Vegetation of a piece of Australia’s prime rainforest

Australia’s prime rainforest estate at Cape Tribulation.

Having started this blog almost 6 years ago and spending some years learning the flora of the region, I have had the great previlege to examine closer, in a scientific way, the flora of a patch of Australia’s prime rainforest estate. And there is probably few places that can match the Daintree to have such an opportunity.

These research culminated in a recently published paper [download pdf] in the free-to-read open access Biodiversity Data Journal, an apt place to publish forest plot and species diversity data.

The lowland rainforests at the Daintree and areas around Cape Tribulation have been touted as representing the prime development of rainforest in Australia, because of their complex structure. Alluding to this complexity, these forests have locally been called “Complex Mesophyll Vine Forest”.

When I first got the opportunity to work at the Daintree in earnest in 2013, there was already a 0.95 hectare (now extended to 1-ha) long-term rainforest monitoring plot in existence. This plot was set up in the year 2000 and so has been monitored for over 15 years.

Although other tropical countries have much larger monitoring plots, this plot is Australia’s largest lowland rainforest plot. Strategically, this plot is also situated under the canopy crane, and is in fact the only place in Australia with a canopy crane to study rainforest, and one of a few in the world.

Such is the significance of this infrastructure that a research station, the Daintree Rainforest Observatory, was built to administer research activities on the canopy crane. Not surprising, there has been quite a wonderful list of ecological and biological research conducted from the crane.

The Daintree Rainforest Observatory “rebooted” in 2014. Now furnished with space for over 40 people.

I was tasked to set up another 1-ha plot to complement the one already in existence, and this involved going out into the forest, tagging, marking, identifying and measuring the trunk diameters of these trees.

It was gruelling and bloody (literally) work – a kind of intensive outdoor gardening which required the pruning of spiny vines to create access paths and to lay out 20x20m grids. And it was certainly not possible to complete without the help of many kind volunteers.

Working in the canopy crane

But I was in a kind of “plant heaven”, having an opportunity to make close friends with the plants in such a beautiful rainforest region, and not just the trees.

Later between 2014-2015, I when back to lay out a few small plots in the understorey to have a closer look at the abundance of shrubs and tree saplings, and also to do an overall flora survey of the 42-ha research station. While such an ad hoc survey may not be very precise in terms of the number of the species present at the site, we did find some 385 native plant species at the site which is certainly a good representation of the diversity of the forests in the Daintree region.

In terms of the plot, the tree diversity of ~80 species per ha was not particularly high by world standards, but what was interesting was the number of stems exceeding 10cm diameter (>800 stems per ha). This is higher than most places with permanent plots, and could be a result of regeneration from cyclones that occasionally visit these lands.

I hope that this work will form a firm ecological basis for other hypothesis-driven studies, and also for further studies looking at the rainforest vegetation of the Wet Tropics of Australia.

Carpentaria acuminata (Arecaceae)

Carpentaria acuminata (Carpentaria Palm) is the sole species in the genus Carpentaria, which is native to tropical coastal regions in the north of Northern Territory, Australia. Due to it’s attractive form and red fruits, it is widely grown in Cairns as an ornamental.

As in the Northern Territory, the Carpentaria Palm is an important food source for Torresian Imperial Pigeons (Ducula spilorrhoa).

Clerodendrum splendens (Lamiaceae)

Commonly by various names such as the Flaming Glorybower, this vigorous vine, native to tropical Africa, is grown for its showy and ornamental red blossoms.

Beautiful these flowers are! – brilliant bright red, very showy, and borne in terminal clusters. The flower corolla is fused into a tube, lobes spreading to 2 cm long. The stamens with their red filaments protrude quite conspicuously out of the corolla like whiskers.

Few people who cultivate this vine probably know that they have an ornamental pharmacopeia at they doorsteps.

In it’s native range in Western Africa, extracts of roots, leaves, and bark from C. splendens are used in traditional medicine to treat various ailments ranging from malaria, coughs, skin diseases, ulcers, rheumatism, asthma, and uterine fibroid, and venereal infections, including gonorrhea and syphilis (Shrivastava & Patel 2007; Okwu & Iroabuchi 2008, 2009; Gbedema et al. 2010).

Recent research further suggests that polysaccharides from leaves of the plant have ability to modulate the immune systems, and may thus have beneficial effects for people with autoimmune disease (Kouakou et al. 2013).

Impressive list for a garden ornamental!

References

Gbedema SY, Emelia K, Francis A, Kofi A, Eric W. 2010. Wound healing properties and kill kinetics of Clerodendron splendens G. Don, a Ghanaian wound healing plant. Pharmacognosy Res 2:63–68.

Kouakou K, Schepetkin IA, Jun S, Kirpotina LN, Yapi A, Khramova DS, Pascual DW, Ovodov YS, Jutila MA, Quinn MT. 2013. Immunomodulatory activity of polysaccharides isolated from Clerodendrum splendens: Beneficial effects in experimental autoimmune encephalomyelitis. BMC complementary and alternative medicine 13: 149.

Okwu DE, Iroabuchi F. 2008. Isolation of an antioxidant flavanone diglycoside from the Nigeria medicinal plant Clerodendron splendens, a. Cheval. Int J Chem Sci 2008, 6:631–636.

