Fauna Species Diversity of the Subtropical Rainforest of Lamington National Park versus that of the Schlerophyll Forest of North Stradbroke Island

Jackie Lamme
Terrestrial Report

This paper examines the species diversity in two distinct environments, the subtropical rainforest of Lamington National Park and the sclerophyll forest of North Stradbroke Island. The floral diversity is first observed in the two locations. Then, the effects of this diversity on the faunal communities is examined. The question of what effects, if any the flora diversity has on the fauna diversity and abundance is posed. Why these effects occur is also questioned. Research shows that the rich rainforest community supports the larger and more diverse fauna population. Environmental factors such as temperature, water availability and nutrient availability all play an important role in this relationship. All of these interactions are looked at and discussed in this paper.

Two distinct types of forests were observed on this trip, the subtropical rain forest of Lamington National Park and a schlerophyll forest on North Stradbroke Island. The two locations are very distinct and very different. Lamington National Park is a lush subtropical rainforest with a diverse plant population. North Stradbroke Island, on the other hand, is located in a much more inhospitable location with a few dominant species of sclerophyllous plants. This paper discusses question of what these vegetative differences mean for the fauna diversity of each location. There appears to be a much greater variety of faunal species in the rainforest but is this the actual case and if it is, what are the biological and ecological reasons behind it?

Environment 1
The first environment that will be discussed is the subtropical rain forest of Lamington National Park. The rain forest was observed in the area surrounding O'Reiley's guest House. This area is made up of primary and secondary Complex Notophyll Vine forest (Hopkins 1975). Hopkins characterizes a rainforest by the complexity of structure, its equal of distribution of the available resources, diversity of plants (1975). A subtropical rain forest does not have the intense diversity of a tropical rain forest, but it is still a highly diverse environment (Figgis (ed) 1985). Rain forests contain up to 50% of all the plant species in Australia. There tend to be two to three highly visible strata within the forest. The canopy in a subtropical rain forest tends to be lower than that in a tropical rain forest (Figgis (ed.) 1985). The understory is also much thicker in a subtropical rain forest. There can be anywhere from 10 to 60 species of flora located within the canopy (Adam 1992). The canopy tends to reach around 35 m but it get as high as 50-55 m. Such tree species as Ficus spp., Argyrondendron spp., Sloanea woollsii, and Dysoxylum fraseranum are some of the most common. Large notophyll leaves are predominant and compound leaves are found on many of the species within the rainforest. According to Hopkins, one species rarely dominates the forest numerically (1985) though the larger trees seem to dominate visually. One of the most obvious features of the rain forest are the strangler figs engulfing many of the trees. These vines are long and can be very thick around. Huge plank buttresses are also highly visible and cover a large ground area per tree. The subtropical rain forest contains a large and diverse variety of epiphytes such as orchids and ferns. These are seen on almost every tree within a mature forest. Ground ferns and herbs with large leaves are found especially within the subtropical rain forest. Many of the species are morphologically similar. Epiphytes tend to be large and leafy. Canopy trees all tend to reach the same maximum height. They are also characterized by large leafy leaves that are often compound. Another characterization of these leaves is their shiny dark color.

