|Thai Forests > Characteristics of Forests
Thailand is covered by tropical forests that have a wide variety of vegetation. This can be attributed to many factors such as the climate, amount of rainfall, temperature, geography. and soil type. The forests can be divided into 2 major types: evergreen and deciduous.
1. Evergreen Forests
These types of forests are green all year round. The trees shed their leaves and create new ones but do so gradually over the course of the year .The forests do not look different during the different seasons as in the case of the deciduous forests. The evergreen forests are found in all areas of Thailand. They can be divided into four major types based on their characteristics.
Tropical Evergreen Forest
The tropical evergreen forest is found in all areas of Thailand. However, they are found in more abundance in the south and the east especially in Rayong, Chanthaburi and Trad. This is due to the heavy rainfall and high moisture levels. In other areas the tropical evergreen forests are concentrated in pockets of high moisture such as valleys and close to water sources such as rivers, streams and mountains.
A common characteristic of tropical evergreen forest is the appearance of a lush green vegetation all year round. The forest is home to hundreds of species of flora that grow in close proximity, all of which do not lose their leaves. The north and northeast is drier than other areas thus the forest has slightly different vegetation. The tropical evergreen forest is home to many economically important trees such as rubber and other hardwoods. In addition to large trees smaller plants such as bamboo, rakam and wicker also grow in this type of forest.
Hill Evergreen Forest
The hill evergreen forest is found in the north at altitudes of over 1.000 meters above sea level. In other regions they are found in areas of high altitudes. These include Phu Luang and Phu Kradung in Loei, Khao Yai in Nakhon Nayok and Khao Luang in Nakhonsritamarat.
This type of forest is less dense than the tropical evergreen forest because it has less large trees. This type of forest too is green all year round. The climate is quite cool because it is found at high altitudes. The hill evergreen forest is very important to the preservation of water sources.
Trees are mainly shrubs mixed with some pines. Smaller plants in the forest include ground orchids and other tropical plants such as wild roses, violets, and lilacs. In addition there are small plants that grow on the larger trees such as moss and orchids.
The coniferous forest is found in altitudes of over 700 meters above sea level. The coniferous forest is found in abundance in the north. To a lesser degree they can be found in the central region and the northeast. Sometimes this forest can be found at the altitude of 200-300 meters above sea level. However, this type of forest is not found naturally to the south of Chumporn.
The coniferous forest is not as dense because of the soil is acidic. The trees in this forest do not lose their leaves and remain green all year round. In some coniferous forests the only trees are pines but in some areas small plants might grow along the forest floor. The coniferous forest might be found together with hill evergreen forests or dry dipterocarp forests.
Important vegetation in this type of forest are the various varieties of pines. Other trees include those that grow in the hill evergreen forests.
The trees in the mangrove forest do not lose their leaves and the forest floor is very dense. The roots of the trees are both for anchoring it in the soil and for breathing. This type of forest is found close to the seat of the mouth of major rivers where the sea washes ashore.
The mangroves are found in every province in the east especially at the mouth of Mae Nam Wal, Chanthaburi. In the south they are found on both sides of the peninsula. On the eastern side it is found along the coast from Prachuab Kirikhan to Pattani. On the west coast it is concentrated from Ranong to Stul.
Mangrove vegetation consists mainly of small trees that are useful for charcoal and firewood. Important trees include the Kongklang, Prasak. The plants grow on the forest floor include the various types of sea grasses.
Other types of forests
In addition to these major types of forests there are other types that are of less importance because of their relatively small size. These types of forests are native to specific areas.
This type of forest is a low density evergreen forest. It is found in areas where the sea washes up on to the land. The important type of vegetation includes the sea pine and other woods. Weeds and vines tend to grow on the forest floor and along the edge of the mountains that jut into the sea.
This type of forest is native to areas where freshwater floods over land for a long period of time. The soil in these areas tend to absorb water poorly. The swamps of the south are covered with water almost all year round and is usually densely populated. The peat of the south can be classified into two types: the Samet Swamp named so because the samet tree dominates the area while the other type of swamp is characterized by a presence of a large variety of trees such as Intanin with vines growing on the forest floor.
2. Deciduous Forest
This type of forest is characterized by the falling of leaves of the forests at about the same time during the dry season. The fallen leaves on the forest floor serves as good fuel thus forests fires are particularly frequent and often devastating. When the rains arrive the forest will burst into life with new leaves and flowers. The forest floor plants will also grow rapidly giving the forest a lush look. This type of forest can be divided Into three types.
Mixed Deciduous Forest
These are open and not dense and are populated by large and mid-sized trees. Bamboos generally grow in pockets in this type of forest. The soil in usually porous with sand mixed into it. During the dry season the trees lose their leaves and forest fires generally sweep these areas once a year. When the rainy season arrives the forest would then become green and lush.
Mixed deciduous forests of the north include teak trees. They spread down in area to Kanchanaburi. The mixed deciduous forest of the northeast and east are few and do not have teak trees. The mixed deciduous forest of the south are scarce and scattered in specific areas such as Surat Thani, Ranong, Stul, and Nakhonsritamarat.
Dry Deciduous Depterocarp Forest
This type of forest has many names depending on the area they are found. The general characteristics of this type of forest include the low density of the area featuring big to small trees. The forest floor is covered by grasses or small bamboo. The soil is generally porous mixed with sand and rocks. This means that it does a very poor job at absorbing water contributing to the relative dryness of the forest. The trees in this forest all lose their leaves thus annual forest fires are common.
Dry deciduous depterocarp forest is common to the plains and mountain areas. In the north it is native to areas where the soil is shallow and very dry. The trees are usually small. This results in a very open forest environment. The dry deciduous depterocarp forest of the northeast and east grow in areas that have better soil thus they are more dense and lush. In some areas they look very much like a mixed deciduous forest.
Trees native to the dry deciduous depterocarp forest include redwood. Plants that grow along the forest floor include various types of grass.
The savannas can be found in all of the regions in Thailand. This type of forest is the result of man's effort to clear land for agriculture. All of the trees in the area are then destroyed leaving the soil to dry. The nutrients in the soil are then lost so the grasses grow over the land. Due to its relative dryness forest fires are common. The fires generally extend close to the tree line causing the grassland to expand every year.
The savannas are characterized by grass and trees that are fire resistant. Other trees cannot survive the area because the samplings and seed are all destroyed by the annual forest fires.