Forest, Range & Recreation Resource Analysis Table of Contents
3.2 Timber Resource Maps
This section presents and describes a series of inventory maps for British Columbia’s timber resource. Inventory maps for range and recreation resources are presented in Chapters 4 and 5, respectively.
Most maps in this section are presented at a scale of 1:10 million, but have been derived from forest cover maps at a scale of 1:20 000. B.C.’s 7027 forest cover maps were combined to produce the provincial map. These maps have all been updated by regional and district inventory staff.
Maps for 15 larger, older provincial parks were derived from the 1956-1958 Continuous Forest Inventory. These maps are considered less reliable than the rest of the provincial maps.
Provincial maps were produced by superimposing a 2-kilometre by 2-kilometre grid over the map of B.C. and summarizing inventory information within each 400 hectares (2-kilometre by 2-kilometre) square. For the “Leading species groups” map, for example, the area occupied by each species within the 2-kilometre grid was determined from the area and percent species composition of each polygon within or intersected by the grid. Each grid was then allocated to the species group occupying the greatest area of the grid. For example, if Douglas-fir is the leading species on 150 hectares (out of 400 hectares) in the grid and no other species occupies more than 150 hectares, the grid is labelled “Douglas-fir.” Because this methodology may potentially under- or over-represent themes on the maps, tables comparing mapped areas and actual areas are provided for each map.
The description of each map is found on its facing page.
3.2.1 Tree Species
Figure 3.19 shows the leading tree species groups in the province.
The species groups mapped here are described in Table 3.2.
Interpretation of Database
In creating the map, the 2-kilometre grid was labelled according to the tree species group occupying the greatest area in each grid. For instance, a polygon with one leading species was allocated to that species. Where a polygon had two or more leading species, 60% of the polygon area was allocated to the first leading species and 40% to the second leading species.
The 2-kilometre grid summary process used to produce these maps may result in discrepancies between the actual and displayed areas and percentages for each theme. To address concerns about over- or under-representation of a theme on a map, Table 3.3 compares actual area and percentage to displayed area and percentage for each theme.
Comparison with 1984 FRRA
Species group designations are the same as those found in the 1984 FRRA (Figure B 15), with three primary exceptions. In the 1984 analysis, ponderosa pine and western white pine were grouped with Douglas-fir; here they are grouped with the other pines. Two species group names have been changed: fir and balsam (1984 FRRA) are now called Douglas-fir and true firs, respectively.
3.2.2 Age Classes
Figure 3.20 shows the leading age classes of B.C. forests.
Each 2-kilometre grid is labelled according to the age class group occupying the largest area in the grid. Themes are:
- 0-40 years (age classes 1, 2; includes not-satisfactorily-restocked [NSR] and non-commercial [NC] stands)
- 41-80 years (age classes 3, 4)
- 81-120 years (age classes 5, 6)
- 121-140 years (age class 7)
- 141-250 years (age class 8)
- 251+ years (age class 9)
- not forested (all areas with no tree species, e.g., rock, alpine, meadow, grasslands, wetlands, transportation routes, urban and industrial areas).
Interpretation of Database
The 2-kilometre grid summary process used to produce these maps may result in discrepancies between the actual and displayed areas and percentages for each theme. To address concerns about over- or under-representation of a theme on a map, Table 3.4 compares actual area and percentage to displayed area and percentage for each theme.
Comparison with 1984 FRRA
This map is similar to Figure B-17 “Forest Cover–Degree of Disturbance” in the 1984 FRRA, with two major differences:
- the 1984 map grouped age classes 7-9 as “average age over 121 years”; here they appear as three themes
- the 1984 map used a “weighted mean average” approach in designating age class (e.g., if half the grid is 50 years old and half is 100 years old, it would be classed as “75 years old”); here, the grid is allocated to the age class occupying the largest area.
3.2.3 Site Index Classes
Figure 3.21 shows site index classes for B.C. forest lands. Site index is a measure of the relative productivity of a site based on the height of dominant trees in a stand at an arbitrary age. Site index distribution provides a measure of site productivity for tree growth (and indirectly for productivity of other vegetation and some other groups of organisms).
Site index at 50 years is calculated for all leading species in the 2-kilometre grid using tree species, height, age and the computer program FREDTAB. The grid is allocated to the site index class occupying the greatest area in each 2-kilometre grid.
Interpretation of Database
The 2-kilometre grid summary process used to produce these maps may result in discrepancies between the actual and displayed areas and percentages for each theme. To address concerns about over- or under-representation of a theme on a map, Table 3.5 compares actual area and percentage to displayed area and percentage for each theme.
Comparison with 1984 FRRA
The analogous map in the 1984 FRRA is Figure B-16 “Forest Cover–Productivity,” though the measures of productivity are quite different:
- in the 1984 FRRA, productivity was expressed in wood volumes produced (cubic metres per hectare per year); here productivity is expressed as height growth over 50 years
- the values in the 1984 map are weighted means; values in the 1994 map represent the class occupying the greatest area.
