Unlike Sri Lanka's rainforests, the monsoon sasonal forests have to contend with periods of drought sometimes lasting up to six months. They are, however, the main type of forest found on Sri Lanka covering about 75% of the forested areas. The trees are a combination of evergreen, semi-evergreen and semi-deciduous, but the forests as a whole have a general deciduous character. Not surprisingly, the species diversity of these monsoon forests is not as great as the rainforest and they usually have a simple two-storied structure. The canopy is predominantly composed of Hemicyclia sepiara, while associated species include Adina cordifolia, Alseodaphne semicarpifolia, Berrya cordifolia, Chloroxylon swietenia, Diospyros ebenum, Elaeodendron glaucum, Holoptelia integrifolia, Manilkara hexandra, Mitragyna parvifolia, Pterospermum canescens, Schleichera trijuga, Sterculia foetida, Stereospermum chelonioides, Strychnos nux-vomica, Syzygium cuminii and Vitex pinnata. The subcanopy is usually dominated by Nephilium langana while other common species include Aglaia roxburghiana, Alatantia monophylla, Alphonsea sclerocarpa, Cassia marginata, Cordia domestica, Dimorphocalyx glabellus, Diospyros ovalifolia, Euphorbia antiquorum, Garcinia spicata, Gleniea zeylanica, Grewia polygama, Hesperethusa alata, Holorrhena mitis, Lapisanthes trichocarpa, Morinda tinctoria, Memycylon capitellatum, Phyllochlamys taxoides, Pityranthe verrucosa, Pleurostylia wightii, Premna tomentosa, Walsaru piscidia, Sapindus emarginatus,Tricalysia dalzelli and the endemic Canthium dicoccum (Rubiaceae). Climbers and creepers are noticeable less conspicuous but may include Cissus quandrangularis, Columnella trifida, Derris scandens, Hugonia mystax and Ventilago maderaspalam. Epiphytes, on the other hand, are well represented and include several orchids such as Habenaria plantaginea, Rhynchostylis retusa, Saccolabium guttatum, Vanda spathulata and Vanilla walkeri. They also have very rich field and shrub layers including ferns such as Adiantum caudatum, Cheilanthus mysorensis, Gymnopteris quercifolia, Hemionitis arifolia, Micromelum minutum and Ophioglossum lustanicum, while the shrubs typically include Allangium lamarkii, Allophyllus cobbe, Croton aromaticus, Ehretia buxifolia, Glycosmis pentaphylla, Gmeliana asiatica, Ixora arborea, Murraya koenigii, Polyalthia koronii, Randia dumetorum, Stenosiphonium cordifolium, Tarana asiatica and Webera corymbosa. In the transition zones between monsoon and rainforest there are forests of intermediate character known as intermonsoon forests. Among the trees characteristic of these zones is the endemic Hopea cordifolia (Diperocarpaceae).

References

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