IX, A, 6 Brown and Mathews: Dipterocarp Forests 417 



the coast in most regions, because where situations suitable for 

 it are found near the beach the original forest has been for 

 the most part cleared away and the land put under cultivation. 



The accompanying map, which is a modification of Whitford's,' 

 shows the distribution of forest areas throughout the Philippine 

 Islands. The pine forest shown on the map in double hatch 

 is a high mountain type and need not interest us here. No 

 distinction is made in the map between large areas of commercial 

 forest which are chiefly dipterocarp, small areas of high 

 mountain forest, and forests of the drier sites that occur 

 scattered through the larger forest areas. For the purposes 

 of this paper the forest area may be considered for the most 

 part dipterocarp. Large portions of the forests have been only 

 partially explored, but will probably prove to be of the same 

 general character as those in better-known parts of the Islands. 



The distribution of the forests as shown in this map is in 

 part due to climatic differences and in part to the influence 

 of man aided by climatic conditions. Temperature plays little 

 part in this distribution, as temperature in the Archipelago 

 is regulated by altitude rather than by latitude.* Moisture 

 conditions seem to be the determining factor. In general, the 

 climate of the Philippine Islands, in regard to rainfall, may 

 be classified as a monsoon climate; that is, rains depend upon 

 rain-bearing winds which shift their direction twice a year. 

 This statement is essentially correct for the entire western 

 side of the Archipelago, but cannot be taken literally for the 

 eastern portion. The rainfall of the Islands can be divided 

 into two general classes. The first class may be distinguished 

 as a seasonal rainfall, the climate being marked by very distinct 

 wet and dry seasons. This climate is found in the western 

 half of the Archipelago. In the eastern part of the Islands 

 rainfall is distributed throughout all the months of the year, 

 and there are therefore no pronounced wet and dry seasons. 

 The explanation of this difference between the eastern and 

 western coasts of the Islands is that the northeastern monsoon, 

 striking the Islands on the eastern coast, deposits a large part 

 of its moisture before passing over the mountain masses and 

 then continues over the western half of the Islands as a drying 

 wind. The southwestern monsoon, on the other hand, is not 



' Bidl. P. I. Bur. Forestry (1911), No. 10. 



' Cox, A. J., Philippine soils and some of the factors which influence them, 

 This Journal, Sec. A (1911), 6, 279-330. 



