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... Sub-Boreal Spruce zone (SBS) is the montane zone dominating the landscape of the central interior of British Columbia ( Figure 50). It occupies the gently rolling terrain of the Nechako and Fraser plateaus and the Fraser Basin and fingers into more mountainous areas along its western, northern, and eastern boundaries. ...
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Citations
... The SBS has a continental climate with a mean annual temperature below 0°C for 4-5 months of the year, and above 10°C for 2-5 months. Mean annual precipitation ranges from 440 to 900 mm with 25-50 % falling as snow ( Meidinger et al., 1991). ...
Accurate, reliable, and cost-effective methods of evaluating forest regeneration success are needed to improve forest inventories and silvicultural operations. While traditional surveys are relatively inexpensive and meet current data requirements, their annual coverage of over 1 million hectares in British Columbia alone are operationally and logistically intensive. To improve the efficiency and utility of forest regeneration inventories, the incorporation of multi-temporal monitoring linked to years since planting (YSP) could help improve understanding of rates and characteristics of vegetative succession while providing a means to evaluate the economic and operational success of management actions on public land. In this study, we evaluate the potential of utilizing Unmanned Aerial System (UAS)-acquired very high spatial resolution imagery to provide spatial, spectral, and structural information on forest regeneration in previously clear-cut stands near Nakusp and Quesnel, British Columbia, Canada. Three stands approximately 5, 10, and 15 YSP were chosen at both sites. Using wall-to-wall UAS-acquired red–green–blue (RGB) imagery, dense Digital Aerial Photogrammetric (DAP) point clouds were produced providing forest structure information. Spectral data in the form of Visible Vegetation Indices (VVI) including the Normalized Green Red Difference Index (NGRDI), visible atmospherically resistant index (VARIg), and Green Leaf Indices (GLIx) were computed. Spectral and structural information from the VVI and DAP were combined to perform Object-Based Image Analyses (OBIA) facilitating supervised classifications of forest cover into conifer, deciduous, and ground classes. Independent classifications were performed on each stand, yielding high overall accuracies (86–95% for Nakusp; 93–95% for Quesnel). Spectral and structural differences amongst classes and YSP were analysed. Height and area coverage of conifers were found to increase with YSP in both sites (0.7–2.7 m for Nakusp; 0.3–2.2 m for Quesnel), while VVI metrics were shown to be more successful than standard RGB at differentiating forest cover through time. The results of this study indicate that UAS-acquired imagery has a potential niche for quickly, accurately, and reliably providing highly detailed spatial, spectral, and structural information on forest regeneration. Methodology and data products from this study show promise for benefiting silvicultural monitoring and operations while improving multi-temporal forest inventory knowledge.
... The Sub-Boreal Spruce (SBS) biogeoclimatic zone, which is situated primarily in central British Columbia, occupies nearly 11% of the area of the province. 1 It includes a wide range of climatic conditions, being broadly transitional between true boreal forests to the north and east, and the warmer and/or drier montane or sub-boreal forest types to the south and southwest (Meidinger et al. 1991). Site preparation has been used extensively since 1980 to facilitate conifer seedling regeneration in the SBS zone ( Figure 1). ...
In 1984 and 1987, two experiments were initiated in wet and very wet Sub-Boreal Spruce biogeoclimatic units in north–central British Columbia to examine the effectiveness of different site preparation techniques in relieving constraints on hybrid white spruce (Picea engelmannii × glauca) establishment.
The experiments were not replicates; however, mechanical mounding, patch scarification, and blade scarification treatments were included in both.
Responses were examined for bareroot spruce planting stock at the Upper Coalmine site in the Very Wet Cool Sub-Boreal Spruce subzone (SBSvk) and for container spruce planting stock at the Mackenzie site in the Finlay-Peace Wet Cool variant of the Sub-Boreal Spruce zone (SBSwk2). At the Mackenzie site, disc trenching and chemical site preparation treatments were also tested.
