Level of Confidence in revegetating with non-grazing species

1.     Farmer experiences
Groundcover and improved visual amenity are key motivators for farmers with saline land. Non-grazing options offer probably the greatest gain in visual amenity of all the Saltland Solutions. Murray and Trish Brimblecombe from Capella in Qld have been ‘experimenting’ with trees on their saline land:

A variety of trees were planted to gauge their effectiveness at lowering the water table. River red gum had the best survival rate of 80%, compared to coolibah 69%, blackbutt 58%, Queensland white gum 60%, tipuana 38% and yapunya 16%.

Most tree deaths occurred at the seedling stage soon after planting and there have been very few deaths in the last seven years. The water table has dropped allowing rainfall to leach the salt lower into the soil profile enabling the return of native grasses such as blue grass, wiregrass and windmill grass
.”

2.     Research
CSIRO Forestry and Forest Products has evaluated a wide range of forestry options for survival, growth and water use on saline sites. As a general rule, growth rates on saline sites decrease significantly with increasing salinity. Commercial lines of hybrid eucalypts combining the salt tolerance and timber characteristics of E. camaldulensis with the growth rate, wood quality and form of E. grandis and E. globulus have been developed but have not performed consistently in field trials.

3.     Risks and challenges
Most of the risks associated with revegetation of saltland with trees apply to commercial rather than to conservation plantings. The main risks are:

  • Tree growth rates will be too slow on saltland to provide a commercial return;
  • Saltland sites are often smaller than required for commercial forestry operations, and are often located at challenging distances from markets;
  • Initially suitable sites may become more saline over the time span needed for forests to mature; and
  • Tree water use may lead to a build up of salts in the root zone, rendering this option unsustainable.

4.     Future prospects
There are strong prospects for the continued use of this non-grazing option for saltland – in particular the use of trees and shrubs for conservation and visual amenity. Mixed species plantings, with only occasional grazing, or use as emergency shelter for sheep off shears or with lambs, is a good long term prospect for saline sites. As there are few commercial options, it makes sense to focus efforts on these salines sites around non-commercial activities.

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