Stand tending refers to activities carried out to maintain a healthy forest and to increase the quality and quantity of timber produced. These include juvenile spacing, pruning, fertilizing and commercial thinning. Production of healthy, well-managed forest stands can improve wildlife habitat for some species and create opportunities for forest recreation.
Spacing opens up a stand, allowing more sunlight to reach the forest floor. This practice can increase understorey biomass and the diversity of herbs and shrubs.
Juvenile spacing increased significantly with FRDA I funding. An average of about 22 000 hectares were spaced annually from 1985-86 to 1989-90. FRDA II funding for stand tending, combined with provincial funding, supported a further increase in spacing: during 1991-92 and 1992-93 approximately 46 000 hectares were spaced annually (Figure 3.59).
From 1984 to 1990, Vancouver Forest Region did the most spacing. This was due to the region’s many stands of spaceable age — a legacy of earlier logging — and to the numerous good-quality stands which provide the highest rate of return for spacing. The Cariboo Forest Region spacing program increased in 1991-92 and 1992-93 to treat the many high-density stands of lodgepole pine and to control the spread of mistletoe in young pine stands.
Areas to be pruned are usually spaced first to ensure that trees can fully respond to pruning and are not in danger of competition.
Prior to 1990-91, pruning was done primarily on a trial basis in British Columbia. Vancouver Forest Region, the exception, had an annual average of 246 hectares of pruning from 1983-84 to 1989-90 (Figure 3.60). The region’s high-quality growing sites support high growth rates and potentially good financial returns after pruning.
In 1991-92, the first year of FRDA II, over 2600 hectares were pruned. The area pruned increased again in 1992-93.
During the last four years of FRDA I, about 15 000 hectares were fertilized annually (Figure 3.61). This figure dropped to 3426 hectares in 1990-91, as a result of lower funding because no federal-provincial agreement was in place. FRDA II, initiated in 1991-92, increased the level of fertilization to about half the average annual area of FRDA I. Significant annual fluctuations in the amount of fertilization carried out are common. Since stands should ideally be spaced before being fertilized and the biological window for positive response to fertilization is larger than for juvenile spacing or pruning, forest districts may postpone fertilization for several years and later catch up. In the absence of plans strongly indicating the need for fertilization, district efforts may concentrate on juvenile spacing, which provides greater employment and increases wood value.
The suitability of individual stands for commercial thinning is based upon the productivity of the site, stand density and the age and species of trees growing on the site. Desirable characteristics in candidate stands for thinning include:
Currently, commercial thinning makes up a very small portion of the total harvest in British Columbia. This has been due to a past abundance of old growth timber with its inherent higher value and to a lack of manufacturing equipment and accessible markets for smaller material. This picture may soon change as the province’s forest industry retools for second-growth timber. Commercial thinning has averaged approximately 150 hectares per year over the last 10 years or about 0.1% of the area harvested each year. An additional 1 600 hectares of private land were commercially thinned in 1994.
As described in Section 3.3.1, pest damage to B.C. forests is equivalent to approximately 25% of the annual allowable timber harvest. Some of this damage is due to unusually severe or widespread outbreaks of insects or disease that could be prevented or reduced. Other damage results from natural forest ecosystem processes. For example, bark beetles kill weakened or old trees, creating habitat for birds and animals and aiding forest renewal and nutrient cycling.
Detailed surveys are carried out to assess particular outbreaks or conditions, to determine if populations are increasing and what levels of damage can be expected and to provide a basis for treatment. Hazard or risk maps also are developed to determine high-hazard forest ecosystems. Once identified, high-hazard ecosystems can be managed to minimize potential problems.
The long-term strategy to manage beetle populations and prevent large-scale outbreaks is to reduce vulnerability of forests by creating mosaics or mixtures of tree species and ages. The short-term strategies or treatments to save trees include:
Bark beetle management activities have recently tripled. Current program levels include:
This program is expected to save trees representing annual volumes of approximately 3 to 4 million cubic metres that would otherwise be unsalvageable, thereby extending current timber supplies by several decades. Extraction and sale of beetle-infested trees is becoming a prominent activity of the Small Business Forest Enterprise Program.
