24 BULLETIN 234, U. S. DEPARTMENT OF AGRICULTURE. 



clean and the remainder left for seed. Even in the seed blocks 

 thinnings were made to remove lagging, converter poles, and large 

 stull trees, so that the seed groups finally consisted of from 30 to 60 

 trees ranging from 7 to 1 1 inches in diameter. In exposed situations 

 over 90 per cent of the trees left have been blown down, and many 

 others have died from sun scald or from the drying out of the soil. 

 In the more sheltered situations, particularly where the original 

 stand had been somewhat open, windfall has been much less. This 

 heavy loss from windfall quickly demonstrated the impractibility 

 of such a system for general use in lodgepole-pine stands. These cut- 

 tings were not a fair test of the wind firmness of the species, however, 

 for to reduce the number of trees per acre of any species from 500 

 or 1,000 to about 50, particularly when the individual trees were 

 tall and slender, could hardly result otherwise than in excessive 

 windfall. 



The next change in the marking system naturally aimed to elimi- 

 nate windfall. In the spring of 1909 the strip system was applied. 

 The timber was clean cut in strips, with seed strips from 100 to 150 

 feet wide left absolutely intact between them. The width of the 

 clean-cut areas was from one to three times that of the seed strips. 

 This system proved successful in reducing .windfall to a negligible 

 amount, but in other respects had no advantage over the seed-tree 

 group system. In both systems the operator gradually accumulated 

 a surplus of cordwood and small stulls in excess of the market de- 

 mand, while the Government lost from the clean-cut areas many 

 small, thrifty trees capable of rapidly developing into large material 

 under better management. At the same time there remained in 

 the seed strips many large, slowly growing trees wanted by the 

 operator and not of use in the stand except to prevent windfall. 

 Neither of the systems is satisfactory in regard to watershed pro- 

 tection, nor does either tend to increase the volume or better the 

 quality of the succeeding stand. 



Another important drawback to the systems mentioned was their 

 lack of adaptability to the great variety of conditions found on the 

 sale area. Overdense stands of lagging and converter poles, badly 

 in need of thinning, remained untouched, because a sufficient amount 

 of such material was being obtained from the clear-cut areas. Over- 

 dense and moderately dense even-aged stands, uneven-aged stands, 

 and old and young stands were all cut in exactly the same way. 

 For this reason the system of cutting was still further modified in the 

 fall of 1910 and again slightly modified in the summer of 1913. The 

 present marking rules are as follows: 