A relationship between climate and leaf size has been shown (Adam 1992). Therefore, the large leaves found in the rainforest are due, at least in part, to the conditions found there. The average rainfall and temperature figures are taken at Mt. Tamborine which is located 520 m above sea level. O'Reilly's is located at 900 m above sea level so it is very likely the average rainfall is greater and the average temperature is lower. The area of Lamington which we observed is in an almost constant mist stratum which would significantly increase the annual moisture levels (Hopkins 1975). However, the data taken at Mt. Tamborine gives at least a rough estimation of the environmental conditions. The data show a definite seasonality for the annual rainfall with a the greatest amount of rain during the summer months (December to March). Even during the dry spring months, more than 250 mm of rain is received and there are at least 20 rainy days from August to November (Hopkins 1975). This is one of conditions for it to be considered a Notophyll Vine forest. The annual rainfall at Mt. Tamborine is 1500 mm to 1700 mm. Another requirement for Notophyll vine forests is that the temperature never falls below 9.5 C, and this requirement is fulfilled in Lamington.
The soil composition is very important for the development of a vine forest. "Dramatic soil changes between adjacent area mean equally dramatic changes in the vegetation, even when rainfall and altitude are similar" (Figgis 1985). Rain forests tend to be located on basaltic type soils. Near O'Reilly's the upper basalt layer is over 50 m deep (Hopkins 1975). The soils is a definite red color in the area, which is a result of the kraznozem soils. There is little analysis of the actual nutrient content of the soil and most of the information is simply inferred from the type of soil in the area (Adam 1992). It is known though that the fertility of the soil correlates with the "physiognomic forest type" (Adam 1992). In the northern part of New South Wales, which Lamington borders, it has been shown that simple notophyll forests have higher aluminum content and lower calcium, nitrogen and phosphorus levels than those in complex notophyll forests. This is very likely a factor in their inability to develop into a complex notophyll forest.

Environment 2
The second environment discussed in this paper is the sclerophyll forests on North Stradbroke Island. The forest is located on the high dunes of the island. The specific area visited was in the eucalypt open-woodland by Brown Lake. A fire swept through the area in 1965. Research showed that as the forest aged and the over story cover increased, the number of species in the understory decreased (Specht 1984). It is an area that has been heavily mined for sand in the past, as has most of the island, and is dominated by a few schlerophyllous species such as Eucalyptus spp., Acacia spp., and Casuarina spp. The area is made up of open woodland that moves into open-forest and has a sclerophyllous understory (Specht 1984). Tall Eucalypt trees dominate the canopy. There is a layer of sclerophyllous shrubs at 2-5 m and another sclerophyllous shrub layer at less than 1 m. Sedge is the dominant sclerophyllous ground cover. Specht's research (1984) showed that soon after the fire in 1965 there was a greater species diversity than was found in 1984. The number of species in the area dropped from 67 species to about 31 in 30 years.

The area is on a dune ridge and the soil is very fine and sandy (Specht 1984). The stability of the environment is low, due to the high mobility of the sand substrate it is located on in this area. The water table is close to the surface, but the texture of the soil causes water to quickly drain down to it rather than remaining in the topsoil. The area is very nutrient poor, both due to the sandy substrate and the extensive mining that has occurred on the island. The majority of the minerals found naturally in the area come from sea spray. There are no nearby streams on the island to bring water down from more rich environments. In the research conducted by Specht (1984) it was discovered that the addition of nutrients to the soil actually decreased the sclerophyll vegetation. This shows that the sclerophyllous vegetation is specifically adapted to the nutrient poor conditions found on North Stradbroke Island. In another study by Specht (1989), he showed that all sclerophyll forests are located on nutrient poor soils, especially those poor in phosphorous.

Comparison and Contrast
There is a significantly greater floral diversity in the subtropical rain forest than in the sclerophyll forest. The rain forest contains a wide variety of lush plants while the sclerophyll forest is dominated by a few specialized plants at every level, Eucalyptus spp. and Casuarina spp. in the canopy, sclerophyllous shrubs in the understory, and sclerophyllous ground cover such as sedge. There are environmental factors that play an important role in the environment. They are temperature, rainfall and soil nutrient status (Adam 1992). Both the total annual rainfall and the seasonal distribution of rainfall are important. The most important of these environmental factors in determining the type of vegetation is the substrate and nutrient level. Lamington is located on nutrient rich basalt while North Stradbroke is a nutrient poor sand island. "Soil fertility is a major determination of productivity" (Adam 1992). It was also noted in Adam (1992) that the soil chemistry can also be used to differentiate a sclerophyll forest from a rainforest. The more moderate climate at Lamington is also a factor in the rich species diversity in the rainforest that is not found at North Stradbroke. Water availability plays a major role in the diversity within an environment as well. There is a much greater availability of water at Lamington due to many factors. One was simply the higher elevation of the park and the fact that it is often shrouded in a cloud of mist. Also, when it rains the water remains in the topsoil for longer periods of time because the high clay content within the soil traps the water and prevents it from sinking to the water table. On North Stradbroke the soil is made up of sand, which allows the water to pass through to the water table very rapidly. Plants on North Stradbroke have had to adapt specifically for the more arid conditions. Plants such as the large epiphytes found in Lamington would not be possible in the arid conditions of North Stradbroke. "A species presumably survives at any site because its morphological and physiological properties permit it to do so" (Dale 1984).

