Green-up Guidebook
[Green-up Guidebook Table of Contents]
Appendix 1. Green-up survey procedures
Objective
The objective of the green-up survey is to determine whether or not a cut block is greened-up as specified or varied in the Operational Planning Regulation. In general, to make this assessment the surveyor must:
- Estimate the total density of commercially valuable species that are at least 1.3 m in height
- Estimate the green-up height
- Determine what proportion of the net area meets density, species and green-up height requirements.
Prior to commencing a survey, a surveyor must be aware of any variances to green-up requirements that may be set out for the opening in higher level plans or through district manager written notices.
Definitions
For the purpose of establishing green-up status, as defined in OPR, the measurement criteria for green-up height shall be the tallest tree of any commercially valuable species (unless the species has been excluded by the district manager), or other species acceptable to the district manager, in a 0.01 hectare (5.64 metre radius) plot. Commercially valuable species are defined by the district manager (see note on commercially valuable species on page 5).
Survey area
Green-up requirements apply only to the net area (e.g., net area to be reforested for areas under a silviculture prescription). Net area excludes: permanent access structures; rock, wetland or other area incapable in its natural state of growing commercially valuable trees; contiguous areas of non-commercial cover greater than four hectares; and any area reserved from harvesting because of wildlife trees or riparian reserve zones. Areas in which 40% or more of the pre-harvest basal area has been retained will contribute to the greened-up area, but will not form part of the sample area.
To fulfill green-up requirements, at least 75% of the net area must meet the green-up criteria unless otherwise specified by the district manager (see "Block coverage requirements"). Surveyors must, therefore, identify all mappable areas (as defined by district policy on minimum strata size) that fail to meet the green-up criteria. This could include areas that do not meet the required green-up height, stocking or species.
Survey methods
Free growing survey
If a free growing survey (or equivalent) has recently been conducted on a cutblock, results can be used to assist in determining green-up status. If the total free growing trees on all strata is more than 1000 trees per hectare in the interior and 800 trees per hectare on the coast, and the height of the well-spaced trees exceeds three metres (unless otherwise varied), the block is greened-up. If the total free growing trees on all strata is between 700-1000 trees per hectare in the interior and 500-800 trees per hectare on the coast, and the height of the well-spaced trees is at least 3.5 metres (unless otherwise varied), the block is greened-up.
If free growing trees alone are insufficient to meet the requirement of "adequately stocked," the area may still be adequately stocked because:
- an additional component of the total stocking, which is greater than or equal to 1.3 metres in height, may contribute to adequate stocking
- for the purpose of green-up, trees are not required to be well spaced
- green-up forest health standards are less restrictive than free
growing standards.
The average height of the well-spaced trees is not the same as the green-up height because green-up height refers only to the average height of the tallest tree in each 0.01 hectare plot. Therefore, if the free growing survey results indicate that the stand is "adequately stocked" but the mean height of the well-spaced trees is less than the required green-up height, the block may still be greened-up. If the average height of the well-spaced trees is greater than two metres, and the block is near target stocking, there is a good chance a green-up height of three metres has been achieved. However, in such circumstances, an on-site assessment should be conducted to verify green-up height.
The need for a separate green-up survey can usually be eliminated by collecting the following additional stocking and height data at a free growing survey plot:
- total trees of a commercially valuable species greater than 1.3 metres tall
- height of the tallest tree of any commercially valuable species, or other species acceptable to the district manager, in a 5.64 metre radius plot.
Also, sufficient plots must be established to meet the required minimum of 10 green-up survey plots.
Finally, by collecting leader lengths during a free growing survey, it will be possible to project height increment and estimate when green-up will be achieved. A subsequent walk-through is recommended to confirm achievement of green-up height prior to harvesting.
Walk-through
Where there are no reliable free growing survey data, or it is not obvious from the survey data that the block is greened-up, an on-site inspection will be required. If, during the site inspection, it becomes obvious that the block is greened-up, or not greened-up, a walk-through assessment can be conducted. Field notes describing the stocking, species composition, green-up height and what proportion of the NAR meets top height requirements and/or the minimum stocking requirement should be recorded and filed.