In both experiments, mounding was the only treatment that substantially improved survival and significantly increased spruce growth relative to the untreated controls. The other mechanical treatments (patch scarification, blade scarification, and disc trenching) that exposed mineral soil but did not create raised microsites were ineffective, indicating that relieving cold, wet soil conditions was of primary importance at these sites. Due to its terrain, as well as to its lower meso-slope position, the Mackenzie site was also subject to frequent summer frosts; damage was highest in the chemical site preparation treatment, probably because the herbicide completely eliminated overtopping vegetation that, in other treatments, is assumed to have provided some protection through the prevention of nighttime radiative heat loss. Damage from hares and white pine weevil was also common at the Mackenzie site; the former had the greatest effect in treatments that did not reduce vegetation abundance, and the latter predominantly affected trees in the mounding treatment that were least overtopped. The complexity of limiting factors observed in the Mackenzie experiment demonstrates the importance of correctly identifying the primary limiting factor to seedling establishment, as well as the difficulty in relieving multiple constraints that interact with each other.
... The sampled area was located in the sub-boreal spruce (SBS) biogeoclimatic/ecological zone with three broad subzones dry, mesic, and moist of central British Columbia [18]. All investigated stands were lodgepole pine-dominated, unsalvaged stands. ...
... Seventy percent (70%) of the sampled stands were selected randomly and the remaining thirty percent (30%) were targeted to ensure complete coverage of ecological zones and different age classes. Prior to temporary sample plot (TSP) establishment and sampling, reconnaissance was carried out to determine if stands met the following criteria: (a) lodgepole pine-leading (dominated); (b) within the SBS biogeoclimatic/ecological zone [18]; and (c) based on forest cover maps, age class 1 or AC1 (13-20 years), 2 or AC2 (21-40 years), 3 or AC3 (41-60 years) and 4 or AC4 (61-80 years) ( Table 1). Large scale harvesting and silvicultural practices have created a legacy of managed age class 1 and 2 stands in central BC. ...
The current mountain pine beetle (MPB) (Dendroctonous ponderosae Hopkins) epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest. Generally, MPB attack larger and older (diameter > 20 cm or >60 years of age) trees, but the current epidemic extends this limit with attacks on even younger and smaller trees. The study’s aim was to investigate the extent of MPB attack in young pine stands and its possible impact on stand dynamics. Although MPB attacks were observed in trees as small as 7.5 cm diameter at breast height (DBH) and as young as 13 years old, the degree of MPB attack (percent stems ha⁻¹) increased with increasing tree diameter and age class (13–20, 21–40, 41–60, and 61–80 years old) (6.4%, 49.4%, 62.6%, and 69.5% attack, respectively, by age class) which is greater than that reported from previous epidemics for stands of this age. The mean density of surviving residual structure varied widely among age classes and ecological subzones. Depending on age class, 65% to 77% of the attacked stands could contribute to mid-term timber supply. The surviving residual structure of young stands offers an opportunity to mitigate the effects of MPB-attack on future timber supply, increase age class diversity, and enhance ecological resilience in younger stands.
... Management practices resulted in vast areas of relatively even-aged, mature lodgepole pine stands, much of which was killed during the most recent mountain pine beetle outbreak (Wulder et al., 2010). The forests of the central interior plateau of BC are dominated by lodgepole pine, and classified as the Sub-Boreal Spruce (SBS) zone (Meidinger et al., 1991 ) in British Columbia's biogeoclimatic ecosystem classification (BEC). The SBS zone is characterized by severe winters and warm, moist, short summers. ...
... Mean annual temperatures range between 1.7 °C and 5 °C with average monthly temperatures above 10 °C for 2–5 months of the year. Mean annual precipitation ranges from 440 mm to 900 mm with as much as 50% falling as snow (Meidinger et al., 1991). The Carrot Lake study site is characterized as the Kluskus moist cold variant of the SBS BEC zone (SBSmc3), at an elevation of 1100 m. ...
... The study site, Vama Vama Creek, is located in central BC within the Prince George Timber Supply Area (forest district). It is located in the warm cool (wk1) sub zone of the SBS (Sub-Boreal Spruce) biogeoclimatic zone (Meidinger et al., 1991). Soils at the study site are formed on medium-textured (silt loam) morainal deposits. ...
