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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3.4.2 PREDOMINANT HEIGHT, TOP HEIGHT, DOMINANT HEIGHT
Because thinning can affect mean height (h - )foresters were prompted to seek a crop parameter which was relatively unaffected by thinning. The parameters they chose were predominant height, top height and dominant height. These are derived as the average total height of respectively, a specified number of the tallest (predominant height), or largest diameter (top height) trees in the stand (whether the tallest or thickest trees are used depends on whether or not the tallest trees are easily identified from the ground), or of all or some of the dominants with or without the codominants (dominant height). The international symbol is hdom.
In Australia, predominant height (incorrectly called top height in some areas) is defined as the arithmetic mean height of the tallest trees in the stand generally at the rate of 40-75 /ha (viz. NSW and ACT, 40 /ha; Q'ld., 50 /ha; South Aust., 75 /ha) .
Assuming that a rate of 50 trees /ha is specified, proceed with assessment of predominant height as follows (the procedure for top height assessment is similar):
(i) Experimental plots of defined area (< 0.1 ha)
- Determine the number of trees required for measurement in a given plot by multiplying its area in hectares by 50 and rounding off to the nearest whole number (n1).
- Divide the plot into two or four sections of equivalent area and shape with at least one internal boundary line aligned perpendicular to the fertility gradient if it is apparent, e.g.
- Allocate selection of the n1 trees as evenly as possible to the two or four defined sections, e.g. if n1 = 5 and there are four sections, allocate one selection to each of the four sections and the fifth to the section which has the tallest tree not yet selected (see next below).
- Because tree height is difficult to judge by eye, measure the height of twice the number of trees required in each section, unless the tallest tree(s) in a section is (are) obvious, and identify the tallest tree(s) in each required to make up the n1 trees.
- Average the height of the n1 trees so identified.
- Decide the size and shape of the plots to be used in the assessment. Conventionally, given a selection rate of 50 trees /ha, circular plots of 0.02 or 0.04 ha would be used, requiring the choice of 1 or 2 trees per plot.
- Select and measure for height what is judged by eye to be the 2 or 4 tallest trees per plot and accept for the assessment of predominant height the 1 or 2 tallest of these.
- Record in detail the definition of height used and how this was implemented.