Ever wondered what would natural superpowers look like? I was delighted to witness some exhibited by the tropical lowland rainforest plants during my GE4224 Fieldtrip. Under the guidance of Dr Gretchen, we visited the Learning Forest located in the UNESCO World Heritage-listed Singapore Botanical Gardens on 12th February 2022. This area was slated for restoration as part of the larger Tyersall-Gallop Core and adopts a framework species reforestation method where the existing non-native rubber trees support the growth of native trees before the former is removed from the area upon substantial restoration.

Our minds often focus on the animals whenever we think about nature with plants mostly taking the backseat. Surprisingly, plants are also actively evolving and adapting to their environment by developing ‘superpowers’. One of the adaptions you can observe right away is at the base of the trees in the Learning Forest. The moment you enter the Learning Forest, you will notice the shade provided by trees towering at about 25-40 m, with their crowns interlocking to form the canopy layer. Some trees, standing at 40-65 m, will emerge taller from this canopy layer and form the so-called emergent layer. To support their enormous weight, they grow buttress roots (Figure 1) which are large, wide roots at the base of these tall trees that anchor and prevent them from toppling over no matter how tall they grow. This superpower enables visitors to enjoy a cool and shaded walk through the Learning Forest, which is a nice respite from the glazing sun!

Figure 1: Buttress roots of a native Tembusu Tree (Cyrtophyllum fragrans) [IUCN Status: Least Concern] found in the Learning Forest that was at least 1.5 m tall and 2 m wide (Source: Mohamed Ridzuan, 12/02/2022)

However, this thick canopy provides an additional challenge for young trees and shrubs in the understory layer, which is found right under the canopy layer. They are not able to receive much sunlight since most of it is blocked by the canopy. Here comes the second adaption I observed: large leaves. Plants like the Vanuatu Fan Palm (Licuala grandis) grow huge leaves (Figure 2) to maximise the surface area available to capture light crucial for photosynthesis.

 

Figure 2: Large (about 40-50 cm) fan-like leaves of the non-native Vanuatu Fan Palm (Licuala grandis) found in the understory layer of the Learning Forest (Source: Adriana Chan, 12/02/2022)

With leaves being an integral part of the food production mechanism in plants, this leads to some interesting interactions with the wildlife, especially herbivores, in the rainforest. Since herbivores rely on leaves as their main food source, some plants have developed spiny bark (Figure 3) as a defence mechanism to prevent these animals from climbing up the trunk to get to the leaves. Additionally, this superpower also protects the inner bark and fruits from potential damage.

Figure 3: Spiny bark of a regionally-native Salak/Snake fruit tree (Salacca zalacca) that prevents animals from climbing it (Source: Mohamed Ridzuan, 12/02/2022)

 

Figure 4: A map indicating Singapore’s primeval vegetation coverage (Source: Corlett, 1991)

Restoring sites like the Learning Forest is crucial in Singapore. Tropical lowland rainforests used to cover more than 70% of the land here and have a huge plant diversity since it was part of Tropical East Asia. However, primary forests with trees over 100 years old, make up less than 0.3% of our land area today. Hence, we ought to conserve our remaining primary forests and restore new secondary forests. Only then can we continue to preserve these natural superpowers rainforest plants possess, some of which serve to our benefit as well!

 

Your friendly neighbourhood Geographer,
Mohamed Ridzuan

~ P.S: Special thanks to Dr Gretchen and her team of student volunteers for organising the GE4224 fieldtrip with the support of the NUS Geography Department.