Western Hemlock Research Articles

A chemistry-based explainable machine learning model based on NIR spectra for predicting wood properties and understanding wavelength selection

ABSTRACT A chemistry-based explainable machine learning (ML) approach was used to predict wood properties using near infrared (NIR) spectral data collected from rough and smooth surfaces, and to provide better understanding of the role of important NIR wavelengths (features) in the performance of ML models. NIR spectra collected from western hemlock (Tsuga heterophylla) and coastal Douglas-fir (Pseudotsuga menziesii) boards with rough and smooth surfaces were fed into random forest and TreeNet; a gradient boosting machine algorithm, for predicting wood density, modulus of elasticity (MOE) and modulus of rupture (MOR). The TreeNet model could predict the MOE, MOR, and density with R2 of 0.66, 0.64, and 0.64 using spectra collected from rough surface and R2 of 0.54, 0.46, and 0.46 using spectra collected from smooth surface. TreeNet outperformed the random forest, and for both ML algorithms higher R2 and lower error were obtained using NIR data collected from rough surfaces. This suggested that for Douglass fir and western hemlock, NIR spectra could be collected on a sawn surface prior to surface planing. However, it is difficult to generalize the impact of surface roughness on the performance of predictive model as different factors (e.g. what constitutes a smooth or rough surface, variability of data set in terms of wood properties) impact the success of predictive models. NIR features having the greatest influence on TreeNet models were examined and consistently had wood chemistry specific band assignments. The most important features occurred in the O-H first overtone, and C–H second overtone regions and a narrow zone (approximately 2400–2500 nm) of the C–H stretch C–C stretch combination region. Important features also differed by property and with surface roughness. Explaining ML model performance using the relative importance of the NIR features showed the importance of wood chemistry related information when developing models, however MOE and MOR TreeNet models based on smooth surface NIR spectra showed an increased importance of water related features. Overall, the chemistry-based explainable machine learning model approach allows for identification of important NIR features, and regions, and aids in understanding how they contribute to the performance of NIR-based wood property predictive models.

Sporocarp nutrition of ectomycorrhizal fungi indicates an important role for endemic species in a high productivity temperate rainforest.

Endemic species of ectomycorrhizal fungi (EMF) are found throughout many biomes, but it is unclear whether their localized distribution is dictated by habitat filtering or geographical barriers to dispersal. We examined community composition (via long-read metabarcoding) and differences in sporocarp nutrition between endemic and cosmopolitan EMF species across perhumid temperate rainforests of British Columbia, characterized by soils with high nitrogen (N) supply alongside low phosphorus (P) and cation availability. Endemic EMF species, representing almost half of the community, had significantly greater sporocarp N (24% higher), potassium (+16%), and magnesium (+17%) concentrations than cosmopolitan species. Sporocarp P concentrations were comparatively low and did not differ by fungal range. However, sporocarp N% and P% were well correlated, supporting evidence for linkages in N and P acquisition. Endemics were more likely to occur on Tsuga heterophylla (a disjunct host genus) than Picea sitchensis (a circumpolar genus). The Inocybaceae and Thelephoraceae families had high proportions of endemic taxa, while species in Cortinariaceae were largely cosmopolitan, indicating some niche conservatism among genera. We conclude that superior adaptive traits in relation to perhumid soils were skewed toward the endemic community, underscoring the potentially important contribution of these localized fungi to rainforest nutrition and productivity.

Effect of thermal modification on the ballistic performance of coastal western hemlock Cross-laminated Timber (CLT)

To test and understand the potential for integration of thermally modified coastal western hemlock CLT systems in military applications, 109 ballistic experiments were conducted at the United States Army Engineer Research Development Center's Fragmentation Simulation Facility. For a range of CLT thicknesses, the depth of penetration and residual velocities were recorded for different striking velocities utilizing a 0.50 caliber steel sphere projectile. This information was used to compare and add to the existing ballistics data for CLT, investigate the effects of thermal modification on high strain rate loading of wood, assess physics-based empirical design equations used by the Unified Facilities Criteria, and evaluate energy absorbing behavior at a range of thicknesses and striking velocities.The experimental results showed that thermal modification does not significantly alter the full and partial penetration performance of coastal western hemlock CLT. However, the mechanism of fracture along the path of the projectile differed, which indicates that the model parameters used in the UFC design equation (density, hardness, and projectile properties) may not fully encompass the ballistic failure mechanisms of CLT.

