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.

Tuesday, 9 April 2013

A year in the life of a temperate grassland - Autumn

April 2013 - the end of the dry season

This year, as part of my Blog updates, I plan to document the changes that occur in the Kangaroo Grass grasslands that dominate the western plains near my home town of Melbourne. Ecologists have long-known that grasslands are dynamic ecosystems but I've not captured this very well in my own photos, so I thought I better change that!

Following the seasonal changes that occur in ecosystems is one way to understand the dynamism of nature.

Grasslands are brilliant for illustrating such changes - they respond to the changes of the season quite dramatically. The onset of autumn rains will see a greening up of the grassland, mostly by C3 grasses (including the many exotics that now co-exist with the native flora). As spring approaches, a riot of colour etches its way into the grassland (first whites and yellow, then pink, and finally blue) - this is the flowering of the forbs that contribute most of the diversity. As temperatures rise and rainfall declines, the C4 grass Kangaroo Grass greens up and flowers, before dying back in the heat of summer. In mid to late summer, it is very likely that the grassland will get burnt as part of its ongoing management. I look forward to capturing these changes by using photos to trace the changes of the seasons.

Temperate grasslands at the end of summer look pretty lifeless.
This grassland is found on the Mt Mercer Rd at Shelford. I'll be returning to this same spot throughout the year to illustrate the changes that occur.
(Photo: John Morgan)
 Currently, the grassland is straw-coloured and dry. Kangaroo Grass leaves have died back to the very base of the tillers and no green is evident. This reflects the fact that the summer has been particularly dry this year, perhaps a sign of things to come? All forbs are now dormant, waiting for the rains to release dormant buds.

The dead grass has formed a thatch, smothering the inter-tussock spaces. Without fire, it'll be interesting to see what forbs germinate, if any, and how the biological soil crust is represented this year.

Kangaroo Grass has died back with the long summer drought. The dead grass crowds out the inter-tussock space.
(Photo: John Morgan)
On the basalt soils that are high in clay content, deep cracks have formed. These are important for two reasons. First, cracks provide refuges for animals such as Legless Lizards to avoid late summer fires. I'm guessing they are also important as refuges per se - places to avoid the effects of heat or cold. Second, the cracks are one of the reasons that trees don't grow here.  The cracking is thought to sheer their woody roots, disrupting water uptake. These cracks won't close until soils swell with the onset of autumn rains.

An example of a soil crack that has formed as the basalt soils dry over summer. I can easily put my finger in this crack.
(Photo: John Morgan)

I'll return in about 10 weeks to see just how the grassland looks. It's highly likely that drought breaking rains will have arrived, but will this have cued germination, and will any species be in flower? Till next time.

Sunset on the plains, Truganina Cemetery
(Photo: John Morgan)