126 



soil. It is also recommended following 

 the cutting of species with persistent 

 cones that open best at high tempera- 

 tures. In the process of disking, the cone- 

 bearing limbs of cut trees are broken 

 and forced close to the soil; there the 

 high surface temperatures slowly open 

 the cones and release the seed. 



THE REACTION OF MATURE stands to 

 partial cuttings of the selection and the 

 shelterwood systems is adverse for some 

 species. That reaction takes the form 

 of increased death of trees left in the 

 cutting area for future growth and for 

 seed sources. So far, we can give only 

 theoretical explanations for this in- 

 creased death rate. One explanation 

 is that temperature and soil moisture 

 are suddenly changed by the cutting, 

 so that new conditions are created to 

 which the older trees cannot adapt 

 themselves. Freed wind movement may 

 increase the rate at which water is 

 evaporated from leaves and needles, 

 thus upsetting physiological processes 

 in the tree. Mechanical injury to roots 

 from severe bending as falling trees 

 strike some of their neighbors is an- 

 other possible contributor to the in- 

 creased death rate. 



Except for the particularly sheltered 

 areas, the reaction frequently takes 

 place in the older stands of both east- 

 ern and western hemlock, Douglas-fir, 

 the yellow birch, and some species of 

 spruce. Other species may show the 

 same reactions to lesser degrees. Thus 

 we find that the tolerant hemlocks 

 which should respond well to the selec- 

 tion system have other characteristics 

 that require clear-cutting methods in 

 many localities. 



SHALLOW SOILS over the bedrock 

 may make the selection or shelterwood 

 systems dangerous, because a partial 

 cutting removes some mutual mechan- 

 ical support and permits increased wind 

 velocity. Loss from windthrow may 

 be serious. An inherent lack of wind- 

 firmness due to typical shallow-root 

 systems also results in windthrow. En- 

 gelmann spruce is a species that re- 



of Agriculture 1949 



quires clear cutting in spots because of 

 a lack of wind firmness. 



ADAM SGHWAPPAGH, a distinguished 

 European forester of the past century, 

 cites an experience that carries an im- 

 portant message for all who seek suc- 

 cess in forest renewal. In tracing the 

 development of European forestry, he 

 related : 



"An important step in the progress 

 of sylviculture was the evolution of the 

 so-called Selection System, introduced 

 at the end of the eighteenth century. 

 By it, single trees or small groups in the 

 forest are chosen and felled, according 

 as their state of maturity suggests, and 

 the necessity for younger growth re- 

 quires. Originally adopted for the 

 utilisation and regeneration of decidu- 

 ous species, particularly Beech, the sys- 

 tem met with the commendation of 

 those pioneers in scientific forestry, G. 

 L. Hartig and Heinrich von Gotta. 

 Upon the selection method being ap- 

 plied to the Scots Pine the species 

 least suited to this treatment failure 

 resulted, which caused a sudden reac- 

 tion in favour of clear-felling with sub- 

 sequent planting. Both the selection 

 and the clear-felling systems have their 

 peculiar advantages under particular 

 circumstances; but the indiscriminate 

 use of either leads naturally enough to 

 disappointments." 



LEONARD I. BARRETT is chief of the 

 Division of Forest Management Re- 

 search of the Forest Service. Before 

 taking that position in 1945, he was 

 director of the Central States Forest 

 Experiment Station in Columbus, 

 Ohio; chief of the Division of Forest 

 Management Research in the South- 

 eastern Forest Experiment Station in 

 Asheville, N. C.; junior forester and as- 

 sistant silviculturist in the Central 

 States and Southern Forest Experi- 

 ment Stations. Before entering on his 

 research career in 1926, Mr. Barrett 

 served 2 years as a fire lookout, survey- 

 or, and timber estimator on various 

 national forests in the Pacific North- 

 west and Alaska. 



