From the Lahey Report, on Irregular Shelterwood silviculture:
p iv: In many of Nova Scotia’s forests, forestry that emulates natural disturbance regimes would consist of partial or selection harvesting and modified or reduced scale clearcutting. This is because much of the province’s natural forest is composed mainly of multi-aged, mixed species stands affected by disturbance regimes that generally affect individual trees within stands, as opposed to whole stands, at frequent intervals. Carefully done, partial or selection harvesting, including small scale irregular shelterwood harvests, emulates that kind of disturbance regime, or pattern. In contrast, clearcutting at large scales does not, because it generally is applied to stands as a whole and because it promotes the regrowth of single species, even aged forests.
Conclusion 28: There are silvicultural alternatives to clearcutting that can mitigate the increase in harvesting expense associated with reduced reliance on conventional clearcutting.
Conclusion 17 These alternatives reduce the ecological concerns with harvesting that are associated with clearcutting. They are more consistent with making uneven aged (i.e., multi aged) forests a core objective of forest practices. Some of them, such as the so called string of pearls approach, are being used in Nova Scotia. Others that may hold more promise, such as irregular shelterwood silviculture, are not being used as widely, although they are being used with success in comparable jurisdictions of eastern North America. While they can increase harvesting cost relative to conventional clearcutting, they are also less expensive than partial or selection harvesting methods implemented by removing scattered single trees which, if carelessly done, can also result in high grading. In the longer term, alternative methods would contribute to healthy forests and the availability of larger trees and potentially a reduction in harvesting cost as compared to continued clearcutting of forests of small trees.
Conclusion 35: The third leg of the triad is the wider landscape matrix in which conservation and forestry objectives are blended. It is also not clearly identified or managed as such in Nova Scotia. It would encompass the rest of the forest landscape not dedicated to either conservation or to high production objectives. Under the triad, timber production is one of the activities that occurs on this landscape (excluding inoperable lands and other excluded sites such as old forest), but generally with practices, such as partial or irregular shelterwood harvesting, that have a lower ecological impact than conventional clearcutting. In this branch of the triad, forest management is expected to be dominated by practices that perpetuate multi aged forest conditions. This does not mean forestry that makes negligible contribution to the needs of the forest products industry: high rates and qualities of timber production can, in many cases, also be realized in situations where stands are multi-aged and managed under partial and shelterwood systems, including the irregular shelterwood approach that represents exemplary ecological forestry. In addition, some clearcutting can occur in this part of the triad, based on applicable disturbance patterns and stand specific conditions.
Conclusion 66. My conclusion is that the EBM framework DNR has created should be amended to remove the features that artificially favour even aged silviculture in natural forests and to strengthen the support it provides for multi aged silviculture prescriptions….The critical changes to be made are these: a. Drawing on work from other nearby jurisdictions, revamp the Forest Management Guide to describe and emphasize a wider range of ecologically based silvicultural systems, especially irregular shelterwood, that result in at least two age classes after harvesting to improve management of growing stock, conserve biological diversity, better manage light and regeneration, retain and enhance stand structures, and improve aesthetics of harvested sites. Eliminate complete overstory removals from all keys and replace with a requirement for retention of residual trees in all (former) single aged prescriptions…
From the Interim Retention Guidelines
The “Independent Review of Forest Practices in Nova Scotia”, referred to as the Forestry Review, (https://novascotia.ca/natr/forestry/Forest_Review/) recommends Implementing the “Triad” approach to Forest Management. The three legs of this “Triad” include Protected areas, High Production Forest areas and an Ecologically based Matrix (Recommendation 4, Page 61 of the Forestry Review). The Review recommends that the area managed in the “Matrix” portion of the Landscape focus on multiaged forest and reduced clearcutting. It also recommends increasing the amount of retention above the requirements for Legacy Tree Clumps as mandated under the Wildlife Habitat & Watercourse Protection regulations (WH&WP). Additionally, the Forestry Review recommends prescribing “Irregular Shelterwoods” and other changes, as part of an amended Forest Management Guide that will form the basis for managing the “Matrix” (https://novascotia.ca/natr/forestry/programs/timberman/pdf/FMG.pdf). The pertinent Forestry Review recommendation are No. 3, 4, 8, 9, 10, 12, 14, 15 21, 22 & 26 on pages 61-66.
… To implement these recommendations, it is proposed that a two-phase approach be used. A comprehensive revision of the existing Forest Management Guide, to incorporate new treatments such as “Irregular Shelterwoods”, will require a longer-term effort. Time is required to incorporate these new prescriptions into the existing Forest Management Guide framework and to make the changes required in the data collection and summary tools used to produce and evaluate Forest Harvest Plans. While this work is being conducted, an Interim Retention Guide is being introduced, in the short-term, to address recommendations to increase retention in situations where the Forest Management Guide currently prescribes Clearcuts (Overstory Removals and Seed Tree Harvests). In this way, the objectives identified in the Forestry Review to increase retention and promote multi-aged and multi-species forests can be supported while waiting for the longer-term changes to the Forest Management Guide framework.
The emphasis on Irregular Shelterwood reflects strongly the key role of Prof Bob Seymour of the University Maine in the Independent Review (also in the earlier Natural Resources Strategy). Says Seymour in the Addendum to the Independent Review
Multi‐aged systems of silviculture appear to be unfamiliar or novel to many Nova Scotian foresters, especially the variants of irregular shelterwood (Raymond et al. 2009; Seymour 2017) that are so flexible in replicating natural forest dynamics while still producing significant volumes of timber economically. Irregular shelterwood is not even mentioned in the new Forest Management Guide (McGrath 2018), and it is not among the practices that qualify for silviculture funding under the Nova Scotia Registry of Buyers system.
The critical step in addressing this issue is the revision of the Forest Management Guide, described in considerable detail in Section 14.4. We recommend that this be done as a small‐group project using a team of foresters from the region experienced in natural forest management. This is too large a task for
any single individual. The Guide in its current form is highly prescriptive and would likely benefit from relaxing many of the detailed decision criteria while keeping within clearly defined ecological sideboards. It is also a large, highly technical reference (as it should be) aimed at professional foresters
for making rigorous silvicultural decisions and, as such, will tend to become the “last word” on silviculture in Nova Scotia. Such a format is not readily accessible to landowners without forestry training, so we urge that a much‐simplified version, emphasizing the benefits of multi‐aged silviculture for both wood production and ecosystem conservation, be developed.
…If forest management in Nova Scotia were truly ecosystem based, using natural disturbance regimes and other ecological science to guide silvicultural decision making, one would expect the Forest Management Guide to prescribe multi‐aged silvicultural systems on the vast majority of the natural forest landscape. As described below, this appears not to be the case. Here, multi‐aged silviculture is defined, following O’Hara (2014), as any system that creates and maintains stand structures with two or more age classes. Multi‐aged silviculture is thus not limited to classical single‐tree selection cutting, but rather includes a broad array of two‐ and three‐aged systems as would be maintained under irregular shelterwood systems, which are arguably better suited to most conditions than balanced selection systems (Raymond et al. 2009; Raymond and Bedard 2017; Arsenault et al. 2011; Seymour 1994, 2005, 2017).