GENERAL CONDITIONS 



149 



to make tree types based on differences in soil conditions as well 

 as climatic differences. That can only come with more intensive 

 study than even was possible for L. S. Murphy in his careful ex- 

 amination of the forest resources of the island.* In view of 

 more detailed information his types are followed, viz. : 



Percent 



1. Mangrove type 8 



2. Dry tidal woodland type. 



3. Moist deciduous type 7 



4. Rain forest type , 62 



5. Dry deciduous type 23 



The area percentages do not represent present acreages but the 

 areas contained within the various types now and before the 

 settlement of the island. 



The first, or mangrove type, is confined to the margins of tide 

 water not subject to strong wave action and on the northern and 

 eastern sides of the island where the precipitation is high. In 

 other words, it needi protection from direct wind and abundant 

 moisture. Hence, on the leeward south and west portions of the 

 island where the rain bearing winds are shut off by the mountains 

 the type is only found along the mouths of the larger streams 

 where the sea water is diluted enough to offset the lack of rain 

 water. Commercially the mangrove type is valuable for two 

 purposes, firewood and tanning material. Virgin stands should 

 yield six cords per acre of fuel and 10 tons of bark, but there are 

 few such stands in Porto Rico because thi^ type is usually found 

 close to the settlements and has consequently been heavily 

 exploited. 



Immediately above the mangrove swamps on the sandy and 

 gravelly beaches occurs a type which has become purely man- 

 made in its composition. This is where the introduced cocoanut 

 pahn has taken root most readily until it is characteristic of the 

 West Indies that the shores of the sheltered coast line should be 

 fringed with stands of this exotic species. In fact it is impossible 

 to determine at this time what the original species were but rather 



* U, S. Forest Service Bulletin 354, " The Forests of Porto Rico," L. S. Murphy, 

 1916. 



