Highland Grassland

Highland grassland sceneHighland grasslands are found in fertile valleys and plains between 600 m above sea level and the lower limit of alpine vegetation (approximately 1000 m above sea level). Many of the original upland tussock grasslands survive though often in a degraded state. The dominant grass is silver tussock (Poa labillardierei) which is a narrow-leaved species that forms dense tussocks up to 1 m in height. In some cases, such as at Paradise Plains in the north-east highlands, the grassland has replaced rainforest after fire. In most cases it seems that it has occupied the plains for thousands of years.

All of these highland grasslands have been used for stock grazing and most are still used for this purpose. The lower altitude plains on the Central Plateau have been partly converted to improved pasture, a conversion that is still continuing. Only a small proportion of highland grassland is managed to maintain biodiversity. While introduced grasses and herbs are found in most areas of highland grassland, the number of different species is still high and spectacular wildflower displays can be seen at places such as the Vale of Belvoir and Middlesex Plains.

Where to see highland grassland

Highland grassland can be seen at Middlesex Plains and the Vale of Belvoir near Cradle Mountain, and at Paradise Plains in the north east. Montane grassy forests can be seen in the vicinity of these plains.

Biodiversity values of highland grassland

Grasslands have been extensively cleared and modified. They are an extremely high priority for conservation, especially for threatened animal and plant species. A number of Tasmanian grassland plant species are extinct, as is the Tasmanian emu.

Management issues of highland grassland

Highland grassland sceneFire and grazing are the main tools used to maintain the health of native grasslands. In many cases fire is not essential as grazing by stock or native animals performs a similar role of reducing the competition from dense grasses. One of the main aims of managing grassy bush is to retain a rich and diverse flora by maintaining the gaps between the tussocks. Once the grass becomes rank and dense the gaps between the tussocks disappear. As a result wildflowers, trees and shrubs fail to flower and set seed, and eventually they become sparse or disappear. Grasslands may have over 50 different species in an area of 10 square metres but once the inter-tussock gaps close up this may drop to as low as 10-15 species. Both fire and grazing can be used to maintain the gaps between the tussocks.

The best management regime for grasslands will depend on condition. Management guidelines based on condition are given below. However, the specific needs of threatened plants may override these recommendations. If you are unsure what condition your bush is in refer to Condition of Your Bush.

Managing by condition

The best management regime for highland grassland will depend on the condition of the vegetation. Management guidelines based on the condition of the habitat are given below. However, the specific needs of threatened plants may override these recommendations.

Excellent condition

Grassland in excellent condition is characterised by:
  • a rich diversity of species and a mixture of dominant grasses, including kangaroo grass, wallaby grass, weeping grass, tussock grasses and wheat grass. There is a rich variety of wildflowers.
  • inter-tussock spaces (gaps between the grass tussocks) that are important areas for the germination of trees, shrubs and wildflowers.
  • a cryptogamic mat (a mat of lichens and mosses) on the soil surface. This protects the soil from erosion, helps the infiltration of water, helps nutrient recycling, and plays a role in seed germination
  • low levels of weed invasion.
Grassland in excellent condition is an asset. Maintain your current management. There is no need to change your farming practices unless there is an obvious reason to do so.

Recommendations for grazing and fire management are given below. However, other aspects of your farm may affect what is practical and the particular requirements of threatened plants may override these recommendations.

Ungrazed native grasslands will need some form of regular management to reduce the growth of grasses and maintain the gaps between the tussocks. This can be achieved by occasional crash grazing so that the rank grasses are reduced to a short sward. Burning can also result in a healthy grassland. A hot burn in autumn is preferable. It will probably be needed about every three years to maintain the gaps. Mowing or slashing is an option in the short term but unless the grass clippings or hay are removed they will cover the inter-tussock gaps and suppress germination of the native species and favour the invasion of weeds.

An active weed control program, particularly of gorse and broom, is vital for maintaining the integrity of grassland.

Tree planting is undesirable and is not needed in grasslands in excellent condition.

Good condition

Grassland in good condition is characterised by:
  • a lack of inter-tussock spaces
  • weed invasion - native pastures are occasionally top-dressed with superphosphate and aerially seeded with pasture grasses and clovers. As a result these sites are often weedy. Gorse can be a major problem, as can annual grasses and herbs.
  • many areas of bare soil, especially on the warm north-facing slopes preferred by stock
Management will need to focus on reducing the stocking levels so that the grassland can recover. Destocking may be the best option in some situations. This will also reduce the risk of soil erosion by restoring a perennial grass cover. You may decide to limit access to sensitive areas through strategic fencing. Sensitive areas include areas with highly palatable threatened species and north-facing slopes where soil erosion is a major problem.

