Australasian Plant Conservation
Originally published in Australasian Plant Conservation 21(2) September - November 2012, p 9-10
Habitat reconstruction at Gunnedah Research Centre, Gunnedah. New South Wales
John Lemon¹, Warren Martin¹, Brian Wilson², Chris Nadolny¹ and Daniel Lunney¹
1) NSW Office of Environment and Heritage, 2) University of New England & NSW Office of Environment and Heritage.
Common Dunnart captured in the 2001 plantings. Photo: John Lemon
A tagged Koala in the 1993 plantings. Photo: John Lemon
In 1943 the NSW Soil Conservation Service purchased a 214 ha property 6 km south of Gunnedah to demonstrate how severely degraded and eroded farmland could be rehabilitated using soil conservation earthworks and improved farming methods. The level of degradation was so severe that one significant rainfall event resulted in the adjacent main rail line being blocked by soil eroded from the property.
The Gunnedah Research Centre (the Centre) has evolved from its initial tenure as a farming property in 1905 to the present day property which has been used for research as well as production of wool, fat lambs, cattle and grain. Since 1991 a series of habitat reconstruction trials has been undertaken. At present the 90 ha of available grazing country has 20 ha of habitat reconstruction sites, with the remaining 70 ha planted with a combination of native and semi-tropical perennial grass pasture. The remainder of the property consists of steep hills of the Porcupine Range where the native vegetation has been left to regenerate naturally.
In December 1988, it was evident that many of the River Red Gums (Eucalyptus camaldulensis), had been severely browsed by Koalas (Phascolarctos cinereus) resulting in a serious decline in tree health. Replacement trees were planted along the fence lines but it was soon realised that more needed to be done.
In 1991, a 1 ha direct seeding trial was initiated using one kilogram of mixed native species, including 635 g of Eucalyptus species - approximately 200 000 seeds - but only 12 trees became established. In 1993, the first of a sequence of habitat plantings using tubestock was commenced, as well as direct seeding understorey species. Additional plantings were undertaken in 1995, 1998, 2001, 2003, 2004 and 2005. It is intended to establish an additional 10 ha of plantings to connect the present sites to native vegetation on the Porcupine Range.
From the initial direct seeding trial in 1991, it was soon realised that the smaller seeds such as Eucalyptus were difficult to establish locally, while the larger seeds, such as the acacias, were easier to establish. That is why tubestock are used for canopy species, and direct seeding for the establishment of understorey species. Key actions that have led to the successful establishment of the plantings include:
- excluding stock and fencing the area to be planted
- deep ripping the tree lines – try to do this when the soil is dry as that will shatter any compaction layer
- weed control – spray out rip lines to build up soil moisture 6 to 12 months prior to planting
- choosing a species mix that best fits the local plant communities – up to 16 different species have been used at the Centre, including larger trees as well as understorey species. The range of species chosen to suit the position in the landscape has been important for the survival of plantings during extended drought
- planting density and method is important and can vary depending on geographical location. In the sheep/wheat belt a maximum of 200 stems/ha, including both overstorey and understorey species, with spacing of 6 m between stems and 7 m between rows worked best
- post planting - water if needed, control weeds, and use hay mulch to suppress weed competition and to conserve soil moisture. If stock are to use the plantings they should be managed carefully and introduced for only short periods at a time.
These actions maximised the establishment success and growth rate of the vegetation, and also created a floristically diverse and structurally complex vegetation that has increased the habitat value for a range of fauna. Over time the ground cover has developed into a mosaic of leaf litter under and around the trees, and native grasses in the open spaces, benefiting a range of ground foraging birds. Fallen branches have created additional habitat complexity.
The habitat reconstruction sites have been used extensively as a demonstration site and for local field days, encouraging other landholders to undertake revegetation projects. More detailed information on the methods used at the Centre is contained in a Guide to successful tree establishment for environmental plantings which is available from the corresponding author on request.
