Habitat restoration at Snowy Adit, Kosciuszko National Park
Key words: revegetation, habitat construction, montane, high altitude,fauna.
Introduction. Island Bend Downstream Spoil Dump, known as ‘Snowy Adit’, is one of approximately 30 former-‘Snowy Scheme’ sites in Kosciuszko National Park (KNP) that have undergone rehabilitation and restoration treatments in the last 10 years. The work is part of a program to remediate environmental risks associated with large volumes of rock dumped following underground blasting of tunnels and the cutting of benches for aqueduct pipelines constructed during the former hydro-electric scheme. At Snowy Adit, up to 950,000m3 of rock spoil was excavated and dumped. The footprint of the site is roughly 11 hectares, about 750m long and 150m wide.
The site sits at an altitude of 1000m on the northern bank of the Snowy River at the junction with the Gungarlin River. The surrounding landscape is relatively intact, providing a reference ecosystem for the project, and occurs in a transitional zone between montane and sub-alpine vegetation. The dominant overstorey species is Ribbon Gum (Eucalyptus viminalis) with the sporadic occurrence of Candlebark (Eucalyptus rubida). The mid layer is dominated by wattle (Acacia species), and the shrub to ground layer includes Narrow-leaf Bitter Pea (Daviesia mimosoides), Burgan (Kunzea ericoides), Bidgee-widgee (Aceana nove-zelandiae), Carex (Carex appressa) and native grass (Poa helmsii). Within the rehabilitation site prior to works, the dominant species were weeds, aside from several shrubs of Burgan and the occasional Ribbon Gum.
Rehabilitation at Snowy Adit aims to restore a level of ecological function and stability by reducing erosion and re-establishing native vegetation. This gives long term protection to adjoining waterways and reduces the risk of weed invasion and habitat loss to the adjoining national park (Figs 1 and 2).
Works undertaken. The site was split into three management zones, with zones one and two progressively rehabilitated between 2008 and 2010, and zone 3 retained as an ongoing rock resource and storage area with some buffer planting. The rehabilitation techniques employed at each zone included:
- Earthworks to reduce steep embankments, provide track and bench access across the site for revegetation works and provide for future potential water flow across the site with a series of shallow swales and pond depressions (Figs 3 and 4);
- Ground disturbance to address highly compacted nature of existing surface;
- Removal of waste materials where possible – this included the recycling of 260 tonnes of metal that had been buried/dumped across the site;
- Addition of Coarse Woody Debris, primarily in windrows to provide wind shelter and thatch to hold straw and create microclimate. This material was sourced from logs and tree crowns removed during local trail clearing;
- Addition of compost production and water crystals to individual planting holes
- Planting 110,000 tubestock of 11 species from locally collected seed and cuttings in three stages;
- Mulching with rice straw;
- Weed control prior to pre works;
- Spreading of woodchip in weed prone areas such as access tracks and temporary nursery location.
After high initial browsing on planted seedlings by wallabies, deer and rabbits, most planting areas were progressively fenced. The steel 1.8 metre high fence had rabbit-proof netting to 1.05m high with a 300mm skirt pinned/rocked to ground, and hinge joint wire to 1.8m (Photo 4). Once in place, almost 100 percent plant establishment success was achieved.
Results to date. Soils and soil function. Monitoring has shown that three years after revegetation, soil infiltration, nutrient cycling and leaf litter values are still lower than the reference site, but soil stability measures are currently higher, possibly due to the role of young plants in binding the soil. Litter levels have understandably decreased since the original application of mulch and the amount of exposed rock has increased. It is expected that the growth of the revegetation will produce increasing amounts of litter and reverse this trend.
Vegetation. BioMetric http://www.environment.nsw.gov.au/papers/BioMetricOpManualV3-1.pdf was used to assess the condition of the vegetation along a 30m transect at 4 years after planting. This showed that the plantings had not yet developed to overstorey height but many of the Ribbon Gum had grown to midstorey height, providing a cover of 7.5%. The ground cover was mostly litter (52%) and rock (52%) with 2% bare ground. Native shrub cover of the ground layer was 20%, grasses 2% and forbs 8%. No exotic species were encountered along the transect so the total of 30% plant cover in the ground layer was all native. The number of woody stems was high (990) and similar to the control site. The level of exotic species incursion to the site was very low.
