CHAPTER III 



LOCALITY 



It has already been indicated in the foregoing chapters 

 that, apart from variations in the composition of the 

 soil and climatic changes, certain local conditions may 

 either modify the climate in these particular regions or 

 have some other effect on forest vegetation. The most 

 important of these are : elevation above the sea-level 

 due to mountain regions, proximity to standing or 

 flowing water, winds, aspect, and conformation of the 

 ground. To these we shall now 7 devote our attention. 



I have already stated in the last chapter that, at 

 least as regards my own observation within the Tropics, 

 the influence of elevation on forest growth, due to the 

 lowering of the mean temperature and rarefaction of 

 the air, does not make itself markedly felt at below 

 GOO metres (approximately 2000 ft.), and probably 

 more, although, on isolated hills, the effect of greater 

 isolation may bring changes more quickly, and, in the 

 neighbourhood of large sheets of water, more slowly. 



The decrease of temperature per 100 metres (328 

 ft.) is approximately 0*58 C. 1 (1*0 4" Fahr.), and is due 

 to the rarefaction of the air, which has thus less power 

 to absorb heat; it would thus only amount to 3"48 C. 

 (6'26 Fahr.) at 600 metres. All the basal forests 

 situated at elevations up to this altitude, if not more, 

 may be considered as low-country forests." 



1 Schimper, op. cit. p. 691. 



- With tlic proviso that, as the rainfall increases with increasing elevation, 

 the flora has also a tendency to become ruore hygrophilous. 



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