Okwu DE, Iroabuchi F: Phytochemical composition and biological activities of Uvaria chamae and Clerodendoron splendens . E-Journal Chem 2009, 6:553–560.

Shrivastava N, Patel T. 2007. Clerodendrum and healthcare: an overview. Medicinal Aromatic Plant Sci Biotech 1:140–150.

Loropetalum chinense (Hamamelidaceae)

Loropetalum chinense, known commonly as the Chinese fringe flower, is a ornamental species of the witch hazel family, grown as a hedge plant in certain places around Cairns and the Tablelands.

Cladopus queenslandicus (Podostemaceae)

Plant life is believed to have begun from aquatic origins. As any biology textbook would show, the oldest lineages of land plants (i.e. bryophytes – liverworts, hornworts and mosses) are highly dependent on water for sexual reproduction, and are therefore often found close to permanent freshwater sources or moist conditions.

Many liverworts for example have thalloid bodies – i.e. rather than leaves they have a body consisting of a flatten film of photosynthetic tissue, very much like a lichen. This allowed them to adhere tightly to substrates. Later in their evolution, liverworts started to evolve leaf-like structures (Read the fascinating story of how liverworts may have started making leaves)

When flowering plants came onto the scene, they also radiated into freshwater habitats, and they found a myriad of exciting ways to live in water.

For one family of aquatic flowering plants, the Podostemaceae, the return to life in the water came with a “reverse innovation” – it seems to have “relearnt” how to be a liverwort.

One very prominent member of the family in tropical Queensland is Cladopus queenslandicus. This aquatic flowering herb has very interesting plant form. The stems have very basic fleshy leaf-like structures which are ridged on the back. These fleshy structures resemble those of liverworts that have are in a transitional stage between being thalloid and leafy (See illustrations online).

The stems of Cladopus queenslandicus showing liverwort-like overlapping fleshy leaves.

The roots have a thalloid form like a liverwort, and is obviously quite specialized to be able to grip onto rock substrates. Indeed, Thus, experts on the family suggest that the root is the leading organ in the
body plan of most Podostemaceae, reflecting a remarkable adaptation to a unique aquatic environment, i.e., the border between rock surfaces and fast-running water (Koi et al. 2006).

The flattened thalloid roots of Cladopus clasping onto rock substrates.

Fascinatingly, the closest relatives of the Podostemaceae are from the mangosteen family – an excellent example of how evolutionarily plastic plant form can be.

C. queenslandicus is found in fast-flowing water or torrents near waterfalls around the Ravenshoe region (i.e. Little Millstream Falls), and also in some localities in Malaysia and PNG. It was previously and much more descriptively named Torrenticola queenslandica by karl Domin.

References

Koi S, Fujinami R, Kubo N, Tsukamoto I, Inagawa R, Imaichi R, Kato M. 2006. Comparative anatomy of root meristem and root cap in some species of Podostemaceae and the evolution of root dorsiventrality. American Journal of Botany, 93, 682-692.

van Steenis CGGJ (ed). 1948. Flora Malesiana: being an illustrated systematic account of the Malaysian flora including keys for determination, diagnostic descriptions, references to the literature, synonymy, and distribution, and notes on the ecology of its wild and commonly cultivated plants. [See 1949, Series 1, Volume 42, pg 68 (Read relevant page here)]

Leea novoguineensis (Vitaceae)

Known in Australia as the Bandicoot berry, this shrub is a well-known pioneer species, and related Leea species occur throughout Southeast Asia and Asia, usually also in successional habitats.

The leaves of this species are alternate and two-times compound and the leaflets are toothed. At the base of the leaf stalk there is a large stipule.

An astute observer might notice the similarity of the flowers and fruits to those of grape vines, and indeed, this shrubs belong to the grape family (Vitaceae).

This fast-growing can grow to a 4m or higher, but plants that are commonly encountered by roadsides are typically no taller than 2 meters.

The species produces very straight green stems, and have to my understanding been used by aboriginal people as spears.

This species was previously know in Australia as Leea indica, but recent molecular studies (Molina et al. 2013) have restricted the name of this species to specimens from India, and named the Australian specimens L. novoguineensis.

References

Molina, J. E., Wen, J., & Struwe, L. (2013). Systematics and biogeography of the non‐viny grape relative Leea (Vitaceae). Botanical Journal of the Linnean Society, 171(2), 354-376.

Cyrtandra baileyi (Gesneriaceae)

In wet places in the Australian rainforest dwells Cyrtandra baileyi, a delicate relative of the African violet. This shrub which appears to be restricted to permanently wet places in rainforest, is endemic to the region and was first collected by botanist Frederick Manson Bailey.

At a first glance, one might interpret Cyrtandra to have alternate leaves, but closer inspection would reveal a rather strange feature – at each leaf node, there is pointed appendage opposite each leaf. Cyrtandra actually has opposite leaves, one of which is greatly reduced.

What came to my mind was a rather macabre analogy: Cyrtandra has a leaf with a “vanishing twin” – the phenomenon in animals where a fetus in a multi-gestation pregnancy which dies in utero and is then partially or completely reabsorbed by the twin.

Interestingly, there are other plants that do this, but that is another story for another time.