We noted in the April 2009 edition of Indigenotes that there had recently been a number of new ecological communities listed as nationally threatened, under the Federal Government’s Environment Protection and Biodiversity Conservation Act 1999.

Grasslands and grassy woodlands have featured strongly in recent listings –not surprisingly, given that they are regarded as being among the most threatened ecosystems in the State. We mentioned the “Gippsland Red Gum (Eucalyptus tereticornis subsp. mediana) Grassy Woodland and Associated Native Grassland” and the “Buloke Woodlands of the Riverina and Murray-Darling Depression Bioregions”.

Now the “Lowland Native Grasslands of Tasmania” and the “Natural grasslands on basalt and fine-textured alluvial plains of northern New South Wales and southern Queensland” have joined them. But of more local importance, the “Grassy Eucalypt Woodland of the Victorian Volcanic Plain” was recently listed. This is a terrific outcome, because now this complements the 2008 listing of the “Natural Temperate Grassland of the Victorian Volcanic Plain” (VVP).

To provide a background, one of the problems in the past has been that it’s been hard to distinguish between grassy woodlands from which trees have been cleared, and natural grasslands. The grasslands of the “woodlands-from-which-trees-have-been-removed” type are sometimes called “secondary” or “derived” grasslands – terms which imply that the grasslands are of lesser value than the “natural” ones. But grasslands, whether they be historically treeless or have just become so recently, are critically endangered. There is an alarming number of plant and animal species that are restricted to native grasslands, and it doesn’t matter a great deal whether the grasslands in question were with or without trees a hundred and fifty years ago.

To give the accepted definitions, a “natural” native grassland is dominated by native grasses with many species of wildflowers (orchids, daisies, lilies, peas) and few or no trees. A grassy woodland has from 5-30% tree cover, but by and large the understorey is very similar. The major difference relates to management. So if a grassland is free of stock grazing and has its biomass of smothering grasses reduced by regular burning, you tend to see a highly diverse herbfield with lots of geophytes (i.e. lilies and orchids) and those species which are burning-tolerant but grazing-sensitive. A burning history will also mean that the grassland/grassy woodland will have few or no trees. In contrast, grasslands/grassy woodlands that have undergone stock grazing but little burning tend to have fewer herbs and wildflowers, and those that occur are generally grazing-tolerant but may be fire-sensitive. So today, what we see as the “native grasslands” of the Victorian Volcanic Plain occur as two types:

1.  Grasslands with a management history of regular (every 1-4 years) burning. These grassland remnants tend to occur on roadsides, rail reserves and other public land such as cemeteries, racing tracks, town commons and so on. Although their primary use is not for conservation - quite the reverse in many cases - this history of burning has been a regime of “benign neglect” that has allowed many of these high quality, florally diverse remnants to survive. Because of the frequent fire regimes few or no trees remain.

2.  Large areas of private land with a history of grazing. These tend to retain at least some tree cover, were historically regarded as grassy woodlands, and provide better fauna habitat although they may be less florally diverse. Such sites only retain native grassy remnants if they have been grazed lightly, seldom ploughed and never fertilised or sown with exotic species. The best sites have generally had stock reduced or removed in spring, to allow flowering and seed set.

This is borne out by the noted work of Dr Ian Lunt, on the Gippsland Plains grassland and grassy woodlands – ecosystems which are very similar to those on the VVP. Lunt (1997) drew the hypothesis that grasslands and grassy woodlands are selective remnants of an original grassy woodland ecosystem - that the two distinct communities have evolved since European invasion. This ecological segregation has been created by management methods; that is, grazing for grassy woodlands, and burning for grasslands. Frequent burning on small grasslands created an open, treeless, diverse community of flora, with many rare or threatened species, including those sensitive to grazing. Regular low level grazing management retained the trees of an open woodland, and the habitat complexity necessary for fauna diversity, but reduced the quality of the ground layer. Therefore, to conserve the biodiversity of the entire grassy ecosystem, both grasslands and grassy woodlands must be saved.

With the listing of both the Grassy Eucalypt Woodland of the VVP and the Natural Temperate Grassland of the VVP, we no longer have to worry whether a “grassland” is part of the treed or treeless variety. Some environmental consultants have been known to classify treeless grassy woodlands as “degraded treeless vegetation” (see DSE (2007) Native Vegetation Guide for assessment of referred planning permit application.) and therefore downgrade their ecological significance. Hopefully now, the grassy bits won’t fall so easily through the cracks - regardless of whether they have trees or not.

For more information, the “listing advice” for the grassy woodland community can be found on the DEWHA website, at http://www.environment.gov.au/cgi-bin/sprat/public/publicshowcommunity.pl?id=46&status=Critically%20Endangered

This notes that “The Grassy Eucalypt Woodland of the Victorian Volcanic Plain was an open woodland that naturally intergraded with the nationally-listed Natural Temperate Grassland of the Victorian Volcanic Plain, forming a mosaic of grassy vegetation across the plain.” So the woodland assists the grasslands in supporting such threatened species as the Eastern Barred Bandicoot, Southern Brown Bandicoot , Swift Parrot, Plains-wanderer, Bush Stone-curlew, Striped Legless Lizard, Corangamite Water-skink, Growling Grass Frog, Golden Sun-moth and many others.

The advice goes on to say “To determine whether an area of vegetation is part of the listed community, and therefore requires a permit to clear or damage it, the following condition thresholds apply:

“The minimum patch size for the listed ecological community is 0.5 h" and

“1. One or more of the following native grass genera accounts for at least 50% of the perennial ground layer cover: Themeda, Austrodanthonia, Austrostipa, Poa and/or Microlaena. OR

2.  If native grasses account for less than 50% of the perennial ground layer cover, then the patch is either:

1. A valuable wildflower site where at least 50% of the ground layer vegetative cover is represented by native dryland forbs (including geophytes) during spring-summer (i.e. September to February inclusive but noting that the ground layer may be sparse in some situations); OR
2. Not heavily invaded by perennial weeds such that perennial weeds comprise less than 70% of the ground layer vegetative cover; OR
   

3. If perennial weeds comprise more than 70% of the ground layer vegetative cover, then the patch must have more than ten native perennial species per 100 m²

AND a density of at least three big trees per hectare. Big trees are defined here as trees with at least 70 cm diameter at breast height (dbh) for eucalypts and at least 40 cm dbh for non-eucalypt species, in line with DSE (2008)”

There are other provisos in the thresholds which are too lengthy to replicate here but are worth reading. Other useful information includes a list of plant species characteristic of the Grassy Eucalypt Woodland community, and on the same web location, a map of the potential distribution of the community, and the “Approved Conservation Advice for the Grassy Eucalypt Woodland of the Victorian Volcanic Plain.”

References:

DSE (2008) EVC Benchmarks - Victorian Volcanic Plain bioregion. (DSE website at http://www.dse.vic.gov.au/dse/nrence.nsf/LinkView/A2A7B7D2CABBEE3CCA256F2B000257048062D358172E420C4A256DEA0012F71C

Lunt, I.D. (1997) Effects of long-term vegetation management on remnant grassy forests and anthropogenic native grasslands in south-eastern Australia.  Biol. Conservation 81: 287-297.