Numinbah Valley Environmental Education Centre
Springbrook National Park
Forest Study
Student
April 2014
Geological and Geomorphological History of the Region
The Gold Coast hinterland is on the Indo-Australian crustal plate which is moving 7cm north each year. The Gold
Coast hinterland was over a ‘hot spot’ between 24 - 23 million years ago. Hot spots are weaknesses in the Earth’s
crust that periodically force basaltic magma to the surface and erupt to form broad volcanoes. Two large volcanoes
were created at that time; the Focal Peak Volcano near Mount Barney, and the Tweed Volcano. The Tweed Volcano
area stretched north to south from Lismore (NSW to Tamborine (QLD), and west to east from Mt Lindesay (QLD)
in the west to 14 kilometres off the east coast.
Figure 1 – Volcano formation due to continental drift.
The Tweed Volcano built up broad, shield shaped mountains (approximately 100km in diameter) predominantly
from great piles of highly fluid basalt lava that flowed long distances. Towards the end of their activity, the magma
deep below distilled into other types of lava, such as rhyolite. The viscous (sticky) rhyolite erupted explosively and
plugged vents on the northeastern flank of the shield volcano. The rhyolite flows covered a much more limited
area than the basalt flows. Some rhyolite magma, forming tall bodies of rock that can still be seen today as Egg
Rock and Page’s Pinacle.
Figure 2 - Tweed Shield Volcano cross section
1
The central summit of the Tweed Volcano was located over the present Mount Warning and is estimated to have
reached about 2000m above sea level. After the Tweed Volcano became extinct 10 million years ago, the tall
mountain attracted heavy rainfall. The igneous rock gradually weathered to form rich soils that supported thick
rainforests and many streams flowed from the peak. The streams slowly cut deep gorges into the sides of the
mountain (erosion), and these widened into valleys over time.
1
2
3
Figure 3 - Progressive Erosion of the Tweed Volcano (vertical scale exaggerated)
2
Gondwana Rainforests of Australia World Heritage Area
The Gondwana Rainforests of Australia World Heritage area, originally listed in 1986 to cover rainforests
in New South Wales, was extended in 1994 to include rainforests on the Queensland side of the border.
The Gondwana Rainforests of Australia World Heritage area meets three of the four natural criteria for
listing:
•
represents a major stage of the earth's evolutionary history;
•
is an outstanding example of ongoing ecological and biological processes; and
•
contains the most important natural habitats for conserving biological diversity.
Protected areas in this property include Lamington, Springbrook, Mt Barney and Main Range National
Parks. An estimated two million people a year visit this World Heritage area.
Rainforests on both sides of the border contain more frog, snake, bird and marsupial species than
anywhere else in Australia. This area also provides a home for many rare and threatened plants, animals,
and ancient life forms.
The sub-tropical rainforest in Springbrook provide habitat for ground-dwelling birds such as the rare
Albert's lyrebird and the endangered eastern bristlebird.
History of Numinbah Valley
For thousands of years prior to the European settlement, the Aborigines freely roamed Nerang River
Valley and the adjacent land. The Kombumerries visited the Numinbah Valley and the high plateau in
summer searching for and gathering food and medicines. In winter they moved closer to the coast,
gathering fish and seafood. In Bushranger’s Cave, Aboriginal artifacts have been discovered by the
Anthropology Department of the University of Queensland and these have been estimated to be 10,000
years old. The original forests of the Numinbah Valley were thick, lush rainforests or towering
schlerophyll forests in the drier sections. The lowland sub-tropical rainforest was extremely rich in
diversity and these towering giant trees attracted the pioneering cedar getters in the 1860s. Red Cedar,
Hoop Pine, Silky Oak, Crow’s Ash, Black Bean and Booyongs promised wealth to these early loggers. For
the next 100 years, the woodcutter’s axe dominated the landscape as the valley was stripped of its timber
with the clearing often reaching high up into the hills. Five sawmills were kept busy supporting this
industry. Farming, mainly dairying, beef cattle, pig raising and banana plantations became the main
industries as the land was cleared. In recent times, tourist visitation in the area has increased.
3
Natural Patterns of Succession
Huge trees collapse and crush other plants as they fall, creeks flood and landslides cause large scars in
the forest. In heavily disturbed areas where landslides have occurred frequently, four stages of
succession take place before the climax is reached, often taking place over hundreds of years.
Stage 1 –
Vigorous growth of short-lived herbs and soft woody shrubs to 2m (e.g. native 1, wild
raspberries, native 2, native 3)
Stage 2 –
Secondary pioneer shrubs grow 4-8m high, which are intolerant to shade (e.g. wild tobacco,
bleeding heart, poison peach and macaranga)
Stage 3 –
Short-lived trees or nomads (fast growing) (e.g celery wood, giant stinging tree, wattles,
and sweet pittosporum). Late colonisers include white cedar, flame trees, hoop pines and
red cedar.
