Biodiversity Gardens Capacity Building Workshop

Native Trees by Adam Kamal

from Biodiversity Gardens Capacity Building Workshop with Adam Kamal, TRCRC (Project Consultant)

Adam Kamal is a conservation biologist working with Tropical Rainforest Conservation and Research Centre (TRCRC). To him, conservation is an interdisciplinary science that require experts from different backgrounds.

History of wilderness in Peninsular Malaysia

The history of wilderness starts out with a very long period of stability, that lasted for around 150 million years, and is followed by a short period of time of tragic land-use. Looking at the Malaysian rainforest, it is a wonderfully diverse and complex ecosystem. 2,830 tree species are found in several different ecosystems in Malaysia. The main ecosystem is the lowland dipterocarp forest which once blanketed 69% of Peninsular Malaysia.

However, the extent of forest cover is not the same today. So, what happened to the wilderness?

Land use in recent history has been a series of chaotic and turbulent events. The original 69% of lowland dipterocarp forest has now shrunk to a mere 28% and only 6.8% of primary rainforest (undisturbed) still exists. Aside from protected forests in Royal Belum State Park, Taman Negara and Endau Rompin, the rest of the original forest cover is in some sort of flux as we extract resources from the forest. Conservation biology is about finding the balance in the use of those resources, which is an incredibly complex endeavour given the ecology of these forests.    

In response to emerging demands for sustainable forest management, the logging industry has started to adopt more holistic practices in logging. A lot of these practices originate from temperate countries. For example, selective timber management in which loggers remove certain patches of the forest, with the assumption that the cleared area will recover quickly by itself. However, the lowland dipterocarp forest is very different from the temperate forest because of its long period of stability and evolutionary history.  Over millions of years, tropical rainforests developed a very interesting disturbance regime by which the natural cycle of death and growth occurs.

The tropical rainforest regenerates by having a canopy-gap regime. There are trees which thrive for hundreds of years or even up to thousands of years; for example, the Borneo Ironwood (Eusideroxylon zwageri) and chengal (Neobalanocarpus) tree. While these emergent trees tower over the rest of the forest, there are lots of smaller trees in the understory, waiting for an opportunity to shoot up. When the emergent trees experience destructive events (for example, a lightning strike or termite attack) and fall, a gap will form and allow sunlight and water to penetrate. The understory trees will then compete and grow to become the new emergent trees. 

The understory trees that wait for opportunity to shoot up. Photo by Goh Shang Ming

But, when we chop away many trees at once, we kill off all understory trees that could have grown to fill the canopy gap. We also disturb the soil. When the patch of cleared area is very big or is far from a source of new seeds, the soil is left without cover. This will cause the land to dry up and after being exposed to the sun for too long, the soil will become poor, laterite soil. Also, when it rains, the rainwater will result in a severe leaching effect: all the resources and nutrients that were held within the soil will get washed away. It takes a long time to turn the bare, laterite soil into a secondary forest or belukar. The transition could take ten years or more, not to mention the time needed to form a primary forest.  

The regeneration of forests depends largely on underground seed banks. Almost all seeds are recalcitrant, that is, they do not tolerate drying and freezing, or are difficult to germinate. Few are able to germinate and get big, because the seeds are also easily attacked by fungus and fruit-eating animals or crushed by animals or human. When there are no seeds in the soil, other fast-growing plants will invade the forest. The False Bracket Fern (Dicranopteris linearis) is a notorious example. This plant can spread and dominate in a cleared forest, and modify the environment so that it can continue to thrive. As a result, the forest is kept from re-establishing, or becomes degraded as the trees are no longer able to grow successfully.

History of urban landscaping in Malaysia

Since we have lost so much of our forest, one of the ways of recovering them is bringing these forest species to our concrete jungle. This did not happen in the past since urban landscaping in Malaysia has historically focused on the aesthetic qualities of trees. This is reflected in the design of gardens, parks, streets, etc that we have today.

There are three main phases in the history of urban tree planting development that start all the way back in the era prior to independence.

Phase 1: The Colonial Era

The British chose some interesting trees to plant. They brought in the Angsana (Pterocarpus indicus), a gorgeous legume tree with a beautiful papery bark. However, this species was propagated and planted everywhere using stem cuttings from a few parent trees, resulting in little genetic diversity among the trees. As a result, the tree populations were vulnerable to attacks by pests such as Neolithocolletis pentadesma, the Angsana leaf miner, and pathogens like the fungus Fusarium oxysporum.  Fusarium oxysporum was behind the Fusarium Wilt epidemic which wiped out a lot of Angsana trees. Their popularity faded in the 1990s.

This would have been a great time to replace the Angsana with other rainforest trees. However, this did not happen. Many native trees were planted in the 1920s and 1930s, but not the rainforest species. Instead, a lot of the selected trees were coastal species. These trees are tough. They can tolerate salt, strong winds and unfavourable weather. Hence, they require little maintenance. Some of the most common species included Kelat jambu (Syzigium grande), Tulang daing (Callerya atropurpurea), and yellow flame (Peltophorum pterocarpum). These tree species are still popular and you can see them almost everywhere on the road today.

