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An Introduction to Forest Measurements

from a field forester's perspective

as applied in the appalachian hardwoods of Eastern Kentucky

by Duane Bristow

See also:
  1. A description of a timber cruising computer program
  2. Forest Mensuration info from Australia
  3. A sample timber cruise report.
Meanings of values in terms of average stands
It is necessary to be able to look at a stand of timber and know what typical values to expect or to look at values in a report and visualize the stand from which they came.
The Numbers
Below is a discussion of the meaning of the numbers obtained by some common forest measurement methods. This applies to typical mid slope oak-hickory stands in Eastern Kentucky. Timber volumes are commonly expressed in terms of board feet (bf) or thousand board feet (mbf) on the doyle log scale. Dbh means diameter breast high or 4 1/2 feet above the ground.
Timber Cruising
Timber cruising is done to determine the condition of a stand, its timber volume, and its dollar value in order to plan harvests, make recommendations for future management or for purposes of financial analysis such as obtaining loans or evaluation for land sales or for testimony in court cases involving timber trespass.
Forms
Below are some sample forms for use in field collection of data.

Instructions for Data Collection

Field Equipment needed:
Prism or angle gauge, D-tape, 100 foot tape, Cruiser stick, Compass, Increment borer, clinometer, topo map, covered metal clipboard, pencils, field data sheets, sounding ax
Office Equipment needed:
Computer with proper software or Volume factor tables, tree factor tables, and calculator.
Field procedures:
Each crew is to take data on at least ten plots.
Office procedures:
In the office calculate:

FORMULAS

BAF = Basal Area Factor
A 1:33 angle gauge is BAF 10 meaning that each tree sampled represents a basal area of 10 sq. ft. per acre.
The Plot radius factor is 33 times the tree diameter or the PRF in feet is 2.75 times the tree diameter in inches.
Therefore the PRF for a 20 inch tree is 55 feet (2.75 X 20).
The area of a circle 55 feet in radius is pi or 3.14 X 55 X 55 or 9,498.50 square feet.
43,560 sq. feet per acre divided by 9,498.5 equals 4.586 which is the Ft (tree factor) for a BAF 10 sampled tree 20 inches dbh.
This means that each 20 inch tree sampled represents 4.586 trees per acre.

Expansion Factors

dbh      Ft      dbh*Ft
------  -------  -------
  5      73.34    367
  6      50.93    306
  7      37.42    262
  8      28.65    229
  9      22.64    204
 10      18.34    183
 11      15.15    167
 12      12.74    153
 13      10.85    141
 14       9.35    131
 15       8.15    122
 16       7.16    115
 17       6.34    108
 18       5.66    102
 19       5.08     97
 20       4.59     92
 21       4.16     87
 22       3.79     83
 23       3.47     80
 24       3.18     76
 25       2.93     73
 26       2.71     70
 27       2.52     68
 28       2.34     66
 29       2.18     63
 30       2.04     61
 31       1.91     59
 32       1.79     57
 33       1.68     55
 34       1.586    54
 35       1.496    52
 36       1.414    51
 37       1.339    50
 38       1.269    48
 39       1.205    47
 40       1.145    46


Fv FC 78 doyle scale

dbh      1/2      1     1 1/2   2       2 1/2   3       3 1/2
---------------------------------------------------------------
10       128      257   312     367     385     403
11       167      333   409     485     530     576
12       185      369   459     548     612     675     688
13       206      412   521     640     716     792     825
14       224      449   580     701     785     870     916
15       244      489   636     782     880     986    1043
16       258      516   673     831     945    1067    1146
17       273      545   716     888    1021    1154    1243
18       283      566   747     928    1075    1217    1313
19       300      599   792     986    1143    1300    1402
20       309      618   824    1030    1195    1360    1475
21       320      641   861    1082    1256    1431    1556
22       330      659   887    1118    1304    1486    1618
23       338      677   916    1152    1346    1541    1676
24       343      687   932    1177    1377    1577    1714
25       353      706   961    1213    1424    1635    1784
26       360      721   981    1244    1461    1677    1837
27       368      736  1003    1273    1497    1724    1887
28       371      742  1016    1289    1521    1755    1919
29       377      754  1036    1317    1557    1796    1966
30       384      767  1055    1342    1587    1832    2007
  



Woodland Preliminary Examination Field Data

Name ________________________________ Address _______________________
County _________________ Forester ______________________ Acres ______
Agent __________________ Location ___________________________________
Accessibility _______________________________________________________
Owner's Interest ____________________________________________________

Plot Data

Plot no. _____ Date _______ slope positon _____ % slope _____ Aspect __
Location ______________________________________________________________
Soil Description ______________________________________________________
Reproduction amount _______________ Species __________________________
D or CD tree of selected species nearest PC Tree no. ______ Age ______
........... Total ht. _________ Growth dbh - last 5 yrs. ___________
Stand Condition and recommendations:
 
 
 
 
 
 
 
Tree Data:
------------------------------------------------------------------------
Tree  Species   dbh  Merc. Ht.  Grade  Vigor  CC  LHC  Trees/   Vol/
No.                   (logs)                           Acre     Acre
------------------------------------------------------------------------
1.   ________  ____   ________   ___    ___  ____ ___ ________  ________
2.   ________  ____   ________   ___    ___  ____ ___ ________  ________
3.   ________  ____   ________   ___    ___  ____ ___ ________  ________
4.   ________  ____   ________   ___    ___  ____ ___ ________  ________
5.   ________  ____   ________   ___    ___  ____ ___ ________  ________
6.   ________  ____   ________   ___    ___  ____ ___ ________  ________
7.   ________  ____   ________   ___    ___  ____ ___ ________  ________
8.   ________  ____   ________   ___    ___  ____ ___ ________  ________
9.   ________  ____   ________   ___    ___  ____ ___ ________  ________
10.  ________  ____   ________   ___    ___  ____ ___ ________  ________
11.  ________  ____   ________   ___    ___  ____ ___ ________  ________
12.  ________  ____   ________   ___    ___  ____ ___ ________  ________
13.  ________  ____   ________   ___    ___  ____ ___ ________  ________
14.  ________  ____   ________   ___    ___  ____ ___ ________  ________
15.  ________  ____   ________   ___    ___  ____ ___ ________  ________

                                 Totals               ________  ________

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Last revised February 17, 1997.

URL: http://www.webcom.com/duane/wood/measure.html

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Duane Bristow (oldky@webcom.com)

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All contents copyright (C) 1997, Duane Bristow. All rights reserved.