230 FORESTRY IN NEW ENGLAND 



As it is absolutely necessary to get rid of the other species, in 

 order to secure pure or nearly pure stands of birch and poplar, 

 burning must be used. This should be done preferably in the 

 late spring or early fall and never in the summer. Winter, 



By Permission of the U. S. Forest Service. 



Fig. 81. — Old field spruce type. Stand just after a strip tliinning. 



theoretically, would be the safest time to burn, but snow prevents 

 clean burning at that time. , Where a mixture of seedlings is 

 wanted with the root suckers, the fire must be set when the 

 ground is free from snow and the litter is not too dry to burn. 



