Excursions: 3 & 7 Managing vegetation at the Ocean Grove Nature Reserve

Saturday 28 March, morning and repeat in afternoon
Leaders: Peter Sullivan, Susanne Hudgell (morning)
Barry Lingham, Bernie Lingham, Andrea Dennett (afternoon)

The Ocean Grove Nature Reserve was created in the early 1970s by the purchase of land by public subscription and grant moneys. The site was previously occupied by a farm held by the Cuthbertson family from the mid-1850s. They used the farm to harvest large quantities of wattle bark for the tanning industries based in Geelong, leaving most of vegetation of the site untouched. The reserve was initially run by a committee of management before being passed to Parks Victoria in the 1990s.

The 143 ha reserve is the largest stand of woodland remaining on the Bellarine Peninsula.  Habitats vary. Grassy woodland containing Bellarine Yellow Gums, Swamp Gums, Black Sheoaks and Silver Banksias with an understorey of grasses and wildflowers is the dominant habitat. A smaller sandy section of Heathy woodland contains Manna Gums and grasstrees. Some 80 years without fire had allowed the build-up of Hedge Wattle and Black Sheoaks in some zones. When an extensive area was impacted by wildfire in 1997, the prolific seed bank in the soil germinated creating dense stands of those two species. The fire killed most Manna Gums in its path and the thick regrowth of scrubby species prevented successful germination of eucalypt species.

The close proximity of the reserve to the Ocean Grove urban development led to many residents worrying about a perceived fire threat from the high fuel levels. It was extremely difficult to create a cool burn due to the amount of fuel present. A planned burn would almost certainly flare into a blaze that would reach the crowns of the remaining Yellow Gums and Swamp Gums. In the early 2000s, Forest Fire Management began experimentation using a forest mulcher to change the structure of the vegetation. These machines could easily reduce scrubby tree growth to a layer of woodchips but leave some intact areas to act as shelter for small birds. Eucalypts were avoided and some old Black Sheoaks were also retained as shelter trees.

The result of the intervention was a sudden increase in a range of indigenous grasses and wildflowers due to the availability of extra light and reduced competition from the scrub. A cool burn could then be introduced, as the mulched zone vegetation was less than a metre high and did not allow fire to flare. Supplementary planting by the Friends of OGNR included a range of indigenous eucalypts, shrubs and flowers. This assists in speeding up the transition of the burned zones into biodiverse grassy woodlands.

During the excursions participants were shown a range of sites in the reserve. Some sites had been recently mulched, others had been cool-burned in recent years and some sites had been untouched and no treatment had occurred. The best management of the vegetation to promote maximum biodiversity is still being determined, with the optimum time between burns dependent upon the levels of scrubby regrowth after each burn. As the seed bank of Hedge Wattle and Black Sheoak is depleted by the regular burning process and grasses and forbs become more dominant, the period between burns will be extended.