FORMATION OF FIRE SCARS 



639 



species subject to serious loss from heartrots. Close examination 

 where thin bark is charred will often show the bark to be split ver- 

 tically in places, disclosing dead sapwood. Tapping on the bark will 

 sometimes indicate that it is loose. Again it may be ridged and cracked 

 over the calluses or sunken over the center of the wound. In other 

 cases it is only by chopping through the bark that the existence of the 

 hidden wound may be ascertained. 



Once the cambium and sapwood are exposed conditions are favorable 

 for the actual burning out of the wood in the next fire. This might 

 especially be expected in the pines and in Douglas fir where the wound 

 surface generally is more or less covered by a film of resin. This 

 film, however, appears not to be essential for the production of large 

 or deep fire scars, to judge from the following data collected on 

 California timber sales during cull studies carried on under the direc- 

 tion of Dr. E. P. Meinecke, Office of Forest Patholog}'. The data 

 cover all trees of merchantable size, with the exception of sugar pine 

 and seed trees, on portion of six Forest Service timber sales in Cali- 

 fornia. The data on sugar pine being too scanty for consideration are 

 disregarded. The areas studied are fairly representative with regard 

 to fire injury for the 1)ulk of the mixed coniferous forests of the 

 Sierra Nevada. Only open fire scars are here considered. 



Number of trees: 



Incense cedar, T02 ; vellow pine, 1,271; white fir. 359; Douglas 

 fir, 425. 



Per cents of frees sJiowing open fire scars of all types: 



Inccn-e cedar. (;i.5; vellow pine, 1:2.7; white fir. 25.0; Douglas 

 fir. 17.2. 



Per cents of the above fire-scarred trees u'ith large or deep fire scars: 

 Incense cedar, 58.1; yellow pine. 44.2; Douglas fir, 39. S ; white 

 fir. 32.2. 



Of all four species incense cedar is by far the most susceptible to fi' ; 

 injury and in more than half of the cases the fire eats deeply into ti.e 

 tree. In vellow pine not only is a smaller per cent of trees scarred 

 than in incense cedar, but the percentage of deep burns also falls ott. 

 Both Douglas fir and white fir resist initial fire action to a far higher 

 degree than either incense cedar or yellow pine, but a different relation 

 obtains between the species as to the occurrence of heavier burns. 

 Douglas fir stands lowest in percentage of trees scarred but approaches 



