564 



PROTECTION AGAINST SNOW. 



injury is common with pines, and branches up to 2J inches 

 thick are thus torn out, the holes becoming filled with resin, 

 and the torn branches eventually falling off, so that the 

 damage done to the tree may escape notice. In the case of 

 spruce, the branches thus torn out are not generally more 

 than 1J inches thick. 



Amongst broadleaved species, softwoods, including birch, 

 suffer most in this way, then ash and maples ; beech and oaks 

 suffer less, though much similar damage was done by snow to 

 oaks in Windsor Forest in October, 1878, when they were in 

 full leaf. 



According to the age of woods so affected, sometimes the 

 leaders and branches, at others the stem at different heights 

 above the ground, are more subject to snowbreak. 



The former mode of injury is commonest in seed-years 

 among older conifers, as the cones increase the weight on the 

 crown of the tree. 



Stem-breakage usually occurs in the case of trees injured by 

 resin-tapping, game, or by other causes, or trees which are 

 forked or cankered at or above the seat of injury. The 

 exuding resin and the usual local decay at the wound 

 reduces more or less the elasticity and strength of the 

 stems. Observations in the Harz show the influence of 

 wounds on snowbreak most clearly up to an age of about 

 45 years. Even thinnings have an influence, as most 

 stem breakage at wounds occurred in heavily thinned 

 woods. Thus the percentage of broken stems in the Harz, 

 as counted by von Hague (1859-60), in 32-year-old 

 spruce poles injured by game and resin-tappers, is as 

 follows : 



BREAKAGE OF STK.MS. 



