Silviculture treatments are used to enhance timber quality, increase timber volume, promote economic development and contribute to community stability by providing seasonal employment. Treatments can also be used to promote biodiversity and enhance wildlife habitat.
Silviculture activities fall under the categories of regeneration, stand tending and forest health.
Another 1987 amendment to the Forest Act was the requirement that a Pre-Harvest Silviculture Prescription (PHSP) be prepared and approved by the Ministry of Forests before any site could be harvested. In essence, the PHSP establishes an integrated plan for managing a site that is based on sound ecological principles, considers all forest resource values and includes provisions to maintain site productivity. The PHSP must integrate all factors that are considered and addressed in developing specific operational plans for harvesting, regeneration and stand tending.[36]
The PHSP is thus the first step in regenerating a stand, since it sets out the framework for species selection, stocking standards, method of regeneration, site preparation and subsequent tending to bring the trees to a free-growing stage.
In such situations, site preparation is often undertaken to produce favorable seedbeds or planting spots and to improve the early performance of seedlings.
Site preparation treatments commonly used in British Columbia can be grouped into three categories: prescribed burning, mechanical methods and chemical methods. In some cases, treatments are used in combination. Treatments are selected based on: their ability to achieve regeneration objectives with minimum impact on the site, available resources, and legislation and policy relating to the methods available.
Since 1987, the area treated by prescribed burning has steadily decreased and the area treated mechanically has steadily increased (Figure 3.42). Factors contributing to this trend include: increasing public pressure to limit burning, introduction of smoke management guidelines, risk of fire escaping, risk of missing the burning “window”, and increasing cost of burning. As well, alternative mechanical treatments — such as windrowing and preparation with excavators — are now readily available at competitive costs. Prescribed fire will remain the most appropriate treatment for some areas; it is anticipated that the area treated with prescribed fire will level off to about 25% of annual site preparation treatments for recently logged areas.
One advantage with natural regeneration is that planting costs are avoided. In addition, the new trees will better represent the species and genetic diversity of the area. However, irregular spacing and timing of natural regeneration can result in additional costs throughout the silvicultural cycle. Natural regeneration, even under favorable conditions, is usually slower and less certain than planting. The cost of regeneration delays in terms of wood production foregone and the delay of “green-up” for other values may be substantial.
In some cases, regeneration is present on-site prior to harvesting (advanced regeneration). If advanced regeneration is to be relied upon to restock an area, sufficient numbers of trees must be present before harvest to compensate for logging and post-logging losses. Trees must remain undamaged and exhibit good form and a healthy, vigorous appearance.
Figure 3.43 presents the proportion of total regeneration prescribed for natural regeneration by major licensees and the Small Business Forest Enterprise Program (SBFEP) over the period 1988-1993. Overall, the trend has been towards a decline in area prescribed for natural regeneration, from approximately 50% six years ago, to levels for the past two years at or below 35%. Reasons for the decline include:
The number of trees planted annually on Crown land increased substantially from 116 million in 1984-85 to over 245 million in 1990-91 as reforestation efforts concentrated on reducing backlog NSR (Figure 3.44). In recent years, as the backlog has shrunk, the number of trees planted annually has declined. Most backlog NSR areas will be reforested by the year 2000 and planting is expected to level off between 170 million and 200 million seedlings annually over the next 10 years.
The cumulative total number of seedlings planted on Crown and private lands exceeded one billion in 1981, two billion by 1989 and three billion by 1993 (Figure 3.45).
Planting on the Coast has remained relatively steady since about 1970 as the area harvested has remained fairly constant. Planting in the interior of the province has increased every year since 1975 due to increased harvesting and reforesting the large backlog of NSR lands. Figure 3.46 shows the area of Crown land planted by forest region in 1983-1993.
Nineteen different tree species are planted on B.C. Crown lands, often with two or three different species on the same site (Figure 3.47). Since 1991-92 the most extensively planted species is lodgepole pine in the Interior. White and Engelmann spruce, which predominated in the past, have now fallen to second place. Minor amounts of hardwoods such as birch, black cottonwood and willow are also planted.
Second year survival rates of planted trees have improved from a low of 54% in 1982 to about 87% for all species and stock types (Figure 3.48). Increased survival is attributed to better quality seedlings, improved seedling handling techniques, more comprehensive guidelines on species selection and stocking standards, and increased stand tending activities.
Seed orchards are established and intensively managed to produce a reliable supply of high genetic quality seeds. Over the past 10 years, cone and seed production, collection and processing have increased dramatically to meet regeneration demands. As well, seed is collected from an increasing variety of forest tree species. Where high quality seed is lacking, cuttings from some species can be used for regeneration. This is the case for yellow-cedar, which has very poor seed production and germination in both natural stands and seed orchards.
