HPFnote
Reference to nutrient budgeting in High Production Forestry in Nova Scotia Phase 1 Final Report (HPF Report July 2021)
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In keeping with the Triad concept, three key criteria were used to identify area potentially suitable for inclusion in the HPF zone. The first criterion was that HPF sites should not include any land where conservation and non-timber values take primacy. Thus, protected natural areas, sensitive habitats, wildlife special management zones, and known old growth forest areas were not considered for inclusion. Second, the HPF zone should not include rich ecosites which commonly support tolerant hardwood forests as conversion of such sites to softwood plantations is ecologically inappropriate. Third, of the area remaining after application of these two criteria, the HPF zone should include land capable of supporting fast softwood tree growth, and thus must have the inherent fertility and drainage characteristics conducive to such growth.
Application of these three criteria to Nova Scotia Crown land results in approximately 246,000 ha (~16% of forested land) being potentially suitable for the HPF zone. If fully allocated, this area could generate close to 1.3 million green metric tonnes (gmt) per year of high-quality spruce timber after full program implementation.
Realizing and sustaining high timber yields in the HPF zone will involve the use of intensive silvicultural practices, comparable in some ways to an agricultural model but with a much longer crop rotation. This will include management regimes comprising mechanical and/or chemical site preparation, planting of improved growing stock, and competition control with herbicides and manual thinning to lessen natural vegetative competition. The periodic use of soil amendments, a common practice in agriculture, may also be included to sustain site productivity over successive rotations. The resulting cumulative effects of these practices are expected to result in minimum production rates of 6 m3/ha/yr of high-value forest products at time of harvest – approximately double that currently achieved in natural forests.
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6. Yield Projections
Numerous stakeholders felt that yield targets discussed in the Phase 1 Discussion Paper were very aggressive and optimistic and that high production forestry was unproven in our region. More details were requested with respect to the validity of yield forecasts and the sustainability of such high production. As a result, additional information and references to empirical data have been added to support yield assumptions and targets associated with HPF management, including new information on growth and yield research and detailed discussions on tree improvement and nutrient management research.
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4. Nutrient Management
By definition, HPF sites are expected to produce merchantable volumes at rates of 6 m3/ha/yr or more at time of final harvest. This type of production is nutrient-demanding and will likely match or exceed the natural long-term nutrient supply rates on many sites. Therefore, soil monitoring and development of nutrient management plans are necessary components of high production forestry.
Over the last several years, NSDLF has been directly involved with several soil and site productivity related projects including: (i) development of a forest soil classification system (Neily et al. 2013), (ii) development and calibration of a forest nutrient budget model (Keys et al. 2016), (iii) development of a forest soil and tree tissue sampling program, (iv) research on ground disturbance and soil damage assessment, (v) research on forest liming, and (vi) research on soil amendment use in spruce plantations (Keys et al. 2018). All this work, combined with ongoing research, will be used to develop science-based and effective soil monitoring and nutrient management regimes for HPF sites.
Nutrient Budgets: Nutrient management starts with knowing what nutrients are available, what the demands are, and what the natural supply rates are. The Department’s nutrient budget model (NBM-NS) can be used to model species and site-specific nutrient demands and supplies under various HPF management scenarios. In addition, soil sampling program data (augmented by site-specific sampling) can be used to estimate current nutrient stores by soil/site type. Results can then be used to develop silviculture and amendment prescriptions aimed at restoring, balancing, and/or maintaining soil nutrient conditions over time (to be confirmed by soil monitoring and periodic testing). As part of this assessment, it has already been determined that HPF management cannot and will not include removal of nutrient-rich foliage and slash through either full-tree or whole-tree harvesting practices. This will also enhance biodiversity on HPF sites by periodically providing potential habitat for insects, amphibians, reptiles, small mammals, and birds.
