WET TROPICS RESTORATION ALLIANCE WORKSHOP - Bronwyn Robertson

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On 3rd September, around 70 people attended a Restoration Methods Workshop and Field Trip in Malanda. The event was hosted by the Wet Tropics Restoration Alliance, in collaboration with Malanda Landcare Group, NQ Land Management Services and Terrain NRM. 

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The workshop provided an overview of different restoration methods that can be used to reinstate native vegetation and assist the ongoing development of regrowth forests. This included well-tested methods and newer innovations that have not been widely used.

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The morning session included presentations that described six different approaches to restoration methods.

 

1. Assisted Natural Regeneration

Kylie Freebody spoke about trials at Cloudland Nature Refuge, where different assisted natural regeneration approaches were investigated to facilitate pasture conversion to native forest. Activities such as weed control, installing bird perches and conducting island plantings were undertaken. The results from various interventions were variable and difficult to predict, however after 13 years, some sites were well established with good canopy cover. The benefits of such an approach include lower upfront costs compared to standard biodiverse plantings, but disadvantages included much longer maintenance periods and an increased risk of poor project outcomes. Kylie highlighted that it could be a useful approach at the right site and with the right management, as long as it was clear what the primary objective of the project was and there was sufficient commitment and resources over a long time frame to achieve outcomes.

 

2. Modified Miyawaki

Peter Rowles from C4 (Community for Coastal and Cassowary Conservation) described their experience applying the Miyawaki restoration method at their Gurrbum Nature Refuge. Miyawaki is an approach that involves careful soil preparation, then planting multiple species at very high densities (3-4 plants/m2) to give very fast early growth and canopy closure. While results were good, the establishment costs of Miyawaki are high, so this approach could only be used in small areas. A modified Miyawaki approach is now used, with strips sprayed 4m apart, which are then ripped, rotary hoed and heavily mulched, before planting densely. Limited maintenance is required within the rows, with serious weeds hand pulled, reducing herbicide application. Canopy cover within the rows is achieved quickly. The inter-row spaces are slashed and mowed and, over time, the canopy closes across the inter-rows. C4 have kept records of the various costs of their different approaches and have found their modified Miyawaki is cheaper than full Miyawaki or standard biodiverse plantings, and is still relatively easy to plant and maintain.

 

3. Direct Seeding of Pioneer Species at Garriya Nature Refuge

Bess Murphy described an experiment direct seeding pioneer species, which she undertook with her partner at their Topaz property. They trialled the approach on 1ha of their property, which has very poor soil and had been sitting at a stage of arrested succession for 16 years. They used seed from Acacia celsa, A. melanoxylon, Alphitonia petrei, Glochidion ferdinandi and Homalanthus populifolius. The seed was planted in single-species rows, alternating with rows of planted trees, with 1m between rows. The seeded rows were ripped to 5-10cm with seed manually sprinkled along the row. The site now has good canopy cover, with no maintenance required after the first 2-3 years. Some difficulties were encountered. A seed planter was initially used, but wasn’t successful. Seed viability was inconsistent, resulting in variable germination rates and density. The availability of some seed was also restricted. The costs of this approach were much lower than standard biodiverse plantings, but it’s likely that the biodiversity outcomes are lower or at least more variable. The opportunity to test related approaches was also highlighted, perhaps using other species, equipment or planting designs.

 

4.Massey Creek Wide-spaced Revegetation Trial

Peter Snodgrass provided an overview of a wide-spaced revegetation trial established in 1998 by QPWS at Massey Creek. Plantings were established using various row spacings from 2m - 5m and a higher proportion (40%) of pioneer species than normal. The inter-rows were slashed and mowed to control grass. After 5 years, canopy cover still wasn’t well developed in the wider spaced plantings, with up to 25% weed cover. After 6 years, canopy breakdown was noticeable from some of the pioneer species (e.g. bleeding heart), however the site had good germination of native recruits in the understorey. A second site was also planted, using a more typical proportion of pioneers (15%) and in rows 3m apart, with trees planted at 2m within the rows. Canopy closure was found to be quicker at this site compared to the first site, however canopy gaps and weeds were still present after 6 years.

