Learning Intention: Students will understand the process of ecological succession and be able to identify growth stages of a eucalypt forest.
Mountain Ash (Eucalyptus regnans) is an iconic Victorian species, the tallest flowering plant and the second tallest tree in the world, after the Californian redwood. It only germinates after hot and periodic bushfire, greater than 20 years apart. The forest goes through stages of growth:
- Germination (1-8 weeks)
- Seedlings (0-4 years)
- Saplings (4-15 years)
- Pole stage (15-30 years)
- Spar stage (30-100 years)
- Mature forest (100-300 years)
- Old Growth Forest (300-400 years)
Forest Secrets – Stages of succession in Mountain Ash forests
Eucalyptus regnans on Wikipedia – Description, Tallest trees and Ecology.
What is ecological succession? This is the answer from Rolcam at the Ask Me Help Desk.
“Changes in communities occur over time in a process called ecological succession. This process occurs as a series of slow, generally orderly changes in the number and kinds of organisms that live in an area take place. Differences in the intensity of sunlight, protection from wind, and changes in the soil may alter the kinds of organisms that live in an area. These changes may also alter the number of populations that make up the community. Then, as the number and kinds of species change, the physical and chemical characteristics of the area undergo further changes. The area may reach a relatively stable condition called the climax community, which may last hundreds or even thousands of years. ”
The first plants that germinate in an area are called ‘pioneers’ and are usually grasses or ground covers. Weeds are effective pioneers on roadside verges for example, where they colonise bare round and provide shelter for other plants to grow.
“Ecologists distinguish two types of succession–primary and secondary. In primary succession, organisms begin to inhabit an area that had no life, such as a new island formed by a volcanic eruption. Secondary succession takes place after an existing community suffers a major disruption–for example, after a climax forest community is destroyed by fire. In this example, a meadow community of wild flowers and grasses will grow first, followed by a community of shrubs. Finally trees will reappear, and the area will eventually become a forest again. Thus, the forces of nature ultimately cause even climax communities to change.”
Do the following situations demonstrate primary or secondary succession?
- Growth of grass trees after an intense bushfire in the Grampians National Park
- Pisonia sp. forest that grows on a coral cay, Heron Island on the Great Barrier Reef
- Open Acacia and Eucalyptus woodland that grows after volcanic action at Mt Eccles National Park
- Sand dune vegetation that grows at Griffith’s Island, Port Fairy
- Fern forest growing after glacier action in New Zealand
Here you can see just a few of the marine invertebrates we met in the touch tank at Heron Island Research Station, 65km east of Gladstone, on the southern end of the Great Barrier Reef. We learnt about molluscs (such as the blue-lipped clam, sea hare and cone shells), echinoderms (sea stars and sea cucumbers), corals and cnidarians (jellyfish). A coral cay is a great example of succession – how a landscape changes over time as new plants and animals colonize an area.