APPENDIX: WOODLAND TREE 

 VISUAL SEGMENTATION 

 PROCEDURE 



This appendix contains a field procedure for visually 

 estimating cubic foot volume of woodland tree species. 

 The procedure is updated slightly over that used for the 

 data collected in this study. The main difference is that 

 the segment length classes were changed from 2-foot to 

 1-foot intervals. Species included for the Rocky Moun- 

 tain States are all hardwoods except aspen and cotton- 

 wood, and piny on and juniper softwoods. 



What To Segment 



Trees to be measured for volume must have at least 

 one live stem 3 inches or larger in diameter at the root 

 collar (DRC) measurement point. A stem, as opposed to 

 a branch, generally grows in an upright position and 

 contributes to the main structural support of a tree 

 crown. All stems, branches, and bark, whether live or 

 dead, are included. Even severed branches lying on the 

 ground are measured. If a tree portion is missing (from 

 fencepost cutting, firewood cutting, and so forth), esti- 

 mate the size of the missing portion and record the miss- 

 ing segments. Omit a tree if more than half is missing or 

 if it is unreasonable to estimate the missing parts. 



A woodland tree is defined as a woodland species capa- 

 ble of yielding at least one stem 3 inches or larger DRC 

 with at least 8 feet of wood meeting minimum segment 

 size standards. Tree species not meeting these specifica- 

 tions are considered brush form and are not inventoried 

 as trees. 



In practice, trees meeting the specifications must 

 presently or potentially stock an area of at least 1 acre 

 surrounding a sample plot for the vegetation to qualify 

 as forest. Present stocking of tree form vegetation, or 

 evidence of prior stocking, must exceed 10 percent crown 

 cover for minimum stocking, and each individual species 

 must have the potential to meet tree form specifications 

 for the species to be included. 



What Is a Segment? 



A segment is a piece of wood classified by midpoint of 

 length and diameter. The 1-foot length and 2-inch 

 diameter classes are: 



1-foot length classes 2-inch diameter classes 



Midpoint Midpoint Actual diameters 



class 



Actual lengths 



class 



(outside bark) 



1 



1-1.49 



2 



1.5- 2.9 



2 



1.5-2.49 



4 



3- 4.9 



3 



2.5-3.49 



6 



5- 6.9 



4 



3.5-4.49 



8 



7- 8.9 



5 



4.5-5.49 



10 



9-10.9 



6 



5.5-6.49 



12 



11-12.9 







14 



13-14.9 







16 



15-16.9 







etc. 





The field estimator chooses the actual segment dimen- 

 sions by visually dividing stem and branch wood into 

 consecutive lengths for classification. Success of the seg- 



mentation procedure is completely dependent upon the 

 good judgment and care exercised by the estimator. 



To qualify, a segment must be at least 1.5 inches at 

 midpoint diameter, 1.5 inches at the small end diameter, 

 and 1 foot in total length. Unless the segment is a cylin- 

 der, the minimum midpoint diameter will be larger than 

 1.5 inches. Segments may be any diameter (class), but 

 lengths are limited to 6 feet maximum to minimize 

 errors in estimating dimensions and in computing 

 volume. 



As a rule of thumb, segments should be selected so 

 they approximate a paraboloid frustum or a cylinder. 

 Avoid breaking a stem or branch into segments that 

 look like neiloid or cone frustums. 



PARABOLOID FRUSTUM 



CONE FRUSTUM 



When in doubt, always select short segments ( < 3 feet) 

 because they will minimize errors due to odd shapes 

 when calculating volume. Keep in mind that length class 

 spans a 1-foot interval and the diameter class spans a 

 2-inch interval. For greatest accuracy, choose segment 

 lengths as close to the class midpoint as possible. Occa- 

 sionally segments must be "adjusted" to fit length cate- 

 gories by mentally moving sections from one segment to 

 an adjacent segment. This is likely to occur around forks 

 or other abrupt changes in segment form. Care must 

 also be exercised when classifying lengths of segments 

 from branches originating at angles less than 45 degrees. 

 The length class should be the average length of the 

 upper and lower sides. 



How To Segment 



A systematic method is used to (1) avoid omitting seg- 

 ments and (2) avoid recording a segment more than 

 once. Begin visual segmentation on the main stem at the 

 ground line. On multiple stem trees, begin segmentation 

 with the smallest DRC stem. Proceed up the stem until 

 you encounter a branch that contains a qualifying seg- 

 ment(s) or the stem forks. Make sure all branches having 



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