The goal of the Tree Seed Centre is to maintain a five- to 15-year supply of forest tree seed to mitigate the infrequency of cone crops in the wild. This infrequency is reflected in the varying amount of seed deposited to the Tree Seed Centre from natural stands over the years (Figure 3.50b, c). Approximately 90% of the current seed inventory is from natural stands. This percentage is expected to drop as more seed orchard material becomes available.
Prior to 1988, many of the province’s existing private seed orchards were developed and established in cooperation with the Ministry of Forests. Since 1988, forest licensees have been responsible for all costs associated with basic silviculture — including seed procurement. Since 1990, the private sector has maintained private orchards at its own expense. All orchards that produce seed for the regeneration of Crown land must be licensed by the Ministry of Forests.
Initially, seed orchards focused almost exclusively on coastal Douglas-fir. Over the past 10 years the seed orchard program has expanded to include many coastal and interior tree species including lodgepole pine, interior spruce and western larch. British Columbia’s 82 seed orchards produce seed for 12 tree species (Figure 3.51a, b).
Since 1967, seed orchards have produced enough seed to grow 350 million seedlings, and about 200 million seedlings derived from seed orchard seed have been planted in B.C. to date. Seed produced from seed orchards now accounts for 11% of the seed used to produce seedlings annually. Present silviculture regulations require that seed from seed orchards be used when available. By the year 2000 seed orchards are expected to provide 50% of the seed needs of the province.
As the tree breeding and seed orchard programs progress, higher quality, genetically improved seed for particular species, planting zones and elevations will become available. Geneticists are working to improve tree growth, wood quality and resistance to certain pests. All orchards are designed and managed to ensure that genetic diversity is maintained. In 1992, the Ministry of Forests established the first advanced generation coastal Douglas-fir seed orchard at Bowser on Vancouver Island.[37] Plantations from seed orchard seed are expected to show a 10% increase in growth rates. Other advanced generation seed orchards have been or are being established by forest companies and the ministry for interior spruce, lodgepole pine, western hemlock and for blister rust resistance in western white pine.
Total annual seedling production has averaged about 220 million over the past decade. Government nurseries currently produce approximately 25 million trees annually — 35% of ministry requirements and 10-12% of the total seedling program. Forty-two private nurseries produce approximately 200 million seedlings annually (90% of the total seedling program).
Based on plantation establishment and performance, field foresters have directed a steady movement towards container seedlings which can be produced through controlled greenhouse conditions. Bareroot seedling production decreased from 20% of total seedling production in 1984 to 1% in 1994.
Technical advancements in planting stock requisition and production over the past 10 years have included:
Forest vegetation can be controlled by biological (e.g., sheep), chemical (herbicides), fire, mechanical and physical (e.g., manual cutting) methods. Since each method has advantages and limitations, treatments are selected after evaluating each site. The use of sheep and other non-chemical methods has increased in recent years. Currently, herbicides account for less than half the brushing treatments in regenerated sites (Figure 3.52).
Figure 3.53 shows an increase in annual vegetation management activities in regenerated forest sites. Brushing increased substantially from 3300 hectares in 1981-82 to 60 000 hectares in 1989-90. In the last four years, brushing activities have averaged about 57 000 hectares per year. Prior to 1989-90, most brushing activities were conducted in Vancouver Forest Region; since then Prince George has been the most active region.
As shown in Figure 3.54, the annual area of silviculture surveys conducted in B.C. has increased from 365 677 hectares in 1984-85 to 810 582 hectares in 1992-93. The over one million hectares surveyed in 1991-92 includes almost 300 000 hectares of aerial and ground surveys of areas affected by wildfire before 1982 in the Prince George Forest Region.
The area audited for compliance with basic silviculture has increased substantially in recent years; the 1991-92 area tripled the area audited in 1990-91 and the area audited almost doubled again in 1992-93 (Figures 3.55, 3.56).
Audits of areas recently harvested by major licensees (Figure 3.57) consistently show over 92% projected as successful or "free-growing likely." Audits of areas recently harvested by SBFEP (Figure 3.58) project slightly less success (85-92%).
Silviculture audits are also conducted to ensure licensee compliance with existing silviculture regulations. The ministry’s review of the PHSP process between January and March 1993 indicated that 97% of all harvested areas had a PHSP in place, and of these 98% were properly approved.
The audit results for 1992-93 suggest a slight increase in the area reported as “free-growing not likely” (Figure 3.58). This result is not considered to be a trend but due to the increased focus of inspections on areas of higher risk. For major licensees, failure to meet free-growing status within the specified time period can result in a reduction in allowable annual cut and/or a fine. Where areas have been identified as “free-growing not likely,” corrective action must be taken.
Experience has shown that it is increasingly difficult to predict plantation performance over time frames that extend 15 to 20 years into the future. A more reliable measure is to assess the success of forest operations which have been completed. Future inspection and audits will focus on an evaluation of performance up to the date of assessment.
