MARYLAND GEOLOGICAL SURVEY 283 



Two factors explain the rapid recovery and small injury to large 

 timber. The largest areas of timber land are comprised in the prin- 

 cipal mountain ranges. The most prevalent fires have occurred in 

 these localities. Now the principal reason that destructive fires do 

 not occur, is in the fact that there is no deep humus and little accumu- 

 lated debris to feed a deep burning fire. In its present condition, the 

 soil and humus cover in these forests is only from one to two inches 

 deep and lies on bare rock and shale. Large areas bear no soil or 

 humus at all, except in the crevices of the rock, while elsewhere the 

 bare soil is composed largely of slaty shale. 



With very little dry, fallen timber or brush, the fires occurring in 

 these sections are fed mostly by the heavy fall of leaves. The ex- 

 posed rock and shale immediately beneath permits only a surface 

 fire, which almost never reaches the tree roots lying deep in crevices 

 or beneath the shale. 



The ordinary effect upon the larger timber trees is a noticeable 

 but harmless scorching of the thick bark from two to six feet up ; the 

 resin-covered trunks of the Table-mountain, Pitch and Shortleaf Pine 

 bear the higher fire marks. The greatest damage to large timber 

 observable within recent times resulted from a fire which occurred 

 about six years ago. Considerable dry, down timber in some locali- 

 ties where selective cutting for saw-timber had been done, attended 

 by a dry season, resulted in an unusually severe fire. Few large 

 trees were killed, but many were badly burned in spots at the collar, 

 evidently from the burning of unused logs and treetops lying near 

 or in contact with green trunks. While these burney trees sur- 

 vived the fire perfectly, the trunks are, as a result of burning, with- 

 out an exception, decaying at the heart and deteriorating for saw- 

 timber. 



The effect of surface fires on seedlings and coppice sprouts is disas- 

 trous in killing most growth from one to ten feet high. The thin- 

 barked stems of all species are severely scorched so that they die 

 down to the ground. An encouraging feature is, however, that the 

 roots of seedlings over one year old are rarely killed. They pro- 

 duce vigorous sprouts the following season. The scorching of Chest- 