Green-up survey
When it is not clear whether the block, or a portion of the block, is greened-up, a more detailed survey (as described below) is recommended. A minimum of 10 well-distributed plots should be established in each stratum. More plots (up to a maximum of 1.5 per hectare) may be required to meet the required precision. When using less than 1.5 plots per hectare, statistical requirements must be met (see Appendix 1-A).
Stratification and sampling design
Strata identified for green-up purposes will not necessarily be the same as those used during a free growing survey. Stratification during a green-up survey is based on changes in:
- stocking; adequately or not adequately stocked
- green-up height; greater than or less than three metres or 3.5 metres or as otherwise specified.
In the following example (Table A-1), only stratum 1 would be sampled during a green-up survey. The greened-up area exceeds 75% of the net area (stratum 1 + stratum 3 = 82.9%).
Table A-1. Identifying the sample area
If in the example above, the greened-up area in stratum 1 contained two or more distinct strata based on total density relative to the adequately stocked level, and/or green-up height, the area can be further stratified accordingly (Table A-2).
Table A-2. Stratification of the sample area
Once potential strata have been refined in the field, a detailed green-up survey can be conducted. Plots must be established throughout the stratum in a manner that will ensure complete and uniform coverage. This can be achieved using either a systematic grid or a random pattern.
Plot sizes
To estimate both density and green-up height during the same survey, a nested plot design is recommended. At each sample point, establish a 0.005 hectare (3.99 m radius) plot to obtain stocking information and a 0.01 hectare (5.64 m radius) plot to obtain green-up height information.
Plot data
In the 0.005 hectare (3.99 m radius) plot, tally the total number of commercially valuable species greater than 1.3 metres tall up to a maximum plot tally. The maximum plot tally used in the statistical analysis (M value) is six on the coast and seven in the interior. This maximum plot tally should not be confused with the M value used to determine stocking or free growing status. There is no inter-tree spacing requirement.
However, a tree can only be tallied and be a "countable tree" for the purposes of green-up if it is:
- a commercially valuable species or another species acceptable to the district manager
- at least 1.3 metres in height
- free of damage, insects or pathogens that make mortality imminent (e.g., root disease, comandra or stalactiform stem cankers, white pine blister rust).
- stems on a single stump are to be tallied as one tree.
From the same plot centre, a 0.01 hectare (5.64 m) plot is used to identify the green-up height tree. Identify the largest acceptable tree and accurately determine its total height. An ocular estimate of height is inadequate; height must be measured. To be acceptable, a tree must be at least 1.3 metres in height, of an acceptable species, free from insects or pathogens that make mortality imminent (defects such as weeviled or broken tops are acceptable) and must not include trees that are not representative of the population being sampled for green-up. For example, scattered residuals or seed trees should not be measured in a stand where the stand structure that will satisfy green-up objectives is dependent on the understorey. Including the seed trees in the sample would inappropriately bias the estimate of top height upwards. However, if these trees meet the criteria of a "countable tree" they can be tallied for the estimate of stocking.
If protection of advance regeneration during harvesting was used to regenerate the area, and where this advance regeneration creates a stand structure that will satisfy green-up objectives, green-up height sample trees may include acceptable residuals.
Compilation
Total stand density of countable trees is estimated by summing 0.005 hectare (3.99 m) plot totals (using the M value) multiplying by 200 and dividing by the number of plots. Statistical tolerances must be met on each stratum, if less than the maximum number of plots is established.
Green-up height is determined by summing the sample tree heights collected from 0.01 hectare (5.64 m) plots and dividing by the number of plots that have at least one countable tree. Statistical tolerances must be met if less than the maximum number of plots are established.
When the district manager specifies a minimum number of trees required to reach three metres, stocking for the purposes of green-up is estimated by only tallying trees greater than three metres in the countable trees column. Totals in the countable trees column are then multiplied by 200 and divided by the number of plots.
