Australasian Plant Conservation
Originally published in Australasian Plant Conservation 21(1) June - August 2012, p 9-11
High impact bush regeneration: is there a role for heavy machinery?
Ballina Coastcare Inc., NSW. Email: firstname.lastname@example.org
(top to bottom) Eco-mulching operation (April 2010). Compensatory replanting (June 2010). Photos: Lee Andresen.
Victorian Coastal Tea Tree (Leptospermum laevigatum) has had damaging consequences for dunal ecosystems of the NSW Far North Coast, equaling those of Bitou Bush (Chrysanthemoides monilifera subsp. rotundata). Forty years since the species’ introduction, substantial forests of durable bushfire prone hardwood have developed. Large populations of juveniles have spread, posing additional challenges to other areas under regeneration.
By 1989, when dune restoration began at Angels Beach in East Ballina, L. laevigatum had already colonised hectare sized patches forming impenetrable monocultures. Originally planted to stabilise high dunes, when works installations were abandoned after heavy mineral sand mining in the 1960s, they have seriously obstructed Littoral Rainforest recovery 50 years on.
Senescent Coastal Tea Tree, often 10 m high with trunks 25 cm wide, were found collapsing leeward, while younger fruiting trees invaded distant areas, raining seed downwind. Conventional strategies had little to say about rectifying such a problem.
The Coastal Tea Tree’s legendary hardness made chainsawing unlikely. If sawn, the logs were too heavy for volunteers to shift. And even then, abandoned logs remained undegraded for years. Layered piles of collapsed trunks inhibited natural regeneration by shading the sand. The high oil content contributed to the wood’s resilience but possibly also suppressed local species germination.
Within this milieu the only surviving natives comprised Banksia integrifolia, Persoonia stradbrokensis, Acacia longifolia subsp. sophorae and Monotoca scoparia. A few vines (Hibbertia scandens, Stephania japonica, Pandorea pandorana) climbed the dead Coastal Tea Trees.
The first-line challenges were to safely remove and dispose of the virtually indestructible timber, and to establish forest regrowth in an evidently hostile soil.
Legislative and technical barriers
Since Coastal Tea Treeis an Australian native species, the NSW Native Vegetation Act 2003 made its removal illegal. The Catchment Management Authority could not approve grant funding for a removal project.
Moves were, however, already in play to have the species declared feral. The green light came in January 2009 when Coastal Tea Tree on the NSW Far North Coast was listed by Ministerial Regulation as a ‘feral native species’ within the Coastal Zone and on or adjoining land previously sand‑mined for heavy metals.
With funding now legal, what would it be used for? How could these seemingly immovable trunks be shifted without disruption to the dunes and without damaging the recovering native vegetation that bordered, and in places merged, into the affected areas?
Coastal Tea Tree had however been successfully removed on the Tweed and Evans Head coasts, mainly for bushfire protection, using a heavy duty machine - the imported German C100 Rayco track mulcher.
A local company quoted their price for mulching, approximately 1 hectare over 2 days. With approvals in hand, a successful Caring for our Country ‘Community Coastcare’ grant application for $8,390 was lodged. The primary job was completed over two days in April 2010.
The project was undertaken over ten stages:
- Hand removing a suite of ground level weeds that might otherwise be buried or mulched up and spread during the operation – Asparagus Fern (Asparagus aethiopicus), Morning Glory (Ipomoea cairica), Passionfruit (Passiflora spp.), Lantana (Lantana camara), and Bitou Bush (Chrysanthemoides monilifera subsp. rotundata).
- Protecting existing natural recovery by flagging all native trees, bushes and groundcovers within and on the margins of the Coastal Tea Tree using fluoro tape. Callitris columellaris had principal priority protection.
- Mapping the area of an Endangered Ecological Community (Coast Cypress Forest), to locate boundaries for the area to be mulched then staking these out using white posts to guide the machinery operator.
- Rostering and equipping volunteers with hard hats and walkie talkies and briefing them on how to assist the machinery operator. OH&S considerations were paramount since the mulcher throws lethally heavy pieces of hardwood debris randomly up to 50 m.
- Enlisting an Indigenous heritage site supervisor, given that the entire beach is a sacred Indigenous site of traditional significance and closely associated with a 19th Century massacre.
- Guiding the machinery operator, avoiding flagged native trees, pausing the operation whenever possible damage to standing native plants loomed then negotiating which trees were of least value and could be sacrificed to achieve best economic outcomes while minimising ecological loss.
- Intensive follow up during the following weeks. Some upright unmulched Coastal Tea Trees remained in close proximity to significant native species so were then either removed with a chainsaw or ring barked to stand as bird perches.
- The area was left two months to settle until June 2010 when we enlisted local school students to start replanting selected rainforest species. Ten seedlings were planted to compensate for each of about ten significant individuals cleared, the smaller of which were buried under debris and the remainder had branches damaged. Cupaniopsis anacardioides (Tuckeroo) tubestock, grown from local seeds, was the choice to provide a head start to the structure for a future Tuckeroo-association Littoral Rainforest.
- After one year of significant natural recovery, on National Tree Day July 2011, the area was included with a neighbouring site for selected diversification with locally sourced, site specific rainforest species.
- Over the second year (to June 2012) the site continued natural recovery with no further investment other than hand removing emergent weeds – Asparagus Fern, annual herbs and grasses.
(top to bottom) Collapsed senescent Leptospermum laevigatum (April 2010). Natural recovery of rainforest pioneers, groundcovers and heath species (May 2012).
Photos: Lee Andresen.
Heavy machine mulching produced variable sized fragments ranging from dust and woodchip up to slabs and splinters 0.5 m long. A thick layer of wood fragments remained on the sand, and roots remained buried. This unusual soil surface will persist for years but we have learned to work with it.
- This method provided some excellent results for native diversity:
- Today, 27 months after mulching, a very high survival rate of all replacement rainforest trees;
- Impressive growth rate for the original naturally surviving trees (those ‘saved’ by tagging) that are now prospering within and on the boundaries of the cleared site;
- A spectacular abundance of fast growing pioneer species, spontaneously recruited from surrounding old growth and regrowth forest areas. A low canopy now partly shades out the mulched avenue that was once an exposed desert of woodchips and hardwood fragments. Naturally regenerating species (excluding replacement plantings) include:
Acacia longifolia subsp. sophorae
Notelaea longifolia f. glabra
What once was a feral forest now merges with surrounding restored areas forming a continuous green recovery zone. It is not yet a recognisable Littoral Rainforest, but one will eventually develop successionally from the present community of pioneers and transitional heath.
Removing senescentCoastal Tea Tree forest initially presented a challenge when examined from the perspective of conventional bushland recovery strategies. That has been handled through a well-planned, carefully executed project beginning with the targeted, high impact employment of heavy machinery followed by a combination of replacement planting and natural regeneration.
The strategy emerged only after study, consultation, small scale experimentation and local debate. There were early fears and objections but despite forebodings the project delivered what we wanted.
When faced with a really hard problem rehabilitation teams may sometimes need to grasp the opportunity and embrace a relatively ‘heroic’ and untested measure. We did, and it has worked. We hope our experience may be a model for others facing a similar challenge.