Revegetation Preparation

To maximise the survival rate of your precious seedlings, good site preparation and weed control is vital.

Weeds

In the spring before the planting, initial weed control begins. Heavy weed burdens greatly reduce success due to weeds competing for light, moisture, and nutrients. Studies have shown a decrease in early growth by up to 70 % at weedy sites when compared with weed-free sites, and a decrease in expected survival rates from 90 % to as low as 10% (Greening Australia, 2003).

Weeds should be controlled when they are actively growing, before they set seed and before they begin to compete with newly established plants. Different weeds will germinate at different times of the year so monitoring becomes key to triggering a management response. Look at your site each month after planting and schedule weed control when weeds are growing but still small.

Chemical weed control should be undertaken for at least three years at your revegetation site:

• If possible, spraying the year before planting will significantly reduce the intensity of follow up weed control required.
• At least once, in the months prior to planting.
• Once in the year after planting – creating a 1m weed-free buffer around each seedling.
• Once two years after planting – creating a 1m weed-free buffer around each seedling.

Spraying with glyphosate

Bare land planting

• Use 2 litres of glyphosate 360 per hectare for annual weeds.

Infill planting

• Spot spray locations within the remnant, where you intend to revegetate (don’t spray the entire remnant).
• Use 500-700mL of glyphosate per 100L of water (as per the label).
• Use a spray guard on your spray equipment and be very careful to avoid spraying native species already growing within your remnant.

Post planting spray

• Ensure that you spot spray carefully, keeping a 1m weed-free buffer around each seedling.
• Use a spray guard on your spray equipment and be very careful to avoid spraying the seedlings you have already planted.

Other Site Preparation

Scalping for weed control

• To be effective the soil must be scalped at a sufficient depth to get below the weed seedbank – which will vary from site to site.
• Grader blades and bulldozer blades can be used.
• Scalping is not recommended at hilly sites, or within the stream bed, due to the risk of erosion.

Mulching for weed control

• This is best suited to small-scale projects.
• The mulch material must effectively block out light and/or smother the growth of weeds.
• Organic materials, such as leaf litter, prunings, wood chips and organic jute mattings can help to improve soil structure and modify soil temperatures.
• Ensure the material being used is free of weeds or weed seed (aging or composting freshly cut mulch material is recommended).
• Keep mulch clear of the seedling stems to prevent collar rot.
• Obtain good coverage and thickness to smother weeds.
• Anchor any weed mats or newspaper mulches.

Deep ripping

Deep ripping is appropriate for most soil types, except deep sand and cracking clays. It assists with strong root development and water penetration, by breaking up impenetrable layers in the soil profile. Roots will grow faster and penetrate deeper into the soil allowing them to access subsurface soil moisture quickly. In most situations infill planting will not allow for ripping, due to the damage this will have on existing vegetation

• Rip lines should be 2-3m apart and 0.3-0.5 metres deep.
• Ripping along contour lines will result in harvesting of water moving down slope.

Mounding

Even salt and water tolerant species are highly susceptible to water logging and salinity as they are establishing. This is especially so of seedlings that have been grown under normal conditions in a nursery. Mounding saline and/or waterlogged sites will:

• Raise the seedlings above the water line as they establish, helping to prevent root rot.
• Allow rain to leach salt out of the root zone.

Weeds and fire

Removing stock from grazed waterways can lead to a proliferation of grassy weeds (Water and Rivers Commission, 2000h) which many landholders consider an unacceptable fire risk. The best plan to minimising problems with weeds is good site preparation:

• Spray weeds at least three times with waterway- friendly chemicals prior to planting. Spray before seed set in spring the year prior to planting, after summer rains and directly prior to planting.
• If not using chemicals, slash weeds prior to seed-set in spring, after summer rains, prior to planting and consider a combination of weed control methods including heavy mulching/weed matting, cool burns, hand pulling and organic spray alternatives.
• Construct “wick breaks” in your revegetation area every kilometre. Wick breaks are a cleared break in revegetation along waterways to act as a barrier to fires running along a waterway corridor. Maintain fire breaks along the boundary of the revegetation areas
• Spray weeds for two years following planting, using a spray shield on your sprayer and being careful to avoid any spray contact with your newly planted seedlings – this will also help your new seedlings to establish, by reducing competition from weeds
• Plant densely enough to outcompete the weed species present along the waterway to reduce the amount of dry vegetation that readily carries fire

Planting plan

Preparing a plan and doing some research on the ecological tolerances of your species will make sure you put the right plant in the right spot to maximise success.

Weed control

As above, control the weeds prior to planting while they are small and before they set seed, allowing enough time after opening rains for the majority of weed species at the site to germinate.

Look at your site each month after planting and schedule weed control when weeds are growing.

