The guest speaker for our May meeting was Kate Brown from the Department of Parks and Wildlife who presented a talk entitled “Restoration of native plant communities and critical habitat on Penguin Island and the reintroduction of a species that has disappeared from Penguin Island – Native Hollyhock (Malva preissiana)”. The restoration project was initiated after a researcher studying Bridled Terns (Onychoprion anaethetus) on Penguin Island noticed that the vegetation favoured by the terns for nesting was quite disturbed. Seabirds can have a significant impact on island ecology due to trampling of vegetation and the deposition of guano at significant nesting sites.

Kate presented a geology map of Penguin Island, stating that soil types drive the vegetation types. It has been previously noted that in areas used by cormorants as massed nesting sites there is a transition from woody shrubs, through hairy leaved shrubs, succulent shrubs, bower formers, succulent creepers, and annuals to bare sand. The birds will not nest on bare sand so they occupy a new site allowing the old site to slowly regenerate. Intact systems used by Bridled Terns feature Tetragonia implexicoma and Rhagodia baccata , however an influx of Silver Gulls has resulted in trampling and guano deposition leading to a replacement of the Tetragonia/Rhagodia vegetation with annual weeds. In June 2014 a project to investigate suitable methods for the restoration of the Tetragonia/Rhagodia vegetation commenced. Trial plots were planted with Tetragonia implexicoma and Rhagodia baccata seedlings; however, by December 2014 the Silver Gulls had pulled out all but three of 490 seedlings. It was evident that the seedlings would require protection if the restoration was to be successful.

In June 2015 the trials were repeated with steel mesh cages installed over the plots to protect the plantings. The June 2015 trials investigated a number of techniques; direct planting of seedlings, direct seeding, with and without matting to prevent weeds and brushing with cuttings of Rhagodia baccata covered in ripe fruit. The brushed sites showed prolific germination during winter with seedlings rapidly covering the whole plots. Direct seeding did not deliver the same rate of success. However, by late October the dense stands of Rhagodia baccata in the brushed sites appeared to be drought affected and many seedlings died but the remaining cover was then stable through to December. The use of weed mats the cover in December was much better than in plots without matting. The conclusion was that brushing with Rhagodia baccata cuttings was the most cost effective method of creating native cover.

The second part of the presentation discussed the restoration of Native Hollyhocks (Malva preissiana), which had disappeared from Penguin Island in the 1970’s. Malva preissiana is a short-lived perennial and a guano loving species. It used to occur in different areas of the island previously used by the bird colonies. A site was selected that had previously been used as a nesting site by Pelicans. Seeds were collected on Carnac Island and sown into a number of trial plots in June 2014. Germination occurred and the plants flowered in November and December. They re-grew in 2015 and then died off towards the end of 2015. The findings of the trials were that the sites should be weeded first, if no weeding the success rate was low. After the Malva dies off in an area the shrubs return. For a more detailed report on the trials an illustrated scientific report can be found in the following Link to DPAW document (opens in new tab)

The audience thanked Kate for her informative presentation.

 Colin Prickett