Money can grow on trees

Trees improve the quality of life on farms in many ways. They can provide shade and shelter, not only for animals but also for humans - a very important feature in our harsh Western Australian environment. One of the greatest contributions trees make, however, is to the economy of a farm and region.

Everyone has heard the sheep weather alerts graziers are given during winter, when cold, wet and windy weather is on the way. During these periods, lambs and newly shorn sheep are vulnerable. Half of all lamb deaths in Australia are caused by exposure. Shelter from shrubs and trees not only drastically reduces these losses; livestock production also increases when shelter from extreme weather conditions is available.

Besides giving shelter, shrubs and trees can supply animal fodder. Tagasaste or tree lucerne, can supply a nutritious, high-protein fodder to animals in mid-winter and mid-summer, when pasture growth is minimal. What is more, it grows on the sandy, wind-erosion-prone soils.

Keith and Kerry Parnell farm in the upper slopes of the eastern part of the Toolibin catchment in a 400mm rainfall zone.

In 1981 they were looking to expand the home farm and bought what they call the sandplain block. The first year it was cropped it produced 0.25 tonnes per hectare of wheat and wind erosion was a problem on the deep infertile banksia sands.

Since then the Parnells have been separating out the area os deep sands and planting tagasaste, improving pastures on the cropping areas with the addition of potash and clover and planting windbreaks to provide shelter for continuous wheat/lupin rotations.

Fifteen years later, tagasaste plantations on the deep sands support at least seven sheep to the hectare in there have been summer rains and four sheep to the hectare after a dry summer. The remaining cropping areas are producing two tonnes of wheat to the hectare.

Plants also benefit greatly from tree or shrub shelterbelts. The benefits from protection offered by shelterbelts usually outweigh the localised competitive effects created by their roots. Reducing wind velocity reduces evapo-transpiration and therefore moisture loss. Shelterbelts protect crops from being flattened by wind and similarly provide benefits for pastures.

Shrubs and trees in themselves can also be a source of income. Pine trees planted in shelterbelts can be selectively harvested to produce saw logs after 30 years, while thinning and pruning in early years can provide chips and posts. The production of eucalyptus oil, firewood, honey, wildflowers and seeds can also make growing trees economically attractive.

Tasmanian bluegum plantations are part of a strategy to overcome eutrophication of the Peel-Harvey estuary. Besides reducing nutrient flow into the estuary, the trees can be harvested after five to ten years for woodchip production.

The above are benefits to the individual landholder, but trees also have enormous national economic significance. This is illustrated in many varied aspects of conservation - one of the most important being protection of soil, regarded as being one of Australia's greatest assets.

Most people realise the value of trees in reducing wind erosion, but trees and other vegetation can also alleviate water erosion problems. Trees in the upper reaches of a catchment can reduce flooding; they even out the volume of water running onto cleared areas, lessening peak flow and reducing the erosive power of the flow.

Salinity caused by rising water tables can be prevented and, in some cases eliminated, by trees. Trees can also contribute to soil fertility. Deep-rooted vegetation is able to draw nutrients from deep within the soil and add them to the topsoil through leaf litter and other organic material containing these nutrients.

Native trees and shrubs provide a habitat for many birds and other animals. This is a good thing from several points of view. Insect-eating birds can play their part in keeping pests in check. Since farming landscapes are mostly monocultures and therefore ecologically unstable, native trees and shrubs and the animals that find a home in them add much-needed diversity to the landscape, thus making it more sustainable. Apart from adding to ecosystem diversity, trees and shrubs greatly enhance a landscape's attractiveness.

Trees and shrubs can be incorporated into the farming environment as 'alley farming'. Alley farming means using a planned, managed combination of woody perennials (shrubs and/or trees) in lines, with cropping or grazing in-between.

There are two main forms of alley farming being developed in Western Australia.

1. Sandplain alley farming. Commonly the 'hedges' are composed of fodder shrubs and sometimes other small to medium sized tree. Pastures or crops (where suitable) are managed in the 'alley'. Perennial pastures are beginning to play more of a role in this system in the medium to high rainfall areas.
2. Salinity/watertable control. A common example is on valley floors in the wheatbelt that are affected by a shallow and saline watertable. The 'hedges', or tree lines, are less likely to contain fodder shrubs. However, there is considerable interest in salt tolerant acacias for fodder and legume values