Hypothetical Case Study

Probably the easiest way to discuss the various management issues is to use a hypothetical case study example. I propose the following, which hopefully will help clarify discussion

Designation of Block area, Standards Units and NAR:

Designation of Block Area

All across British Columbia, the USA and Europe, it is well-established with existing group selection and group shelterwood systems that the cutting unit (i.e. block) is designated as the entire area under management over the rotation, to which the group selection or group shelterwood prescription applies.

Designation of Standards Units

Standards units for group selection systems become the entire area of each pass, or all of the group openings in a given pass combined, provided these openings occur on similar sites to which the same standards and prescriptions for future silvicultural treatments can be applied. In this way the various age classes can be tracked individually through time. In our group shelterwood example, the same approach will apply, even though our long-term objective is even-aged management rather than uneven-aged management. This is because the passes will be separated by ten years, requiring different regeneration and free-growing delay periods in the prescription.

It is unreasonable, and likely unworkable to expect that each small group opening be set up as an individual standards unit. Most other group selection systems used in British Columbia have much larger block sizes with many more group openings per harvesting entry. In Vernon the Ministry of Forests Small Business program and several licencees, including Tolko and Weyerhauser, have each used group selection systems with block sizes of 40 - 60 ha and 20 to 45 openings (0.2 - 0.4 ha) per harvesting entry. In McBride a 44 ha group selection system was harvested with 23 group openings in the first pass.

Although I have used a much smaller scale for the hypothetical group shelterwood example, it becomes clear that operationally, the potential myriad of tiny openings in these systems must be viewed as one cumulative standards unit, or perhaps several standards units differentiated by significantly different site series. In our case study if we assume uniformity of site series and other site features then:

group openings a + b + c + d + e + f + g + h + i = Standards UnitA (5 ha)

As future passes are logged each pass will be another standards unit, broken into smaller standards units only due to variations in site features which are significant for management. Assuming that the passes do proceed at ten year intervals, at some point once all groups are logged, regenerated and free-growing we may be able to amalgamate them into one potential standards unit for the purposes of management.

Designation of Net Area to be Reforested (NAR).

Currently, Silviculture Prescriptions generally include an area summary which differentiates between the Net Area to be Reforested (NAR) and the area of No Planned Reforestation (NPR). The NAR describes the Standards Units(SU) to which regeneration stocking and soil conservation standards will be applied. The NPR has been broken down into: permanent access structures, natural non-productive areas, non-commercial cover (> 4 ha), reserves, and other non-planned reforestation areas.

Clearly the only portion of our hypothetical group shelterwood area which should be logically included in the NAR is Standards Unit A (all groups in the first pass). The tricky part of the prescription will be to decide how to designate the rest of the block. In some Districts licencees designate such areas as a separate Standards Unit (SU) with no regeneration or free-growing delay period, declaring them free-growing right after harvest. While it may satisfy the requirements of the Forest Practices Code, such an approach unnecessarily complicates and confuses the prescription.

Several other options are available. The unharvested portion of the block can be designated as a short term reserve (ISIS symbol SHT) which implies an area reserved for less than 20% of the rotation. If the unharvested area is called a “reserve” , it must be clear in the structure of the prescription that these reserves are short term and will all be harvested within 30 years (in our case study and at Britainia Beach). This is important since reserves are normally considered to be areas left for longer periods, often the whole rotation.

The other option is to place the non-harvested area in a given pass in the “other” column of the area summary, which hopefully would preclude the requirement to complete further information on this area. This option could make prescription writing slightly easier. Also the intent of the non-harvested area would still not be lost, since it should be made clear in the description of the silvicultural system and the stand structure and composition goals within the prescription.

Mapping

To adequately distinguish the SU(s) and determine the NAR within a block, the openings for the currently harvesting entry must be accurately mapped. This will also assist in conducting all future treatments and surveys on the block. GPS is often a preferred method to accomplish such a mapping exercise.

Although Richmond Plywood have shown all openings in all passes on their TRP, it should not be necessary to do so for the SP. Planning all passes at the TRP stage is useful in making strategic decisions and assumptions. However, decisions at the SP stage should focus on the current harvesting entry since the determination of the exact size and location of future passes is an iterative process which will be determined by future management objectives, future windthrow and pest problems. Also, delineation of future passes in the intial SP will confuse the designation of SUs, NAR and current unharvested area.

