Grassy Woodland and Forest

Grassy woodland and forest sceneGrassy woodland and forest is one of the most characteristic bush types of the Midlands and central east coast. It occurs naturally on fertile soils, usually in low rainfall areas. The trees in woodland are spaced such that the gaps between their crowns are wider than crowns. The crowns are closer together in forest. The terms grassy woodland and forest are used interchangeably and the management guidelines apply to both. The understorey of grassy woodland and forest is dominated by a diversity of grasses, saggs, sedges, lilies, daisies, orchids, peas and other wildflowers. The canopy can be dominated by white gum (Eucalyptus viminalis), cabbage gum (Eucalyptus pauciflora), black gum (Eucalyptus ovata), black peppermint (Eucalyptus amygdalina), silver peppermint (Eucalyptus tenuiramis), swamp peppermint (Eucalyptus rodwayi), blue gum (Eucalyptus globulus), or gum-topped stringybark (Eucalyptus delegatensis). In montane regions grassy forests occur, often adjacent to grassy plains. Areas of sedgey forest may occur on poorly drained sites within grassy woodland and forest. They are generally managed in the same way as the surrounding grassy bush.

Grassy woodland and forest can intergrade with heathy woodland and forest. If there is a dominant heathy component in the understorey then the management is different to that of grassy bush and you should refer to Grassy/Heathy Woodland and Forest.

Grassy bush is used for rough grazing and is an important part of farming enterprises. Much of this bush has been cleared for crops, pasture and housing.

Where to see grassy woodland and forest

Grassy woodland and forest can be seen on the Domain in Hobart and in the Trevallyn State Recreation Area in Launceston. They are also widespread on north Bruny Island. The rest area on the Midland Highway near St Peters Pass is an excellent and typical example of grassy forest, with white gums, cabbage gums and a diverse understorey. This area has not been burned frequently and it has a dense understorey of small trees such as prickly box.

Biodiversity values of grassy woodland and forest

Grassy woodland and forest is one of the bush types that has been most extensively cleared and modified. It is an extremely high priority for conservation, especially of threatened animal and plant species. A number of Tasmanian grassland plant species are extinct, as is the Tasmanian emu.

Refer to Threatened Species for more information.

Management issues in grassy woodland and forest

Fire and grazing are the main tools used to maintain the health of native grassy bush. 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. Grassy bush 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.

Rural tree decline is one of the most pressing management issues of grassy bush. Vegetation types with grassy understoreys are the most affected by dieback or rural tree decline and white gums are the most affected of all the eucalypts.

Managing by condition

The best management regime for grassy bush will depend on the condition of the bush. Management guidelines based on the condition of the bush 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.

Excellent condition

Grassy bush 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.
  • Young trees of different ages.
Bush 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 and grassy woodland and forest 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 grassy bush.

Tree planting is undesirable and is not needed in grassy bush in excellent condition.

Good condition

Grassy woodland and forest - good condition.Grassy bush in good condition is characterised by:
  • A lack of inter-tussock spaces.
  • Weed invasion. Native pastures and bush runs 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 bush 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 woodland and forest - 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.
  • No regeneration of trees and shrubs in the forests and woodlands.
Threatened species are often found in grassy bush 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 grassy bush 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 trees and shrubs, and controlling weeds.

Grazing

Grassy woodland and forest - grazing areaGrazing management will depend on the management aims and the condition of the bush. Some general guidelines are outlined below.
  • Do not set stock or stock heavily for extended periods. Native grasslands and grassy woodlands and forests 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 grassy bush over late spring and summer. Some of the healthiest and most diverse areas of grassy bush are those that are spelled in late spring and summer. This allows grasses, herbs and shrubs to flower and set seed.
  • Stock grassy bush 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).

Fire

Fire is often used in grassy bush 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 grassy bush 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. Grassy woodlands and forests also need less frequent fires than grasslands. Recommended fire intervals are 4-10 years for grassy woodlands and 6-18 years for grassy forests. 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.
  • Don't burn if fire-sensitive threatened species are present. If you have Midlands wattle (Acacia axillaris) on your property it can be eliminated by fire, unlike most wattles. The role of fire in the regeneration of austral thornbush (Discaria pubescens) is not clear. It resprouts after some fires but the young shoots are highly palatable and the resprouting stems and leaves are heavily browsed. It is best to seek expert advice from the Threatened Species Unit if you wish to burn the riparian (i.e. riverside) grassy forests where austral thornbush is found.

Weeds

Weed invasion is also a critical issue, particularly for woody weeds such as broom and gorse.

White gum woodlands are used extensively as bush run country in the Midlands. They are occasionally top-dressed with superphosphate and aerially seeded with pasture species. As a result these sites are often weedy and gorse can be a major problem. 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.

The weeds listed below are the common weeds found in grassy forest that threaten biodiversity.
  • Woody shrubs such as gorse, broom and Spanish heath are the most serious weeds. Gorse is widespread in much of the grassy bush run country.
  • Introduced grasses such as browntop bent, Yorkshire fog-grass and cocksfoot are widespread in native grassy understories. 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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