Strategies for managing mixed broadleaf-conifer stands in British Columbia (BC) have been under review in recent years as the benefits of mixedwood management have been recognized. More has been learned about the role of broadleaves in forest ecosystems however ecosystem-specific know-ledge about the competitive interactions between mixed broadleaf-conifer stands is still scarce. Therefore a competitive interactions study was conducted to facilitate ecosystem-specific manage-ment for lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling as-pen (Populus tremuloides Michx.) in the sub-boreal spruce (SBS) zone of central BC. The experi-ment was a completely randomized block design with six different aspen densities replicated three times. Each replicate was sampled three times between ages 14 to 19 years. Pine diameter and height growth were influenced by aspen density. Our current quantitative findings suggest that lodgepole pine growth was not impacted when growing with aspen densities up to 2500 stems ha −1 . Considering free growing (FTG) and not free growing (NFTG) pine at the time of trial estab-lishment, an insignificant difference was found for DBH, height and crown volume responses. Leaf area index (LAI) and diffuse non-interceptance (DIFN) radiation were also not significantly dif-ferent between FTG or NFTG trees suggesting our results exceed the current BC's free growing standard. Further work is recommended to determine whether or not the current free growing standards are appropriate for producing the desired crop outcome.
... Most of the outbreak activity of both insects occurred in the sub-boreal spruce and the Engelmann sprucesubalpine fir biogeoclimatic zones. The climate of the sub-boreal spruce zone is continental and therefore exhibits seasonal extremes resulting in severe winters and warm, moist summers (Meidinger et al. 1991). The sub-boreal landscape is characterized by upland coniferous forests wherein interior spruce and subalpine fir trees predominate as climax species (Meidinger et al. 1991 ). ...
... The climate of the sub-boreal spruce zone is continental and therefore exhibits seasonal extremes resulting in severe winters and warm, moist summers (Meidinger et al. 1991). The sub-boreal landscape is characterized by upland coniferous forests wherein interior spruce and subalpine fir trees predominate as climax species (Meidinger et al. 1991 ). The climate of the Engelmann sprucesubalpine fir zone is more extreme than that of the subboreal spruce zone in that growing seasons are cooler and shorter while winters are colder (Coupé et al. 1991). ...
Context
Species distributions are influenced by how individuals interact with conspecifics, how they interact with other species, and by abiotic environmental factors. Resolving the nature of interspecific interactions using the relative spatial distributions of multiple species can therefore be considered an inverse problem.
Objective
We wished to determine whether defoliation by a lepidopteran (Choristoneura biennis [Freeman]) facilitates subsequent spruce beetle (Dendroctonus rufipennis [Kirby]) attack using spatiotemporal infestation patterns.
Methods
We used convergent cross mapping to probe time series of historical outbreaks of C. biennis and D. rufipennis in British Columbia, Canada, for evidence of interspecific interactions. We then fitted mixed model logistic regressions to spatial outbreak data to determine whether the probability of D. rufipennis infestation is impacted by prior defoliation by C. biennis.
Results
Convergent cross-mapping suggested that prior defoliation by C. biennis impacts D. rufipennis populations but this method cannot give information on the nature of the interaction. Our logistic regressions, however, provided insight into the nature of interactions by showing that the odds of moderate D. rufipennis infestation increased after moderate C. biennis infestation but decreased after severe C. biennis outbreaks. Thus, interactions between C. biennis and D. rufipennis are facilitative at moderate severities of C. biennis defoliation, but increasingly competitive as C. biennis outbreak severity increases.
Conclusions
Interactions between our study insects shifted from facilitative to competitive depending on outbreak severity—a proxy for population density. Density-dependent shifts from facilitation to competition are likely common in the animal kingdom.
... In 2005, initial plots were established in 203 lodgepole pine dominated stands within an area of 8600 km 2 in the southwest Prince George forest district of central BC for continuous monitoring of the impact of MPB attack. The area is in the sub-boreal spruce biogeoclimatic zone with four different sub-zones; dry cool (dk), dry warm (dw, variants 2 and 3), and moist cold (mc) (Meidinger et al., 1991). Most of the sampled stands were lodgepole pine-dominated from eight different age classes and ages from 13 to 250 years (Table 1). ...
... The experimental site Sinclair Mills is located 100 km north east (54801 0 N, 121838 0 W, elevation 710 m a.s.l.) of Prince George, BC. It is in the subboreal spruce very wet and cool biogeoclimatic subzone (SBSvk1): mean annual precipitation 900– 1635 mm of which two-thirds falls as snow, and mean annual temperature 1.3–48C (Meidinger et al. 1991). The block was winter logged in 1987–1988, broadcast burned in spring 1988, planted with interior spruce in the spring of 1989. ...
