120 Forestry Quarterly 



3>4 x6.5, soon reduced to 6.5 foot square (1800 plants) ^hows 

 in all directions advantage of the latter in increment of height, 

 diameter, volume and in even development over a plantation with 

 2660 plants except in clearing of branches. 



Die Ergebnisse forsUicher KuUurversuche. Zeitschrift fur Forst- und 

 Jagdwesen, February, 1915, pp. 65-84. 



Old teachers of silviculture and practi- 

 Value tioners have held as an incontrovertible 



of tenet that to secure good soil conditions 



Early crown cover must not be interrupted. Dr. 



Thinnings Albert points out with Ramann that the 



critical period for pine on poor sites when 

 it makes the most demand on the soil falls about the 30th year. 

 Hence, a little before that time site conditions must be improved 

 by thinnings — reduction in numbers, equalizing of crown space. 

 To furnish definite data to demonstrate the influence of such 

 early thinning, pine thickets 20 to 25 years old were thinned, in 

 some areas removing the brush, in others leaving it, and then in- 

 vestigating for two years the water conditions of the soil from 

 week to week at 8 and 16 inch depth, sampling with borer and 

 preserving the layering of the soil; check tests being made in 

 each case and average curves constructed, which immediately 

 showed the influence of the different treatment. 



As was to be expected, the decrease in stem number produced 

 not insignificant and continuous increase of water in the soil, 

 and the leaving of the brush increased this considerably. This 

 occurred at both depths. Numerically, the influence of the thin- 

 ning increased the water contents 1.12 to 1.23 at the 8-inch depth; 

 .71 to .74 at the 16-inch depth, to which for brush cover need 

 to be added .59 to .64 and .53 to .88 respectively. These differ- 

 ences are not as small as they appear, for if translated into area 

 figures it means 90 cbm per hectare, which for poor sand soils 

 is a considerable addition. Sometimes the increases were as 

 much as 3 per cent in the upper, and 2 per cent in the lower, 

 strata during the summer months. It was also apparent that a 

 larger accumulation of winter waters occurred in the thinned 

 stands, reduced interception and evaporation from the crowns 

 being responsible. 



Comparison is also made with rainfall data, which confirms 

 the influence of treatment. 



