Forest Renewal 



forest regeneration is a knowledge of 

 these long-time trends, of the natural 

 factors and their variations that affect 

 tree growth, and of how the variations 

 meet the basic requirements of the 

 trees for best development. Thus the 

 manager of woodlands must have as 

 fully developed a knowledge of plants 

 and the specific environments with 

 which he is dealing as the farmer. But 

 the woodland manager necessarily 

 seeks his objective by guiding and 

 modifying these natural trends and 

 factors, rather than by attempting 

 such complete environmental control 

 as the farmer. His methods are less 

 obvious therefore than those of farm- 

 ing and often may not be apparent to 

 the untrained eye. 



THE BASIC REQUIREMENTS of treCS 



are light, heat, moisture, and wind 

 particularly in the early stages of seed 

 production and dissemination, germi- 

 nation, and survival. When a tree is 

 beyond its first stages, the texture and 

 chemical composition of the soil must 

 be added. Because a man cannot 

 change the requirements of trees, suc- 

 cess in securing natural regeneration 

 depends upon how well he can change 

 and modify the natural factors to meet 

 the requirements of the tree. 



Reactions of tree species to changes 

 in these factors vary widely. I. T. Haig 

 learned from experiments in Montana 

 that only 8 percent of lowland white 

 fir seedlings on mineral soil survived 

 in full sunlight, whereas about 90 per- 

 cent survived under intensities of 24 

 percent and less of full sunlight. At the 

 same locality, less than 15 percent of 

 western larch seedlings survived under 

 either full sunlight or almost complete 

 shade, while more than 80 percent 

 survived under one-fourth of full sun- 

 light. 



George P. Burns at the Vermont 

 Agricultural Experiment Station found 

 that sugar maple seedlings required 

 only about 2 percent of full sunlight. 



Paul J. Kramer at Duke University 

 discovered that loblolly pine seedlings 

 required nearly full sunlight for best 



121 



development. At the same time he dis- 

 covered that the life processes of east- 

 ern red oak could be fully satisfied 

 under about one-third of full sunlight. 



Working in the Lake States, Hardy 

 L. Shirley showed that, under unmodi- 

 fied conditions with only the amount 

 of light varied, the dry weight of 2- 

 year-old jack pines in 80-percent light 

 was four times that of those in 23 per- 

 cent light. Within those variations of 

 light, white spruce showed no signifi- 

 cant difference in dry weight. 



Similar variations in requirements 

 between species could be cited for the 

 other factors that affect tree growth. 

 The important point to keep in mind 

 is that trees vary widely in the condi- 

 tions under which they develop well, 

 and the creation of those conditions is 

 vital to successful forest renewal. 



Because these factors are all inter- 

 related, a modification of one affects 

 another. For example, light is one of 

 the most easily controlled. That is 

 accomplished by cutting that changes 

 the density of the forest canopy and 

 allows light to enter the stand in pro- 

 portion to intensity of the cut. A 

 change in the amount of light reach- 

 ing the forest floor affects soil tempera- 

 ture. Soil moisture also is affected, be- 

 cause the trees that are removed no 

 longer draw upon it. 



Light is so important and (more 

 than any other single factor) is so 

 closely correlated with other factors 

 that species of forest trees are often 

 classified on the basis of their apparent 

 tolerance or intolerance to shade. This 

 concept of tolerance is really an expres- 

 sion not only of the shade-enduring 

 capacity of a species but also of its abil- 

 ity to develop well under the complex 

 of all factors associated with various 

 degrees of light. The concept is im- 

 perfect in several respects and is un- 

 satisfactory if it is universally applied 

 to the exclusion of other considera- 

 tions, but it provides a useful working 

 principle in devising methods of forest 

 renewal. 



Under this concept, tolerant species 

 are those that can become established 



