26 THE NATIONAL FOREST MANUAL. 



GENERAL SILVICAL STUDIES. 



On each National Forest a complete silvical description of the forest 

 types and characteristics of the species composing 

 ^suivicaidescrip- tnem s h ou ld be worked up and extended from time 

 to time. The following ground should be covered : 



I. THE FOREST. 



1 . A complete list of trees, giving the scientific names and all com- 

 mon names in use. 



2. A complete list of shrubs. 



3. The fundamental forest types into which the Forest is divided 

 and the factors which differentiate them (climate, exposure, topog- 

 raphy, altitude, soil, etc. The proper basis for separating forest types 

 is the physical conditions of the locality, and not the composition or 

 age of the stand or any other variable condition.) 



4. General silvical description of each type, to include: 

 (a) Its approximate proportion in the Forest. 



(6) Its physical conditions of site, such as climate, soil, altitude, 

 topography, exposure, etc. 



(c) Its forestal characteristics, such as composition, interrelation of 

 the various species, even or uneven aged stands, ground cover, humus 

 conditions, etc. 



(d) External influences which are operative in the type, such as 

 fires, grazing, storms, etc. 



(e) Recommendations for Ihe silvicultural management of each 

 type. 



(/) The division of each type into subtypes on the basis of differ- 

 ences in composition, age, etc., and the presence of temporary types, 

 discussing the cause and future of each temporary type. 



II. THE SPECIES. 



1. Habit: Average mature and maximum diameter and height. 

 Form of crown and bole at different ages. Root system at different 

 ages and under different conditions. 



2. Occurrence: Distribution throughout the Forest and the effect of 

 altitude, exposure, soil, atmospheric and soil moisture, and other 

 factors, in limiting its distribution; the species with which it is com- 

 monly associated. 



3. Soil and moisture : Preference of each species as to soil. Require- 

 ments in regard to soil and atmospheric moisture. Arrange the 

 species in order of their demands for soil quality and soil moisture. 



4. Tolerance of shade: Tolerance of each species at different ages. 

 Compare its tolerance with that of its important associates by means 

 of a scale of tolerance. Discuss its ability to grow in dense shade, in 

 dense stands, and to recover from suppression. 



5. Growth and longevity: Rapidity of height and diameter growth 

 of all species. Compare with associates. Give growth tables when 

 possible. Average age to which each species remains sound and 

 vigorous. Maximum age recorded. 



6. Reproduction: (a) Seed production Abundance of seed pro- 

 duction and frequency of seed years. Method of seed dissemination. 

 Time at which seed is disseminated. Agencies which destroy seed 

 and decrease its vigor. 



