AMERICAN SYLVICULTURE 



Paragraph L. The shelterwood ^roup type of 

 natural seed regeneration. 



A. Characteristic features. 



I. Species: All species can be dealt with in a group system; 

 those endangered by windfall, however, require a modification of 

 the system, or a small rotation, or a regular progress of the groups 

 toward the storm danger. 



II. Beginning: In the shelterwood system, the nuclei for groups 

 are formed at a time, at which the soil begins to be, here and there, 

 a ready recipient for seed. In the nucleus, two or three trees are 

 cut, to begin with, and a few seedlings soon enter an appearance. 



III. Continuation: The young growth gradually spreads out, 

 more or less peripherically, from the nucleus, appearing at the feet 

 of the nearest trees. These trees, in turn, are gradually removed, 

 whilst the groups of seedlings continue to enlarge. Finally one 

 group will flow into the other, and the regeneration will present 

 a waving leaf canopy. The regularity of the canopy depends on 

 the rapidity with which the groups could be enlarged. 



IV. Means of transportation: The type obviously requires a 

 finely meshed, permanent network of transportation. The axe 

 returns to the group under formation periodically, say every three 

 to ten years, during a period of regeneration comprising from fifteen 

 to fifty years. 



V. Soil protection: The soil is continuously protected from 

 intensive insolation, and is hence kept in continuous productiveness. 



VI. Dangers: Protection from fire is very difficult; protection 

 from storm difficult, although easier than in the shelterwood com- 

 partment type. Insects, fungi, and snowbreak are not to be dreaded 

 much more than under the selection system. 



VII. Lumbering: Mother trees are always felled in a manner 

 forcing them away from the group. Hypermatiu-e trees close to 

 the group are extracted at the same time. Lumbering operations 

 are necessarily scattered. The logging expenses and the cost of 

 supervision range very high. The removal (snaking) of the trees 

 cut takes place through the benches of trees left between the groups 

 so that the soil is stirred up continuously within the benches. 



The groups should be started, if possible, at the upper end of a 

 slope so that the logs need not be snaked through young growth. 



VIII. Artificial help: To start regeneration of a nucleus, and 

 to accelerate the enlargement of a group, mosses, weeds and litter 

 on the ground may be removed previous to a seed year (bastardiz- 

 ing with advance growth group type). 



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