Planting

The process for planting a tree:

• If you have rip lines, plant directly into the rip lines.
• Create a hole about 10-15cm deep.
• Place the seedling root ball as deep into the hole as possible, while ensuring there are leaves and some stem above the soil surface.
• Firmly push the soil in around the root ball – removing any subsurface air pockets (doing this with your boot is fast and effective at removing air pockets).
• Ensure that there is at least 3-5cm of soil above the top of the root ball, as this will help to prevent moisture loss.

With hand planting, tools such as pottiputkis and kidney buckets will significantly decrease the time it takes to plant your seedlings. Hand planting is recognised as having higher success rates than machine planting, due to the personal touch each seedling gets – i.e., if the conditions vary across the site the planter is able to respond to this easily, when compared to a mechanical tree-planter.

One-pass tree-planters are also commonly used in the Wheatbelt and, if correctly adjusted for the site conditions and monitored throughout the planting process, will also have high seedling survival rates. It is useful to have someone following behind a mechanical tree planter on foot. This way they can pick up any issues in the planting technique as you go, while also further pressing the soil around the seedlings to ensure good planting.

Feral control

Rabbits should be controlled to keep them from devouring newly established seedlings. Summer/autumn rabbit control is the most effective. There are several methods that can be used for rabbit control and more than one should be used in combination to ensure effective management.

1080 Baiting

1080 is a restricted poison and requires a permit that is administered through the Department of Primary Industries and Regional Development. 1080 baiting is recommended rabbit control because it is highly toxic to feral animals but non-lethal to native animals. Deploying 1080 for rabbits involves the use of rabbit bait stations that protect the baits from rain and other animals. Bait stations can be placed near locations of rabbit activity, such as near warrens. It is recommended that rabbit baiting programs span a six-week period in summer, when other food sources are scarce.

Phostoxin fumigation

To successfully control rabbit populations with phostoxin fumigation you need to identify every entrance to the warren. Fumigation can be done at any time of year if soil is sufficiently damp to allow an effective seal when blocking burrow entrances, however it is most effective if done just before the start of the rabbit breeding season.

Warren and harbour destruction

Follow-up control activities with warren and harbour destruction wherever possible to enhance the success of other control methods. Warren destruction through ripping increases the time it takes for rabbits to re-colonise. Plan to rip warrens in hot, dry conditions, when the soil is soft and loose.

Predator control

To maintain the balance between predator and prey, foxes and cats should be controlled concurrently with rabbits. This will reduce “prey-switching” from rabbits to native animals. Cats and foxes can be controlled by several methods including cage trapping and 1080 baiting.

Post-planting maintenance

Weed control is usually the single most important factor in the success or failure of tree plantings. As above, try to maintain a weed-free area of 1m diameter should be maintained around each plant for two years after planting. There are also some species-specific herbicides that can be used to reduce the impact of the chemical on your revegetation species.

Rabbit control is vital during the establishment phase of your revegetation. It will also assist with natural regeneration of your revegetation site.

You should not need to undertake thinning of your revegetation site - the plants will naturally self-thin; with the strongest individuals being the ones that survive.

Maintenance - Replacement Planting

Despite best efforts, you may end up with seedling deaths in the first year or poor germination and survival. In this case it is sometimes necessary to carry out additional plantings to fill gaps or to replace species that have failed or are under-represented.

Before you plant you should decide on a percentage of seedling survival below which you will replant or fill in gaps. This is often a personal judgement, but many planters will replant if they get less than 50-75% survival. You should monitor within one month of planting when deciding on replacing failed plants. This allows you to take advantage of the existing weed control and ground preparation and to conduct your replants in the most suitable season. Replanting beyond 3 months after planting is rarely successful. You should, however, monitor survival at 10 months after planting. If survival is poor at this stage, you will need to prepare your site again for replanting. You can spot spray with herbicide to remove weeds and then replant again in the ideal season. In some cases, you may need to prepare the ground again if it has compacted or is difficult to plant into. You can use a rotary hoe to get between existing trees or use a tractor-mounted auger to prepare individual planting holes. If survival is very poor it may be worth cutting your losses and preparing the site properly before replanting.

As the successful trees get bigger, it is more difficult to successfully establish other plants among them as their roots become very competitive and they begin to shade out new plants. If you intend to revegetate your site in stages it is best to leave whole rows unplanted, rather than try to plant between existing trees.

Challenges in your revegetation program

Difficult soil conditions

Heavy clay, coarse sandy deposits, salinity, and nutrient accumulation all make planting difficult and can affect survival rates.

