Mulloon Creek Natural Farms, following nature

Tree Planting

The Mulloon Institute's tree planting programme is an integral part of our landscape rehabilitation programme. In addition to eucalypts, we have a commitment to creating wood rows of specific native and non-native deciduous trees in order to meet the following objectives:

  • Provide readily compostable leaf fall to enrich the soil, increase soil humidity and temperature during winter
  • Reduce summer litter or litter that quickly decomposes in summer to reduce fire load
  • Deflect Radiant heat during summer and specifically the fire season
  • Be slow to ignite and burn
  • Slow an approaching fire-front
  • Create a wind-break in summer to reduce dehydration and top-soil loss
  • Survive in a low-rainfall environment

While not all species will meet all of these objectives we aim to select tree species that assist us to meet as many of these objectives as possible.

Fire Mitigation

To quote Debbie Hebbard who has extensively reviewed the work of Permaculture co-founder - David Holmgren, deciduous trees are an important part of a fire-mitigation plan because of their reduced flammability through:
  • Moisture content - most natives have a moisture content of 80 to 150% of their oven dry weight (ODW) while deciduous trees contain 250 to 400% of their ODW. The higher the moisture the slower the ignition. Lush, green material must be dried out by the fire before it will ignite.
  • Ash content , or the solid matter left after burning - tends to be made up of alkaline compounds that are naturally fire retarding, so low ash plants like Eucalypts (usually < 10% ash) will glow (and therefore can cause further flare ups) for longer periods than deciduous trees of 30 to 40% ash. This ash cools quickly and can smother remaining hot spots.
  • Volatile oil ontent - in Eucalyptus, Melaleuca, Callistemon and other Myrtaceae range up to 5% oil this is generally higher than other plants. When heated, this oil can explode, intensifying the heat ahead of the fire front. This in turn heats and ignites more volatile oils.
  • Ignition temperature - plants with higher oil levels tend to have lower ignition temperatures, the Myrtaceae family ignite at 80 to 100 degrees Celsius, so they burn with less preheating than other species which ignite at 200 to 400 degrees. Loose, flaky or rough bark will trap embers. This can produce enough heat for ignition.
  • Salt content - is more related to location than to species. Plants growing in saline conditions will have a higher salt content and this retards burning.

Erosion

Most of our tree planting occurs along swales that follow the natural contour lines of the landscape. The trees reduce erosion and evaporation, while the swales disperse water gently through the landscape reducing erosion and loss of surface water by slowing rainwater down and giving it enough time to be absorbed by the soil. In addition, the planting of trees is an essential part of our creek rehabilitation programme. Following the guidelines of Peter Andrews and Natural Sequence Farming we use pioneer plants to stabilise the creek bank, allowing the under storey to regenerate, and then follow this with large plantings of natives.

Fodder

We also select some plants as fodder for grazing. Currently we are part of a DAFF ‘Action on the Ground' project to determine the value of Australian native shrubs for cattle and sheep. A range of species are due to be planted in Spring 2013. They have been selected for their ability to fix carbon and to reduce methane production by the ruminant. Stay tuned for updates as this project commences and the research outcomes are published by Mingenew-Irwin.

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