Our research focuses on the population dynamics of plants and how they are influenced by impacts of natural disturbances and global environmental change. We are particularly interested in the interactive effects of fire, grazing and drought in grasslands and woodlands in southern Australia, and how climate change, fragmentation and shrub encroachment affect ecosystems.

Saturday, 16 June 2012

Recent improvements to native grassland conservation

Native grasslands are one of the most endangered ecosystems in Australia. More than a century of agricultural use, coupled with increasing urbanization, has reduced these once abundant ecosystems on fertile soils to distinct rarities. In some areas, much less than 1% of the original system persists.

But this isn't the case everywhere across the range of native grasslands in southern Australia. In the more xeric areas (300-400 mm rainfall), native grasslands are still a feature of the landscape, e.g. the Riverine Plains grasslands of northern Victoria. In part, they survive because agricultural use has been of lower intensity, i.e. sheep grazing has been rather conservative and cropping largely unsuccessful. Additionally, perennial exotic grasses are absent (it's too dry) meaning that the integrity (if not composition) of the native grasslands remains largely intact.

For many years, however, the extent of xeric grasslands in southern Australia was overlooked. The conservation imperative first focused on the mesic C4 grasslands on volcanic soils near Melbourne. Xeric grasslands protection was so poor that  by the early 1990s, none of the ecosystem was under conservation management.

Thankfully, this has changed - reservation has increased the area of xeric native grasslands in the National Reserve System from zero hectares in 1995 to an estate now in excess of 10 000 ha. This is a remarkable achievement. This increase has been driven, to a large extent, by government land purchase coupled with private conservation agreements. I, for one, have much greater hope that grasslands in these areas can now be conserved in a meaningful way. The challenge now will be to manage them for their biodiversity and ecosystem processes in the face of a changing climate. Understanding the factors that affect the resilience of these systems to change is a pressing research need.

I recently undertook a tour of some of the new conservation reserves protecting grasslands in northern Victoria and I thought I'd share some of these sites with you. While it's mid-winter here (and not the best time to see the diversity and colour of grasslands), I was impressed by the scale of grassland protection being achieved.

Chenopod grassland at Boundary Bend, north of Nyah.
Rainfall here is about 320 mm per annum. The grasslands
are dominated by widely-spaced C4  grasses (Sporobolus is common)
as well as scattered chenopod shrubs. Soil crusts - dominated by crustose and foliose 

lichens - are well developed. Black Box can be seen in the background.

Wanderer's Plain, west of Kerang. This is a large grassland (2000 ha)
acquired and managed by the Trust for Nature. Annual rainfall is
approx. 375 mm. Dominant grasses are C4 type, including Sporobolus and
Enteropogon. The grassland plains are often fringed by Buloke and Black Box.

Korrak Korrak grassland, west of Kerang. Another Trust for Nature
grassland, in the 350-375 mm rainfall zone. C4 grasses co-dominate
with C3 grasses (Austrostipa), along with scattered chenopods.
Exotic species are non-existent while native annual forbs are ubiquitous.

In some areas, it is obvious that overgrazing in the past has
led to dramatic soil loss. Large, bare scalds result and there is almost
no recolonization by native species from the surrounding grassland.

Travelling Stock Routes, like this one on the Cobb Hwy near Echuca,
have had minimal disturbance from grazing relative to grazed paddocks. They support many
endangered species that have been grazed out of the broader landscape. Their linear nature, 

however, makes them vulnerable to edge effects

Fabians grassland at Terrick Terrick National Park, an example
of C3 grassland with an intertussock flora dominated by lillies, orchids and
daisies. Rainfall is approx. 400 mm per annum.H ere, the first disturbance
manipulation experiments were conducted in the mid-1990s (the Foreman Plots)
to determine how xeric grasslands respond to fire, grazing exclusion, and soil disturbance.