Reversing the Decline of Sheoak Grassy Woodlands on Eyre Peninsula
Drooping Sheoak (Allocasuarina verticillata) Grassy Woodlands on western Eyre Peninsula are among the most highly cleared and degraded vegetation community of any region of South Australia. Intensive grazing along with the introduction of rabbits and clearance for agriculture has led to a dramatic decline in their condition and extent. Once one of the most widespread vegetation communities on Eyre Peninsula, Sheoak woodlands are now restricted to small pockets of variable condition across the landscape.
The ground layer in Sheoak Grassy Woodlands is dominated by grasses, sedges and/or tussocky lilies. There may be a rich herb layer where grazing pressure is minimal. Healthy examples of these ecosystems also contain multiple age cohorts of Sheoak trees. Heavily degraded examples may lack over storey trees, and appear as open grasslands or may maintain scattered mature Sheoaks with an understorey of mainly exotic annual grasses and broadleaf weeds.
Drooping Sheoak is a relatively short-lived tree (to around 80 years) which often results in only senescing or dead trees remaining in grazed paddocks. A lack of recruitment means the older generation is the only age class and when these die out the paddock becomes an open grassy area.
In order to naturally recover a Sheoak over storey, paddocks need to be rested from stock for between 5-9 years for trees to mature above browse height, and for there to be more than one age class in the paddock. Rabbit and kangaroo control is also essential during this period as animal grazing pressure will suppress Sheoak regeneration.
What is WildEyre doing to restore Drooping Sheoak Woodlands?
The considerable change in the condition and extent of this vegetation community that has occurred since European settlement identifies this as a priority. For this reason, Drooping Sheoak Woodlands were identified as an important ecological asset in the WildEyre Conservation Action Plan. Sheoak Grassy Woodlands scored lowest in terms of their overall viability (**see explanation below). The impacts of large scale vegetation clearance and highly degraded understorey vegetation resulted in a viability rating of ‘poor’.
** Viability as a function of the critical factors required for the long term viability of the conservation assets in the landscape. These relate to the size, condition and landscape context of the assets and may include appropriate hydrological regimes, fire regimes, water quality, fauna and flora species diversity, total remnant area and the size and configuration of patches