CHAP, xi.] Effects of Underplanting 235 



found J that in Oak forest, with an eighteen-year-old under- 

 growth, mostly of Hornbeam and Hazel in close canopy, the 

 increment was practically the same as was to be found on the 

 trees in another part of the same crop, which had been fenced 

 off as a game-park, and had been browsed on by deer to such 

 an extent that there really was no underwood to speak of. As 

 accurate details were not collected with respect to the nature 

 and physical properties of the soil and situation (as to depth, 

 moisture, exposure, &c.}, it would not be justifiable to argue 

 from such meagre data that undergrowth was unnecessary for 

 the retention of the productive capacity of the soil. It is, 

 indeed, quite true that the main food-supplies are derived 

 from the lower layers of soil only ; but, as those are only avail- 

 able whilst dissolved in water, and as the layer of mould 

 assists percolation by preventing the rapid off-flow of aqueous 

 precipitations, it can easily be understood how beneficial must 

 be the action of humus and of a good soil-covering on all such 

 soils as are apt to suffer from want of moisture. 



Among the advocates of underplanting, Frombling in 1886 

 published 2 measurements made on Oaks of 1 60 years in age 

 growing on old grazing land, but which had been underplanted 

 for thirty-five years. In three stems growing close together and 

 not thinned, the breadth of the annual rings had sunk to their 

 minimum at the time of underplanting, but had broadened as 

 the undergrowth formed canopy, and became broader than any 

 of the annual zones during any of the previous fifty to sixty 

 years when the natural energy of growth of the trees was at its 

 maximum. Other stems, which had been thinned or partially 

 cleared, formed considerably broader zones at first in con- 

 sequence of the freer exposure to light ; but this fell off again 

 for three years, and then recommenced in response to the 

 improvement in the productive capacity of the soil consequent 

 on the formation of canopy by the underwood and of humus 



1 Forstliche Blatter, 1884, p. 345. 



* Zeitschrift fiir Forst- und Jagdwesen, 1886, p. 632. 



