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PACIFIC SCIENCE, VoL VII, October, 1953 
of the barren area is due to dehydration. In 
the dehydration of the colloidal hydrated iron 
oxides, water is lost and the oxides are con- 
verted to hematite or related dehydrated iron 
oxides. The process will cause an increase in 
particle density and, according to Fujimoto 
et al. (1948), an increase in particle size. The 
question arises as to the length of time re- 
quired for a ferruginous horizon to harden 
to the laterite crust on exposure. Aubert (1949, 
1950) has reported the formation of laterite 
crusts under normal conditions in 35 to 60 
years. Chevalier (1949) states that, if the forest 
is removed by cutting, burning, or loss of 
cover due to other reasons, the senile stage 
(the laterite crust) will develop very rapidly. 
Davis (1940) found that because of the clear 
culture required in the culture of teak and 
because teak trees lose their leaves during the 
dry season, the laterite crust will develop in 
a very short period of time [one dry season]. 
The hardening of Hawaiian soils on exposure 
is very rapid, occuring in less than a year. 
0 300 500 700 lOOO'C 
Fig. 2. The differential thermal curves of the profile 
from the barren area of a humic ferruginous latosol 
soil. 
Fig. 3. The differential thermal curves of a profile 
with a vegetative cover of a humic ferruginous latosol 
soil. 
The dehydration ' of the soil causes very 
important changes in the physical and chem- 
ical properties of the soil. There is an obvious 
change in compaction, bulk density, particle 
density, and particle size. The most impor- 
tant change is the loss of cation exchange 
capacity. It has been observed that these bar- 
ren areas are infertile. This infertility very 
likely is due to the loss of adsorptive surface 
and to the poor physical condition of the soil. 
The reforestation of these laterite areas is a 
slow process as the conditions for growth are 
very poor. 