Silviculture Surveys and Associated Obligations

The current situation

British Columbia has a well-established silviculture survey system to determine stocking, plantability and free-growing status. While minor changes continue to occur almost annually, the system is still the same conceptually to that developed in the early 1980’s. A multi-storied approach to surveying was refined last year, however this approach is useful in uniformly multi-layered or uneven-aged stands, not in true group selection or group shelterwood situations.

Since the regulations require similar standards for group selection and group shelterwood as for clearcut systems, the same survey system will be used. The problem however is in determining how many plots to establish in each group opening, without requiring extraordinarily high numbers of plots in a relatively small area.

Usually in a standard clearcut the provincial approach to silviculture surveys is: 5 plots per stratum (to a maximum of 1.5 plots per ha). In our example of 9 openings comprising one 5 ha SU in the first pass, a survey would require between 5 and 8 plots if conditions in all openings were similar. While this may seem reasonable for our simple example, for blocks which have between 20 or more openings in the first entry, all within one SU, how do we approach sampling? It seems reckless to assume that all of these openings will be similar in stocking, and to just establish 5 plots (one plot in 5 randomly chosen openings).

Many would suggest that each opening should have a walk-through to initially determine the sampling strata, and then plots can be distributed between strata. While this sounds logical and it fits with the current approach on clearcut areas, differences in stocking status which are often subtle may not be very apparent and surveyors may find that they might just as well establish at least one plot in each opening if they have to visit them all.

Even if we establish one plot per opening in a group selection or group shelterwood, sampling could be onerous for the large blocks. In the Southern Interior where some group selection areas have forty-five 0.25 ha openings, one plot per opening would result in 45 plots for 11 ha, or about 4 plots per ha.

To establish some guidelines for sampling group selection or group shelterwood blocks several principles must be considered and weighed against one another:

The shear physical complexity of these systems will make surveys more expensive than in clearcuts.

Very excessive requirements for surveying may help to discourage use of these systems.

How important is “missing” one opening which may be NSR, especially where these openings are 0.2-0.5 ha in size? Can we safely assume that such NSR patches are not often missed in clearcut surveys where 1 plot per ha is often established on a 100 m x 100 m grid?

An approach which does not sample all of the openings should only be used if it gives us some reasonable statistical confidence that the openings sampled are representative of the entire stratum.

Any new guidelines for establishment of plots in these systems should be reasonably simple, as the survey system itself already has a high degree of complexity.

A Suggested Approach

After several discussions with Don Purdy, District Silviculturist in Vernon, Paul Rehsler, Surveys Specialist in Silviculture Practices Branch, and Peter Bradford, Forest Practices Forester in Silviculture Practices Branch, the following approach was developed. Note that this is a minimum sampling approach. Some managers may want to establish an unusually high number of plots (say 3 per opening), to gain a comfort level with a group selection or shelterwood system in a particular area. However, such a high degree of sampling should be voluntary and not a management requirement.

1.Establish one plot, approximately in the center of the opening in half of the openings in the block (well distributed) down to a minimum requirement of 5 plots total for a standards unit.

To determine the center of the opening, draw the longest sampling line on the map that you can, through the middle of the opening. Divide the length of the line in half and determine the bearing and a tie point.

Example (openings e and f in our case study):

2.Where all of the plots in the openings initially sampled are stocked, sample no further. The data will be assumed to represent all openings in the first pass of the block.

3.Where one plot in one opening is NSR (for blocks with up to 20 openings), sample all of the openings (one plot per opening) in the block. Where two plots in two openings are NSR (for blocks with 20 or more openings), sample all of the openings (one plot per opening) in the block

4.Determine your minimum stratum size. Often this will be set at 1.0 ha, however, some managers may wish to set this minimum lower based on the site index, strategic level planning objectives, or site-specific considerations.

5.Where one or several of the openings sampled comprise a suspected NSR area equal to, or greater than the minimum stratum size based on the plot data and observations within the openings, stratify this out as a separate stratum and designate as NSR.

6.Where the area within one or several openings is identified as NSR, and it adds up to less than the minimum stratum size based on plot data and observations, note the NSR openings on the plot card, but do not separate into a different stratum, unless combining the data makes the entire area NSR. Keeping a record of the small openings where stocking is low, but not enough area exists to meet the minimum stratum size will allow managers to use these areas as planting overflow areas.

7.In a group shelterwood situation as at Britainia Beach, you may want to set your free-growing time frames such that openings from the first pass can be assessed for free-growing status while assessing regeneration status of second pass openings.