Abstract
This is one of a series of reports detailing the potential for partial cutting to mitigate the allowable annual cut (AAC) reductions indicated by the latest round of Timber Supply Reviews conducted in the Nelson Forest Region (NFR). This report is a background analysis of the use of partial-cutting systems by both licensees and the Small Business Forest Enterprise Program (SBFEP) in each district, from 1988 to the present.
Partial-cutting silvicultural systems are seen as having significant potential for mitigating AAC reductions by reducing the impact of two key constraints on harvest levels: adjacency rules and non-timber values. The purpose of this report is to provide a clear picture of where we stand now in terms of partial cutting in various districts and forest cover types throughout the region, so that we can identify opportunities for increased use of these systems in the future. The increased use of various partial-cutting systems will allow short-term increases in wood supply through greater flexibility of harvest scheduling, as well as long-term increases in wood supply through access to highly constrained areas that would otherwise be unavailable for harvesting.
The analysis was conducted using information obtained from the Integrated Silviculture Information System (ISIS) and Major Licensee Silviculture Information System (MLSIS) databases for the seven districts in the Nelson Forest Region. The analysis generated a number of interesting results in terms of logging patterns over the past 8 years. It also raised a number of issues about the collection and tracking of silvicultural systems data.
In terms of results, three of the seven districts in the region (Golden, Kootenay Lake, and Revelstoke) do very little partial cutting and the remaining four districts (Arrow, Boundary. Cranbrook, and Invermere) use quite a variety of the silvicultural systems. However, closer examination shows that, even in the districts with greater use of partial cutting, the majority of silvicultural systems used are low- or no-volume retention ones (clearcutting or seedtree cuts) with much less representation of higher-volume retention systems such as uniform shelterwoods or single-tree selection cuts. Even in forest types (analysis units) where high-volume retention partial cutting is commonly used, there are often substantial amounts of clearcut and seedtree systems used.
Another interesting trend seen in the analysis is that the cutting profile of the Small Business Forest Enterprise Program over the past 8 years has included a greater proportion of higher-volume retention silvicultural systems (on an area basis) than the cutting profile for licensees. However, in both cases, there is substantial room for increased application of alternative partial-cutting systems that retain more volume. Greater application of these systems (various types of shelterwood and selection cuts) could be a very useful tool in mitigating the effects of various harvesting constraints including adjacency rules and non-timber values.
Discussions with a number of licensee and Small Business Program foresters throughout the region in 1995 suggested that the introduction of the Forest Practices Code would likely be a catalyst leading to greater use of non-clearcut silvicultural systems. Many of the foresters interviewed indicated that they were already beginning to develop more and more partial-cutting prescriptions. Therefore, the numbers presented in this report may not be truly reflective of the degree of partial cutting being done currently, and this should be kept in mind when reviewing the summary tables provided in the report.
Root disease concerns appear to be a significant factor limiting the application of partial cutting systems on a more widespread basis in some districts (Golden and Kootenay Lake). However, in other districts partial-cutting systems are applied in a wide variety of analysis units / biogeoclimatic subzones, even those indicated as being high-hazard areas according to the Root Disease Management Guidebook (Arrow, Invermere).
In several districts there are concerns about whether or not it is feasible or appropriate to partially cut overmature forest types. Revelstoke and Kootenay Lake in particular have significant areas of overmature cedar-hemlock forest types that may present problems for some forms of partial cutting. Options for these types may be limited to systems such as group selection; however, other systems could be tested on a small-scale, trial basis to determine suitability.
It is important to caution that although a variety of silvicultural systems have been used in various forest types, in various districts, there has been little work done to judge the success of these treatments in terms of regeneration, post-harvest stand structure, susceptibility to disease, rates of growth, or other parameters that may be of interest to forest managers and that may have implications for future harvest levels. If the increased use of higher-volume retention partial-cutting systems is to be promoted, an extensive retrospective study needs to be undertaken in each district to determine the success of various systems to date in the different analysis units in which they are applied. It is especially important to monitor the success of partial-cutting systems that are applied in analysis units in which they are rarely prescribed. Other critical areas in which a range of partial-cutting systems need to be tested include higher-risk root disease areas, and old/decadent forest types. This will help determine the potential for the use of various systems in situations for which we have little past experience. Results of small trials in areas such as these can then be extended to other districts or licensees with similar forest types and similar management problems.
The issues raised by the analysis in terms of data collection and tracking stem for the most part from database deficiencies that became obvious part way through the process. These deficiencies include substantial amounts of missing information in certain fields, outdated information, incorrect or questionable data, and occasional missing records. The most significant of these for the purposes of this report is likely the incorrect or questionable data, specifically with regard to silvicultural system nomenclature. Often the MLSIS or ISIS label applied to a silvicultural system for a specific cutblock did not correspond to the treatment described in the prescription for the block. Unfortunately, a manual verification of all the records in the silvicultural system data field was not possible and the analysis was completed using the information at hand.
In order to improve the results of future Timber Supply Reviews, it is critical that, wherever possible, they be based on accurate and comprehensive information about past and current harvesting activities, rather than on assumptions. This will provide modellers and analysts with a reliable picture of where we stand at present so they can more successfully model future timber supplies and develop appropriate cutting levels.
In general, this analysis showed that districts that currently use little partial cutting (Golden, Revelstoke, Kootenay Lake) may have good potential for increasing the application of partial-cutting silvicultural systems, and therefore mitigating AAC reductions. However, even districts that currently use a variety of silvicultural systems throughout their land base (Invermere, Cranbrook, Boundary, Arrow) have potential for additional use of alternative silvicultural systems. These districts generally use either clearcut systems or low-volume retention systems (seedtree) on more than 50% of their land base. These systems do not help reduce adjacency constraints, and generally are not considered appropriate for protecting non-timber values. A shift towards lower proportions of these systems will allow the districts more flexibility in harvest scheduling and more access to highly constrained areas.
Districts with a greater proportion of high-volume retention silvicultural systems may also tend to have a greater area logged because, in order to remove an equivalent volume, more area must be harvested than would be required with clearcut systems. This has a number of implications including increased initial development costs, increased harvesting costs, and increased maintenance costs. These disadvantages must be weighed against the potential benefits of a shift towards more partial cutting. In general, a good mix of systems is likely the most effective option, with considerable attention given to where each system is applied. Harvest schedule models would be a very useful tool for achieving this and would provide a much better overall development plan than that provided by planning and prescribing on a block-by-block basis.
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Updated April 12, 2007
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