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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3.6 CROWN CLOSURE

Crown or canopy closure is a concept applied to even-aged stands or to the upper canopy level (dominant/codominant stratum) of uneven-aged stands. It is expressed as a proportion or percent of the ground area covered by the vertical projection of the tree crowns. Because it is an approximate indicator of stand density, crown closure is an important variable in the estimation of stand volume from aerial photographs and in evaluating silvicultural operations and ecological conditions. It also has a significant influence on snow pack accumulation and snow melt.

Instruments used to estimate crown closure include the 'crown-meter' or 'crownometer' (see Weir 1959, Khan 1971, Tihonov 1971, Jackson and Petty 1973), spherical densiometer (Lemmon 1957), and moose horn (Robinson 1947, Garrison 1949). Establishing a reliable estimate of the crown closure of a forest stand requires a valid sampling frame and due consideration of the variability of the crown cover. 		 

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January, 1999.