712 



TIMBER RESOURCES FOR AMERICA'S FUTURE 



Page 

 Roundwood factors — Continued 



Mine timbers and miscellaneous 643 



Utilization factors 643 



Adequacy of Data 649 



Overall appraisal 649 



Possible errors are of three kinds 649 



All data are not equally reliable 650 



Forest land, timber volume, and growth 650 



Forest Survey provided data for 33 States 650 



Special surveys made in 15 States and Coastal 



Alaska 651 



Adequacy of data depends chiefly on intensity of 



sampling 651 



Nonsampling errors cannot be measured 654 



Comparisons with 1 945 estimates 655 



Estimates for Interior Alaska are only indicative. 655 



Timber utilization 655 



Data provided mainly by the Census 656 



Saw-log data have major effect on sampling 



accuracy 656 



Nonsampling errors are possible 657 



Plant residues data from special study 658 



Forest protection 658 



Fire damage data most adequate 658 



Growth loss calculated in several ways 658 



Reliability of estimates rests on extensive body 



of data. 659 



Productivity 660 



A special study of productivity was made 660 



Sampling procedure affects reliability 660 



Nonsampling errors may have occurred 664 



Forest land and timber ownership 664 



Ownership data tied to Forest Survey 664 



Sampling errors apply to part of ownership data. 664 



Some ownerships difficult to classify 665 



Forest tree planting 665 



Timber resources of North America and the world. 665 



Future demand and supply 666 



Future demand closely related to future economic 



expansion 666 



Future supply data involve additional assump- 

 tions 666 



Criteria for Rating Productivity 67 1 



Introduction 67 1 



Definition and explanation of terms 671 



Crop tree 671 



Effect of felling age 67 1 



Seed trees 672 



Forest types 672 



Species classification 672 



Established seedlings 672 



Clear cuttings 672 



Procedures for Eastern United States 672 



Sample calculation of productivity 672 



Existing stocking 674 



Existing stocking modified by composition 674 



Prospective stocking 675 



Effect of felling age 675 



Final productivity rating 676 



Page 



Procedures for Western United States 676 



Existing stocking 676 



Prosp)ective stocking 676 



Effect of composition 676 



Effect of felling age 677 



Sample calculation 677 



General standards of classification applicable to all 



regions 677 



Standards for the New England and Middle Atlantic 



Regions 679 



Forest type groups 679 



Species classification 679 



Existing stocking 679 



Prospective stocking 679 



Spruce-fir type group 679 



White pine type 679 



Maple-beech-birch and oak-hickory type 



groups 680 



Loblollj'-shortleaf pine tyjje group 680 



Oak-pine type group 680 



Effect of felling age 680 



Standards for the Lake States Region 680 



Forest type groups 680 



Species classification 680 



Existing stocking 680 



Prospective stocking ^ 680 



Aspen-paper birch type group 680 



Spruce-fir type group 680 



White-red-jack pine typ)e group 682 



Maple-beech-birch type group 682 



Oak-hickory type group 682 



Effect of felling age 683 



Standards for the Central Region 685 



Forest type groups 685 



Species classification 685 



Existing stocking 685 



Prospective stocking . 685 



Hardwood type groups 685 



Loblolly-shortleaf pine type group 686 



Effect of felling age 686 



Standards for the Plains Region 687 



Forest type groups 687 



Species classification 687 



Existing stocking 687 



Prospective stocking 687 



Effect of felling age 688 



Standards for the South Atlantic, Southeast, and 



West Gulf Regions 688 



Forest type groups 688 



Species classification 688 



Existing stocking 688 



Prospective stocking 689 



Loblolly-shortleaf pine and longleaf-slash pine 



type groups 689 



Oak-hickory, oak-gum-cypress, and oak-pine 



type groups 690 



Effect of felling age 690 