• Wet, heavy clays should be ripped so that seedlings can be planted into loose soil that can be backfilled around the root ball.
• Sandy deposits that have been deposited by flood events are highly erosive and quickly dry out, they need to be planted early to allow plants to get their roots deep into the wetter soil profile before summer with plants that are tolerant of sandy soils.
• Saline soils also tend to be prone to waterlogging and should be mounded to elevate the seedling above salty soilwater and be planted with halophytic species that can tolerate these conditions.
• High phosphorous levels can be toxic to Australian native plants (Lambers et al. 2013) so planting species like rushes and sedges that filter nutrients from a site can be a useful tool (Water and Rivers Commission, 2000f).
• Flooding and sedimentation – revegetation efforts can be inundated with water or buried by sediments during floods. Choosing species with a good tolerance to waterlogging and leaving large woody debris and other obstacles in the channel and floodplain to trap sediments can help to minimise losses (Water and Rivers Commission, 2000b). Moreover, collaborating with upstream neighbours to manage their sediment and nutrient outputs will reduce the amount of sediment entering your property.

Altering the environment

Some activities such as engineering interventions can provide solutions to management issues that are difficult to achieve through revegetation and protection. It is important that before you undertake an activity that may alter environmental components such as waterways that you check regulations on their management. It is also important to consult with tools such as the Aboriginal Cultural Heritage Inquiry System which can indicate whether further consultation is required.

Any activity that physically interferes with a waterway requires a permit. If you are unsure, it’s best to contact the Department of Water and Environmental Regulation (DWER) before site works commence. Moreover, catchment modifications such as deep drains have implications that affect downstream conditions and should be considered with great care in conjunction with neighbouring landholders and DPIRD.

Engineering solutions to mitigate erosion, stabilize banks, slow water flows and improve water quality can vary immensely in scale. In the simplest sense, leaving fallen limbs and logs in-situ creates natural barriers or snags that trap sediment and reduce the velocity of water creating more diverse habitats for animals and reducing sediment movement (Water and Rivers Commission, 2000g).

Riffles (rock barriers) are naturally occurring geomorphological features that form part of a sequence of pool-riffles that were common in the Avon before the River Training Scheme. Building artificial riffles can create habitat diversity in a stretch of waterway as well as trap sediment but does need careful planning to prevent unwanted consequences.

References and useful resources

Brendan Oversby, 2004. Riparian Plants of the Avon Catchment: A Field Guide. Department of Environment, Perth,

DEC, 2009. Fencing and gates to reduce kangaroo damage. Fauna Note number 32, Department of Environment and Conservation, Perth.

Greening Australia, 2003. Revegetation Techniques: A Guide for Establishing Native Vegetation in Victoria. Greening Australia, Victoria

Gouldthorpe, J, 2008. Athel pine national best practice management manual : managing athel pine and other Tamarix weeds in Australia, Australia. National Athel Pine Management Committee. Northern Territory. Department of Natural Resources, Environment and the Arts.

Lambers, H, Ahmedi, I, Berkowitz, O, Dunne, C, Finnegan, P, St J. Hardy, G, Jost, R,Laliberté, E, Pearse, S, Teste, F, 2013. Phosphorus nutrition of phosphorus-sensitive Australian native plants: threats to plant communities in a global biodiversity hotspot, Conservation Physiology, Volume 1, Issue 1 https://doi.org/10.1093/conphys/cot010

NSW DPI, date unknown. Fact Sheet 3: Monitoring Erosion, Soil Erosion Solutions series, New South Wales Department of Primary Industries, Woolongbar, NSW.

Viv Read and Associates, 2008. Managing waterways in the Avon Wheatbelt: Field Guide. Government of Western Australia, Perth.

Water and Rivers Commission, 2000a. Flood proofing fencing for waterways. Water Notes WN19 July 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000b. Identifying the riparian zone. Water Notes WN11 January 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000c. Livestock management: construction of livestock crossing. Water Notes WN6 January 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000d. Livestock management: fence location and grazing control. Water Notes WN18 July 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000e. Livestock management: Watering points and pumps. Water Notes WN7 January 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000f. Rushes and sedges. Water Notes WN20 July 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000g. The value of Large Woody Debris (Snags). Water Notes WN9 January 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2000h. Weeds in waterways. Water Notes WN15 January 2000, Water and Rivers Commission, Perth.

Water and Rivers Commission, 2003. Revegetating with native grasses in the Avon catchment. Water Notes WN31 January 2003, Water and Rivers Commission, Perth.

Weeds Australia. Centre for Invasive Species Solutions, Canberra. [Date Accessed: [18/11/2022], https://weeds.org.au

Western Australian Herbarium (1998–). Florabase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. [Date Accessed: [18/11/2022], https://florabase.dpaw.wa.gov.au/

White, P and Mullan, G, 2006. Revegetation Techniques and Timelines. Department of Environment and Conservation, Perth.