Tidal forests or mangroves are situated within the tidal limits on alluvial flats in the delta and on sheltered muddy coastal areas. They are stratified depending on how much the area is affected by the daily rise and fall of the tides. The most abundant species are Rhizophora apiculata, R. mucronata, Heritiera fomes, Carapa moluccensis, Sonneratia apetala and Excoecaria agallocha.
Beach and dune forests
Form narrow strips along the coasts on sandy beaches and dunes. They are of little importance commercially. They are very often characterised by an abundance of Casuarina equisetifolia.
Found in inland fresh water swamps on low-lying alluvial land, usually near rivers and lakes. The land is inundated for a time during the rains. These forests are relatively open with small and scattered trees. Their total area is negligible.
- Riverine evergreen forests are situated along the banks of streams and in low-lying areas and consist mainly of Hopea odorata and Lagerstroemia speciosa. They occur mainly in southern Myanmar.
- Giant evergreen forests, which are characterised by the presence of giant evergreen trees over a lower storey of smaller evergreen trees, occur mainly in south Tenasserim. A great number of species are present. The most important ones include: kanyin (Dipterocarpus alatus, D. turbinatus and D. griffithii), Parashorea stellata, Anisoptera scaphula, Swintonia floribunda and Eugenia grandis in the upper storey, and Pentacme burmanica, P. griffithii, Hopea minutiflora and Michelia champaca in the lower storey. This subtype is typical of tropical rain forest.
- Typical evergreen forests are characterised by a dense understorey of evergreen trees of numerous species or by a dense growth of bamboo, such as tin-wa (Cephalostachyum pergracile), Oxytenanthera nigrociliata or Dendrocalamus hamiltonii. The subtype, requiring more than 2 000 to 2 500 mm of annual rainfall, occurs throughout Myanmar. Its species composition varies to some degree with location. Various species of kanyin are present, together with Anisoptera scaphula, Parashorea stellata, Hopea odorata, Pentacme burmanica, Swintonia floribunda, Eugenia grandis, Xylia dolabriformis, Gmelina arborea, Salmalia insignis, Salmalia malabarica, Albizia procera and Castanopsis spp.
Mixed deciduous forests
Economically the most important forests of Myanmar, as they produce teak and other commercial hardwoods. They are subdivided into three types moist upper mixed deciduous forests, dry upper mixed deciduous forest and lower mixed deciduous forests.
Moist upper mixed deciduous forest
Characterised in lower Myanmar by the presence of the bamboos, Bambusa polymorpha and Cephalostachyum pergracile. In upper Myanmar, Bambusa polymorpha is replaced by Bambusa hamiltonii or B. membranaceus with Cephalostachyum pergracile. The latter is the most typical bamboo of the subtype. These forests contain the finest teak, usually associated with Xylia dolabriformis. Other important species are Dipterocarpus spp., Gmelina arborea, Eugenia spp., Terminalia tomentosa, Salmalia insignis, Lannea grandis, Pterocarpus macrocarpus and Milletia pendula. The subtype occurs on well-drained slopes and usually indicates a good quality of soil. The dry upper mixed deciduous subtype often replaces it on ridge tops and dry aspects. A peculiar type of forest, which may best be included under this type, is found in Arakan over wide stretches of the Arakan Yoma. A bamboo, Melocanna bambusoides, invades several forest types, including evergreen forest. As the dense growth of this bamboo precludes natural regeneration of most species, the trend over time is to pure stands of Melocanna bambusoides.
Dry upper mixed deciduous forests
Usually characterised by the presence of the bamboo Dendrocalamus strictus. In many places Thyrsotachys oliveri is also a characteristic bamboo and in upper Myanmar may predominate over large areas. Cephalostachyum pergracile and even Bambusa polyphorma may also occur in this subtype but they are usually less frequent than in moist forests and cannot be considered characteristic. In lower Myanmar, Bambusa tulda is found in this subtype and is usually an indicator of stiff soil. Characteristic tree species are teak, Xylia dolabriformis, Terminalia tomentosa, T. chebula, T. pyrifolia, Pterocarpus macrocarpus, Adina cordifolia, Pentacme siamensis, Shorea oblongifolia and occasionally Dipterocarpus tuberculatus.
Lower mixed deciduous forests
Occur on lower ground, usually with clayey soils, and are characterised by a scarcity of bamboos. The most characteristic form of the subtype is found on alluvial flats near streams. Here, teak occurs in quantity, often in pure stands and with trees of large diameters but of a shape not as good as is found on the slopes. Other characteristic species of this subtype are Lagerstroemia speciosa, Dillenia pentagyna, Homalium tomentosum, Albizia procera and Anogeissus acuminata.
Deciduous dipterocarp forests
Characterised by the prevalence of Dipterocarpus tuberculatus, which may form almost a pure stand. In some places Pentacme siamensisand Shorea oblongifolia may replace it, the forest then known as semi-Indaing. The type occurs mainly on laterite, but also on sandy or gravely soil. The forests are usually relatively open with a ground cover of grasses and shrubs.
Serve mainly as protective cover for slopes between 900 m and 1 800 m. They may be somewhat roughly divided into hill evergreen forests and dry hill forests.
- Hill evergreen forests are characteristic of high rainfall areas and resemble evergreen forests in many ways, with high trees and luxuriant growth. The species are, however, usually distinct. Quercus spp., Castanopsis spp., Schima wallichii and species of the families Magnoliaceae and Lauraceae are characteristic of this subtype. The forest usually contains a large number of climbers and dense undergrowth.
- Dry hill forests, occurring in drier localities, have shorter or even stunted trees and the vegetation is less luxuriant. Characteristic species are Quercus serrata with several other species of Quercus and Castanopsis, Schima wallichii, Alnus nepalensis and occasionally, ingyin.
Bamboo and palms
Bamboo grows profusely in Myanmar. There are about 90 different species, of which about a half dozen (mainly Cephalostachyum pergracile, Bambusa polymorpha, Dendrocalamus membranaceus, D. strictus, Melocanna bambusoides and Oxytenanthera nigrociliata) can be considered to be of major economic importance. It is estimated that there are about 9 million ha of bamboo in pure stands and as undergrowth in Myanmar. Arakan, Tenasserim and the Pegu Yoma area contain large reserves of bamboos in continuous blocks as yet unutilised for domestic consumption.
The predominant species to be found in the Arakan area is Melocanna bambusoides, growing in almost pure stands and not associated with other tropical hardwood species. This species is somewhat different from other bamboos in that the growth is in single culms as opposed to clumps. There are extensive areas of bamboo mixed with other hardwood species in the Tenasserim and Pegu Yoma regions.
Pine forest is found in the Shan and Chin states. In the Shan State, Pinus merkusii occurs in the hills of the Salween and Thsungyin drainages. It extends to lower altitudes and may be found associated with Indaing forest, between 150 m and 750 m. It occurs in the hills of upper Myanmar, the Shan state, the hills between Sittang and Salween and in the Arakan Yoma and Chin hills, at heights between about 1 500 m and 2 500 m. It may occur as almost pure pine forest or may be associated with such species as Alnus nepalensis, Quercus spp., Rhododendron arboreum and bracken fern (Pteris aquilina).