Poor condition

Grassy bush in poor condition is characterised by:
  • Little diversity in the ground cover.
  • Many patches of bare ground.
  • No cryptogamic mat to protect the soil.
  • Severe weed problems.
  • Soil compaction with poor water infiltration.
Threatened species are often found in grasslands in poor condition. The species found tend to be those that need disturbance as part of their life cycle. For example, curly sedge (Carex tasmanica) is often found where there has been digging or other soil disturbance and where there is only a handful of native species. Peppercress (Lepidium hyssopifolium) is another threatened plant that thrives on disturbed soils with very low levels of stock grazing.

If your bush has threatened species it is best not to change your management regime without advice from DPIPWE's Threatened Species Unit.

If your poor quality grassland does not contain threatened species you will probably need to change the pattern and intensity of stocking by spelling it over spring and summer. Weed control is a major management issue in degraded native pastures and grassy woodlands and forests. In many cases it may be a matter of learning to live with most of the weeds and directing your management to favour the native species so that they eventually dominate.

Consider rehabilitating the area, including treating the eroded areas, direct seeding of native grasses, and controlling weeds. Weeds in Your Bush and Natural Regeneration Management provide information on managing weeds and rehabilitation.

Grazing

Grazing management will depend on the management aims and the condition of the grassland. Some general guidelines are outlined below.
  • Do not set stock or stock heavily for extended periods. Native grasslands tolerate moderate levels of grazing but their condition deteriorates at high stocking levels. The highly palatable kangaroo grass is eliminated from native pasture at high stocking levels and heavy cattle grazing can eliminate silver tussock grass. Do not stock at levels that cause the loss of tussocks and increase the amount of bare soil.
  • Reduce the rank growth of grasses by crash grazing or burning. Crash grazing is a technique where a mob of sheep is put into an area to graze it heavily for a short period of time.
  • If annual grasses and broad-leaved weeds are a problem stock heavily during early spring to reduce the seed set of weeds. Late winter and early spring is the main growing and flowering period for annual grasses and broad-leaved weeds. Burning in spring can achieve the same effect.
  • Spell grasslands over late spring and summer. Some of the healthiest and most diverse areas of grassland are those that are spelled in late spring and summer. This allows grasses and herbs to flower and set seed.
  • Stock grasslands after the autumn break. Use your native pastures and bush runs for autumn and winter grazing.
  • Do not graze too soon after burning. Grazing stock too soon after a fire will eliminate the regenerating seedlings. Do not graze until the new plants are out of the reach of stock.
  • Limit access to sensitive areas through strategic fencing. This includes areas with grazing-sensitive threatened species, north-facing slopes where soil erosion is a major problem, and where the regeneration of trees and shrubs is needed. Grazing-sensitive threatened species include austral thornbush (Discaria pubescens), Gunns mignonette (Stackhousia gunnii), young seedlings of Midlands wattle (Acacia axillaris), and peppercress (Lepidium hyssopifolium).
See Threatened Species for more information.

Fire

Fire is often used in highland grassland to produce green-pick for stock. Fire can also be used to control silver wattle and prickly box if they become too dense. It is an important method of managing woody weeds.
  • Autumn is the best season to burn for most species. Most of the plants and animals have completed their life cycle in autumn and conditions are more likely to be suitable for a controlled burn. Burning in spring and summer will stop flowering and seed set for that season. Spring burning could be useful for the control of weeds, particularly annual grasses.
  • Burn grassland when the gaps between the tussocks start to close up. Intervals of 2-5 years between fires are recommended in ungrazed native grasslands to maintain the inter-tussock gaps. Highland silver tussock grasslands need less frequent fires than the lowland communities because of their slower growth rates. The recommended interval for highland grassland is 5-20 years. However, this is only a guide and the appropriate interval will vary from situation to situation.
  • Fairly hot burns are better than cool burns in most situations. The fire should at least remove all the ground litter.

Weeds

Weed invasion is a critical issue for management of grassland, particularly for woody weeds such as broom, gorse and Spanish heath.

In some districts gorse is tolerated by landowners because of the valuable shelter it provides for stock in the absence of native shrubs. It can also provide an important habitat for bandicoots by providing protection from cats and dogs.

Some native woody species such as prickly box and silver wattle can also become dense in native pastures and may be considered weeds by landowners. The invasion of native pastures by both native and introduced woody shrubs leads to changes in the structure of the vegetation. It can be a serious management issue because the quality of the pasture is reduced and wool can be contaminated by twigs, seeds and other woody material.

Annual weedy grasses and herbs are present even in remnants that are in excellent condition but they are only a problem when they are at high levels.

Introduced grasses such as browntop bent, Yorkshire fog-grass and cocksfoot are widespread in native grassy understoreys. A number of farmers have commented that hairs-tail grass has been invading aggressively in the past few years.

Horehound has become invasive in the past decade and is a serious problem for wool growers. It tends to establish where sheep camp. Other common herbaceous weeds include yellow daisies such as flatweed, hawkbit and dandelion.

See also:
Weeds on this site for more information.


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