Stage 4 –
Long-lived trees over 100 years old (e.g. red-cedar, strangler figs, rosewood, brush box,
deep yellow wood lilly pilly, coachwood).
Source: National Trust of Australia (NSW)
4
Abiotic Factors Influencing Forest Type
A number of environmental factors combine to determine the type and variety of plants that grow in an
area. A change in these factors can result in different forest types separated by short distances. Generally
no single factor is dominant, but rather a variety of factors influence the forest type.
Soil
The geology of an area dictates the type of soil produced which in turn determines the types of plants
that can grow there. Different plants prefer different soil types. Characteristics such as fertility, depth and
drainage influence plant growth. Soil subjected to repeated fires may be nutrient-depleted.
Aspect
Aspect refers to the direction and exposure that an area faces. It determines the amount and duration of
sunlight that reaches the area, along with its exposure to drying winds and rain-bearing winds. The
aspect may influence the amount of rainfall, temperate, humidity, frost susceptibility and fire regime of
the site.
Rainfall
Plants vary greatly in their water requirements. The amount of rainfall an area receives has a major
influence on the types of plants that can grow there.
Altitude/Latitude
Species diversity and forest complexity tend to decrease with increasing altitude and latitude. Higher
altitudes result in lower temperatures and often higher rainfall, particularly in coastal areas.
Slope
The top of steep slopes may be drier (due to drainage) and nutrient-depleted in comparison to
surrounding, lower lying areas. Steep slopes without large trees may be unstable, with landslips
hindering the development of forests.
Fire
Australian plant communities have developed in association with fire. Many plants have evolved ways of
coping with fire. Nevertheless, plant communities may be wiped out in an area if fires are too frequent,
too hot or even not frequent enough. Hence the fire regime, or frequency of fire in an area, is a significant
environmental factor. Many open forests are stimulated by fires. Rainforest plants are not tolerant of fire.
Springbrook National Park – Best of All Lookout
Cool Temperate Rainforest
Cool temperate rainforest occurs at altitudes more than 900 meters above sea level, where the climate is
cool with high annual rainfall (1700 – 3000mm) and there are fertile soils. The forest structure is simple
with one or two strata of canopy. There are only one to three dominant tree species. Trees have simple
leaves with toothed margins, generally under 7.5cm long. Epiphytes, mosses, and lichens form dense
coverings on tree trunks and branches. The forest floor has various ferns including tree ferns.
Strangler figs, palms, buttress roots, large epiphytes (e.g. staghorns) and woody vines are rare or absent
in cool temperate rainforest.
5
Figure 6. Cool Temperate Forest
Antarctic Beech
Antarctic Beech (Nothofagus moorei) is only found in cool temperate rainforests of NSW and southeast
Queensland. Springbrook National Park contains nearly all of the world's living Antarctic Beech trees.
The Antarctic Beech was very common when Australia was a part of the Gondwana supercontinent
(sometimes between 510 to 180 million years ago), but as Australia moved north and became hotter and
drier, the species became less common. Fossil evidence of Antarctic Beech has been found in South
America, New Zealand, and Papua New Guinea indicating that these landmasses were once connected.
1. What abiotic factors allow the Antarctic Beech to grow at this location?
6
Warm Temperate Rainforest
Figure 11 - Warm Temperate rainforest
Warm temperate rainforests are cool moist habitat on fertile soils with an annual rainfall of over
3000mm. Two tree strata form an even canopy. Its vegetation is less diverse than in Subtropical
Rainforests, with usually only three to fifteen species in canopy. Leaves are mostly simple and toothed,
over 7.5cm long and on average smaller than in Subtropical Rainforests. Dominant species are
coachwood and brushbox. Strangler figs, palms, plank buttresses, and woody vines are rare or absent.
Tree trunks are slender and uniform. Epiphytes (mainly lichens) are common but not obvious. Ground
ferns are common.
2. Name the two dominant tree species at this point and describe some distinctive features of
each.
3. Warm temperate rainforests are common in SE Queensland and NSW. What abiotic factors
would determine the change of vegetation from the Best of All Lookout to the forest here?
4. Most of the forest here is termed ‘Climax Forest’. Explain the term.
Glowworms
Some of the caves and soil embankments next to the track are inhabited by glowworms, which can
clearly be seen at night. The glowworms, which represent the larval stage of a fungus gnat, produce
sticky filaments, which hang down and are used to trap insects. The light produced by the worm attracts
the insects, which are caught in the sticky threads and are then hauled up and eaten. Trapdoor spiders
also frequent the area and eat the insects attracted to the light. They can protect the glowworms from
predatory huntsman spiders.
5. When both organisms benefit they have a
_______________
relationship.
Twin Falls
The pool at the bottom of Twin Falls was a site of major environmental damage in 1991. Land clearing
above the falls and outside the National Park resulted in the deposition of 200 – 300 tonnes of sediment
in the pool following a period of rainfall. Mud, up to one metre deep, blanketed the substrate in and
around the rock pool. This resulted in significant environmental damage, which is evident today.
