Included here are the lowlands of the lower courses of the Ganges and Brahmaputra, the lowlands of Orissa north of the Mahanadi River and the tropical parts of Assam, Manipur, Nagaland and Tripura.

In places such as the Patloi Range and Naga Hills in the Assam Valley these forests are characterized by the giant dipteropcarps Dipterocarpus macrocarpus and Shorea assamica, which can attain heights of up to 50 m. They often occurs as emergents standing over a canopy at about 30 m. Common canopy trees are species of Mesua (such as M. ferrea) and Vatica (such as V. lanceaefolia), but many others occur such as Altingia excelsa, Amoora wallichii, Artocarpus chaplasha, Canarium species, Dysoxylum procers, Stereospermum personatum and the endemic or near endemic Mallotus roxburghianus (Euphorbiaceae). There is also a rich understory of bamboos, palms and shrubs such as Bambusa pallida, Livistona jenkinsiana, Pseudostachyum polymorphum and the endemic bamboo Dendrocalamus hamiltonii (Poaceae). Climbers and epiphytes are also well represented but the shaded ground layer can be almost devoid of plants. On the other hand, colourful species such as Thunbergia grandiflora may be present. In the upper Assam Valley these forests eventually give way to tropical evergreen forests of a lower stature. These include forests dominated by Kayea assamica (Kayea Forests), found on the northern bank of the Brahmaputra Valley, and forests dominated by species of Mesua (Mesua Forest), which occur, for example, in the foothills of the Balipara Frontier.



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