The Broader Context
Economic and increased international demand for livestock products are important drivers of land clearing in Australia (Australian Government, 2013). The change in land use have resulted in considerable alterations to the structure and composition of nature (Dorrough et al., 2004). Such actions resulted in the loss of habitat for native fauna, reduced carbon sequestration, coupled with problems of land degradation, biodiversity loss and salinity. Given the reduced resilience of the ecosystem, climate change has exacerbated environmental stressors and increased the difficulty in managing the degraded pasture land.
Whole of Paddock Rehabilitation (WOPR)
Greening Australia has taken the initiative and come up with an innovative solution to the problem: WOPR, an Australian Government funded scheme, aiming to help farmers restore the productivity of degraded or cleared farmland while creating habitat for native fauna by re-vegetate the sites with native species (Greening Australia, 2016). Farmers are paid to stop using the sites for 5 years, the period of time necessary to leave the sites to recover. Scottsdale reserve is part of the bigger project of WOPR.
The place that I volunteered at is Scottsdale, which is located 5 km north of Bredbo, NSW. The Scottsdale Reserve is a former grazing property and has now been bought by Hush Heritage Australia for its close approximate to Canberra and habitat value to threatened native grasslands and woodlands. For instance, both native temperate grassland and Yellow-box grassy woodland are listed as critically endangered ecological community under the Environment Protection and Biodiversity Conservation Act 1999. The restoration site is about 300 hectors, one of the biggest sites of WOPR.
Restoration in Scottsdale Reserve
Due to past grazing pressure, the majority of the untreated site has an elevated nitrogen and phosphorus content, providing abiotic conditions for the growth of exotic species. The site now is infested with weeds, dominated by African Lovegrass (Eragrostis curvula).
In providing a competitive advantage for native species, top 10cm of soil is scraped off to reduce the nutrients level and remove the seed bank of exotic species.
For easier site prep, Parallel Line Seedling is used. Around 90% (6km) of Scottsdale is re-vegetated through direct seeding using a specialised seeding machine. One of the limitation of scalping is that the method is only suitable for large area of flat ground or gentle slops with no vertical obstacles. For sites with mature trees or stones, tube-stocks are planted by hand. Apart from geological constraints, compared to direct seeding, tube-stock planting is much more labour intensive and 10 times more expansive with each plant cost at AUD$5. However, at the moment, the survival rate of direct seedling falls bellow an expected of 200-250 plant/km. This could be due to harsher climatic conditions in the south east of NSW. One interesting finding is that despite the initial difference in survival rate of tube-stock planting over direct seedling, the difference in performance is significantly reduced after around 5 years.
The objective of my work is to monitor the success of direct seeding which were planted in October 2014 after scalping. It involves recording the GPS coordinates of germinated plants. The GPS coordinates of Eucalyptus and Acacias are stored separately with two GPS devices for future management purposes.
Ben Hanrahan (Project Manager of Greening Australia) patiently walked me through a few of the scalp lines and taught me how to identify Eucalyptus and Acacia seedlings before I take the task independently.
Despite the straightforward nature of the task, it is rather challenging for a beginner like me to look for tiny juveniles among weeds.
Of course, there are easier ones like these.
I have noticed that the soil of the sites with little weeds around, are much more reddish and yellowing in colour. Given that native species do better in infertile sites, I think it would be interesting to work out the soil composition of sites with high survival rate of native species, and match the scalping level to that level of the soil horizon. For instance, for sites with thick nutrient rich organic layers, more than 10-15 cm of top soil might be needed to be removed for effective regrowth.
As mentioned earlier, the Scottsdale reserve is infested with African Lovegrass. Burning is not recommended as a strategy for weed removal, due to the highly flammable nature of the species and difficulty for fire control. Also, it is found that the population of the species thrive after fire, making fire undesirable for the site. Given the limited budget, the current method employed for weed removal is the labour intensive slash and spray.
Burning is restricted on the site and this limits the growth of obligated seedling plant which rely on fire to germinate. Also, it hinders the natural regeneration process as Eucalyptus seed release is triggered by fire.
I have also spotted a few sites with high erosion risk. One recommendation is that erosion can be treated by bring in leaf litters, coarse woody debris and rocks to reduce and water flow and traps sediments from flowing down stream.
Bush Heritage Australia volunteers have done an excellent job in rabbit control. These efforts include regular rabbit baiting, gasing their warrens and fill in the rabbit holes. The low rabbit population ensures that the re-vegetated seedlings have a higher change of survival and reduce erosion caused by their warrens.
On the other hand, increased kangaroo numbers, higher than government guidelines, has posed great challenge on the restoration process as these marsupials chew on the juvenile leaves and damage the plant. Bush Heritage faced huge backlash from planned kangaroo cull in order to control the numbers. Supporters have pulled their donations after the kangaroo cull. The idea of pest is a human construct, and many times, scientific finding is not the only variable in the equation. Therefore, it is a constant challenge to find a balance between scientific findings and people’s emotional tie with the national icon.
In conclusion, it is worth investing to explore the reason behind the low survival rate of direct seeding to improve its efficiency. Also, it is important to bare in mind that the restoration of the Box-grassy woodland is a long term project that requires the undertaking of a multi-faceted approach and the cooperation of all stakeholders.
Last but not least, I would like to thank Ben Hanrahan, Project Officer of Greening Australia for the opportunity and for providing the above information!
U5625189, Chloe Sun XiaoJun
Australian Government, (2013). Australian National Greenhouse Accounts- Australian Land Use, Land Use Change and Forestry Emissions Projections to 2030, Commonwealth of Australia.
Dorrough J., Yen A., Turner V., Crosthwaite J., and Hirth J. R., (2004). Livestock grazing management and biodiversity conservation in Australian temperate grassy landscapes, CSIRO Publishing, Australian Journal of Agricultural Research, 55, 279-295.
Greening Australia, (2016). Whole of Paddock Rehabilitation, Greening Australia.
Lievre K. L., (2016). Bush Heritage Australia faces backlash after kangaroo culling claims, The Sydney Morning Herald.