Kent Ridge handout[1]

SSS1207: NATURAL HERITAGE OF SINGAPORE

KENT RIDGE (SECONDARY FOREST) About this Habitat Kent Ridge earned its place in Singapore history as the site of a grim last stand by the Allied forces against the Japanese during World War II. The “Battle for Pasir Panjang” was fought around the slopes of Kent Ridge (then known as Pasir Panjang Ridge) ending in a decisive victory for the invading forces, despite the heroic defense. Aside from its historical significance, the Ridge is a part of Singapore’s natural heritage. It is covered by secondary forest vegetation, and is home to around 240 vascular plant species, as well as a number of animals. The original lowland primary forest was cleared for cultivation of crops such as rubber and gambier (Uncaria gambier), but after these were abandoned, the vegetation developed into a forest type called “adinandra belukar”, after the dominant tree species (Adinandra dumosa). The old agricultural practices have made the soil acidic and low in nutrient content, which led to lower plant diversity. This is compounded by Kent Ridge being cut off from any primary forest and being exposed to high heat and low humidity. When you walk around the ridge, be mindful of the different adaptations of the organisms to the challenges of living in this kind of environment. The flora and fauna of the Ridge present an interesting mix of both introduced and native species. It is not always easy to observe the different animals that inhabit Kent Ridge during the day since they also avoid the high temperatures. Most of them, particularly the birds, are best observed at dawn or dusk while others, like many reptiles, amphibians and invertebrates are more active at night. Smaller, less conspicuous invertebrates such as bees and ants can be seen busily going about their business, even in the warmest part of the day. The main crest of Kent Ridge is located in the middle of the NUS campus, and the tree line can often be seen from the lower-lying parts of the university. The forested areas surrounding Kent Ridge Road is cut off from the much larger Kent Ridge Park by South Buona Vista Road. What to bring Wear comfortable clothing and good footwear with sure grip and bring drinking water to keep yourself hydrated. There also may be some mosquitoes and other insects, so apply some insect repellant before you set out. A pair of binoculars is useful for observing the animals, but is not essential. It is recommended that you walk the ridge during fair weather, as there are few places to shelter from sudden downpours. Attentiveness to your surroundings and patient, quiet observation will be rewarded with new discoveries about the inhabitants of the ridge. How to get there Kent Ridge Road traces the length of the ridge and runs from South Buona Vista Road and Prince George’s Park (PGP) at its east end to the Center for Development of Teaching and Learning (CDTL) at its west end. Walking along this road is the easiest and best way to observe and appreciate the plants and animals of the ridge. The four stations marked on the route map are also points where you can access Kent Ridge Road. You may start walking from either end of Kent Ridge Road. Alternatively, you can ascend the link-way between the Faculty of Science at S2 and the Temasek Life Sciences Laboratories (TLL) or the stairs from the National University Hospital (NUH). Specific Health and Safety Proper precautions should be taken against getting dehydrated in warm weather, as well as in avoiding mosquito bites. At all times be aware of traffic and avoid obstructing any passing vehicles by staying at the side of the road.

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Map and Route

Station: 1 (CDTL building) - The CDTL building is at the west end of Kent Ridge Road. Across the road from the center there is a steep slope with a thick growth of plants. On the left, the resam ferns present a lower profile than taller shrubs. You can immediately recognize the simpoh air shrubs which dominate the slope. Try to look for any open flowers or fruits, which attract pollinators like carpenter bees or frugivorous birds like the black-naped oriole and yellow-vented bulbul. Walk up the slope away from the CDTL building and note the large saga tree near the lamp post. Its curled fruits and red seeds will sometimes be found on the sidewalk. Below the saga tree, look out for Koster's curse among the undergrowth. Station: 2 (S2 and TLL Linkway) - On either side of the stairs leading down to the S2 building can be found sendudok and white-leaved fig treelets. Beyond the stairs, weaver ants are often seen marching along the metal rail guard. Behind the yellow and black metal barrier you can see the tiup-tiup trees with their distinctive flowers. Across the road along the stairs leading down to TLL, note the sarsaparilla vine climbing over many of the trees. In the evenings before dusk, a white-crested laughing thrush or two are often seen in this area, while during the day cicadas fill the air with their constant buzzing. Station: 3 (NUH staircase and KE VII) - Two large trees are found on either side of the stairs leading down to NUH. Attached to the bark of the tree on the left, you can find dragon's scales, which is a fern. On the tree to the right, two large bird nest ferns are found. You might spot pink-necked green pigeons feeding on the palms across the road bordering the driveway to KE VII. Walk down the road towards PGP approximately 10 meters and you will see several para-rubber trees behind the yellow and black road barrier. Station: 4 (PGP and South Buona Vista Rd) - At the east end of Kent Ridge Road, a large saga tree is found growing to the left of the entrance to the parking lot. Walking down towards South Buona Vista Road, common acacia and tembusu trees are found in front of the parking lot. Across the road, to the left of the drive leading up to CRISP is a thicket of resam ferns.

