200 



H.WALTER 



or 100 g/m^. If we compare the same vegetative types, we can assume that 

 the transpiring surface is more or less proportional to the dry weight. That 

 means: The transpiring surface decreases in proportion to the rainfall, that is, the 



100 



200 3K i%% I 



500 



Fig. I. Rainfall map of South-West Africa in mm. 



D Sites of samples for determination of the dry weight production in grassland. 

 • Samples for determination of the nutrition value of grassland plants (from H. 

 Walter, 1954). 



water supply of a unit of transpiring surface is the same under arid or humid 

 conditions up to a rainfall of 500 mm. 



This statement was checked in south-west Austraha in the Eucalyptus- 

 forest region with a rainfall from 500 mm up to 1 500 mm (Tables i and 2) 

 (Walter, 1962) : 



