IX, A, 5 



Brown and Mathews: Dipterocarp Forests 



419 



Table I. — Areas covered by different classes of vegetation in the Philippine 



Islands. 



Class of vegetation. 



Virgin forests 



Second-growth forests 



Grasslands 



Cultivated lands 



Total 



Area. 



Sg. miles. 

 40.000 

 20,000 

 48,000 

 12,000 



120,000 



Per cent. 

 33i 

 162 

 40 

 10 



100 



As will be seen here, the grasslands are more extensive 

 than virgin forests, vi^hile the extent of cultivated lands is only 

 one-fourth as great as that of the grasslands. There can be 

 no doubt that these grass areas are a result of cultivation. The 

 cogon grass (Imperata exaltata) readily invades cultivated 

 areas and often leads to their abandonment, or the land, after a 

 lapse of cultivation, becomes overgrown with this grass, which 

 effectually prevents further cultivation. By reference to map 

 1 it will be seen that the nonforested areas largely overgrown 

 with grass are most abundant in the region of the pronounced 

 dry season. The reason for this is that the grass becomes very 

 inflammable during the dry season and is regularly burned. 

 This results in the death of nearly all tree seedlings and in the 

 extension of the grass areas. These fires do little or no damage 

 to the grass on account of its large underground rhizomes. In 

 the region of nonseasonal rainfall the grass areas more rarely 

 become dry enough to bum readily. Consequently, forest spe- 

 cies can become established in areas abandoned after cultivation 

 and the forest is able to maintain itself. Thus, it seems evi- 

 dent that the present distribution of forests in the Philippines 

 is largely due to the combined effect of the action of man and 

 the influence of climate, human activity in destroying the forest 

 being aided in the western half of the Archipelago by climate 

 and retarded in the eastern half. 



IMPORTANCE OP DIPTEROCARP FORESTS 



The importance of the dipterocarp family as the source of 

 the chief timber supply of the Philippine Islands was first 

 clearly shown by Whitford.^^ Whitford estimates that the dip- 

 terocarp forests contain 95 per cent of the standing timber in 

 the Philippines and that 75 per cent of this timber is diptero- 

 carp," As stated in the above paper, 144 out of a total of 200 



Forests of the Philippines, Bull. P. I. B%ir. Forestry (1911), No. 10. 



