26 August 2005
E H Graham Centre PhD students featured in Salinity CRC publication
The research of CSU PhD students Alison Southwell and Bree Wilson was recently publicised in the Cooperative Research Centre for Plant-Based Management of Dryland Salinity (CRC Salinity) and CRC Landscape Environments and Mineral Exploration (CRC LEME) newsletter, Focus On Salt (issue 35, Dec 2005).
The aim of Alison's research is to assess how the composition of pastures (species present and their abundance) influences the water use of these systems. The work is framed around a historical trend that has seen the composition of native pastures shift under grazing pressure from being dominated by summer active grasses (such as kangaroo and red grass) to winter grasses (such as wallaby and weeping grasses), and, with the addition of fertilizers, to a mix of winter and annual species. Tillage in more arable areas has also reduced the abundance of native pastures.
With this context in mind, Alison has been monitoring two trial sites: a set of native pasture sites near Yass, and a series of planted plots at Wagga Wagga. At Yass, Alison observed that soil in plots containing perennial grasses was always drier than soil in plots containing annual grasses. Alison's observations of in situ roots at Wagga Wagga indicated that summer-active red grass has a more extensive and deeper root system than winter-active wallaby grass.
The implication of Alison's research is that, if graziers desire more even pasture production and are committed to recharge management, then managing the proportion of native perennial grasses, particularly those that are summer-active, may be an economically-beneficial and environmentally-responsible choice of pasture species.
Alison using a neutron moisture probe to record soil moisture at her Wagga Wagga pasture trial site. Photo courtesy Alison Southwell.
November flourish of red grass, a native summer-active species. Photo courtesy Alison Southwell.
Bree Wilson, whose research was also featured in Focus on Salt, has begun research that explores the diversity and ecology of mycorrhizal fungi in salt affected agricultural landscapes. Mycorrhizal fungi have a symbiotic relationship with the majority of land plants; the fungi increase the uptake of nutrients and water by plants by effectively increasing the surface area of their roots. In return, the fungi receive sugars for growth.
Bree's research is based on two sites, one near Wagga Wagga and the other near Orange . DNA fingerprinting techniques are to be used to assess the genetic diversity of mycorrhizal fungi communities across salinity gradients at both sites. The aim is then to select some of the fungi present and design glass-house experiments to see how they may differ functionally. Of particular interest would be differences in their ability to confer salt tolerance to their host plants. It is research of this kind that leads to the development of seed inoculum programs that are best-suited to saline environments. Interestingly, preliminary greenhouse results indicate that the types of fungi found in remnant vegetation stands are also active in salt-effected agricultural soils. Confirmation of this finding would lead to the conclusion that wise plant selection, rather than inoculation with fungi, may be the most productive approach in salt-effected soils.
From left to right: Leek root inoculated with mycorrhizal fungi originating in saline agricultural soil, stained with trypan blue (x200 magnification); clover root inoculated with mycorrhizal fungi originating in soil of remnant vegetation, stained with acid fuchsin (x200); clover root inoculated with mycorrhizal fungi originating in soil of remnant vegetation, stained with acid fuchsin (x200). Images courtesy of Bree Wilson.
Alison and Bree are recipients of CRC Salinity PhD scholarships, and both have benefited from the networking the CRC offers in the form of scientific and industry collaborations, as well as the opportunity to attend workshops and conferences. According to Bree, the CRC should be acknowledged for its willingness to back projects that have the potential to offer novel means of addressing the problem of dryland salinity. Similarly, Alison appreciates the important role the E H Graham Centre plays in strengthening the relationship between CSU and DPI, especially as the collaborations she has enjoyed with DPI have presented the opportunity to interact with people working in related fields of research and access to additional resources and technical assistance.