Location of the Northern Plains Grasslands
The Northern Plains Grassland Community extends to the west from the Patho Plains over the Loddon River at Serpentine on the Powlett Plains. It is also found to the north-west of Kerang in the Bael Bael area associated with the Avoca River. To the east this community extends to Echuca, into NSW at Moama and east of the Campaspe River as far as Kyabram and Corop. This landscape is a mosaic of Black Box, Buloke and Red Gum woodlands interspersed with grasslands wherever soil textures are heavier and less well-drained, and ephemeral wetlands on wetter areas and along drainage lines.
Grasslands occur generally on the heavier-textured quaternary alluvial sediments - calcareous clay loams, or clays on wetter sites. Areas include the self-mulching (cracking) grey clays, and red clay soils.
As soils become sandier and better drained - areas associated with prior stream channels and old dune systems - shrubs, and then trees become increasingly common in the landscape. On the wettest areas, ephemeral wetlands complete the landscape. These grassy wetlands remain inundated for only short periods after flooding, and support swampy vegetation and Lignum or Black Box / Lignum on drainage lines.
The naturally treeless grasslands are a product of their environment. A number of factors have likely contributed to the absence of trees in the landscape, such as cracking clay soils, seasonal rainfall patterns, competitive exclusion, flooding, fire and grazing.
On the heavier self-mulching clays, the swelling and shrinking of the soils - constantly expanding and contracting - kills most tree and shrub seedlings by breaking their tap root systems. Additionally, seasonal rainfall patterns may contribute to the presence of a large sward of grass tussocks, competitively excluding woody species.
History of the Northern Plains Grasslands
Prior to European settlement, Victoria's Northern Plains Grasslands extended across 730,000ha, according to estimates based on vegetation modelling and historical sources (ARI modelling, 2009).
Since the early 1840’s, intensive agriculture and domestic stock grazing has destroyed and degraded much of the Northern Plains Grassland Community. Approximately 6.6% of the original grassland areas remain across the Northern Plains. However all of this area has been subject to some form of agricultural disturbance with the vast majority of these remnants remaining in a highly disturbed state. The area of grasslands that best represents pre-European structure and composition is estimated to be less than 1% of the original extent.
Today, the remaining Northern Plains Grasslands occur broadly in two locations in Victoria (download maps from the right panel):
- Patho Plains of the Loddon catchment - grasslands extend from the Patho/Mitiamo Plains westward over the Loddon River at Serpentine on the Powlett Plains
- Avoca Plains of the Avoca catchment - grasslands are found to the north west of Kerang in the Avoca, Wanderers and Beauchamp Plains areas associated with the Avoca River