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Organisms at Kent Ridge Flora (including fungi) Bird nest fern (Asplenium nidus). Large fern with large and simple leaves forming a nest-like structure. It uses the decaying fallen leaves from other trees trapped in the “nest” as its main source of nutrients. In Singapore, it is a common epiphytic fern on tree trunks. Common acacia (Acacia auriculiformis). A legume tree easily recognised by the curved phyllodes. A naturalised species that is very successful and became weedy. Dragon's scales (Pyrrosia piloselloides). Epiphytic, looking like round, scale-like coverings on trees. Koster's curse (Clidemia hirta). A very common weedy herb or small shrub. One of the more successful invasives of secondary forests. Para-rubber (Hevea brasiliensis). A straight-boled tree species that may grow to 20 m. It has trifoliolate compound leaves. Leaflets have strong secondary veins arising at an angle from the main vein. The compound leaves have long petioles and arise alternately from the stem. When the bark is slashed, it exudes white latex (please do not cut the tree just to see this). Flowers are pale yellow and are inconspicuous due to their small size. Fruits are dry and woody capsules, divided into three lobes. They release their seeds by exploding. Seeds resemble those of the castor oil plant. This is an introduced species originally from Brazil and is the main source of rubber (produced from the latex sap). The trees in Kent Ridge are descended from abandoned plantations. Resam (Dicranopteris linearis). One of the most common ground ferns on Kent Ridge, growing into dense thickets to 2m tall. Herbaceous, with a creeping hairy underground rhizome (term for stems of ferns). Large fronds having very long leaf stalks arise alternately from the rhizome. The leaves branch dichotomously (always into two) and new branches arise at the fork of the branch. Sexually mature fronds have green sori on the underside of the leaflets. Resam is notorious for its fast growth in disturbed areas, and is important in the succession of such areas. Rhizomes can act to prevent erosion and restore nutrients to the soil. However, where resam grows too thick, it is often impossible for other plants to colonize areas where it becomes too dominant. It does well in open areas, as it cannot grow under shade. Saga (Adenanthera pavonina). This tree can grow very large, to 30 m. It has compound bipinnate leaves (divided twice into rows of 6-12 pairs of leaflets) which turn yellow when they are old. Flowers are pale yellow, tiny and inconspicuous. Fruits are curved green pods that become brown, split and twist to release their seeds when they dry at maturity. Seeds are shiny and distinctively red with a hard seed coat. This tree is considered an invasive species that out-competes native plants in some countries although it is commonly planted as an ornamental. Raw seeds are toxic may be eaten when cooked (please do not try this). Smilax/sarsaparilla vine (Smilax bracteata). This species is a conspicuous climbing vine that can be seen from ground level up to the canopy of the trees it climbs. Green stems are covered by stiff brown sharp spines and have coiled tendrils that help them to attach to other plants for support. The oval or heart-shaped leaves arise alternately and have prominent veins that meet at the base and apex of the blade. Flowers and fruits arise in sphere-shaped clusters (umbel) where individual flowers/fruits arise from a singe point on a stalk. When conditions are favourable, Smilax can grow up to the canopy towards sunlight. However, its dense growth can often overshadow its support tree, depriving it of light. Some efforts to control its growth have been undertaken in some of Singapore’s parks. Sendudok (Melastoma malabathricum). A shrub with reddish-brown stems that may grow to 3 m. Pairs of leaves arise opposite each other and grow at right angles to the pair above and below it. Leaves are narrowly elliptic and dark green, with three main veins. Flowers are easily seen due to their bright pinkish-purple petals and yellow (as well as light purple) stamens. Fruits are violet in colour which, when ripe, split open to reveal many tiny seeds. This species’ English common name ("Singapore Rhodedendron") is a misnomer - it is found not only in Singapore, but is distributed from India to Australia. Also it is not a member of the rhododendron family (Ericaceae). It is also considered a keystone species and is pollinated and dispersed by many insects and birds.