Organisms in Environment 1
The species diversity of both the flora and the fauna in the subtropical rainforest of Lamington National Park is intrinsically connected. However, it is difficult to discuss, because very few studies have been directed specifically in this area. Most studies deal with one species behavior, not the general interactions between flora and fauna in an environment. Evolution has allowed for the diversity of the fauna to ensure the diversity of the flora and vice versa. Vegetative damage done by plant predators and parasites can be a significant factor affecting both the establishment and survival of plants (Hopkins 1975). Predation by animals on specific species has encouraged a high level of diversity within the flora community. On the other hand, most types of fauna that inhabit rainforest are less specialized instead of more specialized (class notes 1996). The lush variety of plants has provided a large and diverse food source for the animals of the area. "Intensive grazing was associated with a lack of physiological dominance by one species resulting in an intimate mixture of species" (Hopkins 1975). Predation, by fauna such as rats and insects, at the sapling level is an important factor in preventing monoculture. Not only are there variation in the fauna "assemblages" due to geographic distribution but, they can also be seen in "altitudinal zonations" (Adam 1992). This was shown for the distribution of mammals. The nomadic movement of birds and bats blurred this distinction. The distribution is most likely caused by the changing plant distribution from these altitude changes.

Research has also shown that the diversity of small mammals in more nutrient poor rainforests is significantly less than in nutrient rich soils. This was shown to be especially true in areas of past logging (Barry 1984). It has been shown that bird species diversity rises as the vegetation becomes more complex (Kikkawa 1982). The fauna species diversity is the greatest in more developed rainforests and rainforests tend to be more developed in areas of more fertile soils. The study also showed that there are high correlations between birds and there environment, especially in complex vine forest (Kikkawa 1982).

Organisms in Environment 2
The flora and fauna of the sclerophyll forest of North Stradbroke Island have evolved in a complex pattern, just as that of the subtropical rainforest in Lamington National Park. However, evolution has chosen a path opposite of that of the rainforest. It has been suggested that the low fertility of the soil and variability of the climatic combine to suppress the diversity of fauna in these areas (Barry 1984). The same study showed that the high toxicity plants that is traditionally associated with low soil fertility actually suppresses the abundance and diversity of small mammal. Plants within the nutrient poor soils of the sclerophyll forest have had to adapt to both the lack of nutrients and the lack of water. This has forced plants to specialize for these conditions. They have also developed a high level of toxicity as a result, very likely a defense mechanism against predation. High levels of predation would inhibit, if not completely halt, the success of any plants within this environment, so it was necessary for the plants to develop a way to limit it. The animals, therefore, had to adapt as well to meet the challenge of a more limited and toxic food source. This significantly limited the number of fauna that was able to survive in the sclerophyll forest. This is also backed up by Barry who noted that the limitations of food resources causes the low diversity of Australian small mammal communities, not the lack of opportunity for speciation (1984). There is also evidence to back this up in Woinarski in his note that "differences in species composition and richness are associated with substantial differences in resource availability" (1995).

