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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3.3 BASAL AREA
The basal area of a stand, international symbol G (m2 or m2/ha), is the sum of the basal areas, usually overbark, of all the trees. Mostly G relates to all the living trees or to those of interest to the observer, e.g. the living trees larger than a specified minimum diameter. G values in both coniferous and hardwood forests commonly range from 10 to 60 m2/ha. In rare cases, Gs as large as 150 m2/ha may be reached on exceptionally good sites.
In small stands, G is derived by reference to tables or by summation by calculator:
where di is the dbhob in cm of the i-th tree and the constant 0.000 078 539 8 is approximately π/40 000.
G is an important reference variable for a forest stand and is particularly useful in quantitative description. Also useful is the stand mean basal area, g - . g - = G/N, where N is the number of trees in the stand. The diameter equivalent to g - is called the quadratic mean dbh, the international symbol for which is dg. g - should not be confused with G - , the mean stand basal area of a forest comprising many stands. G - is estimated by sampling the forest using either fixed-area plots (= bounded plots) or angle count sampling (ACS - also known as variable radius plot-sampling or point-sampling).