Though the approaches vary, the resulting maps are quite similar. The 1994 map has greater resolution and has eight productivity classes compared to four in the 1984 analysis.
3.2.4 Mature and Immature Forest
Figure 3.22 shows B.C. forests by maturity.
Mature forests are defined as:
Immature forests are defined as:
- stands with lodgepole pine, whitebark pine or deciduous species as leading species, of stand age greater than 80 years
- stands with conifers other than lodgepole or whitebark pine as leading species, of stand age greater than 120 years.
- stands with lodgepole pine, whitebark pine or deciduous species as leading species, of stand age 80 years or less
- stands with conifers other than lodgepole or whitebark pine as leading species, of stand age 120 years or less.
Interpretation of Database
If non-forested areas (not including “not stocked” [NSR and NC Brush]) cover more than 50% of the area in a 2-kilometre grid (i.e., greater than 200 ha), that grid is mapped as “non-forested.” If forested areas cover more than 50% of the grid, then that grid is classed as “mature forest” or “immature forest,” whichever has the greatest area.
The 2-kilometre grid summary process used to produce these maps may result in discrepancies between the actual and displayed areas and percentages for each theme. To address concerns about over- or under-representation of a theme on a map, Table 3.6 compares actual area and percentage to displayed area and percentage for each theme.
Comparison with 1984 FRRA
There is no comparable map in the 1984 FRRA.
3.3 Condition of the Timber Resource
Forest productivity for timber decreases when forests are damaged by insects or disease (Section 3.3.1), when land is burned by wildfire (Section 3.3.2), when land is not satisfactorily restocked with acceptable (commercially valuable) tree species (Section 3.3.3) or when land is stocked with timber too old or too dense to produce desired timber products (Section 3.3.4).
Figure 3.23 summarizes, by forest region, the annual volume of timber damaged by forest insects and disease over the last decade. Areas and volumes of timber killed or damaged by pests do not necessarily translate into lost wood — salvage logging in many areas of the province recovers much of the wood.
Most of the decline between 1983-84 and 1989-90 can be attributed to a decline in bark beetle activity. The area of annual beetle damage slowly declined from approximately 550 000 hectares in 1983-84 to less than 200 000 hectares by 1987-88. Beetle populations increased slightly after 1987-88. Beetle damage (especially from mountain pine beetle in the Cariboo Forest Region) subsided substantially from the peak period in 1983-84 due to population collapse, due to very cold weather and to increased control efforts during the 1980s and early 1990s. Recently, the warmer and drier weather conditions favored by bark beetles have allowed populations to increase somewhat, although control activities continue to reduce damage.
Most of the annual timber volume affected by pests involves bark beetles (47.8%), defoliators (19.6%), dwarf mistletoe (16.9%) and root disease (15.7%), as shown in Figure 3.24. The gross annual loss to pests averages 14 million cubic metres. These figures do not account for salvaged timber; the net loss will be considerably less.
Figure 3.25 portrays, by region, the annual area damaged by bark beetles, defoliators and other insects between 1984-85 and 1992-93. Mountain pine beetle and western spruce budworm account for most of the area damaged. Kamloops Forest Region is the most severely affected, and damage has increased considerably over the period. Mountain pine beetle activity in the Cariboo Forest Region has recently begun to increase again, after almost a decade of low populations.
Information on areal extent of trees affected by disease damage is unavailable, as such damage often occurs in small pockets in otherwise healthy forests and can be difficult to detect.
Wildfires cause significant damage to B.C. forests each year, though the area affected by wildfire does not necessarily translate into timber volumes lost. Many stands are only lightly burned, leaving either live trees or dead trees that can be salvage logged, though the wood is often of lower quality.
British Columbia’s fire detection and firefighting capabilities are among the best in the world. The area and volume burned each year since 1984 has, in general, remained below 50 000 hectares and 5 million cubic metres (Figures 3.26, 3.27). The summer of 1985 was an exception: extremely hot, dry, windy weather conditions resulted in a substantially larger area and volume burned — mainly in the Nelson and Prince George forest regions.
The 10-year averages (1984-1993), for area and volume burned by wildfire each year are approximately 48 630 hectares and 3.5 million cubic metres, respectively. Averages are used to smooth out large annual fluctuations resulting from the effects of weather on wildfire occurrence. These statistics cover all wildfires in British Columbia, including those on not satisfactorily restocked forest land, non commercial forest land, grazing land and non-productive sites.
Figures 3.28 and 3.29 show the annual area affected by wildfire and pests and the annual area harvested for timber. These histograms show that approximately three times as much area is damaged or killed by pests and wildfire each year as is logged. Much of the area damaged or killed by pests and wildfire is subsequently logged.
