130 SURVEYS OF FOREST RESERVES. 



The burns that occur ia the Cascades depend largely upon the char- 

 acter of the forests in which they lie. For sheep-grazing purposes 

 burns iu the yellow-pine forests are of sifiall importance one way or the 

 other, as very little permanent change in the vegetation is effected by 

 them. The scant grass and underbrush do not make a destructive fire, 

 while the bark of the yellow pines is so thick and so nearly devoid of 

 resin that only under exceptional circumstances is a mature tree killed. 

 The sapling, however, up to an age of 15 or 20 years, are readily killed 

 by fire, and frequently an old tree well supplied with resin about some 

 injury near the base takes fire there year after year, gradually burning 

 deeper and deeper until the tree is destroyed. These scars are commonly 

 known as fire cracks. 



On rocky sloiies in the higher elevations of the yellow-pine forests, 

 where there is a large admixture of white fir and Douglas spruce and 

 the underbrush is thicker, a forest fire is often extremely destructive to 

 the timber, and is followed by a very dense growth of shrubs, made up 

 chiefly of snow brush (Geanothus vehitinus), manzanita [Arctostaphylos 

 patula), willow [Salix nuttallii), and chinquapin {Gastanopsis chry- 

 sophylla minor). Sheep do not browse readily on any of these shrubs, • 

 and they frequently form thickets so dense that a band of sheep can not 

 be driven through them. A fire in such a forest, therefore, is distinctly 

 detrimental to the interests of sheep owners. 



In the lodge- pole pine forests burns are extremely common and their 

 effect upon the timber is very pronounced. The trees have a thin bark, 

 and are easily killed without being burned up. In a few years the bare 

 poles rot at the root just beneath the surface of the ground and are 

 blown over by the wind, forming an inextricable tangle of small logs, 

 sometimes extending for miles, which it is difScult tor sheep to cross, 

 and which at this stage furnish very little grazing. A second fire 

 among these dead logs, wlien dry, burns them to ashes and opens the 

 country, though it destroys whatever humus there may be upon the sur- 

 face of the ground, usually only slight in these forests. After the first 

 burning a dense growth of seedlings usually covers the ground among 

 the dead trunks, but with the second burning these seedlings, too, are 

 destroyed. After a few years, commonly from three to five, an area 

 denuded by the two burnings has become covered with a growth of 

 short sedges, often with an admixture of small vetches. The return of 

 the pines to such an area is extremely slow, there being no old trees to 

 seed the area thoroughly, and certain conditions not now well under- 

 stood in detail evidently preventing chance seedlings from getting a • 

 start in the sod. These old grassy burns in the lodge-pole pine forests 

 form such a distinct type of vegetative covering that they deserve 

 a special designation. They will be referred to in this report as fire- 

 glades. 



The burns in the west-slope forests are very destructive to timber if 

 they occur at a dry season, when the deep litter feeds the flames and 

 everythi ng burns rapidly. By the second year they are usually covered 

 with a dense growth of weeds and browse, often interspersed with tall 

 grasses. Within a few years, however, on account of the humidity of 

 the climate, they grow up with underbrush, if they are not again burned, 

 developing a growth of saplings in a few years ; but if repeatedly burned, 

 supporting only a dense growth of underbrush. The exceptional con- 

 ditions under which the reproduction of these forests is slow are referred 

 to on page 143. 



ITatural meadows are areas on which, on account of an excess of 

 moisture, timber does not grow. The word meadow, therefore, as used 



