332 Forestry Quarterly. 



it often happened that every tree over large areas was killed by 

 them. 



(3) Windfall is not a serious menace in a Yellow pine stand, 

 even where through any one of the various causes the stand 

 may have been considerably thinned. It rarely causes large 

 openings, picking out a tree only here and there. In future stands 

 it will be possible still further to minimize the loss by wind by 

 cutting out the weak and top heavy trees. 



(4) Root competition may exert a slight influence toward keep- 

 ing a stand of Yellow pine open, but it is believed that this' is by 

 no means a very important factor. It would, however, exert a 

 very important influence on the character of a stand, were it 

 not for the fact that Yellow pine is most intolerant, so that the 

 trees, in order to obtain the amount of light which they require 

 for their best development, must be separated by a distance suf- 

 ficiently great to preclude root competition. 



The roots of Yellow pine rarely extend farther out from the 

 tree than the limbs of the crown in normal trees growing on 

 good soils. This was observed by measurements taken, from 

 time to time, on a great many trees which had been recently 

 toppled over by the wind. This estimate should be conservative, 

 as the trees which are most readily thrown by the wind are those 

 whose root systems are superficial and accordingly broad. The 

 area of the crown of a Yellow pine forms, therefore, a good 

 working index of the area of its root system. 



Rain falling upon the earth soaks, for the greater part, 

 straight down with very little lateral spreading, at least until 

 it has sunk below the level where it will be available for the 

 roots of trees. Rain, therefore, which falls beyond the immediate 

 reach of the roots is, for the most part, lost, as far as the trees 

 are concerned. 



That root competition is not very severe, even directly be- 

 neath the crowns of large Yellow pines, is shown by the fact that 

 seedlings often spring up and make good growth in such places. 

 In a Forest Service Bulletin discussing reproduction of Western 

 Yellow pine in the Southwest, the author of that publication shows 

 it to be a fact that reproduction is more prolific under the partial 

 shade of the old trees than it is out in the open. The seedlings 

 derive more benefit from the partial shade than harm from root 



