236 



Studies in Forestry 



[CHAP. XI. 



by its dead foliage. The deductions he drew were therefore 

 diametrically at variance with those previously arrived at by 

 Michaelis ; whilst the data on which they are based leave no 

 possibility of differences existing with regard to the quality and 

 physical conditions of the soil and subsoil. 



But, before then, valuable data had already been contributed 

 by Riinnebaum 1 respecting two areas under Scots Pine, one of 

 which (120 years) was underplanted with Beech, and the other 

 was without underwood (no years). The differences observ- 

 able as to mineral composition were inconsiderable ; but the 

 former had a thick layer of humose soil containing nearly 

 double the quantity of mineral nutrients that were found in 

 the thinner layer of humose soil on the area without under- 

 wood. The yield and returns from these areas (without 

 reckoning 343 cubic ft. of Beech sold from the former for 

 27 13^-. od.} were as follows : 



The slight difference in average annual increment in favour 

 of the younger crop (without underwood) is of course due, not 

 to differences in the soil and situation, or to greater increment 

 without undergrowth, but to the fact of the larger quantity of 

 timber removed in the thinning at the time of underplanting. 

 What must strike one most in the above data is the much 

 higher rate per cubic foot obtained from the standard Pines, 

 grown over underwood, in consequence of the stems being 

 straighter, smoother, less tapering, and with a proportionately 

 larger development of the summer zone in each annual ring. 

 Prof. R. Hartig of Munich was the first to enunciate the theory 



1 Zeitschrift fur Forst- und Jagdwesen, 1885, pp. 156 et seq. 



