92 JOURNAL, OF FORESTRY 



over area to lie idle for a time will have somewhat the same, although 

 a less decisive result. An area in Indalsliden Parish is cited, where 

 measurements were made in 1914 of plants from seed sown 11 years 

 before on neighboring burned and unburned strips, separated by a 10- 

 meter fire-break. Data follows : 



Unburned 

 Burned . . 



"That is, the plants on the unburned ground had developed only one- 

 third as fast as the plants on the burned ground." This beneficial 

 effect of burning applies chiefly to pine and less to spruce-fir. With 

 the former it appears to hold good not only in the stand's youth, but 

 throughout the rotation. Any loss of nitrogen near the soil surface 

 would probably not affect the deeper layers, and would speedily be met 

 by increased action of nitrogen-fixing bacteria, by the gradual reform- 

 ing of a humus layer and through atmospheric electrical discharges. 



What Areas to Burn and When and Hozv to Burn 



Burning is recommended, but not for spruce-fir, only where pine is 

 to be sown and on soils fairly rich in humus or mineral food elements ; 

 also where the sowing is hindered by brush, rich heath vegetation, and 

 decayed material. It is particularly advantageous on clay or marsh 

 soils. 



Too small areas cannot be burned economically. Four to five ha. is 

 about right, while tracts larger than 10 ha. permit too much exposure 

 to the influence of drying winds. Where an area is not to be burned, 

 but is to be seeded from the side of the area, it should not exceed 50 to 

 60 m. in width. Where seed trees on the area are to be depended upon, 

 50 to 150 pine trees per ha. are sufficient, while because of its greater 

 susceptibility to windthrow spruce-fir requires 250 to 300 trees per ha. 



Burning should take place in spring as soon as the ground cover is 

 dry on the cut-over area, but still damp in the near-by woods, while 

 the soil itself in the clearing is yet too cold and damp to permit severe 

 burning. "An old rule is that one should burn while there is one or 

 more snow patches still in the woods." It may also be done in fall, 

 while the soil is damp from rain and yet the ground cover is dry. 



Preliminary preparations for burning include the construction of 

 fire-lines around the area to be burned, the felling with tops inward of 

 all standing snags and dead trees near these fire-lines, and the piling 

 of brush away from seed trees. Ant-hills are a menace, since they 



