Revenue Branch Publications

Cruise Compilation Manual – Percent Reduction Scenarios

Precent Reduction Notes

More reduction examples and a full description of reduction methods can be viewed in Chapter 5 - Reduction Compilations of the Cruise Compilation Manual.

The Revenue Branch Cruise Compilation specialist can be reached by email: Don.Rorison@gov.bc.ca or by phone: (250) 356-7674

1. Double reductions are not permitted. A tree can only qualify for one reduction in a cruise compilation.
2. The STU field is a mandatory entry.
3. Reductions cannot be applied by block using the average line method. The average line method is the only approved method to calculate appraisal information. Therefore, block reductions will always be considered " not for appraisal purposes".
4. When compiling a reduction, pre reduction and post reduction reports are required.
5. In cases where a walk through of the area identifies a component of the stand selected for retention, such as veterans, that do not show up in the cruise plots, no other species or diameter class should be reduced to compensate for the inability to reduce that component ( i.e. veterans ).
6. Diameters are arranged into classes. For example a tree that is 50 cm at DBH is in a class that includes trees with diameters from 47.5 to 52.4. The Diameter Class table can be viewed at Appendix 14 .

Scenario #1

Partial-cut Prescription

The prescription states to reserve 20 to 30 live Douglas Fir trees per hectare from harvest. The trees must have a diameter at breast height (DBH) greater than or equal to the 50 cm class. The silviculture treatment unit (STU A) encompasses timber type 1 in a single block cutting permit with one timber type.

Percent Reduction Format

Since a range of stems per hectare are stated in the partial-cut prescription, the percent reduction input will be based on the average, which is (20 + 30)/2 = 25 stems per hectare. See section 2.1.2.1(3) of the Cruising Manual

The timber type 1 stand information (stems per hectare) must be reviewed in the stand and stock reports of the pre-reduction cruise compilation to determine the number of stems equal to or greater than the 50cm DBH class. Assuming there are 50 live Douglas fir stems per hectare in the 50 plus class or larger, 25sph want/50sph got = a 50% reduction (50% leave).

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet

Note that the timber type, risk group/tree class, and block are blanks since the reduction applies to all of the timber types, risk group/tree classes, and blocks.

Scenario #2

Partial-cut prescription

Reserve all of the live Douglas Fir stems for a seed tree source in STU A larger than or equal to the 70 cm dbh class. The cruise has two blocks with timber types 1 and 2 in each block. The treatment unit, STU A, encompasses block 1 and timber type 1. Since the veteran fir component is confined to block 1, the timber types must be labelled so that they are unique to the blocks. Therefore, timber type 1 in block 1 will be labelled as timber type 51. See Chapter 7, Position 75 of the Cruising Manual.

Percent Reduction Format

There is no need to review the stand information (stems per hectare) in the stand and stock reports of the pre-reduction cruise compilation since all of the Douglas Fir larger than or equal to the 70 cm class will be reserved.

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet

Scenario #3

Partial-Cut Prescription

Reserve all of the dead potential and dead useless trees and risk group 3 live trees.  The treatment units are STU A in timber type 1, B in timber type 2 and C in timber type 3.

Percent Reduction Format

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet

Note that the species codes are blank since the reduction applies to all species. Note that the treatment units are mandatory fields.

Scenario #4

Partial-cut Prescription

Reserve 2.5 m2/ha of the basal area of all Lodgepole Pine stems of good form and vigour in STU A that are between the 30 cm and 60 cm dbh classes. Good form and vigour is defined as trees that are in risk groups 1 or 2, i.e. no conk or blind conk. The cruise has three blocks with timber types 1 and 2 in each block. STU A encompasses block 1 and block 2. The timber types in block 3 must be labelled as unique timber types since treatment unit A does not apply to block 3 and the influence of block 3 in the cruise compilation must be removed. Type 1 in block 3 will be labelled type 3 and type 2 in block 3 will be labelled type 4.

Percent Reduction Format

The prescription is based on the basal area (square metres per hectare) reporting for Lodgepole Pine in the stand and stock reports for timber types 1 and 2 of the pre-reduction cruise compilation using the revised timber types. The timber type 1 basal area/ha for Pl in the 35 to 55 cm classes is 5 m2/ha and for type 2 is 10 m2/ha. The targeted post-reduction basal area for treatment unit A is 2.5 m2/ha, therefore the reduction is;

Type 1 in STU A = 2.5/5.0 = 50%
Type 2 in STU A = 2.5/10.0 = 25%

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet

Scenario #5

Partial-cut prescription

Harvest all of the dead trees and trees with beetle damage in the cutting authority. The cutting authority has two timber types in two blocks. STU A encompasses the whole cutting authority.

Percent Reduction Format

The prescription indicates that all of the live trees will be retained from harvest except for trees with beetle damage.

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet

Note that because all of the trees with the damage code will be cut no coding is required under the DBH classes.

Scenario #6

Partial-cut prescription

Harvest all Lodgepole Pine trees in the cutting authority that are greater than or equal to the 50 cm diameter class. See percent reduction note #6.

Percent Reduction Format

Assuming that the cutting authority is a single 40.0 hectare block and there are Fir, Lodgepole Pine and Balsam trees in the block, then all Fir and Balsam stems will be retained from harvest along with the Lodgepole Pine trees up to and including the 45 cm class.

The percent reduction input will appear as follows: Cruise Percent Reduction Worksheet