12 December, 2005
___Planting additional trees and shrubs leads to a greater diversity of bird and insect species on cotton farms, according to research recently completed by Cotton CRC Summer Scholarship holder, Rhiannon Smith, whose family live at Narrabri._
Her project, which included a survey of tree and shrub plantings on cotton farms in the Namoi Valley was undertaken from January to April 2005. It quantified the potential for tree plantings on cotton farms to contribute to biodiversity conservation, and provided recommendations for maximising this potential.
The survey used birds, invertebrates and herbaceous vegetation as surrogates for biodiversity and related them to stand variables such as projected foliage cover and crown condition in order to assess the ability of different planting configurations and management techniques to encourage biodiversity.
Findings from the study indicated that the presence of trees had the potential to double the species richness and abundance of fauna found in cleared agricultural land.
Plantings consisting of a diversity of both trees and shrubs and therefore higher projected foliage cover contained more biodiversity than plantings consisting wholly of tall, open trees, however management of the planting was also a significant factor influencing the biodiversity of plantings.
Average species richness of bird species was increased by four species in revegetated plots, but at some locations double the number of species were found in plantings compared to cleared agricultural land adjacent to plantings.
Herbaceous vegetation was found to be influenced by projected foliage cover of the planting with increasing woody vegetation cover reducing the cover of herbaceous vegetation and manipulating species composition.
Species richness of herbaceous vegetation was increased by the presence of trees with an average of three more species under tree cover. Mowing and weed control also had an effect on the species richness and composition of the herbaceous vegetation component, which subsequently influenced invertebrate order composition.
Planted tree genera had a significant influence on the ordinal richness and abundance of invertebrates. Acacia species supported significantly greater abundances of invertebrates and were among the most Invertebrate order rich of the tree genera sampled.
Eucalyptus camaldulensis was the most widely planted species, present in all but one planting and was one of the standout performers for growth. The health of Eucalyptus melliodora was consistently high across the valley while Eucalyptus populnea was always ranked among the poor performing species.
The research concluded that revegetation activities on cotton farms have the potential to contribute significantly to biodiversity conservation in the Namoi Valley.
Rhiannon Smith was supervised at UNE by Associate Professors John Duggin and Nick Reid and locally by Guy Roth from the Cotton CRC and Stacey Spanswick from the Namoi CMA.
Stuart Green from UNE helped with the bird sampling while Loretta Hanley, Trudy Staines and Colin Tann CSIRO helped with the insect identification.
Namoi cotton farmers who allowed access to their tree plantings were John and Robyn Watson (Kilmarnock); McNamee Pty Ltd (Milchengowrie); Chris and Amanda Goulden (Glenelg); Jack and Jacqui Warnock (Warilea); Mike and Robyn Logan (Oakville).
Further information: A/Prof Nick Reid UNE firstname.lastname@example.org , Stacey Spanswick 02 6799 1500 or Guy Roth 02 6799 1500.
Pictured: Mike Logan, Robyn Watson, Rhiannon Smith, and Jack Warnock.
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