DIPTEROCARP TYPES I 53 



Dipterocarp Types. — Commercially as well as in extent the dip- 

 terocarp types are the most important. The average stands per 

 acre of valuable timber range from 2 to 45 M board feet with 

 an average of loM. Fortunately, too, a high percentage of the 

 stands consists of species which yield easily worked construction 

 lumber similar in characteristics to the yellow poplar of the 

 southern Appalachians. In fact, the determination of this impor- 

 tant point was unique in tropical lumbering. It had been assumed 

 heretofore that the only valuable species were the cabinet woods 

 like mahogany, ebony, and lignum vitae and that tropical build- 

 ing construction must depend upon the pines of the temperate 

 zone for its cheap building material. Moreover, this puts an 

 entirely different aspect on things for the lumberman. The 

 cabinet woods do not occur in heavy stands but scattered singly 

 so that only the crudest logging methods have been employed in 

 their exploitation but a stand of loM board feet per acre justifies 

 the installation of the economical steam skidding methods 

 developed for the heavy stands of the northwest and reduces 

 greatly the cost per M of getting out tropical lumber. 



Of all the dipterocarp types the one with the heaviest stands per 

 acre is the lauan type on which the lauans, with wood Kke our 

 yellow poplar, predominate, and in which stands of 45M per acre 

 are not uncommon. This occurs, as might be expected, on the 

 deep soiled sites where the rainfall is evenly distributed thruout 

 the year and abundant, i.e. over 60 inches per annum. Given 

 plenty of precipitation it may extend up to an elevation of 1000 

 feet above sea level where the temperature conditions become 

 unfavorable. A good idea of the composition of the type may 

 be obtained from the following table which is based on the 

 measurement of over 100 acres of strip surveys: 



Per cent 



Red lauan 41 



Almon-lauan 20 



Apitong 14 



Tanguile 13 



White lauan 



Bagtican lauan . 



Other species 6 



100 



