Rainforest Journal

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Lower montane rainforest


In tropical regions, lower montane forest refers to the rainforest on mountain slopes that are distinctly different from the lowland rainforest that covers the plains, flatlands, and low hills. Generally, this forest formation can be considered an intermediate zone between the montane cloud forest located at much higher altitudes, generally above the persistent cloud zone, and the tall evergreen rainforest of the lowlands.

In Peninsular Malaysia, lower montane forest is most developed and distinct on the main granitic mountain ranges, such as the Titiwangsa, Bintang, and East Coast mountain ranges. Lower montane forest can be classified into two kinds, the oak-laurel type, and the upper (hill) dipterocarp type. The upper hill dipterocarp/lower montane forest type is basically an extension of the hill dipterocarp forest, but with the absence of the common hill dipterocarp, Shorea curtisii. Instead, the dipterocarps that predominate include montane dipterocarps like Shorea platyclados, Shorea ciliata, Dipterocarpus retusus, and Shorea ovata, which are all capable of large size.

lower montane forest

Lower montane rainforest, as seen from the Main Range of Malaysia, at roughly 1200 meters elevation.

upper hill dipterocarp

Upper hill dipterocarp forest (at roughly 900m elevation here) is a type of montane forest as well, but resembles lowland rainforest in many ways. The huge central tree is Shorea platyclados.

Shorea platyclados can grow to enormous dimensions. One of the biggest trees in Malaysia is in fact, a Shorea platyclados (Meranti bukit in Malay) somewhere in south Kelantan, with a diameter of around 4 m! In valleys/depressions on the granitic mountains where the soil is deep, these mountain dipterocarp trees are a spectacular sight, with their branches and trunks always cloaked in a dense, thick layer of epiphytes and orchids, and their crowns poking high up from the gullies below, sometimes 50-60 meters tall.

upper dipterocarp forest interior

Inside upper (hill) dipterocarp forest, which does still look a lot like lowland dipterocarp forest.

The upper dipterocarp forest normally begins at altitudes above 800m ASL, and continues until conditions get too cold for even these dipterocarps to survive. Oak-laurel /lower montane forest dominated by trees of Fagaceae and Lauraceae then take over above altitudes of 1200m ASL (or on exposed slopes and ridges slightly lower down). This forest has a lower canopy compared to the upper hill dipterocarp forest, and is significantly lower than lowland forest; normally not exceeding 35 m in height. Podocarpus, Syzygium, Eugenia, and Calophyllum species become common here.

oak laurel montane forest

Oak laurel montane forest is another type of lower montane forest which normally begins around 1200m altitude on the main mountain ranges of Peninsular Malaysia.

It’s believed that the oak laurel zone of the lower montane forest develops partly due to the increasing presence of peat. Peat is basically plant matter that is not fully decomposed. At altitudes above 1200m, clouds are more or less a constant feature, the soil is often waterlogged, and many decomposers of plant matter like termites, and many types of fungi, no longer exist. Earthworms and beetles replace the termites as the main detritivores but they are not as efficient as the termites in recycling back plant matter. Therefore, a lot of fallen leaves and branches take longer to decay fully. This is why peat starts accumulating, increasing with altitude. The seedlings of montane dipterocarps are unable to establish in such peaty soil, thus they cease to grow higher up. Instead, species from the familes Fagaceae and Lauraceae are the dominant trees here.

lower montane oak laurel forest

Looking into the oak laurel montane forest, and it’s immediately clear why it differs from forest dominated by dipterocarp trees; trees are shorter and smaller here. The big fern on the right is a oak leaf fern (Drynaria quercifolia).

oak laurel forest understory

Another look at the interior of oak laurel montane forest, this time from ground or understory level.

The oak-laurel montane forest is also distinctive from the upper dipterocarp forest not just because the big dipterocarp trees are absent, but if you notice, the trunks of the trees are always covered in lichens and moss of some sort, which give the appearance of speckled tree trunks everywhere. The lower canopy allows slightly more sunlight to penetrate, thus allowing a proliferation of climbers and undergrowth (ferns, palms, herbs, and gingers). The change from upper hill dipterocarp to oak-laurel forest is a gradual one, with dipterocarps being phased out slowly, the higher the ascent.

big tree in oak laurel montane forest

Looking up a tall tree in oak laurel montane forest. Trees rarely exceed 35m in height here, as the dipterocarps are absent.

Taken as a whole, lower montane forest can be considered as the forest that grows between 800-1500m altitudes on the main granitic mountain ranges of Peninsular Malaysia. On higher mountains above 1500m or on isolated peaks near the coast, upper montane forest occurs (sometimes called montane cloud/mossy forest), which is another distinct forest formation, but this is not the subject of our post today. I mention “granitic” mountain ranges, because on mountains comprising sedimentary/sandstone bedrock, the lower montane zone is noticeably undeveloped, most likely due to shallow and less fertile soil.