Comparison and Contrast
There is an obvious difference in the number of fauna species and the overall abundance between the subtropical rainforest of Lamington National Park and the sclerophyllous forest of North Stradbroke Island. All sources looked at stressed the point that rainforests are among the most diverse terrestrial communities (Adam 1992) while the diversity within sclerophyllous forests is significantly more limited. Adam also noted that "it has been suggested in a number of texts that a consequence of species richness would be the presence of a larger number of specialized links between particular species of plants and animals than in less species-rich communities" (1992). However, he goes on to point out that evidence suggests that if anything a "greater prevalence of diffuse (generalist) relationships" exist rather than "tight obligatory linkages." The rainforest is a predictable, nutrient rich, and water rich environment that is ideal for floral species diversity. The high floral diversity in turn allows for an abundant variety of animals to flourish there without having to adapt significantly simply to survive. Hopkins notes this in his thesis (1975) in his comment on how the "evolutionary process in the comparatively favorable and predictable environment of rain forest has produced a system in which more species can coexist by temporal and spatial 'avoidance' than...in more rigorous or less predictable environment." The sclerophyllous forest is without a doubt a more rigorous and less predictable environment.

The study by Woinarski (1995) shows a difference in the diversity of fauna and sample sizes between Acacia spp. woodlands and that of rainforests. There were fewer "frugivorous birds, nectarivorous birds, skinks and granivorous rodents" in the Acacia spp. woodlands than in the rainforests. Trunk gleaning birds and small macropods seemed to prefer the woodlands to the rainforests. The total abundance of the main taxonomic groups showed a significantly lower number in the Acacia spp. woodlands. Overall, there were fewer vertebrate species within the Acacia sp. woodlands than the rainforests. This study was not taken at the sites focused on in this paper, but the sites are similar and are representative of trends found within the types of forests.


In conclusion, there is a significant difference in the species abundance between Lamington National Park and North Stradbroke Island. The difference in diversity was visibly apparent when visiting the two locations. However, literature from previous research also backed up this opinion. The literature supported the hypothesis that the faunal species diversity and abundance was directly correlated with the floral diversity. It also indicated that species in more difficult environments were much more specialized because their resources were more limited. There are a variety of environmental factors that play a part (soil nutrient content, temperature and water availability) but all of them seem to have an effect on the flora diversity and thus effect the fauna diversity.

Works Cited

Adam, Paul. Australian Rain forest. Clarendon Press, Oxford 1992.

Barry, S.J. "Small mammals in a South-East Queensland Rainforest: the Effects of Soil Fertility and Past Logging Disturbance." Australian Journal of Wildlife Research vol. 11 1984.

Dale, M.B. "Species equivalence and morphological Rediscription: A Stradbroke Island Vegetation Study." Focus on Stradbroke: New Information on Stradbroke Island and Surrounding Areas, 1974-1984. Boolarong Publications, Brisbane 1984.

Figgis, Penny (ed.) Rain forests of Australia. Weldons Pty Ltd. NSW 1985.

Hopkins, M.S. Species Patterns and Diversity in the Subtropical Rain forest. PH.D. Thesis,
Dept. of Botany, University of Queensland 1975.

Kikkawa, Jiro. "Ecological association of birds and vegetation structure in wet tropical forest of Australia." Australian Journal of Ecology. vol. 7 1982.

"Lecture: Life-Histories of Rainforest Animals." Travelearn Field Course. October 1996.

Specht, R.L. "Species Richness in a Eucalypt Open-Woodland on North Stradbroke Island, Queensland-The Effect of Overstory and Fertilizer, 1965-1984." Focus on Stradbroke: New Information on Stradbroke Island and Surrounding Areas, 1974-1984. Boolarong
Publications, Brisbane 1984.

Specht, R. L. "Species Richness of Sclerophyll (Heathy) Plant Communities in Australia-the influence of Overstorey Cover." Focus on Stradbroke: New Information on Stradbroke Island and Surrounding Areas, 1974-1984. Boolarong Publications, Brisbane 1984.

Woinarski, J.C.Z. and A. Fisher. "Wildlife of Lancewood (Acacia shirleyi) Thickets and Woodlands in Northern Australia. 2. Comparisons with Other Environments of the Region (Acacia Woodlands, Eucalyptus Savanna Woodlands and Monsoon Rainforests)" Wildlife Research. vol. 22 (4) 1995.