In central British Columbia (BC), forest management practices have altered natural stand development pathways by controlling ‘‘non commercial’’ tree species and other competing species with the objective of maximizing crop tree growth. This potentially decreases overall diversity within the stand. We conducted a retrospective study on a 13-year-old stand to investigate the impacts of vegetation management with glyphosate on tree growth, species diversity and forest health in central BC. Results revealed that spruce was marginally taller than birch in the herbicide treated area and significantly shorter than birch in the untreated area. There was no difference in spruce diameter at breast height (DBH) and mean stem volume by treatment. White pine weevil attack was significantly reduced in the untreated area. In total, 133 plant species were recorded from 2002 to 2006, but 30% of the species present in 2002 were not present in 2006. Species’ richness and alpha diversity were similar between treatments but beta diversity was relatively low indicating little treatment effect. There was a greater occurrence and abundance of ‘‘weedy’’ and pioneer species in the herbicide-treated area. Overall, this study suggests that glyphosate application does not remove all birch and showed minimal or no impact on under-story vegetation. Therefore, a move away from broadcast vegetation control to spot control where warranted could result in better tree growth, improved forest health and structural diversity.
... The sample area was located within the Prince George forest district from 53°22´to53°22´53°22´to 54°55´N54°55´54°55´N and 120°15´to120°15´120°15´to 125°04´W125°04´125°04´W with a total area of about 54,000 km 2 (Fig. 1). The area is in the sub-boreal spruce biogeoclimatic zone with three broad sub-zones dry, mesic and moist all with a cool thermal regime (Meidinger et al., 1991). Most of the sampled stands were lodgepole pine-dominated covering eight different age classes from 13 to 250 years (Table 1). ...
Lodgepole pine forests in British Columbia (BC) are experiencing the largest mountain pine beetle (MPB) epidemic in recorded history. Now that the peak of the epidemic has passed, information regarding the existing live secondary stand structure (height >4 m but DBH <7.5 cm), regeneration (⩽4 m in height) and residual mature trees (DBH >7.5 cm) in the MPB-attacked stands are needed to assess management options and future timber supply. In total, 459 MPB-attacked pine stands were sampled from eight different age classes (13–250 yr) in three different ecological subzones (dry, mesic, moist) of central BC. Mean MPB attack was greater than 40% when stand age was ⩾20 years. Secondary stand structure and residual mature tree layers offer significant opportunities for mitigating the effects of MPB attack on future commercial wood values and ecological processes. The mean density of secondary stand structure and regeneration varied widely within and among ecological subzones. Depending on stand age, 44–98% of stands still contained sufficient stems after MPB attack to be considered stocked. Species composition varied at the stand level, but most stands had sufficient amounts of BC’s preferred commercial species. Due to MPB caused mortality, most of the stands were moving towards a mixed species and uneven aged condition. A SORTIE-ND model projection suggests that stands which had a minimum of 900 stems/ha of secondary structure >4 m in height can reach merchantable volumes within 30 years
... The plateau was drained by a series of small creeks with poorly developed or nonexistent floodplains. The boundary of the study area was defined by the extent of the Sub-Boreal Spruce biogeoclimatic zone (SBS; Meidinger et al. 1991). Annual precipitation averaged 690 mm in the moist-cool SBS subzone and 905 mm in the wet-cool SBS subzone, and snowfall averaged 335 cm/ year and 1,075 cm/year, respectively (MacKinnon et al. 1990). ...
ABSTRACT To better understand distribution and density of fishers (Martes pennanti) in industrial forests of north-central British Columbia, Canada, we examined factors affecting the probability of a potential home range being occupied by 10 radiotagged resident fishers in the Sub-Boreal Spruce biogeoclimatic zone between 1996 and 2000. Percentage of a home range in wetlands and recently logged (within past 12 yr) best predicted likelihood of occupancy by each fisher. Probability of a home range area being occupied by a resident fisher decreased with increasing amounts of wetlands and recent logging present in the area. We estimated that a 5% increase in wetlands or recent logging decreased the relative probability of occupancy of a potential home range by 50%. The accelerated rate of timber harvest in forests affected by mountain pine beetle (Dendroctonus ponderosae) infestations may have substantial implications for the ability of the landscape of central British Columbia to support sustainable populations of fishers.