On poor or shallow soil, sharp transitions occur. On the Gunung Tahan massif, the hill dipterocarp forest changes into oak-laurel forest almost abruptly, and upper montane forest already appears well below 1500m altitude. This is probably due to substrate factors; the Tahan range being composed of sedimentary/sandstone bedrock, which typically weather into soils that are shallow and less fertile.

Gunung Benom, on the other hand, is a mountain of similar height, but being granitic, it has much deeper, fertile soil, permitting development of the upper hill dipterocarp zone (lower montane ecotone), as mentioned earlier. On Gunung Kinabalu in Borneo (including the neighboring Crocker Range), which are both granitic, the story is similar – a gradual transition into low stature mossy forest from lower montane forest. However, most of Borneo does not have the same tall upper dipterocarp forest that is common in Peninsular Malaysia mainly due to most of the highlands there being sedimentary or sandstone in nature (which give rise to shallow, poor soil).

giant mountain fishtail palm

Giant mountain fishtail palm (Caryota maxima), heavy laden with fruits. These palms are very common in the hill ranges of Peninsular Malaysia.

arudina graminifolia

The lovely Bamboo Orchid (Arudina graminifolia) is a terrestrial orchid, growing in exposed areas in the highlands.

A rarer type of lower montane forest in Peninsular Malaysia (but common in Borneo) is the type where the Malayan Kauris, Agathis borneensis and Agathis dammara are common or dominant. In the Peninsular, Agathis dominated montane forest is common on sandstone-shale mountains such as Gunung Jerai and Gunung Tahan, but not as common elsewhere. In Borneo, where sandstone and shale is the dominant geological characteristic, such Agathis forest is common, often developing in conjunction with heath forest, or Kerangas forest, a kind of stunted rainforest that grows on very poor soil. As you can imagine, Kerangas forest shares a number of species in common with montane species.

Curiously, within the lower montane and upper montane forests, stunted zones are a common feature on exposed slopes or ridgetops. On exposed areas, a short, stunted version grows, but on saddles, gullies, and sheltered slopes, the taller “normal” version grows. Yet in both lower and upper montane forest, both stunted and developed zones are basically the same, species-wise. So apparently, these montane flora grow stunted when conditions are not so ideal, and develop larger dimensions under more ideal conditions. These different variations in the forest are more apparent when viewed from above.

moss covered tree trunk

Moss grows everywhere in the cool, moist montane environment. There are numerous species of moss in tropical montane forest.

pogonatum species of moss

A large species of moss, possibly Pogonatum cirratum, found growing in montane forest.

All things said, the first thing that anyone will notice in montane forest is the presence of – moss. Moss covers the buttresses, roots, fallen trunks and rocks. The higher one goes, the more moss will appear, Leucobryum genera for example, being common. Also, everywhere you look, the branches of the tall trees all wear a thick layer of epiphytes, especially orchids and ferns. The undergrowth now appears different, and a somewhat different “montane” variety of palms now smother the understory; one of the most common being species from the genus Pinanga, while Caryota and Licuala species are also usually present. Meanwhile, wild gingers can be seen in the undergrowth, literally everywhere. Tree ferns are also extremely common, sprouting up in more exposed areas, alongside the Giant Mountain Fishtail Palm (Caryota maxima).

rainforest ginger

Ginger plants are extremely common in montane forests. Some species can grow 4-5 meters tall.

wild ginger flower

Striking red color of a wild ginger flower. Many rainforest gingers have showy flowers.

pinanga malaiana

Pinanga malaiana, a small, elegant palm encountered in lower montane forest.

ficus auriculata

Ficus auriculata, the Roxburgh fig, whose cauliflorous fruits are devoured by the jungle birds. Often grows near mountain streams.

henckelia quinquevulnera

Henckelia quinquevulnera, a small gesneriad herb formerly grouped under Didymocarpus. Found in hill-montane forest.

Another characteristic of montane forests are pitcher plants. Malaysia is the center of biodiversity for the Nepenthes genera, and there are different varieties growing on different mountains. Nepenthes thrive in the cooler temperatures and relatively poor soils of mountains. In exposed areas, they proliferate, along with ferns like Dipteris conjugata. Overall, the floristic diversity of montane forest is lesser if compared to lowland forest, and decreases the higher you ascend. However, there are also many rare and endemic montane flora which are only found at this altitude zone.

