Seed Vitality as a Factor in Deter- 

 mining Forest Types 



J. V. HOPMANN, M. F. PH. D. 

 In Charge of Wind River Experiment Station, U. S. Forest .Service. 



How many people, including foresters, when expressing ad- 

 miration of a tree, ever think of the adverse conditions which 

 that tree has had to overcome in order to attain its present grace- 

 ful or magnificent form? These adverse factors are met in arti- 

 ficial reforestation yet the forester is able to establish thrifty 

 forests where nature has failed. This success is accomplished 

 by the use of methods which nature cannot supply, such as 

 planting a tree two or three years old, thereby eliminating all 

 the factors which mean failure during the seedling stage. Thus 

 it is within the realm of the forester to improve on nature's 

 methods in tree production the same as this end has been ac- 

 complished in many other activities of man. Just as in the natural 

 state, the eggs of the shad fish produce about 2 fish out of every 

 possible million while man has insured a success of 70%, so is 

 nature producing millions of tree seeds where a very small per 

 cent or none produce trees. It is the endeavor of this article to 

 give some of the reasons for nature's apparent wasteful methods 

 and to show how these facts, when known, may be utilized by the 

 forester. 



The limitations of forest types as the forest gradually or 

 abruptly gives way to prairie, or the clearly drawn lines along 

 ridges where one type occupies the north and east slopes and 

 another the south and west, or the definitely drawn lines- within 

 the forest have been the subject of much discussion and conjecture. 

 At the present time soil temperature and soil moisture are con- 

 ceded to be the controlling factors in these limitations of species. 

 While these no doubt are very important and influential factors 

 the seed and its characteristics, of the species concerned, must 

 not be overlooked, because, after all, the controlling unit of any 

 species is the ability of its seed to perpetuate the species. 



The presence of any species on an area is prima facie evidence 

 of the 4 principal chapters in the establishment of a forest, viz : 



Seed production. 

 Seed distribution. 

 Seed germinability. 

 Seedling establishment. 



Since these stages are distinct and consecutive they may best be 

 considered consecutively. 