Later, landscapers started introducing other, non-native tree species as well. Some examples of the species are Cassia fistula, Swietenia macrophylla, and Khaya senegalensis. The last two species are known as mahogany trees, and are very common in Malaysia. These non-native trees were planted with the intention of quickening the revegetation process in harsh urban areas. However, they do cause some problems, especially Khaya senegalensis, because of their root systems. Since the tree roots are not well adapted to the thin tropical soils, they tend to fall easily.

The British also established public parks and botanical gardens in cities. Taiping Lake Gardens, Kuala Lumpur Lake Garden and Penang Botanical Garden are some of the historical gardens that were built during the colonial era. These green spaces served as recreation sites for the public. However, they were often landscaped to be primarily of aesthetic value.

Phase 2: Dawn of greening programs

A transition came about after Malaysia’s independence. The initial program ‘‘No Road Without Trees’’ was developed to bring greenery into cities via extensive tree planting and landscaping along the roadsides. Again, the trees were selected for their aesthetic values. Some examples include Angsana, mahogany, Samanea saman, Cinnamomum iners, Delonix regia, Mimusop elengi, Lagerstroemia specios. Some of these trees are non-native, while the native ones are either coastal or belukar (secondary vegetation) species.

The City Hall classified five areas of interest in the tree planting program:

  • roadside planting
  • planting in public parks and open spaces
  • planting along highways and expressway
  • planting within industrial areas & housing estates
  • planting or landscaping within major developments in the city center

Some tree selections, for example, the teak trees (Tectona grandis) along highways may not have been good choices as these trees do not grow well in such environments, and thus are not suitable for highway planting.

Phase 3: Towards a Garden Nation

This development program is a good start to bringing back forest species. There have been laws and guidelines made since 1995, such as the Tree Preservation Order from the Town and Country Planning Act, 1995, and the National Landscape Guidelines leading to this program. The program involved not only governmental agencies but also private sectors and the public. Tree-planting activities have been carried out nationwide.

Issues and Challenges

The emphasis on landscape aesthetic in plant selection results in neglect of native forest species. Also, Tree Preservation Act is poorly enforced. Some roadside trees are damaged by vehicles or construction equipment. The trees may not die immediately, but they slowly decline and eventually fall.

Improper pruning and care is another factor that causes tree mortality when citizens and tree planters lack adequate knowledge in tree maintenance.

Biology of Native Trees

To understand the trees in Malaysia, we have to learn about their growth habits and relationships with other organisms. The Tropical Rainforest Conservation and Research Centre (TRCRC) focuses on dipterocarp trees. These trees normally have a gigantic structure. They have unique branching and leaf patterns. They also have interesting relationships with members of the same species and with other species, especially fungus.

There is a type of fungus known as mycorrhizal fungus which develops a two-way relationship with the dipterocarp trees. As the trees shed leaves and provide shade, the soil underneath remains moist and cool. Such soil conditions promote proliferation of mycorrhizal fungi. The fungi reside on the root surface or within the root cells of dipterocarp trees. They absorb any available nutrients from the surrounding soil and send the nutrients to the trees. In return, the trees pay with sugars that they produce during photosynthesis.

When we want to bring native trees to our cities, we have to consider the relationships of these trees with other organisms in their original habitat. The existence of these mutualistic partners is crucial for the survival and development of the trees.

Dipterocarps also establish stratified relationships with other tree species in the forest. Each of them occupies a specific position in a forest. They are either:

  • emergent trees,
  • main canopy stratum, or
  • lower layer

The lower layer comprises shade-tolerant trees and saplings of the emergent trees and main stratum. The seeds that successfully germinate grow into small trees of around 1 to 2 metres. They will be at the lower layer until there is a canopy gap to fill up. When we go into secondary forests, we can sometimes see post-logging remnant trees. 20 years later, the initially 2 metre remnants grow into 30 m gigantic, mature emergent trees.

There are many species present at the lower layer of primary rainforest. Some of them belong to families like Annonaceae, Euphorbiaceae, Flacourtiaceae, Melastomataceae, and Rubiaceae. However, the dominant species are palms and bamboos. In belukar forest, where there is a general lack of shading from an upper story layer, these palm climbers receive plenty of sunlight and grow abundantly.

The height of the main canopy stratum is around 36 m. This layer forms a green blanket over the soil. The trees at the main stratum come from a variety of families, for example, Burseraceae, Guttiferae, Myristicaceae, Myrtaceae (particularly Syzygium), and Sapotaceae.

The emergent layer is up to 70 m tall and half of the trees at this layer are dipterocarps. Once a tree secures a suitable place to grow, it will keep its saplings around this particular spot as there are already beneficial underground microorganisms that can support tree growth. There are also trees from other families such as Dyera costulata from the Apocynaceae family, Koompassia malaccensis from the Leguminosae family, etc.

Since a forest consists of multiple layers and species, arranging plants in a similar way will make green spaces look more natural. This is a point to consider when planning the green spaces of a city.

