MANAGEMENT PLANS THE NATIONAL FORESTS 33 



REVISION OF PLAN 



A general revision of this plan will be made for every 10-year period and 

 at the end of each cutting cycle. Minor revisions will be made every five years 

 if conditions make it necessary. During the first 10-year period it will prob- 

 ably be necessary to check over and revise the plan at more frequent intervals^ 

 as more accurate data are obtained, or as points of importance are brought 

 out that have been overlooked in the original plan. 



Except as mentioned under " Cutting budget for 1921-1930," any changes or 

 revisions made must have the approval of all ofiicers approving the original plan. 



There will be needed for the first revision of this plan : 



1. More accurate data on areas and volumes of merchantable forest in those 

 parts of the circle not covered by intensive surveys at the present time. 



2. A check on the accuracy of the growth figures obtained by Johnson i-: 

 1921-22. 



3. Additional figures showing actual volume left per acre in trees 10 iiicKrb 

 and over d. b. h. on cut-over areas. 



APPENDIX, CUSTER WORKING CIRCLE 



Editorial note. — In addition to the tables here given the Appendix in ihe i-IaiL 

 as submitted contains the following : 



Description of working circle by blocks. 



Marking rules for western yellow pine in the Black Hills and Harney National Forests. 



Superseded marking rules for western yellow pine in the Black Hills and Harney Na- 

 tional Forests in effect previous to 1923. 



Volume table for western yellow pine in the Black Hills and Harney National Forests, 

 by J. V. Leighou, 1916. 



Normal increment in board- feet western yellow pine in the Black Hills ah 5 Harney 

 National Forests, by Notestein, Smith, Phillips, and Bates. 



Volume of national forest timber cut in Custer working circle by commercial saw-timber 

 operators for the fiscal year 1923. 



AREAS AND ESTIMATES (HOW OBTAINED) 



Areas. — Figures given for the areas of various types were obtained from 

 timber-survey data where such were available. For the areas not covered by 

 timber surveys, data were taken from the land-classification maps by planim- 

 eter. Only approximate accuracy was obtained where the land-classification 

 maps were used, since little or no distinction is made between the various 

 forest types, such as reproduction, poles, and merchantable timber. The acre- 

 ages obtained were divided among the various types in accordance with the 

 best judgment of persons familiar with the region. 



Estimates. — Estimates were obtained from timber-survey data where such 

 were available. These data were available for the following areas : 



T. 2 S., R. 3 B., sections 25 to 36, inclusive. 



T. 2 S., R. 5 E., except sections 30 and 31. 



'^r S S R 3 F "ill 



t! 3 Sii R. 5 E.',' except sections 6, 7, 18, 19, 30, and 31. 



T. 4 S., R. 4 E., except sections 1, 2, 3, 5, and 6. 



T. 4 S., R. 5 E., all. 



T. 5 S., R. 3 E., sections 1, 2, 11, 12, 13, and 14. 



T. 5 S., R. 5 E., all. 



T. 5 S., R. 4 E., all. 



T. 4 S., R. 3 E., all. 



For all other parts of the circle only land-classification data were available. 



The timber-survey estimates are reasonably accurate. The land-classification 

 estimates are very rough, usually ocular and not suflaciently detailed to be of 

 great value. 



Since land-classification figures were used for almost half of the area within 

 the circle, the area and volume figures obtained can not be regarded as thor- 

 oughly reliable. Hence a safety factor has been allowed in arriving at the 

 allowable annual cut. 



GEOWTH AND YIELD 



Fred Johnson, of the Denver office of the Forest Service, made detailed growth 

 studies in 1921-22 on areas in the Black Hills that were cut over under Forest 

 Service regulation 10 to 20 years ago. His final report is not yet available, 

 but according to figures in his preliminary report, there is a volume increase 

 on the average acre of 49.2 per cent at the end of the tenth year after cutting. 

 At the end of the twentieth year the volume increase is 116 per cent. 



65771—28 5 