Soil Amendments: Soil amendments come in many forms and provide a range of potential benefits. For example, as a result of decades of acid deposition, many forest soils in Nova Scotia are very low in base cations (calcium, magnesium, potassium) and would benefit from a “lime” application in the form of traditional dolomitic lime, wood ash, and/or alkaline stabilized biosolids (Pugliese et al. 2014; Lawrence et al. 2016; Keys et al. 2018). An early liming treatment will likely be part of many HPF management regimes. When available, use of wood ash generated from the Province’s new Small-Scale Wood Energy Initiative would be a natural extension of this program. Another potential liming option is use of crushed basalt that, in addition to being a slow-release nutrient source, has the potential to promote carbon sequestration through bicarbonate (HCO3-) production – a natural extension of the weathering process (Beerling et al. 2018).
Options with respect to nitrogen and phosphorous amendments include inorganic fertilizers and organic residues (e.g., manures or treated sewage). Organic amendments could also be used to offset potential losses in soil organic matter and related carbon stores. Occasional use of N-fixing nurse crops (e.g., Alnus spp.) may be another option to increase mineral soil nitrogen and carbon stores (Mayer et al. 2020). In future, there may also be options related to biochar use (Page-Dumroese et al. 2016).
Although use of soil amendments may be part of HPF management, its important to note that such use will be infrequent and/or of low rates compared to agriculture. When needed, most applications will occur in association with (i) site preparation, (ii) after planting but before crown closure, or (iii) after commercial thinning. In addition, many of these amendments will be “slow-release” so as not to cause ecosystem shock or excessive leaching.
Monitoring: Periodic monitoring of soil conditions is a necessary and important component of sustainable high production forestry. In addition to soil chemistry (including carbon stores), this includes monitoring of physical properties such as bulk density and aeration porosity that can be negatively impacted by increased machine traffic. Ongoing soil monitoring will allow confirmation of effective treatments, abandonment of ineffective treatments, and testing of alternative management approaches.
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pp 12-14 Under Suitability Critera
To estimate the amount of this Crown land potentially suitable for HPF management, a series of additional “removal” criteria were applied to (i) meet biodiversity objectives and (ii) address productivity and/or land use constraints. As part of this process, only medium to rich ecosites (ecosites AC10 and AC11 as described in Nova Scotia’s forest ecosystem classification system, Neily et al. 2013) were considered for HPF eligibility (Figure 3). The majority of rich and very rich ecosites (AC13, AC14, AC16, AC17) were removed to meet biodiversity objectives (i.e., to avoid conversion of natural tolerant hardwood sites and floodplain sites to softwood plantations). Less productive ecosites, such as those that naturally support pines and black spruce, were removed for site productivity constraints (including AC6, AC7, AC9, low productivity AC10 and AC11 sites, and all MB ecosites). In addition, all very poor, dry, and wet ecosites were removed for productivity and/or biodiversity reasons. Any sites not considered for the HPF zone and not part of the Conservation zone, but eligible for forest management activities, were automatically assigned to the Ecological Matrix zone. This included watercourse buffers embedded or adjacent to potential HPF areas (estimated at < 1% of forested Crown land area).
Figure 3. Edatopic grid showing relative moisture and nutrient regimes for Acadian group ecosites (from Neily et al. 2013). Ecosites suitable and targeted for high production forestry with red spruce, white spruce, and Norway spruce are nutrient medium-rich, fresh to moist sites outlined by the red box. For more information on ecosite characteristics, see Neily et al. (2013)
This approach resulted in approximately 16% (246,000 ha) of forested Crown land being classed as potentially suitable for the HPF zone, with 33% (514,000 ha) currently assigned to the Conservation zone and the remaining 51% (783,000 ha) assigned to the Ecological Matrix zone (Table 2). For comparison purposes, in the Phase 1 Discussion paper, total Crown land area was the reference used when discussing potential HPF land area. At that time, 18% of total Crown land was considered suitable, but after more detailed land base assessment and further consideration of eligibility criteria, this has been reduced to 13% (Table 2). The area removed from HPF consideration was all operable land added to the Ecological Matrix zone within the working forest.