As we walk in the city, we always see tree roots that are physically damaged. The roots spread out and cause cracks, punctures etc. This is because tropical soils are fairly poor in nutrients. The cycling and retention of nutrients take place on top of the soil. Therefore, the roots of tropical trees, for example, dipterocarps, do not normally grow beyond 2 metres deep. However, they extend their lateral roots up to 10 metres around the tree to search for nutrients. In bringing in these tropical trees into our urban environment, we need to consider their rooting strategy and figure out ways to prevent potential damage of infrastructure.

On the other hand, legume trees have root nodules that house nitrogen-fixing microorganisms. These microbes help to convert the atmospheric nitrogen into more usable form. Therefore, legume trees are good for mediating poor soil and increasing nutrient availability.

The two important microclimate requirements for nutrient cycling in tropical soils are the presence of duff (leaf litter) cover and shading provided by trees. The fallen leaves regulate soil temperature and humidity, thus promoting growth of fungi and bacteria, soil microbes. In turn, these soil microbes help to decompose dead organic matter in soil and recycle the nutrients. Also, the leaves prevent rainwater from washing away the nutrients and sending them straight to the river.

When we plant trees, we also need to think of creating habitats for both plants and animals. Natural layers and clumping of species are needed, as many rainforest trees tend to grow close to one another. As ecosystem engineers, they create conditions that are perfect for their growth. It makes no sense to have spacing among trees as it does not appear natural, nor does it allow trees to function as they do in natural environments. We need that entropy (randomness) to make a forest a forest.

Tree diversity is important in sustaining wildlife. We need to have a variety of trees that provide different functions. For example, trees for perching and hiding, fruit trees, nectar-producing trees, trees that provide nesting materials, etc.


  1. Strategic planting

In designing public parks or gardens, we can allocate some spaces for dense vegetation that mimics forest diversity and complexity. In between those, we can still have our picnic areas and neatly arranged ornamental trees, preferably the native species. We also need to support stakeholders such as the National Landscape Department, as they are driving for the use of native trees in landscaping efforts. This can be done by appreciating local species and recognising their importance as part of the natural history and identity of this nation. Other stakeholders, for example, Forest Research Institute Malaysia (FRIM) are also developing helpful resources such as lists of indigenous species which would be suitable for growing in an urban environment.

  • Infrastructure solutions

We need to develop infrastructure solutions to fit the complexity of these forest species. The evolution of trees occurs in populations over generations. If we want to use the urban environment to conserve Malaysia’s native species, we need to be able to adapt to them; for example, the design of built surfaces that allow for root growth. This is where interdisciplinary support is needed to find the best way of coexisting with native forest species.

  • Training urban foresters/arborists

We have to invest in professional urban foresters, arborists and horticulturists. These professions are popular in other countries. Yet, they receive little attention in Malaysia. Without enough professionals, the trees often suffer from excessive pruning and end up dying.

  • Allow nature to exist

Stop raking everything. The wild grasses, thick layers of fallen leaves, large dead trees are integral for natural processes to occur. These dead organic materials contribute to the survival of trees and other wildlife.

Important stakeholders

  1. National Landscape Department (JLN)

JLN provides guidelines on landscape planning and design, planting form, crop selection and landscape reserves requirement. It drives the implementation of National Landscape Policy (Garis Panduan Landskap) which aimed to turn Malaysia into a “Beautiful Garden Nation” by 2020. It has a good focus on preservation and conservation of natural resources, including our native species. However, JLN does not have the main control on tree planting, as the trees actually belong to the states.

  •  State policy

Here, we focus on the Kuala Lumpur City Hall or “DBKL”. The city hall owns the trees. We definitely need its support in order to incorporate native species and green spaces when designing urban landscapes.  Kuala Lumpur Structure Plan is a good example of a plan that proposed an ecological design framework for Kuala Lumpur’s urban landscapes.

3. Private sector

Greening efforts require the commitment of the private sector as well. For example, Sime Darby Property has collaborated with TRCRC to operate the Elmina Rainforest Knowledge Centre (ERKC), which focuses on environmental education, research and development, eco-tourism and other green activities. Also, Sime Darby Property published the Malaysian Threatened and Rare Tree Identification and Landscape Guideline, which provides information for landscape architects, students and others to identify tree species, understand their growth form, aesthetic value and environmental needs.

4. Community/NGO

There are many organisations that contribute to conservation and urban greening. Some of the examples include TRCRC, Malaysian Nature Society (MNS) and Free Tree Society (FTS). Every organisation has its own way of promoting conservation. Some offer their experiences and expertise, while others engage with the public to create awareness.

5. Individual

We can start planting trees. Also, record observations and contribute your data to citizen science platforms such as iNaturalist. This will help to gather information of forest species and improve conservation effort. Individually, we may not be able to do much, but together we can create pressure to drive changes. As we bring in the native trees, we make our cities repositories of seeds and diversity.

Further reading:

This article is supported by The Habitat Foundation Conservation Grant

You can watch the entire session here.

By ShangMing

A plant lover. I like small, medium, gigantic, ordinary, exotic, local, foreign plants. Just because they thrive to stand out.