6. What environmental damage would have resulted from this event?
Landslide Area
In 1890, rural inhabitants of what is now the Gold Coast noticed a sudden appearance of a large scar just
below the Springbrook cliffs. A large rock fall had resulted in the levelling of the forest in the area in
which you now stand.
7. What evidence of this event can be seen today, over 100 years later?
8. This area is presently undergoing succession. What stage of succession has been reached at
present?
9. Indicate factors which may be hampering this progression.
8
Tree Falls
In the forest, trees fall down as a result of storms, cyclones, decay, disease, and old age.
10. Examine such a site and explain what happens when a tree falls and opens a gap in the canopy.
11. What would indicate the length of time the tree has been down?
Subtropical Rainforest
Figure 13. Subtropical rainforest diagram
9
Warm moist habitat on fertile soils with a rainfall of over 1300mm annually; two or three tree strata
forming a multi-layered billowing canopy; ten to sixteen tree species in canopy.
Tree leaves are mostly compound, not toothed; leaves or leaflets over 7.5cm long; stranglers, palms,
plank buttresses, epiphytes and woody vines prominent; and large leaved herbs and ground ferns
common.
Characteristic features of subtropical rainforests include:
•
mixed composition of many tree species with no obvious domination by any one species
•
trees of large to medium size with a range of leaf forms
•
palms, strangler figs, buttressed trunks, large vines and large epiphytes common and diverse
12. What abiotic factors have influenced the formation of subtropical rainforest at this site.
Notice the variety of epiphytes present here. Epiphytes grow on host trees but do not take nourishment
from the host as a parasite would. The host tree is used only as a support from which the epiphyte may
obtain more light, and catch falling leaves for nutrients.
13. List examples of epiphytes found here.
Buttress Roots
Some of the trees in subtropical rainforests have large buttress roots.
14. Read the plaque and describe the advantages these roots would give a tree.
Vines and Lianas
A feature of the subtropical rainforests is the abundance of climbing vines and lianas. These vines grow
from seeds in the ground but use other plants for support as they grow towards the light. One example is
the Giant Pepper Vine whose seed was used by Aborigines to cure mouth ulcers.
15. List three ways that vines use to reach up into the canopy. Can you see any evidence of the
vines affecting the trees?
10
Ecotones
Climbing up, out of the rainforest, a distinct change between ecosystems occurs; an ecotone. The
Rainforest suddenly gives way to Dry Eucalypt Forest as a number of abiotic factors change.
16. Identify the main abiotic factor responsible for this change.
Rainforests such as those visited today represent a species-rich ecosystem that should be conserved for
the future. Rainforest ecologist Len Web (1980) estimated that 75% of Australian Rainforest has
disappeared.
17. Why do you think it is important to conserve our remaining forests?
Strangler Fig
A strangler fig (Ficus watkinsiana) can be seen in the distance at this point on the walking track. These
tiny seeds commence life deposited high in a tree by bird or bat droppings. The aerial roots of the fig
grow down to the ground and eventually form a latticework of roots. These fuse together and grow
thicker around the host tree. Eventually, the roots take over, the tree is overwhelmed by the fig and it
dies, decaying away. The inside of fig is hollow and it can keep growing for many years.
18. What advantage does such an adaptation have for the young fig?
19. Why does the host tree eventually die?
11
Montane Heath
Figure 14 - Montane Heath diagram
Shrubby vegetation on rocky infertile soils, notably along cliff edges and cliff faces.
Characterised by grass trees, banksias, bottlebrushes, hakea, mint bushes, tea trees and other longgrowing heath plants.
Dry Sclerophyll Forest
Figure 9 – Dry Sclerophyll Forest
Dry Sclerophyll Forest communities develop in areas where the rainfall exceeds 600mm. They also occur
in high rainfall areas where the infertile or shallow soil does not retain moisture. Springbrook Plateau
has high rainfall but the soil is very infertile and clayey. The ground cover can be grass or shrubs,
depending on the length of time since the last fire.
Characteristic Features of Dry Sclerophyll Forest: Tall eucalypts, understorey of scrubs, grasses, ferns,
open canopy 30-70%, rainfall 1500mm p.a., nutrient-poor soils, dominant species-eucalypts, acacias and
casuarinas.
12
Rainforest Community Data Table
Cool Temperate
Warm Temperate
Air Temp (°C)
Soil Temp (°C)
Aspect (e.g. NE)
Altitude
Slope/Gradient
Light
Humidity %
Wind Speed
Soil pH
Soil Description
Canopy Cover %
Ground cover
Dominant species
13
Sub- Tropical
Comparison of Forest Types
Cool Temperate
Warm Temperate
Leaf size
Buttress Roots
Lianas and Epiphytes
Palms
Ferns
Mosses and Lichens
Structure – height and
layers
Dominant Species
Determining Abiotic
Factors
14
Sub- Tropical
15