126 forestry in british east india. 



section ii.— the forests of india. 

 1. Types of Forest.* 

 Owing to the great variety of climatic conditions in India and 

 Burma, the flora is extremely varied, from full tropical develop- 

 ment over more than half the area to intermediate conditions, 

 desert and Alpine forest. 



The types of forest depend chiefly on the rainfall, but also on 

 the temperature, elevation above the sea, tidal and riparian 

 positions. According to the heaviness of the rainfall the following 

 four zones have been formed : — 



The Wet zone with a rainfall of over 75 inches. 



The Intermediate zone with a rainfall of 30 to 75 inches. 



The Dry zone with a rainfall of 15 to 30 inches. 



The Arid zone with a rainfall of less than 15 inches. 

 The wet zone is the home of the Evergreen forest ; the intermediate 

 zone, of the Deciduous forest ; the dry zone, of the Dry forest ; 

 and the arid zone is mostly treeless. Additional types are Hill 

 and Alpine forests in the mountains, Tidal and Riparian forests, 

 (a) The Evergreen Forests are found chiefly on the west coast 

 of the Peninsula, on the lower slopes of the eastern Himalayas, 

 in Assam, Eastern Bengal, Chittagong, Burma and the Andaman 

 Islands. The humidity and comparatively even temperature of 

 these tropical and sub-tropical localities favour vigorous growth, 

 so that some of the trees attain a height of 200 feet and a propor- 

 tionate girth, but many of the trees are of small value. 



On the west coast the rainfall is generally over 100 inches, the 

 mean annual temperature 75 degrees, and the relative humidity 

 close on 80 per cent. In the Assam valley the mean annual 

 rainfall exceeds 75 inches, with 410 inches at Cherrapunji in the 

 Khasia hills ; mean annual temperature 77 degrees, and humidity 

 80 per cent. In Burma the evergreen forests are chiefly found in 

 the coast districts extending well into the valleys of the rivers. 

 Lower Burma has a mean annual rainfall of 125 inches, a mean 

 temperature of 79 degrees and a humidity of 77 per cent. On 

 going north a much dryer area is met with, but on approaching 

 the hilly parts of Upper Burma the rainfall increases again. 

 Much of the Andaman Islands forest is evergreen, the climate 

 resembling that of Lower Burma. 



* For a detailed doscription, see Troup'.s "Silviculture of Indian Trees." 



