Contributed by Darren Bailey, Big Scrub Landcare

This report provides a summary of the bush regeneration work undertaken in Isoglossa eranthemoides habitat areas at Booyong Reserve during 2017-2018. The project was funded by the Office of Environment and Heritage Saving Our Species program. The report includes a description of the site, a summary of the bush regeneration work undertaken as well as recommendations for future management of the site.

Site Description

Booyong Flora Reserve is a 13ha remnant of the endangered ecological community Lowland Subtropical Rainforest on Floodplain. The project area incorporates significant Isoglossa habitat areas that support the largest known population of the species in NSW. Isoglossa occurs scattered throughout the core areas of the rainforest remnant and is generally absent from the riverbanks and other forest edges.

Environmental weeds such as Trad, Madeira Vine and Privet reduce the quality and quantity of habitat for the endangered Isoglossa species by actively competing with and excluding it from the critical ground layer habitat. The site has benefited from a long history of restoration work that has reduced the abundance of various environmental weeds and essentially resulted in the opportunity for the Isoglossa population to expand. At Booyong Flora Reserve major new infestations of Trad and Madeira Vine are deposited into the site during flood events. Weeds such as Cocos palm, Privet, Tobacco Bush and White Passionflower are constantly brought into the site via the activity of bats and birds. Recurring outbreaks of Tradescantia fluminensis (Trad) are the main ongoing threat to the Isoglossa population.

Bush Regeneration Work

Initial work at the site involved setting up fixed monitoring quadrats and photo points to measure changes in the site resulting from the weed control work. Structural and floristic data were collected from 2 quadrat sites and details of the existing Isoglossa population recorded.

Infestations of Trad, Madeira Vine and other environmental weeds were then manually removed from areas amongst the Isoglossa population. These weeds were bagged and removed from the site. Key areas of the site occupied by Isoglossa were manually treated 2-3 times during the project. The abundance of these weeds progressively reduced on each subsequent treatment.

Edge and gap infestations of Trad, Madeira Vine, Tobacco Bush, Giant Devils Fig, Cocos Palm, Camphor Laurel, Moth Vine, Corky Passionfruit, Blue Morning Glory, Ochna, Lantana, Smooth Senna, Large and Small-leaved Privet in other parts of the remnant, were either hand weeded, cut and painted or stem injected with herbicide. All remaining areas of Trad and seedlings of other weeds were sprayed around the edges of the site and throughout the core area of rainforest.

Results of Bush Regeneration Work at Booyong Reserve.

Satisfactory results were observed from the bush regeneration work at Booyong Flora Reserve during the 2017-2018 period. The abundance of all major weeds was reduced by about 80% in all parts of the site and off-target damage to native vegetation was minimal. The work has improved the overall condition of the rainforest and benefited various threatened flora species. Trad, Madeira Vine and Small-leaved Privet continue to be the main re-occurring weeds at Booyong Flora Reserve.

Data and photographs were collected from the fixed monitoring quadrats towards the end of the project. This information illustrates a reduction in weed density in these areas and the resulting increase in the number of Isoglossa individuals within the quadrat areas. The increase in the Isoglossa population in these areas can partly be attributed to reduced competition from weeds and more available space for native groundcovers. It is also due to the greater ease at which the Isoglossa plants can be counted given the absence of the treated weeds, particularly Trad.

Recommendations for Future Work

Ongoing follow up work will be required to maintain the overall conservation values of the remnant, including areas of Isoglossa habitat in Booyong Flora Reserve. Regrowth of Trad and Madeira can be expected in most areas of prior infestation. Monitoring of forest gaps and track edges will also be required to prevent new infestations of these weeds from establishing. Future germination of Cocos Palm, Ochna, Large and Small-leaved Privet and to a lesser extent Giant Devils Fig and Tobacco Bush will occur along the riverbank and around the other edges of the site. Periodic follow up treatments will ensure that these weeds do not grow on to impact on the ecological values of the rainforest. Manual removal of weeds immediately around Isoglossa plants is recommended. Data collected when revisiting the fixed monitoring quadrats established at the beginning of the current project should illustrate the changes to the Isoglossa population over time resulting from active bushland restoration work.