Units of measurement, symbols, significant digits and rounding off
1.1 Units of measurement and symbols
1.2 Significant digits
1.3 Rounding off
1.4 Bias, accuracy and precision
Individual Trees and Logs
2.1 Bole characteristics
2.1.1 Diameter
2.1.2 Height
2.1.3 Bark thickness
2.1.4 Volume
2.1.5 Stem form and taper
2.2 Log characteristics
2.2.1 Diameter
2.2.2 Length
2.2.3 Volume
2.2.4 Weight
2.2.5 Allowance for defect
2.3 Crown characteristics
2.3.1 Width
2.3.2 Depth
2.3.3 Surface area
2.3.4 Volume
2.3.5 Biomass
2.4 Stem analysis
Groups of Trees (Stands)
3.1 Number of trees
3.2 Diameter
3.3 Basal area
3.3.1 Fixed-area plots
3.3.2 Angle count sampling
3.3.3 Advantages and disadvantages of angle count sampling
3.4 Height
3.4.1 Mean height
3.4.2 Predominant height, top height, dominant height
3.4.3 Stand height curve
3.5 Volume
3.6 Crown closure
3.7 Crown biomass
3.8 Growth and increment
References
Appendix 1: Checklist of equipment and materials
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2.1.5 STEM FORM AND TAPER
The terms form and taper as applied to tree stems are not synonymous. In forest mensuration, stem form (synonymous with stem shape), is determined by the way the stem tapers, i.e. by the way its diameter decreases from base to tip.
The taper of a solid body of regular outline is governed by the values of 'k' and 'b' in the equation:
Thus, measurements of the form and taper of tree stems involve measuring diameter at specified positions (heights above ground) along their length. Although these positions will vary depending on the particular situation, the basic procedures for measurement outlined in Sections 2.1.1 and 2.1.2 apply.
Change in the way a tree tapers occurs naturally but it can be induced artificially by silvicultural or other treatment, e.g. fertilising, pruning, thinning. Any treatment which affects in some way the crown of a tree is likely to have an effect on the taper and form of its stem! As these effects are (i) manifest over a period of years rather than of months, (ii) tend to be concentrated over the portion of the bole immediately below the green crown, and (iii) have implications for the methods and formulas used to estimate stem volume, it is imperative that points selected for measurement to detect or monitor a change in stem taper or form following treatment, be chosen with care. To ensure that the chosen points are representative and that the measurements have been made without error, plot the diameters or sectional areas against height above ground: a smooth curve or straight line should be evident.