A NATIONAL PLAN FOR AMERICAN FORESTRY 671 



tion of both; the best relationship between silviculture and protection 

 against fire, insects, and forest diseases; the relation of silviculture to 

 erosion, stream flow, and other forest influences. In general, the 

 larger and more important question of bringing forest stands to 

 maturity has had much less attention than that of establishing young 

 forests and preventing forest devastation or deterioration. 



ARTIFICIAL REFORESTATION 



Research in artificial reforestation has made substantial progress in 

 laying the foundation for fairly satisfactory nursery- and field-planting 

 technique for our most common and valuable conifers. For these 

 species, in other words, we have made substantial progress in learning 

 how to grow forest tree seedlings and establish forest plantations. 

 The availability of this information means that planting with the 

 species in question has far greater assurance of success than it would 

 otherwise have. 



On the other hand, the work has barely begun on what is perhaps the 

 larger and much more far-reaching problem of carrying plantations 

 to maturity, the ultimate measure of success. Still ahead is the re- 

 search necessary for growing forest crops of the best species and mix- 

 tures that will give highest yields, or the best quality for particular 

 purposes, or a desired combination of quantity and quality. An enor- 

 mous volume of work is required for practically all species, types, and 

 regions on such problems as the source of seed, planting sites, mix- 

 tures, density, etc. This is the information on which we shall in the 

 last analysis have to depend to avoid failures and to insure ultimate 

 success in growing timber. 



The work thus far on artificial reforestation has been almost entirely 

 on conifers. The development of a satisfactory technique for estab- 

 lishing hardwood plantations lies ahead, as does also the work on 

 which we must rely to bring such plantations to maturity. 



Time is a very important element in practically all aspects of silvi- 

 cultural research on either natural or artificial regeneration, or on 

 carrying established stands to maturity. The results cannot be has- 

 tened. The life span of trees is very long. Extreme climatic condi- 

 tions which may occur only periodically often have a decisive influence 

 on the forest. The oldest silvicultural plots have been in existence 

 from 20 to 30 years, many more from 10 to 15 years, and the largest 

 number from 5 to 10 years. Because of the relatively brief time since 

 the establishment of sample plots, the potential promise of results 

 probably outweighs the results already obtained; but in spite of this 

 there has been a great although as yet intangible gain in the passage 

 of time. 



FOREST MENSURATION 



The work in forest mensuration to date can claim the preparation 

 of volume tables for approximately 50 species, and of yield tables for 

 approximately 12 forest types which normally occur in even-aged 

 stands. American foresters need not apologize for their contribution 

 to a better technique in volume and yield table construction. Neither 

 do they need to apologize for progress in the use of statistical methods 

 as a tool in forest mensuration and other forest research. Practically 

 all of the work, however, has been done in natural as contrasted with 



