584 PROTECTION AGAINST WINDS. 



storms than those on the E. side of the avenue, that have 

 their prop-roots in softer soil. 



Storms not only overthrow single trees, but also whole woods. 

 A wood may have narrow clearings cut into it by storms corre- 

 sponding to their direction, or large blanks may be made. 



Breakage may be of stem, fork, crown, or branches ; the stem 

 may be broken off close to the ground, or at some distance above 

 it, and whirlwinds frequently twist the entire crown off trees. 



The damage done by storms may be direct or indirect. 



To the former class belong : Loss of increment and 

 breakage of timber, which may become only fit for firewood ; 

 damage to young growth owing to the breakage of underwood 

 by trees standing over it which have been blown down ; 

 increased cost of exploitation or of reproduction of woods; 

 reduced prices, owing to an excess of material being suddenly 

 thrown on the market ; irregularities in age-classes and in 

 carrying out working-plans, also disorder in thinnings and in 

 preparatory fellings. The disturbance of a forest working- 

 plan may be so great, that it may become necessary -to 

 recalculate the annual yield of a forest, and to prepare a new 

 table of annual felling-areas. 



Indirect damage done by storms is chiefly confined to 

 invasions of weeds in the blanks and regeneration-areas 

 where the trees have been blown down, and to attacks of bark- 

 beetles. 



B. Damage under Special Conditions. 



(a) Species of Tree. Conifers are far more exposed to 

 damage than broadleaved species. Extensive destruction of 

 broadleaved woods by storms is comparatively rare. 



It would be difficult to draw up a comparative table of trees 

 of different species according to their capacity to withstand 

 storms, as the amount of damage done is greatly modified 

 by local circumstances; but evergreen foliage and shallow 

 root-systems render trees liable to be broken or blown over. 

 As these two qualities are united in the spruce, this species is 

 specially liable to damage by storms, as experience has proved. 

 If, at any time, other trees suffer more than the spruce, 

 tbis is due to the nature of the soil, to the extraordinary 

 violence of the storm, or some other special circumstance. 



