PRODUCTIVITY OF RECENTLY CUT LANDS 



229 



this trend alone still lower standai'ds might have 

 been adopted for small trees. However, other 

 equally important factors indicate that stocking 

 based only on trends of approach toward nor- 

 mality would lead to an inadequate appraisal of 

 productivity. These factors are (a) the adverse 

 effects of low initial stocking upon subsequent 

 form and quality of the timber produced, (b) the 

 limited opportunity for yields of timber prior to 

 maturity by thiiming and partial cutting where 

 early stocking is based only on sufficient numbers 

 of trees to provide a full crop at maturity. 



These two factors indicate the need for greater 

 initial stocking than would result from considera- 

 tion of only the tendency toward normal stocking. 

 Final stocking standards reflect a balance between 

 all these factors affecting the subsequent produc- 

 tivity of young stands. 



Prospective Stocking 



Stocking is often in a state of rapid change for 

 several years after cutting, particularly where 

 conditions are favorable for establishment of new 

 trees. Since field examination was made fre- 

 quently within only a year or two after cutting, a 

 fair appraisal of stocking requires consideration 

 of the prospects for additional new trees. Pros- 

 pects for stocking depend upon a number of factors 

 such as the adequacy of seed sources, including 

 their wind firmness and freedom from insects and 

 disease, the natural seedbed conditions, the den- 

 sity of inhibiting vegetation such as cull trees, 

 noncommercial species or brush, animal popula- 

 tions, topographic features, and others. These 

 individual factors vary widely in importance 

 between forest types, age classes, soil conditions, 

 and localities. All available information regard- 

 ing effects of such factors on establishment of new 

 trees was summarized in standard tabulations and 

 procedures for estimating the additional stocking 

 expected from field measiu'ement of the important 

 factors. The inhibiting nature of some factors as 

 well as the contributing or beneficial nature of 

 others was recognized in these processes. 



Plans for planting were also considered in situa- 

 tions where both existing and prospective stocking 

 were poor. On such areas, stocking was adjusted 

 to the level of past success in planting on the 

 ownership if tangible evidence was available that 

 planting would be done. The evidence required 

 to qualify for such an adjusted rating consisted 

 of outstanding orders, contracts, or similar com- 

 mitments for planting. 



Prospective stocking added to existing stocking 

 provides a more valid estimate of the overall 

 stocking condition than does existing stocking 

 alone. 



Species Composition 



Many forest types in the United States contain 

 large numbers of species. In most types, the 



commercial species vary in ability to grow, in 

 usefulness, and hence in value. Some are of 

 relatively limited use There is frequently a 

 strong tendency, in harvesting forest products, to 

 remove the species of greatest current value, 

 leaving marginal species to occupy the ground in 

 gi'eater proportions than before cutting. Repeti- 

 tion of this process during several cuts on the 

 same area results in deterioiution of species com- 

 position. The degree of this change varies widely 

 with forest types, economic situations, amount of 

 forestry effort, and the time over which periodic 

 cuttings have occurred. 



During recent years, there has been a trend 

 toward greater use of the less valuable species as 

 a result of new products or uses but also in response 

 to high prices and limited supplies of better species. 

 But with few exceptions the species whose in- 

 herent techincal properties have resulted in a 

 preferential position for a long time are still the 

 most useful and valuable in our economy. 



Some of the marginal or less desirable commer- 

 cial species grow wood as fast as some of the pre- 

 ferred species, or even faster. However, poor 

 quality or technical properties of the wood limit 

 the utility of such growth. A measure of such 

 limitations was devised by first classifying the 

 commercial species of each forest type or subtype 

 into the two groups, "desirable species" and 

 "acceptable species." Noncommercial species were 

 not included in either group nor was any direct 

 count of their numbers made at any stage of the 

 rating procedure. However, their influence was 

 reflected in the count of existing crop trees since 

 competitive efl'ects of noncommercial trees occa- 

 sionally disqualified as a crop tree an otherwise 

 desii'able one. Also the presence of noncommer- 

 cial species sometimes limited the area otherwise 

 available for prospective stocking. 



In the classification of commercial species 

 referred to above, recognition was given to many 

 local variations and modifications. Such varia- 

 tions appear in the voluminous footnotes accom- 

 panying the tabulations of species in the appendix- 

 section Criteria. They also have been taken into 

 account in the general instructions appearing in 

 sections of the Criteria dealing with species 

 classification. 



The second step in taking account of composi- 

 tion was establishment of a standard requirement 

 that at least 50 percent of the stocking on a re- 

 cently cut area consist of species classified in the 

 "desirable" category. A procediu-e was devised 

 for computing a composition factor that reduced 

 the stocking percentage if composition was found 

 to be less than 50 percent. vStocking percentage was 

 unchanged if the com.position standard was met. 

 Thus, on any recently cut area, if half or more 

 of the stocking consisted of desirable species, the 

 composition factor was 1 .0. If less than half of the 

 stocking consisted of desirable species, say 40 per- 



