IX, A, 5 Brown and Mathews: Dipterocarp Forests 483 



spp., the slowest of the group, takes three hundred three years 

 to increase from 5 centimeters to 50 centimeters in diameter. 

 It will be seen from the curve that individuals of Shorea teys- 

 manniaTia between 60 and 80 centimeters make a very rapid 

 growth. This part of the curve, however, is based on only 2 

 specimens, and the average of a large number of individuals 

 would probably not show this rapid rate of growth. Certain 

 large individuals of other species of dipterocarps growing in 

 exceptionally favorable situations show similar rapid rates of 

 growth, but this cannot be taken as an index of the rates of 

 growth of the average large-sized trees. 



A glance at the curves for dipterocarps of northern Laguna 

 reveals the facts that only one species, Shorea teysmanniana 

 (tiaong), lies above the curve for yellow poplar for any con- 

 siderable distance; that Shorea polysperma (tanguile) is the 

 only other species which shows itself much more successful in 

 growth than white oak; that Shorea squamata (mayapis) is 

 similar to oak in its development; and that Hopea pierrei 

 and Dipterocarpus spp. lie below the temperate zone curves, 

 Dipterocarpus spp. especially making a very poor showing in 

 comparison with the temperate species. It is probable that 

 Parashorea plicata (bagtican-lauan) may be a more rapid-grow- 

 ing species than any of the dipterocarps here considered, but 

 it is also reasonable to suppose that the slower growth shown 

 by these species is due to the more crowded conditions existing 

 in the better stand in which they have developed. This sup- 

 position seems to be more reasonable when we pass to a con- 

 sideration of the growth of dipterocarps in a still better-stocked 

 stand of dipterocarps in Bataan Province. 



It seems best to consider now the figures from Bataan Prov- 

 ince which were collected on type area B at elevations of from 

 400 to 500 meters. Type area B represents a dense forest 

 dominated by Shorea polysperma. The stand on this area is 

 denser than that of either of the two areas previously discussed, 

 and the site is probably better than that of either. The aver- 

 age yearly growth for dipterocarps on this area is given in 

 Table XXIII. The ages of trees of different diameters, calcu- 

 lated from this table, appear in the form of curves of diameter 

 on age in fig. 3. Individual curves are given for Shorea polys- 

 perma, Dipterocarpus grandiflorus, and Pentacme oontorta, and 

 a separate curve is presented compiled from the averages of all 

 the individuals of dipterocarps measured on the area. In com- 

 piling these curves the trees were considered as originating at 

 5 centimeters. The actual ages, of course, are much greater than 



