110 BULLETIN 1105, U. S. DEPARTMENT OF AGRICULTURE. 



other vigorous herbs are absent, the relation is often reversed. This 

 is very strikingly demonstrated by the clay flats or valleys of the 

 sample plots in Group 9. On most of these sites the original bunch 

 grasses have been exterminated by continued overgrazing and pack- 

 ing of the soil. During the summer rains a low annual known as 

 six-weeks' grass (Spoi^obolus ramulosus) springs up, but it quickly 

 disappears and leaves the ground bare, save for occasional clumps 

 of weeds. It has been shown under " Herbaceous vegetation " that 

 on such sites pine seedlings exhibit a distinct preference for clumps 

 of weeds, and it was further pointed out that any kind of dead soil 

 cover, if not too deep, would favor the establishment of seedlings. 

 On the sample plots in Group 9 these sites are apparently devoid of 

 pine reproduction of all ages. Close examination, however, shows 

 that where tops or scattered brush occur, 3-year-old seedlings of 

 splendid development are fairly numerous, whereas on adjacent 

 brush-free areas seedlings are rare and usually of poor development. 



Some apprehension was felt regarding the survival of seedlings 

 in burned brush piles, because of the usual absence of shelter or 

 soil cover. The examinations made in October, 1921, completely 

 dispel this fear, because not only are the seedlings from two to 

 three times as numerous as on adjoining grassy areas, but they are 

 noticeably larger and more thrifty. From the standpoint of size, 

 the seedlings in burned brush piles are second only to those in stump 

 patches. 



Conditions under irhich burning is desirable. — Since brush, when 

 associated with luxuriant herbaceous vegetation, has been shown to 

 be detrimental to reproduction, the course which suggests itself as 

 most logical under such conditions is to burn it. A further argument 

 for this method lies in the fact that burning actually improves the 

 conditions for reproduction, as shown by the fact that in the spaces 

 where brush piles have been burned the seedlings are usually larger 

 and two or three times more numerous than on natural grassy areas. 

 This condition is accounted for mainly by the fact that the burned 

 spots, usually from 10 to 12 feet in diameter, are almost bare of 

 herbaceous vegetation and remain so for more than 10 years after 

 the fire, even where there is no grazing. The ground area occupied 

 by brush piles on a Forest Service cutting usually does not exceed 

 3 or 4 per cent of the total, but in burning the cleared space may be 

 increased to about 6 per cent. The percentage can be materially 

 increased by spreading the piles out more than has been the custom 

 in the past. The extent to which this practice could be carried 

 would be limited by the need for concentration in order to prevent 

 injury to living trees and young growth. 



