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In cases of severe land degradation the first step towards rehabilitation is identifying the problem and the underlying causal elements. Often there will be a number of contributing factors. Therefore, these factors must be neutralised or rectified in order to obtain as best as possible a complete solution to the problem. With any problem that is encountered, there is a wide range of help and advice available directly from government and initiatives such as Landcare. In many cases, funding (e.g. grants) may be available to either individuals, or groups (e.g. local landcare groups) to carry out such rehabilitation works.
Often rehabilitation programs are required in areas that are extremely hostile (or have become hostile due poor land use) to revegetation. Establishing trees can be especially difficult as they are often quite fragile when young. What constitutes a harsh environment? There are numerous factors that could be considered responsible for creating these conditions as follows:
Weather/Climate (drought, flood, wind, salt laden wind, frost, fire)
Water availability (too much or too little!) & quality
Soil (pH, chemical and physical structure, too much or too little nutrient)
Biological (damage by animals, competition from weeds)
Physical (damage from recreational/agricultural vehicles or persons)
When trying to establish vegetation in a hostile environment, greater care needs to be taken in the planning and preparation stages, as well as during the initial establishing stages.
There are a number of common sense strategies that should be adopted during the planning stage that will enhance the likelihood of a successful rehabilitation project. Firstly, the site needs to be identified and defined. What is meant by this, is that visual and physical reconnaissance needs to be undertaken so that any potential problems will be anticipated and therefore dealt with.
Tests need to be carried out on soil type and composition, research done on weather characteristics, resident and introduced species, and present and likely future land use activities. It is important to understand the state of the local environment, because it may have changed markedly, and have very different factors at work since the degradation occurred. Species of vegetation that once thrived, may be severely affected by the current state of the local environment (eg. rainforest trees will not establish and grow in a large open paddock).
Remember that forests are representative of older ecosystems, they do not develop overnight, but over successive generations of favourable conditions.
It might be necessary to artificially create these favourable conditions before the proposed tree planting takes place. Weed species may need to be controlled, as well as feral or native species. Introduced pigs, rabbits, goats and hares can decimate tree plantings, but so too, can kangaroos and livestock. Fencing or tree guards can be employed until the trees are of sufficient size to withstand foraging animals. It may be better to grow clumps of trees that can be securely fenced, and large enough to withstand grazing. However, it should be noted that during drought conditions, when food is scarce, the ability of an animal to reach the succulent, tender foliage of saplings should not be underestimated. To do so, will prove a waste of your time and money!
Rehabilitation of the land may require that certain primary species such as ground covers, annuals, perennials and shrubs be established before planting tree species, or it needs to be done in conjunction with planting them. This approach is necessary with gully erosion problems. The smaller, faster growing species act to hold the soil together in much quicker time than a tree takes to develop, although trees tend to do the same job on a larger scale once they are established. It may also mean that certain measures need to be used until groundcovers or understorey plants become established.
Managing the water resources of a property is becoming increasingly significant. An increasing population, and a decline in the quality of available water (e.g. increased sediment due to erosion, increased nutrient levels, other chemical impurities, etc.), has meant increased demand on our water supplies. In Australia, which is to a large extent arid to semi-arid, and has generally low fertility levels in it's soils, managing water, and the nutrients it may contain, to ensure it is used effectively, for both production and environmental purposes has become critical to the long term viability of our agricultural land.
Runoff is the term applied to the movement of water (especially rain) when flooding occurs. In the process of moving towards the line of least resistance the water builds up speed and begins to eat away at surface soil. Runoff can be controlled with a number of strategies:-
Cultivating on the contour
This refers to cultivating with the contour of the land rather than across the slope. By doing this, water is slowed down by the ploughed ridges giving it more time to soak into the ground.
Building contour banks
Again these should be designed to follow the land contour. Their purpose is to direct the flow of water into grassed waterways which can slow its movement down slope considerably reducing erosion, and carry the water to catchment areas such as creeks and dams without the loss of soil. This can be an effective way of catching runoff and directing it to a suitable storage site (dam) for later use. The grass will reduce the speed at which water flows over the ground, hence reducing erosion.
The purpose of strip cropping is to spread flowing water. This tends to restrict erosion damage as the water cannot build up in volume and hence speed as it is dispersing. The slower movement of water allows more time for it to infiltrate into the soil, where it can be utilised by the plants growing there.
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