Pasture Expansion technical guide

Before you start

This technical guide on ecological thinning is for landholders and contractors who are managing native vegetation under the Pasture Expansion part of the Code.   

If you are not sure if the Pasture Expansion part of the Code suits your circumstances, read:

• the guide to getting started with native vegetation management
• managing native vegetation under the Land Management Code.

Local Land Services can provide advice to help you:  

• assess your property and proposed treatment areas
• identify vegetation types and formation for a treatment area including forest, woodland, scrub/tall heath
• identify if the area contains an Endangered Ecological Community (EEC), or Vulnerable Ecological Community (VEC).

Will thinning meet your objectives?  

Before you start, find out if the treatment area has suitable native grass cover. It is important to know if and how the existing groundcover respond to thinning.   

One way to determine this is to observe disturbed land close to the treatment area, for example, a cleared track running through the area. If there is grass growth on the track, it is possible there will be grass growth following thinning in the treatment area.  

Learn how to assess the native groundcover on your property.   

You should also ensure the land will support a productive pasture outcome.

You can improve pastures in thinned areas. For example, you may apply fertiliser or over-sow pasture as part of sustainable grazing. You can make these improvements as long as they do not cause a substantial long-term decline in the structure and composition of the native vegetation or significantly degrade the site. 

To learn more about soil and land capabilities, refer to the soil profile data and mapped land and soil information available at eSpade.

Selecting vegetation to thin  

Prioritise thinning stems in the shrub layer, mid-storey and canopy. Focus on removing vegetation that will give the best response in groundcover grasses. Make sure all thinning stays within the terms of your pasture expansion certificate. 

You may sell legally felled timber.

If using contractors to undertake the thinning, it is your responsibility to ensure they are aware of the legislative rules and necessary environmental protections before thinning commences.  

Selecting vegetation to retain  

• Trees over 90 cm diameter breast height over bark (DBHOB) must be retained.
• Threatened plant species (the retention of specific threatened plant species may be stipulated in some certificates).
• A diversity of plant species and tree sizes to allow for development of healthy forest in the future.
• Non-listed genera for Division 2 – Uniform Thinning in the coastal zone.
• Consider retaining trees with hollows, which are usually older and larger. Also consider keeping sub-dominant trees, so they can develop hollows over time. 

Woody vegetation to be retained should be labelled, particularly if contractors are used to undertake the thinning. Spray paint ‘H’ on trunks of important habitat trees, or use ‘R’ for retain. For examples of field tree marking, see the field and tree marking guide.

Calculating vegetation density

Determining vegetation density retention for uniform thinning

You have two options for calculating how much vegetation can be removed.

Only count plant genera that can be thinned according to the pasture expansion certificate.

Option A: Determine the number of stems to retain  

Work out the average distance between woody plants for the vegetation formation in the treatment area and keep this distance in mind when removing trees.

For example, if the minimum stem density to be retained is 225 stems per hectare, calculate as follows:   

1 hectare = 10,000 square metres.
Divide 10,000 by 225 = 44.4.
The square root of 44.4 = 6.66 metres. 

This is the minimum average spacing between retained trees. A laser rangefinder can be used to determine distance between trees.  

Option B: Determine the number of stems to remove

Count the number of woody plants in a 50m by 50m square. Multiply the total by 4 to give a rough count per hectare. Then work out the difference between this count and the minimum stem density for the treatment area. The difference is the number of trees that can be removed in an evenly distributed manner.  

For example, a 50m x 50m square contains 360 woody plants that can be thinned under the terms of the certificate. The vegetation formation is dry sclerophyll, neither EEC nor VEC, therefore the minimum stem density of trees to retain is 150 stems per hectare.

360 x 4 = 1440 = average number of woody plants per hectare. 
1440 – 150 (minimum stem density) = 1290. 

This is the approximate number of woody plants that can be removed in a uniform manner. If the treatment area is large, repeat this process across a representative number of sampling sites to determine an average count.