To protect forest resources, operational spray programs using the bacterial insecticide Bacillus thuringiensis Berliner variety kurstaki (Btk) are undertaken to protect trees from western spruce budworm and Douglas-fir tussock moth. Stands harvested and regenerated through a selection silvicultural system, such as all-aged Douglas-fir forests in the southern Interior, require periodic treatments of Btk to protect young trees from defoliation.
Stands are monitored to determine when damaging outbreaks are imminent, and biological sprays of bacteria or virus are applied to protect young understorey trees. Outbreaks occur usually at six- to eight-year intervals, and a two- to three-year treatment program is usually required until populations subside. Approximately 30 000 hectares were sprayed each year from 1990 to 1992 in the Kamloops Forest Region.
The ministry also supports the Agriculture Canada program to eradicate gypsy moth introductions in British Columbia. Gypsy moth and other insects and diseases that are not native to the province are of concern, because if undetected or uncontrolled, they could become permanently established in B.C. and potentially harm forest ecosystems and resources.
Over the past 15 years, gypsy moth has been repeatedly introduced into southwestern British Columbia. Eggs and larvae, often transported on the undersides of trailers or on garden furniture of people moving to the province from infested areas in eastern Canada or the United States, have been found on Vancouver Island, the Lower Mainland and in Kelowna. In 1991, Asian gypsy moth was introduced to Vancouver on ships from eastern Russia.
An extensive system of pheromone moth traps is deployed in the province each year. Occurrences of gypsy moth, mostly confined to urban settings, have been detected at an early stage and are believed to have been eradicated through the application of Btk.
Laminated root rot in coastal Douglas-fir stands has been studied for many years by Canadian Forest Service scientists and Ministry of Forests staff. The disease is routinely detected and treated or accounted for in planning forest developments and in preparing silvicultural and stand management prescriptions. Work is underway to develop operational adjustment factors that will assist planners in determining the effects of the root disease and of control treatments on forest growth. This will enable better forecasting of the impacts of root disease on timber production and yields.
Armillaria root disease in the southern Interior is another major problem. Current control treatments include planting less susceptible tree species or, on suitable sites, extracting infected stumps and roots. Better survey methods to detect and measure the occurrence of armillaria root disease and laminated root rot are being developed to reduce damage and costs of reforestation on affected sites and to better estimate the effects of these diseases.
Recent silvicultural surveys have indicated that these two root diseases threaten the health of young stands in many southern areas, sometimes to the extent that healthy, free-growing stands are unlikely within the expected time frames. Work is underway to develop better detection and survey methods, to refine free-growing standards, to determine thresholds for application of various treatments and to develop more effective treatment prescriptions and methods. Ministry staff have recently developed mechanical harvesting and thinning methods that remove infected roots and prevent buildup of these diseases.
Tomentosus root rot in spruce stands of central and northern B.C. is widespread and sometimes damaging. Relative to the other root diseases, the biology and ecology of tomentosus root rot are little known, and control methods are less certain. Survey methods to detect and measure the disease are being developed. Biological studies and trials of control methods are being conducted in cooperation with university and Canadian Forest Service scientists.
Current field guides, prescriptions and management operations are incorporating measures to control root diseases wherever possible. Nevertheless, a better understanding of the effects and management of root diseases is urgently needed to ensure that:
In coastal areas, western redcedar seedlings are often shielded with plastic tubing to reduce browsing damage by deer. Ministry staff are also working with university and industrial scientists to develop methods to forecast population levels that result in damage and to develop protectant substances that can be applied directly to seedlings.
Trials to protect trees from porcupines have been initiated. In one program, fishers were reintroduced to an area as natural predators.
Damage caused by squirrels, voles and hares can be managed by several methods, such as:
Damage to young trees by leader weevils (spruce) and stem rusts (lodgepole pine) are also common in many stands. Guidelines are being developed to help field staff prepare stand management prescriptions and undertake practices to reduce damage. Ministry staff also are developing criteria and maps of high-hazard zones, models to predict damage and effects of treatments, and more effective control methods. Recent evidence of the genetic resistance of trees to damage by these agents, and the possibility of selecting and breeding trees for this resistance, appears promising.
For the past 10 years, in cooperation with Canadian Forest Service scientists, the ministry has supported a tree selection and breeding program for western white pine resistance to blister rust. Resistant stocks and methods to protect native trees are now available, and reinstatement of western white pine as an important commercial species is likely in the near future. Western white pine is also resistant to root diseases, especially laminated root rot, and will be more widely planted in affected areas.
