522 



The Philippine Journal of Science 



1914 



Consideration of the above facts, suggests that in tropical 

 regions where a seasonal climate is pronounced, such rings of 

 growth as are found in trees, if due at all to changes in climate, 

 are more likely to be formed semiannually than annually. Also, 

 it appears that to obtain accurate data as to yearly rate of growth 

 of trees in the Philippines, measurements of standing trees must 

 be made at the same time each year in order to avoid the in- 

 accuracy which might result from seasonal changes in rates of 

 growth or in the sizes of the trees. 



GROWTH IN VOLUME 



Data are at hand for computing the growth in volume for the 

 main species of only one region, that of the northern Laguna 

 forest. Growth in volume for the different species of this forest 

 was computed by dividing the difference in volume between any 

 two diameter classes by the number of years which it takes the 

 species in question to grow from one of these classes to another. 

 Growth in volume as far as we have been able to calculate it 

 from the data at hand is given in Table XL. 



From Table XL it is possible to compute the annual rate of 

 growth in volume in cubic meters per hectare for the forest of 

 northern Laguna by applying the figures on rate of volume 

 growth to the figures given in Table VIII (see Laguna forest). 



Table XL. — Annual growth in volume of dipterocarps in northern Laguna 



forest. 



[Growth is given in cubic meters.] 



Species. 



Shorea teysmanniana (tiaone) 

 Shorea squamata (mayapis) .,. 



Hopea pierrei (dalinding-an) 



Shorea polysperma (tangfuile) - 

 IHpterocarpus sp. (apitongr)-.. 



Diameter in centimeters. 



20. 



0.0140 

 0.0100 

 0.0100 

 0.0093 

 0.0041 



25. 



0.0262 

 0.0150 

 0. 0161 

 0.0183 

 0.0064 



30. 



0.0300 

 0. 0162 

 0.0135 

 0.0192 

 0.0084 



I 



35. 



0.0330 

 0.0205 

 0.0122 

 0.0275 

 0.0117 



40. 



0.0382 

 0.0262 



0.0350 

 0.0172 



Species. 



Shorea teysmanniana (tiaong) 

 Shorea squamata (mayapis) ._. 

 Hopea pierrei (dalindingan)... 

 Shorea polysperma (tanguile) . 

 LHpf erocarpjis ap. (apitong) 



Diameter in centimeters. 



45. 



0.0471 

 0. 0336 



50. 



55. 



0.0472 

 0.0211 



0. 0519 

 0. 0381 



0.0476 



0.0609 

 0.0450 



0.0446 



60. 



0.0810 



0.0465 



65. 

 0. 1170 



0.0511 



