Indian Forest Records . 
[Vol. VIII 
62 
(a) Improved soil-aeration and consequently stronger root growth 
during the rains, owing to the partial drying out of the 
soil in the clearings during the intervals of hot sunshine. 
(b) Moister soil in the clearings during the cold and dry season. 
This is caused by the addition of water to the soil in the 
form of heavy dew and light showers, while water loss 
by evaporation is retarded by the side shade afforded 
by the adjoining trees. Very little dew or light rain 
reaches the soil under the shade of trees during this period 
which consequently remains much drier than that 
of the clearings. The moister soil naturally helps the 
plants in the clearings to withstand the hot dry season. 
These results, therefore, indicate that the two factors 
of outstanding importance which affect the healthy deve¬ 
lopment of sal seedlings in this locality are drought and 
bad soil-aeration,* see l.c. part II, 1916, paras. 19, 23 (5) 
and present paper, para. 23 (3) (4). 
(25) Removing the overhead cover in patches, 60 feet in diameter, 
from above 3-years-old seedlings raised in the shade results 
in a high percentage of deaths (79 per cent, of the existing 
seedlings) and weeding becomes necessary two years after 
the felling to prevent the suppression of the surviving plants. 
This indicates that seedlings raised in the shade should not 
be freed from overhead cover until they are considerably 
older than 3 years, see present paper, paras. 27, 28. 
(26) Sowings in areas where the overhead cover has been broken 
give inferior results to those obtained from sowings in com¬ 
pletely cleared narrow strips, see results in Plots XXVI 
and XVII, paras. 40 and 41 (5) (7) above. 
* In a letter to the writer dated 28th August, 1917, Singapore Botanic Gardens, 
Mr. I. H. Burkill writes as follows : “We are having very wet weather and it shows 
how your observations on the need of soil-aeration can be extended from Shorea 
robusta to S. macroptera and S. rigida, for there is a great mortality proceeding among 
last year’s seedlings in the Gardens Jungle.” 
Mr. R. S Troup, also, has recently ascribed the failure of sal regeneration in the 
moist forests of Bengal and Assam to bad soil-aeration. (Note on the Forests of the Duars, 
Simla 1915, p. 36.) 
It is interesting to note that, apart from the question of the establishment of seedlings, 
Mr. R. G. Marriott has recently attributed the poor development of older trees to this 
factor, and suggests that, owing to it, the trees may practically cease to grow during 
the rains which ought to be the period of most vigorous growth (Indian Forester XLIII 
1917, p. 444.) 
These observations indicate that the need for good soil-aeration is not merely a factor 
of local interest but is a widespread phenomenon of general importance. 
[ 224 ] 
