32 PHILIPPINE RESINS, GUMS, AND OILS 
The sapwood is white; the heartwood white and reddish brown ‘ 
with alternate light and dark rings, and very resinous. It is 
used locally for house construction, mining props, etc. 
This species is found in the highlands of central and northern 
Luzon at altitudes varying from 500 to 2,500 meters, but is best 
developed at altitudes ranging from 900 to 1,500 meters. The 
stands vary in density from those composed of scattered indiv- 
iduals to nearly closed patches. The ground in a pine area is 
usually covered with grass. In the ravines, broad-leaved trees 
occur and there is considerable evidence to show that nearly 
the whole area now occupied by the pines was formerly covered 
by broad-leaved trees, the pines being confined to steeper and 
dryer situations, where the other trees did not flourish. Through 
the activities of man in past centuries, the broad-leaved trees 
have been cleared off, and repeated fires have prevented their 
reproduction. The result of successive fires is usually to leave 
the lands in possession of grasses. The pines are less susceptible 
to fire than are the broad-leaved trees and consequently the 
former occur over wide areas. If fires were kept out, the pine, 
in the absence of competition with the broad-leaved trees, would 
quickly occupy the entire area, as its reproduction is abundant 
and rapid. The pines would then gradually be replaced by 
broad-leaved trees, as these will seed under the pines and cast 
such a dense shade as to prevent the growth of pine seedlings. 
Measurements show a volume of 74 cubic meters per hectare 
(equivalent to about 7,400 board feet per acre) of pine trees 
which have a diameter of 25 or more centimeters. 
PINUS MERKUSII Jungh. (Fig. 8). TAPULAU or MINDORO PINE. 
Local names: Agz-u (Mindoro) ; salit, tapilau (Zambales). 
TURPENTINE 
This species has not been investigated chemically, but its 
products are probably similar to those of Pinus insularis. The 
wood is apparently identical with the latter species, but seems 
on the average to be even more resinous. 
Pinus merkusii is a tree reaching a diameter of about 90 cen- 
timeters. The chief difference between this species and Pinus 
insularis is that the needles occur in groups of two rather than 
three. 
This species is found in Zambales and northwestern Mindoro, 
occurring in the latter region in pure stands. In Zambales, both 
Pinus merkusii and Pinus insularis are found at altitudes of 
only one or two hundred meters. 
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