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A CONTRIBUTION TO THE ECOLOGY OF THE 

 UPPER GANGET1C PLAIN 



By Winfield Dudgeon, 

 Eiuing Christian College, Allahabad. 



Introduction. 



There is little published information about the ecological rela- 

 tions of the vegetation of the Upper Gangetic Plain. In their monu- 

 mental survey and summary of the vegetation of India, HOOKER AND 

 THOMSON (4) have little to say of this area. They state that there 

 are no forests except at the base of the Himalayas, and that unculti- 

 vated tracts are usually covered with loose " bush- jungle ". As every 

 writer must do, they call attention to the markedly periodic climate. 

 SCHIMPER (10) concludes that a rainfall below 90 cm. per annum 

 produce " xerophilous scrub ", while above that amount produces 

 " xerophilous woodland ". Allahabad has a mean annual rainfall of 

 very nearly 90 cm., but the connection of the vegetation with some 

 type of a Schimper climatic climax is not so obvious. 



The Upper Gangetic Plain, comprising roughly the United Pro- 

 vinces, is a very distinct ecological area. Eastward it passes into the 

 much more humid climate of Bengal ; southward it merges into the 

 hilly regions of the Vindhias, where the climate is similar but the 

 vegetation is distinct ; westward it passes into the drier Panjab ; and 

 northward it is abruptly limited by the Himalayas. The rainfall 

 diminishes westward, and increases northward and rapidly eastward. 

 The climate is continental, with great range between winter and 

 summer and between day and night. 



This study is restricted to a small area about ten miles in radius 

 with Allahabad at the center. Such a restriction is chosen because I 

 am more familiar with this limited area, and because it is quite repre- 

 sentative of the much larger area of the Upper Gangetic Plain. 



Physical features of the area. 



Allahabad is situated at 25° 26' N. Latitude and 81° 52' E. 

 Longitude, at the southern edge of the great plain of the Ganges and 

 Jamna Eivers, at their junction. The Meteorological Observatory is 319 

 feet above mean sea level, and this may be taken as approximately the 

 level of the surrounding plains. The soil (9) is all alluvial, deposited 

 within recent geological times. It ranges from sand, through a mix- 

 ture of sand and clay, to fine clay. The older alluvium often contains 

 deposits of calcium carbonate in irregular nodules, locally called 