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Work at this site showed that standard plantings conducted by QPWS (15% pioneers, 1.5-1.8m spacing, quarterly weed spraying for first years) provided better outcomes, requiring shorter maintenance, with quicker canopy closure and significant numbers of native recruits.

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5. The Need for all Restoration Tools to Restore the Lost Wet Tropics Forests

Noel Preece started his presentation with an overview of clearing rates in the Wet Tropics, noting around 4,500 ha have been cleared in just the last 4 years in the Wet Tropics alone. Even though there have been various reforestation programs over several decades, at best, less than 10% of cleared land has been reforested in the region. Noel has been researching cost effective methods of restoration that can be applied at a much larger scale in the region, that will deliver biodiversity outcomes, while generating income through carbon credits. Experiments have been conducted at Thiaki using different spacings, species and reforestation methods. Good results have been obtained using 3m spacings, or 1,000 trees/ha, with canopy closure occurring in 3 years, if survival is good. Minimising planting shock was found to have a significant impact on survival. The experiment has highlighted that there are many useful reforestation techniques for different purposes, with shade and timber plantings able to be established for less than $5,000/ha and rainforest plantings for around $8,000/ha. If plantings are registered as carbon projects, there is the possibility to recoup establishment and management costs and even generate an income from reforestation

 

6. Woodland Restoration

Jacqui Diggins described some of the different approaches to restoring woodland communities in the Wet Tropics, which are at risk from rainforest encroachment and clearing. Woodland vegetation communities support many species, including threatened and endemic wildlife, such as the Mahogany Glider. These ecosystems cover a large part of the region, however their restoration can be difficult, due to their open canopy and diverse understorey. Restoration actions can include appropriate fire management, weed management, revegetation and grazing management. Specific restoration techniques should consider the outcomes required and resources available, with careful consideration of canopy tree density. Restoration of woodland ecosystems generally requires a longer maintenance commitment to manage weeds, due to the more open canopy. Connectivity and habitat diversity are important factors in woodland restoration.

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Field Trips

The presentations were followed in the afternoon by field trips to two sites. The first field trip was along the North Johnstone River, adjacent to the Malanda township. During the 1990s, approximately 3 hectares were revegetated at the site. However, in 2006 Cyclone Larry opened up the canopy, allowing an influx of weeds that dominated the understorey. Malanda and Upper Johnstone Landcare Association (Malanda Landcare) have been restoring the site, with weed eradication, infill planting and the restoration of a walking track.

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The second field trip was to Thirlmere Gully on a property purchased by Barry and Jan Thurling in 1965. Since the 1970s, the owners have partnered with CSIRO and other research groups to revegetate waterways on their property. Various restoration techniques have been used over this time. The field visit was to a site which was very heavily mulched before planting, which significantly reduced the need for follow up weed control.

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Conclusion

Many factors will influence what technique to use at a particular site, including the primary objective of the project, the resources available, site conditions, ability to conduct maintenance, access to machinery and equipment, the timescale of a project and surrounding land uses. Kylie summed the workshop up by explaining that we need a range of restoration techniques in the toolbox to support many different landholders to do more replanting projects in our region. To scale up restoration using the current, commonly-used restoration methods, we require a monumental increase in investment. Developing a suite of different restoration methods could engage more landholders to become involved in large-scale projects (tens of hectares) as well as more smaller projects (several hectares).

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To do this, we need more information to compare the risks, benefits, costs and outcomes of the different approaches. If anyone is interested in contributing to data collection and collation of information from different restoration techniques, please contact the Wet Tropics Restoration Alliance. restoration@wtma.qld.gov.au.