20 November 2000


Vital Peaks
On Thailand's highest mountains life begins-they're home to the last remaining forest systems and the birthplace of rivers, and ultimately the balance needed for all living things to flourish

Pannachai Kongsanit

What would Thailand be like if the entire Kingdom was flat? Very different, of course. And one very likely possibility is that there wouldn't be even a single patch of forest left in this country. The truth is this: Mountains are one of nature's final strongholds. These days, forests survive mostly on, and around, these rugged terrains, without which what are now national parks and wildlife sanctuaries would have long been turned into farmlands and human settlements.

Hill evergreen forest on top of Doi Inthanon.

Viewed from a distance, these upland greenery seem pretty much the same. But once you're actually up there, you can almost say that each peak is a different world. Let's take a quick look at some of Thailand's most prominent summits, starting from the highest-Doi Inthanon in Chiang Mai province.

Measuring 2,565 metres above mean sea level, the mighty Doi Inthanon-the core of a national park of the same name-is crowned with a lush hill evergreen forest. The relatively thick topsoil on the granite mountain provides a good foothold for large trees which form a vast and dense canopy that is highly efficient in trapping moisture from the air. The peak is thus so moist and cool that tree trunks and branches are shrouded with mosses, ferns and other epiphytes.

It's undeniable that Doi Inthanon plays an important role in water catchment-it is the origin of several streams and waterfalls. Many of these streams are tributaries of the Ping River, which drains into the Chao Phraya.

Mountains form the core of most national parks and wildlife sanctuaries.

A similar forest thrives on the second highest summit-the 2,285-metre-high Doi Phahom Pok. However, the situation on this mountain, which is a part of the Mae Fang National Park, is not quite the same-much of the original forest has been thoughtlessly stripped off the mountain to make way for highland agriculture. The destruction of Doi Phahom Pok serves as a warning of what may finally happen at Doi Inthanon, unless the ongoing, sporadic encroachments by both farming and state projects are stopped.

As far as height is concerned, the second runner-up is Doi Luang Chiang Dao, which towers at 2,195 metres. The mountain, together with the forest around it, is a designated wildlife sanctuary.

Like the first two peaks, Doi Luang Chiang Dao is also in Chiang Mai, but the similarity seems to end there. This mountain is not made up of igneous rock but limestone, which explains its distinctively ragged top.

Being highly susceptible to weathering by carbonic acid, which is formed when rainwater is mixed with carbon dioxide in the air, the only places on the limestone mountain where soil can accumulate and where trees can firmly take root are in valleys between the jagged ridges.

Up on the wind-blown tops of Doi Luang Chiang Dao only grass and small herbs that do not require much water survive. Lower down, stands of pine trees, dry evergreen forest, mixed deciduous forest, and dry dipterocarp (a forest where most of the trees are deciduous) forest cover the hillsides, from higher to lower altitudes.

Several other mountains in Thailand are flat-backed. One of them is the Phu Soi Dao which straddles the Thai-Laotian border in Uttaradit province. The peak is the main feature of Phu Soi Dao national park.

The flat part of the mountain, which is covered with meadows and pine trees, is 1,800 metres high; the actual peak of the mountain, which stands in the Laotian side, rises to an altitude of 2,120 metres.

Just off the flat top, vegetation on the moist mountainside changes drastically into lush hill evergreen and dry evergreen forests, with mixed deciduous forests in some areas.

The flat upland of Phu Soi Dao is the beginning of the stream that flows down the slope to feed the Phu Soi Dao Waterfall at the base of the mountain, and two smaller streams which run into Laos. From the amount of water that cascades down the Phu Soi Dao waterfall, it is obvious that forested mountains are efficient at water catchment, no matter which types of forest they sustain. What really matters is the fact that the forest should be large enough to perform this natural function.

The most popular flat-backed mountain, however, is Phu Kradueng in Loei province. Like Phu Soi Dao, the wilderness on the top of Phu Kradueng lies on a bed of sandstone, which produces thin layers of sandy soil. Therefore, as on Phu Soi Dao, the levelled highland of this national park is blessed with biologically diverse meadows which intersperse with stands of oaks and pine trees.