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Simpoh air (Dillenia suffruticosa). A common shrub that grows to 5 m, which has large oblong leaves with saw-like margins. Leaves arise alternately from the stem, onto which they attach with a clasping sheath-like stalk, and have one main vein with strong secondary veins found parallel to each other. Flowers are a very showy yellow colour and are only open for a very short time. At maturity, fruits are reddish-pink and split open in several segments in a star shape, each opening to reveal bright red seeds.The leaves of this plant are used to wrap foods such as tempeh (fermented soybean) and rojak. The flowers are “buzz pollinated” meaning that their anthers have to be vibrated at a high frequency, by insects deliberately vibrating their flight muscles, for pollen to be released. Tembusu (Fagraea fragrans). One of the more common trees on Kent Ridge, this tree can grow to 30 m and has a characteristic dark, deeply fissured bark. It has opposite oval-shaped leaves that have tapering tips. It has cream/yellow-coloured flowers with long stamens, which are found in clusters and are sweetly-scented at night (why would it only do this at night? What pollinates these flowers?). Fruits are shiny red berries with many tiny black seeds. Tembusu is considered a commercial timber species with hard, durable wood that is resistant to termites and rot. It is planted at roadsides and in parks. Weaver ant (Oecophylla smaragdina). Lines of these large uniformly orange-red ants are commonly seen marching up and down trunks of trees, as well as along man-made objects like fences, touching antennae when they pass each other. They build nests out of living leaves high up in trees by gluing them together with silk from their larvae. A colony can have several nests, and with some observation you might be able to spot then in the trees on the Ridge. Weaver ants are omnivores that eat other small animals as well as nectar. They can be particularly aggressive, and can inflict painful bites. Some plants (sea hibiscus) and animals (caterpillars) attract these ants by secreting sweet substances and so are protected by their aggressive nature from herbivores and predators. Weaver ant eggs and adults are also eaten in some Southeast Asian cuisines. White-leaved fig (Ficus grossularioides). The most common fig on Kent Ridge, this species is a shrub or small tree that grows to around 9 m. When cut, this plant will exude white latex. It has alternate leaves that are very variable in shape. The blade can be entire (no lobes) or have up to 5 pointed lobes. The underside of the leaves is white, giving the plant its common name. On the stems, you will find round yellow fruit-like structures without stalks called syconia. A fig syconium is a fleshy hollow structure that encloses numerous tiny flowers that will never see the light of day (how are figs pollinated?). When the flowers are pollinated, the syconia ripen and are the fig “fruits”. Many figs are edible, including this species, and others are farmed for commercial foods (such as Fig Newtons). Because they fruit throughout the year, figs are an important food source for vertebrates, and are considered keystone species in tropical forests. Fauna Black-naped oriole (Oriolus chinensis). Medium-sized (27 cm) birds that are easily identified because of their bright yellow colouration, orioles are conspicuous when they fly between trees. Males and females are similar, with a pink bill and black mask across the eyes and the nape. Wings and tail are also black, eyes red and feet grey. Their common call is a melodious descending whistle. They are omnivorous, taking fruit as well as small animals. Carpenter bee (Xylocopa sp.). Large and heavy, resemble bumble bees but for hairless abdomens and a shiny black spot on their back. Cicada (Family Homoptera). Large, noisy sap-sucking insects often heard and rarely seen in the forest. Pink-necked green pigeon (Treron vernans). These medium-sized (25 cm) pigeons are often seen feeding at fruiting trees at the ridge in groups. Males have a mostly grey head with a pinkish upper neck nape and neck, orange breast and green back. Females are like the male but are have a more uniformly green-grey head and breast. Both have a yellow wing stripe and black tips on their wings and tail, as well as red legs. They seldom come to the ground and feed most actively in the early morning.

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Weaver ant (Oecophylla smaragdina). Lines of these large uniformly orange-red ants are commonly seen marching up and down trunks of trees, as well as along man-made objects like fences, touching antennae when they pass each other. They build nests out of living leaves high up in trees by gluing them together with silk from their larvae. A colony can have several nests, and with some observation you might be able to spot then in the trees on the Ridge. Weaver ants are omnivores that eat other small animals as well as nectar. They can be particularly aggressive, and can inflict painful bites. Some plants (sea hibiscus) and animals (caterpillars) attract these ants by secreting sweet substances and so are protected by their aggressive nature from herbivores and predators. Weaver ant eggs and adults are also eaten in some Southeast Asian cuisines. White-crested laughing thrush (Garrulax leucolophus). These very charismatic, social birds are unmistakable. They have a white head with a prominent crest and a black mask. Their throat, breast and belly are white while the rest of the body is a brown chestnut colour. Eyes and feet are black. At Kent Ridge, they are seen moving in pairs or as a small group, sounding off their loud raucous laughing calls. They often stick to the understory, although they are sometimes seen hopping down the road. Males and females have similar colouration. This species is not native to Singapore, and are believed to have escaped and established in the wild. Yellow-vented bulbul (Pycnonotus goiavier). A small (20 cm) bird that has a white face with a black band in front of the eyes and a black bill. It has a slight crest that’s brown in colour. Upperparts are brown, underparts are white streaked with brown. They have yellow undertail coverts near the vent (thus its common name) while the tail feathers are brown. Eyes and feet are black and both males and females have the same colouration. They have a general diet of fruits and insects, and may often be seen at fruiting trees. They have adjusted well to humans and are one of the most common birds in Singapore.

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