The bush regeneration gods have smiled on Scottsdale Reserve, which lies about 75km south of Canberra on Ngunawal country – right in time for our new grassland seeding project.
After many months without rain, we were hesitant to go ahead with the planned sowing of two new Grassland Seed Production sites. Built to enrich the diversity of Scottsdale’s grassland flora, each half-hectare plot had been slowly turning to dust while we waited for the right conditions to sow the summer’s hard-earned haul of finely processed seed.
Approximately 15kg of seed has been collected from over 30 local native grassland species on Scottsdale, which will be sown into four sites across the reserve.
With the onset of summer bearing down and limited availability of Greening Australia staff to help us with their native grass seeder, we all gritted our teeth and locked in the last Wednesday of the sowing calendar with little expectation of rain.
To our complete and total joy, it started raining on the Monday afternoon before! By 6pm Monday it was snowing and it continued to interchange between snow and rain all night.
We arrived at work on Tuesday morning to the Scottsdale high country covered in dazzling white. It continued to drizzle throughout the morning and by Wednesday the sun was shining and the blessed rain had soaked and softened the soil ready for sowing.
Preparations, preparations, preparations!
The four seed production sites had already been scraped, scarified and fenced in preparation for sowing this spring. The half-hectare sites were chosen because they're predominantly weedy and sit within the Love Grass dominated areas of the valley floor.
Site preparation included scraping the monoculture of Love Grass and its seed bank from the surface of the soil. The scrape depth averaged 5cm on three of the sites and we experimented with varying the depths on one of the sites increasing it to 7cm across half this site.
Since scraping, volunteers and contractors have managed the sites for weedy flushes. As these are seed production sites, we've been careful to ensure no seed retardant herbicide has been applied. Volunteers have also been instrumental in collecting, processing and storing the seed.
Volunteers and staff have conducted baseline photographic and vegetation monitoring and a regular volunteer who specialises in agricultural botany has worked closely with us to create some trials that can help determine what conditions may be beneficial in improving seedling survival. These include scrape depth and scarification, irrigation, fertilisation and inoculation.
Additionally, sowing regimes have been altered for drought conditions and sowing of grasses and herbs and forbs have been staggered to suppress weedy flushes.
Greening Australia arrived Wednesday morning and on first inspection of the site, sowing specialist Ben Hanranhan was excited by the shallower scrape depth. He liked that we'd created scrapes with less skeletal soils than most he has seen and is interested to see what combination of native diversity grows on these shallower scrapes and whether two species with higher nutrient tolerance, Bothriochloa macra and Microlaena stipoides, dominate over the other less tolerant species.
Let the sowing commence
A total of 39 species were sown across the ‘Railway’ and ‘Fish Ladder’ sites.
The ‘Railway’ site is the drier of the two and sits higher in the valley just below the railway line and grassy boxy woodland on Scottsdale’s eastern border. Half the site was sown with pure native grass and half with grasses, herbs and forbs. Herbs and forbs will be sown into the pure grass in spring 2020. With current conditions we've been incredibly lucky with the timing of the rain, creating a moist seed bed on an otherwise dry, well-drained site.
The ‘Fish Ladder’ site is the wetter of the sites and sits on a small flood plain on the northern bank of Gungoandra Creek, just above the fish ladder and leaky weir structure. The Fish Ladder site has had a special mix of native herbs, forbs and grasses that will tolerate wetter conditions. Positively, the ‘Fish Ladder’ site contains a thick covering of Goodenia, which wasn’t detected in the surveys prior to scraping the site and has been attributed to a buried seed layer collected in flood debris.
Sowing for success
The grass, herb and forb mix distributed at the ‘Railway’ site contained 34 species, including threatened grassland species Leucochrysum albicans, along with Arthropodium fimbriatus and milleflorum (chocolate and vanilla lillies) and Xerochrysum viscosum.
Over at the wetter ‘Fish Ladder’ site, 31 species were added, including Poa (sieberiana and Calocephalus citreus) and 12 grass species including the ideally named Barbed Wire Grass (Cymbopogon refractus), Bothriochloa macra, three species of Austrostipa, Themeda triandra and Microlaena stipoides.
For 2020 the sowing regime includes over-sowing an existing grassland seed distribution site that was first sown in 2016 but has had limited success. We incorporated this site into our recent project and have expanded its borders. This is the first time Greening Australia will have been involved in over-sowing an existing grassland area and they're understandably very keen to see the results, which may well have applications beyond Scottsdale.
It's wonderful to see the carefully collected seed going back into such an exciting project and we look forward to keeping you posted on the progress!
This project has been assisted by the New South Wales Government through its Environmental Trust.