Fauna. Rehabilitation works have greatly improved the habitat values of Snowy Adit, as evidence by increasing fauna recorded at the site. Pre- and post-treatment surveys have shown that, 5 years after revegetation commenced, the site is now used by at least sixty vertebrate species – 36 birds, 17 mammals, four reptiles and three frogs. Thirty-nine species were not recorded in the original 2006 survey, with 19 species (15 birds, two mammals and two frogs) attributed as a direct result of the rehabilitation works undertaken since 2006. Five threatened species were recorded in the rehabilitation area, with one additional listed species, the Powerful Owl (Ninox strenua), located in immediately adjacent forest. These threatened species were the Eastern Pygmy-possum (Cercartetus nanus), Eastern Bent-winged Bat (Miniopterus orianae oceanensis), Eastern False Pipistrelle (Falsistrellus tasmaniensi ), Gang-gang Cockatoo (Callocephalon fimbriatum ) and Flame Robin (Petroica phoenicea). The first three threatened species were not located in the original 2006 survey. The most outstanding discovery was the location of four Eastern Pygmy-possums within the fenced area of the rehabilitation area. Sixteen bird species now appeared to be either resident or regular visitors within the plantings rather than occasionally ranging into the area from adjacent forest; with nests of five species located. Several species were observed feeding flying dependent young juveniles within the planting area – such as the White-browed Scrubwren (Sericornis frontalis) and Rufous Whistler (Pachycephala rufiventris).
It is considered likely that, over time, some 29 species (23 birds, four reptiles and two mammal species) which were only recorded in adjacent forest and control sites in the current or original surveys will recolonise the area as the plantings continue to grow.
Lessons learned and future directions. The attention to detail in site preparation to create soil surface roughness and niches and microclimates in denuded and exposed sites at Snowy Adit is likely to explain the level of success achieved to date in terms of vegetation and habitat development. Constantly revisiting the site has also played an important role as it allowed measures to be taken to address overgrazing by both native and pest species. Taking the time to plan the works but also having flexibility to adapt and seek opportunities reaped benefits. A fortuitous supply of unwanted coarse woody debris and woodchip stockpiled at a nearby work depot also assisted with the establishment and growth of plants, controlled weeds and accelerated the return of native fauna using the for site as habitat.
Stakeholders and Funding bodies. The Rehabilitation of Former Snowy Scheme Sites Program was established from Snowy Hydro Limited funding and is managed by the Landforms and Rehabilitation Team in National Parks and Wildlife Service, NSW. Nicki Taws (Greening Australia Capital Region, Project Manager) conducted the vegetation monitoring. Martin Schulz conducted the fauna surveying and reporting.
Contact. Gabriel Wilks, Environmental Officer, National Parks & Wildlife Service NSW, PO Box 471 Tumut 2729, phone 062 69477070, Gabriel.firstname.lastname@example.org; Elizabeth MacPhee, Rehabilitation Officer, National Parks & Wildlife Service NSW, PO Box 471 Tumut 2729, Tel: +61 2 69477076, Email: Elizabeth.email@example.com.
Also read full EMR feature:Rehabilitation of former Snowy Scheme sites in Kosciusko National Park
Watch video short presentation by Liz MacPhee
EMR summary Restoration of Bourke’s Spoil Dump #2: https://site.emrprojectsummaries.org/2013/08/22/bourkes-gorge-spoil-dump-2-restoration-kosciuszko-national-park-2/
EMR summary Jindabyne Valve House Restoration: https://site.emrprojectsummaries.org/2013/08/20/jindabyne-valve-house-kosciuszko-national-park-nsw-2/
EMR summary Yarrangobilly Seed and Straw Production Area: https://site.emrprojectsummaries.org/2013/08/17/yarrangobilly-native-seed-and-straw-farm/