Pha Taem National Park, which is separated from the forest of Laos by the Mekong River.

However, because it is much larger, the highland of Phu Kradeung is able to sustain more water than that of Phu Soi Dao. Up on Phu Kradueng streams never run dry. Besides, there are even wetlands on the flat mountain top.

In the valley that forms a long, large crack at the heart of Phu Kradueng, a healthy dry evergreen forest is harboured. In addition, the mountain supports different kinds of forest on its slopes-from dry evergreen forests at the foot of the mountain to dry dipterocarp and mixed deciduous forests and to hill evergreen forests at higher altitudes.

Standing not so far from Phu Kradueng and even sharing a similar geological structure is Phu Luang.

Phu Luang, a natural herbarium.

However, the composition of flora on the flat back of this mountain is much richer than that of its neighbour. Pine trees are not so prominent in this wildlife sanctuary, but the flat-topped peak boasts a rich variety of herbs and shrubs.

There are also patches of dry evergreen forest, grassland and bamboo groves up there. In addition, various species of ground and epiphytic orchids are also a common sight.

Other than Phu Kradueng and Phu Luang, the Northeastern region does not feature many other high mountains. Some forested areas-like Pha Taem and Phu Jong Na Yoy national parks in Ubon Ratchathani, for example-are just 500 to 600 metres above mean sea level.

However, if you stand on the steep eastern edges of these parks, which overlook the low-lying forests of Laos (in the case of Pha Taem) and Cambodia (in the case of Phu Jong Na Yoy), you'd say you're standing on a mountain.

Pine-studded meadow on Phu Soi Dao.

With sandstone as their geological base, these two Thai forests are mainly dry dipterocarps, in which trees are not as dense as in the lowland evergreen forests on the plains on the other side of the border. With dominant trees shedding their leaves in dry months, the dry dipterocarp forests may seem lifeless much of the year. But once rains arrive the entire parks spring back to life-with the trees sporting new leaves and the ground covered with a variety of fascinating plants and wild flowers.

Seasonal changes are not as remarkable in the forests of the Central region. Take Khao Yai, for instance.

The park-which comprises several mountains, among which the 1,350-metre-high Khao Rom ranks first in terms of height-shelters mostly dry evergreen forest, with some mixed deciduous forests, grasslands and a few patches of hill evergreen forest and dry dipterocarp forest.

The jagged peak of Doi Luang Chiang Dao.

Also very effective at water catchment, the mountains of Khao Yai are the sources of dozens of streams and rivers, feeding the five provinces that surround the park as well as provinces beyond.

The forest's large size also enables it to act as a climate controller. Supposing Khao Yai was wiped out, it would be possible that the average temperature in Bangkok and in the entire Central region would rise. The rugged western side of the country is home to several connecting national parks and wildlife sanctuaries, which when combined with the forests of Burma across the border, form a very large complex of tropical forests.

In lowland areas, the dominant type of forest is mixed deciduous forest with some small patches of dry dipterocarp forest. On highlands, dry evergreen forest and moist evergreen forest are common.

The peak of Khao Luang in Prachuap Khiri Khan province is one of the highest in the lower part of the western region, measuring at 1,251 metres. Much of the peak, which is part of the Tanao Si range, is covered with dry evergreen forest. On its misty top, trees are shrouded with epiphytes like those on Doi Inthanon in the North.

Meanwhile, in the South-the region that enjoys a longer period of rainfall than the rest of the country-a good example of forest-covered mountain is Khao Luang in Nakhon Si Thammarat province. Towering at 1,835 metres, the peak supports a hill evergreen forest no less healthy than that on Doi Inthanon. However, the biologically diverse woodland on Khao Luang does not suffer as much human interference as Doi Inthanon.

The natural forest is surrounded by rubber plantations and fruit orchards that help increase the amount of green area and, in turn, the ability to hold moisture in the soil.

Of course, there are several other forest-harbouring mountains not mentioned here. And its not just the forests that owe their survival to the mountains, but also the wild animals that dwell there-and us humans, the beneficiaries of the natural ecosystems.

Copyright The Post Publishing Public Co., Ltd. 2000