Monitoring and research
Part of the success of the habitat reconstruction sites has been the inclusion of a number of research and monitoring activities. Prior to the establishment of these sites, baseline soil cores were taken to enable us to compare changes to soil health over time. Initial results showed that the plantings have resulted in improved soil organic matter and soil fertility (Wilson et al. 2002). Likewise, initial surveys of the groundcover vegetation showed that it is possible for a diversity of native grasses to recolonise sites that are planted with native vegetation (Nadolny and Lemon 2004).
Biodiversity audits were commenced in 1998 and have taken place each spring and autumn; most recently in April 2012. Many reptiles and frogs have been trapped using small mammal traps (Elliott traps) and pitfall traps. The House Mouse (Mus musculus) has invaded the sites but it was not until 1300 trap nights had been completed that, in autumn 2010, a male Common Dunnart (Sminthopsis murina) (a small, insectivorous marsupial about the size of a mouse) was captured. This was in the 9-year-old (2001) plantings, and Common Dunnarts have continued to be recorded in the 1998 and 2001 plantings.
Bird surveys were undertaken in 2000–2001 (Martin et al. 2004) and resurveyed in 2011–2012. Even during the surveys in 2000-2001, when the planted vegetation was only 3-8 years old, 55 bird species were recorded. Following the 2011-2012 surveys, an additional 11 species were recorded in the plantings and the numbers of birds (individuals per area) increased by nearly 40%. A number of threatened or declining birds have been recorded in the plantings: Glossy Black-Cockatoos (Calyptorhynchus lathami) were sighted in 2004 and 2008; Speckled Warblers (Pyrrholaemus sagittatus) and Painted Honeyeaters (Grantiella picta) have also been observed.
Another positive outcome of the plantings is their utilisation by Koalas, as we discovered during a three year koala project (2008-2011) using radio-tracking collars, including GPS units which recorded Koala locations every 4 hours.
The value of this monitoring data for rehabilitation during and after major landscape changes, such as from mining, are now apparent (Lunney et al. 2012).
The major achievements of the Gunnedah Research Centre plantings are:
- the re-colonisation of the sites by native grass species
- the improvement in soil health
- the utilisation of the site by a range of animals, including threatened species
- the importation of additional native understorey species by birds after the seeds passed through their digestive system
- the ability to utilise the plantings for animal production and shelter.
The take home message from this research is that it is possible to achieve effective restoration outcomes, even on sites that have a long history of landscape degradation. It is possible to have a multiplicity of biodiversity, environmental and production benefits with careful planning and maintenance. The ability to use the sites for animal production and shelter, in addition to the environmental benefits, makes this an attractive package for landholders and other stakeholders. The lessons learned from the habitat reconstruction sites at the Centre have contributed towards the establishment of further revegetation sites across the sheep/wheat belt.
Our thanks to Philip Burrell, who was instrumental in setting up the initial biodiversity audits. Dr Ian Oliver provided comments on an earlier draft of this paper.
Lunney, D., Lemon, J., Crowther, M.S., Stalenberg, E., Ross, K. and Wheeler, R. (2012). An Ecological Approach to Koala Conservation in a Mined Landscape. Life-of-Mine Conference. Brisbane, QLD, 10 - 12 July 2012. pp 345-354. The Australasian Institute of Mining and Metallurgy. Carlton, Victoria, Australia.
Martin, W.K., Eyears-Chaddock, M., Wilson, B.R. and Lemon, J. (2004). The value of habitat reconstruction to birds at Gunnedah, New South Wales. Emu 104, 177-189.
Nadolny, C. and Lemon, J. (2004). Re-colonisation patterns of native plants in cultivation paddocks at Gunnedah, NSW. Pastures in Farming Systems – Meet the Challenge. Proceedings of the 19th Grassland Society of NSW Conference, Gunnedah 2004. pp. 146-147. Grassland Society of NSW.
Wilson, B., Eyears-Chaddock, M., Martin, W. and Lemon, J. (2002). Soil changes under ‘habitat reconstruction’ sites near Gunnedah, New South Wales. Ecological Management and Restoration 3, 68-70.