Local Land Services can help you with measurements, demonstrating the use of the calculations on site, or identifying an area that equates to the target stem density.

Determining vegetation density retention for mosaic thinning  

It is important that each separate treatment area retains at least 30% canopy cover in evenly dispersed patches of 5 hectares in a mosaic pattern across the treatment area.  

Local Land Services can provide an advisory map showing what vegetation can be removed.   

Alternatively, you can draw a sketch map of the treatment area. To do this, determine the size of the area, and sketch where woody vegetation will be removed and where woody vegetation will be kept.  

Your sketch should show where woody vegetation will be kept:  

• in at least 30% of the total area
• evenly dispersed in patches of at least 5 hectares
• with a minimum of one 5-hectare patch for every 50 hectares (or part thereof).  

For example, a treatment area that is 100 hectares in size will require at least 2 patches of 5 hectares and a further 20 hectares (of any area or shape) that is evenly distributed. All trees with a DBHOB over 90 cm must also be retained. This meets the requirement of at least 30% retention of the canopy cover in a mosaic pattern of patches and clumps.  

The 5 hectare retention patch in each 50 hectare portion of treatment area must be calculated in ongoing ‘bands’, and must not be reduced pro-rata for treatment areas below 50 hectares.

Method of thinning  

Thinning in a staged process. Observing the results over time may help to determine the most effective thinning method and whether there will be suitable pasture growth.  

Grass growth in response to thinning will vary depending on soil, seed bank, species composition, climatic conditions etc.  

During thinning operations, it is important to:  

• protect soils
• reduce run-off
• maintain high water quality
• keep groundcover as intact as possible.  

The most appropriate thinning method will be determined by total treatment area, soil, vegetation structure and type, access and cost. Using a variety of thinning methods may be the most suitable approach. No single thinning process or method is suitable for all properties.

Minimising soil disturbance  

Some soils are more erodible than others. To check your local soil data, you can use eSpade.  

Steeper land and longer slopes can lead to greater erosive power of water run-off.  

Consider rainfall intensity for the area. More intense rain may lead to more run-off and erosion.   

Maintain good groundcover. The more organic matter in the soil the better.  

Piles of logs should be on ridge tops, away from water bodies and have good drainage-maintain good groundcover where possible. For example, use mulch to cover bare soil.  

Advice when using machinery   

Machinery can compact soils and lead to increased run-off and erosion   

If mechanical thinning methods are used there may be a lot of plant material generated. This can be left on the ground (if it doesn’t create a bush fire hazard) which will be better for the soil in the long term but may suppress grass growth in the short term.   

Removal of the plant matter can be time-consuming and may encourage weed growth due to soil disturbance, but the grass response may be faster.  

To minimise soil disturbance and erosion when using machinery:  

• use existing tracks
• ensure proper track and drainage construction and maintenance
• use walkover techniques when extracting logs
• keep machinery blades up
• drive as to minimise extra drainage requirements
• lift entire logs off ground to avoid log furrowing.  

Ongoing management  

Thinning may encourage tree growth in a forest that has stopped growing due to over-competition for light and space, otherwise known as a ‘lock-up’ state. It may be necessary to control woody vegetation regrowth to allow the pasture grasses to flourish.   

Monitoring and observation of the treatment area is important to determine the best ongoing management methods.  

There are a range of good land management practices to ensure the best pasture results. These should be undertaken in accordance with allowable activities for managing native vegetation.  

• Sustainable grazing with an appropriate grazing regime.
• Ongoing regrowth control (within the term of the certificate).
• Ongoing weed control.
• Ongoing pest animal control.
• Maintenance of soil health.
• Management burning using suitable timing and frequency appropriate for the forest type and history of fire in the area (in accordance with the Environmental Protection Works allowable activity).  

You should also ensure that all necessary infrastructure is in place including fencelines, troughs, dams and livestock laneways.  

Your next steps  

• Notify or request certification.
• Read our resources including how to measure diameter breast height over bark.