Dipteris conjugata

Dipteris conjugata, a montane fern that commonly grows in exposed clearings in the highlands.

Wildlife in montane forests is not as rich if compared to lowland forests, for the same reason – Decreasing optimal conditions for survival with increasing altitude. When the floristic diversity declines, so does the faunal diversity. Nonetheless, there are many species of birds and animals that have carved a niche in the montane environment, and are not found in the lowlands. Being an intermediate zone between the lowlands and the cloud forests above, lower montane forests are invariably very rich in faunal diversity, and you can expect to find many of the familiar lowland animals/birds still present in them, albeit at lower densities.

cyathea tree ferns

Cyathea tree ferns are very common in the montane highlands. They grow very slowly, but some species can attain over 10 meters in height, like these pictured here. These are probably Cyathea gigantea.

Something noticeable to the keen observer is the slower forest regeneration of montane forests. Due to the slower growth rate of many montane trees, any damage takes much longer to recover. Any gap on mountain slopes is quickly smothered over by thick secondary growth, resam ferns, tree ferns, and thorny rattans, rendering successful recovery impossible, at least for many years or even decades. It is doubtful if heavily logged montane forest can recover, even after a hundred years.

Therefore, montane forest needs to be left alone. In addition to having poor timber, montane forests serve as a refuge for many animals fleeing from mankind in the lowlands, and perform a very essential role in watershed protection, because it is up in the mountains where we draw our water sources from. Yet, logging companies have been moving into montane forests in recent decades, having exhausted virtually all the lowland forests for timber. Soil erosion and landslides like what is happening in the Cameron Highlands region (a slow motion environmental disaster in the making) is the last thing we need.

In Peninsular Malaysia, below is a partial list of easily accessible (lower) montane forest:

  • Gunung Bunga Buah (Genting Highlands) – Summit trail
  • Bukit Larut/Maxwell Hill – Upper Hill dipterocarp/Oak-laurel montane forest
  • Gunung Telapak Buruk – Upper Hill dipterocarp forest
  • Fraser’s Hill – Extensive oak-laurel montane forest; one of the best places to explore.
  • Cameron Highlands – Trail behind The LakeHouse, Ringlet, leads through oak-laurel montane forest

Currently, the montane habitats of the main mountain ranges in Malaysia are still relatively intact, and most are probably classified as Protection Forest Reserves, where logging is supposedly prohibited. Hopefully, this state of affairs continues to be maintained. THE center of montane forest biodiversity in Malaysia (perhaps in the world) is at Gunung Kinabalu, Sabah, where you can spend a whole lifetime and not even scratch the surface of the rich biodiversity that exists there. Gunung Kinabalu has the entire plethora of montane forest habitat, from hill dipterocarp forest (at Poring), all the way up to barren rock at its summit.

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  1. Very informative! JungleBoy, your posts are getting better and better!

    Are the palms in the third photo rattans (e.g. Calamus)?

  2. @ KoutaR
    Those palms are probably Pinanga spp. which are the most abundant types on the rainforest floor. Rattans on the other hand, are climbers.

  3. Thanks! As I was in the Queensland rainforests, I experienced shrub-like Calamus spp. to be common in the understory. Perhaps they remain shrubs if they don’t find a tree to climb. These thorny Calamus shrubs were a major obstacle hindering off-trail hiking. Excellent if they are not so prominent in Malaysia!

  4. @ KoutaR

    In virgin (primary) rainforest, rattans are not usually so thick as to hinder walking through the undergrowth; on the contrary, it is usually quite open and sparse – I’d say rather pleasant to walk through.

  5. is there any literature that this could be cited to

  6. @Mon

    I use multiple resources, as well as my own experience, but you can cite TC Whitmore’s publications, if you must have one.

  7. Thanks for another insightful article!

    I find it fascinating that the distribution of a species can vary widely across different geographical regions, based on a combination of soil and terrain types, as well as rainfall pattern. As you mentioned in your article, while Shorea curtisii is a dominant species in the hill dipterocarp forests of Peninsular Malaysia, it seems to disappear once you get into the lower montane region there. The famed botanist Peter Ashton noted that the situation is quite different in much of Borneo, where S. curtisii is pretty widespread at lower elevations (<200 m ASL in coastal lowland forests).

    Interestingly, in the vast Kayan Mentarang National Park in North Kalimantan, Indonesia, S. curtisii has been observed even in the lower montane region at 1000-1600 m ASL. And in at least some areas of eastern Borneo, it's actually the heavy-hardwood, slow-growing species Shorea laevis (Balau/Bangkirai) that dominates hill ridges much like Shorea curtisii does in Peninsular Malaysia.

  8. @Rex
    Thanks for the info.

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