710 JOURNAI, OF FORESTRY 



Not all of the trees upon this area were overthrown, although as greatly 

 exposed to the wind as those that fell. Examination of the stumps and 

 roots of the trees left standing after the windstorn showed less root 

 and butt rot present than in the overthrown trees. Several grand firs, 

 heavily infected with Bchinodontium tinctorium, were broken off sev- 

 eral feet from the ground as a result of the storm. 



A conclusion drawn from the immediate Humbird data favors the 

 following factors as being important as secondary causes : ( i ) Fungi, 

 (2) soft, undrained soil, and (3) old-age class. Of these secondary 

 causes, tlie action of fungi in rotting and weakening the roots stands 

 out as the most important of the causes named. It also indicates that 

 the trees having less root, butt, and heart rot were able to resist over- 

 throw and breakage. 



DISCUSSION 



The review of the literature on the subject of windfall and wind 

 damage in general has disclosed the fact that fungi operating in the 

 roots and butts of timber trees are to be seriously considered as second- 

 ary causes in windfall damage, and that fungi operating in the trunks 

 of trees are the very serious causes of breakage in standing timber 

 when high winds become prevalent. It has also been made evident 

 that the yearly damage to our forests by the overthrow of stands of 

 timber and individual trees through the force of the wind represents a 

 loss which cannot well be overlooked in view of the present need for 

 conservation. The data presented give an insight into the prevalence 

 and distribution of the damage due to windfall, as well as indicate the 

 ■ various secondary causes responsible for the overthrow and their rela- 

 tive importance. They also furnish an index to the important part 

 which fungi play in acting as secondary causes to windfall and wind- 

 break damage, and furnish arguments in favor of enforcing sanitation 

 clauses on all timber-sale areas and the reserving of sound trees for 

 seed trees. 



It is well to take up here the data showing the direct responsibility 

 of fungi in causing windfall. It has been shown that the amount of 

 windfall and wind breakage traceable to fungous activity is large 

 enough to be of economic • importance in the administration of the 

 National Forests. This fact has been emphasized in connection with 

 trees left upon an area for future crops following cutting operations 

 and with trees left as seed trees. The methods by which the deter- 

 mination of the secondary causes are made in the field should be pre- 



