestry
07 Agricultural and Veterinary Sciences > 0701 Agriculture, Land and Farm Management > 070101 Agricultural Land Management
05 Environmental Sciences > 0501 Ecological Applications > 050104 Landscape Ecology
Socio-Economic Objective: D Environment > 96 Environment > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity
Identification Number or DOI: 10.1016/j.agee.2008.06.011
URI: http://eprints.usq.edu.au/id/eprint/4711

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