3.3.3 Not-Satisfactorily-Restocked Forest Land
The term “not-satisfactorily-restocked” (NSR) describes forest lands that are not growing to their full timber production potential due to insufficient stocking of acceptable tree species. NSR lands are grouped into three main administrative categories: those denuded prior to 1982, between 1982 and 1987, and after 1987.
Lands Denuded Pre-1982
NSR lands denuded prior to 1982 are referred to as “backlog” NSR; the Ministry of Forests is responsible for reforesting all backlog NSR sites. An aggressive regeneration program including site preparation, planting and stand tending, combined with regeneration surveys to verify natural restocking, has dramatically reduced the area of backlog NSR. Since 1984, the backlog NSR on good and medium sites decreased from 738 000 hectares to 272 975 hectares.
Lands Denuded 1982-1987
The Ministry of Forests is responsible for funding regeneration of all areas denuded between 1982 and 1987. Reforestation of these lands is undertaken by the agency responsible for harvesting — either the ministry or the licensee. The ministry is responsible for reforesting lands harvested under the Small Business Forest Enterprise Program prior to January 1, 1988. Most of these sites will be reforested by the year 2000.
Lands Denuded Post-1987
Under the Forest Act, areas harvested after 1987 must be reforested — by natural regeneration, planting or a combination thereof — within a specified time frame. Major licence holders are responsible for achieving free-growing status on their tenured Crown lands harvested since October 1, 1987. The Ministry of Forests is responsible for reforesting all lands harvested under the Small Business Forest Enterprise Program after this date, and woodlot licence holders are responsible for reforesting their woodlots. The Ministry of Forests also regenerates all treatable areas denuded by fire or pests after 1987 that have not been harvested; where areas are salvage logged, the licensee is responsible for reforestation.
The stocking requirements for each area are based on ecosystem-specific standards that define acceptable tree species, minimum stocking levels, acceptable regeneration delay and free-growing standards. An area will remain classified as NSR until it meets standards that have been identified and approved in the Pre-Harvest Silviculture Prescription. Regeneration activities must consider all forest resources, including recreation, wildlife, water and aesthetics.
The extent of NSR forest land has a direct bearing on sustainable harvest levels. Areas classified as NSR that are not scheduled to be reforested with commercial species for future harvesting, are not included in the operable timber harvesting land base to calculate timber supply and determine allowable annual cuts. NSR statistics are also used to review government and industry performance in regenerating and protecting the resource base.
In 1982, British Columbia had some 1 634 500 hectares of NSR forest land. NSR area continued to expand throughout the 1980s as regeneration efforts lagged behind harvesting on the operable timber harvesting land base (Figure 3.30). Regeneration efforts significantly increased with the signing in 1985 of the five year Federal–Provincial Forest Resource Development Agreement (FRDA I), which focused on backlog NSR. By 1987, the net area reforested began to exceed the net area being harvested (Figure 3.30). Total NSR area, which peaked at 1 972 151 hectares in 1989, was reduced to 1 362 407 hectares by 1993 (Figure 3.31). This trend will hold at least until the year 2000 as ministry efforts to reduce backlog NSR continue.
In the long term, the rate of reforestation is expected to approximately equal the rate of harvesting and NSR area will reach a steady state of about 600 000 ha. This NSR area is due to the delay between time of harvesting and regeneration.
3.3.4 Decadent and Stagnant Stands
The Ministry of Forests Act (Section 7b) requires this report to contain: “a description of the location and extent of areas of forest land in the Province that…are producing timber at a rate that, in the opinion of the chief forester, is substantially lower than their potential.” This topic was addressed in the 1984 FRRA as “decadent and stagnant stands” (Chapter C-1). Today, as in 1984, there is no inventory information specifically about decadent and stagnant stands.
“Decadent” stands were defined in 1984 as “mature timber either growing very slowly or reducing in volume from decay and for which there are no present or anticipated timber values within the next 10 years.” This corresponds well with some definitions of old growth. The B.C. government’s 1992 Old Growth Strategy recognizes many values (including timber) associated with old-growth forests. Though these stands are often “producing timber at a rate that is…substantially lower than their potential,” their other values (e.g., recreation, biodiversity, spiritual) will, in some cases, take precedence over stand conversion to provide timber yield. The B.C. Ministry of Forests and B.C. Ministry of Environment, Lands and Parks will jointly publish a report on B.C.’s old-growth forests (including inventory information) in summer of 1995.
“Stagnant” stands were defined in 1984 as “immature timber growing very densely and usually [resulting] from wildfires.” This refers primarily to lodgepole pine stands in central interior B.C. No inventory information specifically about stagnant stands is available, though returning these stands to effective wood production (through thinning, fertilizing, and, in some cases, starting over) is a priority in some forest districts.