Tree pruning improves tree form but not understory plant production in mixed stands of Sitka spruce and western hemlock, USA

Abstract Precommercial thinning and tree pruning are frequently used together to improve timber quality and wildlife habitat in even-aged Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) stands. Thinning enhances crop tree growth and understory plant production; however, the benefits and drawbacks of tree pruning have received less attention. Tree pruning was investigated in two long-term experiments on the Tongass National Forest, Alaska, USA. Experiment 1 tracked four uniformly thinned sites for ~30 years that received 2.4, 3.6, and 5.2 m lift, and no pruning treatments. Experiment 2 tracked 11 sites for 16 years that received thinning/no pruning, thinning plus pruning (25% of trees), thinning plus pruning (50% of trees), and no thinning/no pruning treatments. We investigated (i) how pruning lift height affects tree form and understory production and (ii) how pruning density affects canopy closure and understory production. In Experiment 1, pruning reduced butt log taper and did not adversely affect diameter or height in either species. Pruning lift was visible in height-to-live crown measurements. Crown recession occurred first in low lift treatments and later in all treatments until crown form was similar after 28–31 years. Epicormic branching rates in Sitka spruce peaked 6–9 years after treatment before falling sharply. Deer forage declined through time and did not differ between lift treatments. In Experiment 2, canopy closure was lower shortly after thinning and pruning, but did not differ from the control after 16 years. Epicormic branching rates were greater shortly after thinning and pruning but did not differ from the control after 16 years. Deer forage declined with canopy closure and thinned and pruned treatments exhibited greater forage than the control. We conclude that pruning can improve log quality for timber applications but does not enhance understory plant biomass and deer forage over thinning treatment alone.

Abundance of microbial community genes encoding terminal proteins of the aerobic and denitrification respiratory chains as indicators of ecohydrologic gradients in a coastal temperate rainforest

The persistence of soil organic carbon (SOC) is closely linked to the capacity of the soil microbial community to catalyze oxidative degradation of organic matter. This study uses a landscape-scale metagenomics approach to examine the relative abundances of genes encoding different terminal electron acceptors used for aerobic respiration and denitrification between soil microbial communities across an ecohydrologic gradient. The perhumid zone of the North Pacific coastal temperate rainforest serves as a template to test the associations between these differing respiratory pathways, soil conditions, and tree species biomass. We used the occurrence of reads in soil metagenomes as a proxy for the relative abundance of genes across the ecohydrologic gradient and identified distinct microbial fingerprints differentiating the driest (upland forest) and wettest (palustrine scrub-shrub and palustrine emergent wetland) ecosystem types. There was little gene-based differentiation between the ecosystem types at the wettest end of the ecohydrologic gradient - scrub-shrub wetland and emergent wetlands – while forested wetlands, which occur as gradient sites between upland forests and emergent wetlands on the landscape, were characterized by substantial metagenomic variability and, consequently, overlapped in their soil metagenome with the other ecosystem classes. Hydrology, as measured by groundwater depth was a predictor of O2 and N-oxide reductase abundances. High affinity O2 reductase genes were associated with wetter topographic positions, which has not been shown at the ecosystem scale, or in soils in-situ previously. N-oxide reductase genes were more associated with plant communities found at wetland sites but were not related to soil inorganic nitrogen, suggesting that nitrate supply may be limiting to denitrifiers ubiquitously across this gradient. Two plant species, Tsuga heterophylla (TSHE) and Pinus contorta spp. contorta (PICO), were more strongly correlated with O2-reductase and N-oxide reductase genes than site hydrology, respectively. This research represents a step toward fingerprinting the ecosystem microbiome using genes coding for specific terminal electron acceptors that control the fate of SOC and their ecohydrologic controls.

Casehardening characterization in western hemlock wood

Casehardening (σi) is an internal stress-related phenomenon that develops in kiln-dried wood materials, causing shape distortion. This study focuses on the impact of drying schedule and wood parameters (e.g., density, moisture) on σi. Results indicated that the wood's final moisture content level has the highest impact when it is above 15%. However, the wood moisture gradient is the most influential factor when wood's moisture content is below 15%. Drying schedule aggressiveness and post-drying treatments also affect σi; an aggressive drying schedule followed by conditioning remarkably reduces σi occurrence.

Pacific Northwest conifer forest stand carrying capacity under future climate scenarios

AbstractMaximum stand density index (SDIMAX) represents the carrying capacity of a forest stand based on the relationship between the number of trees and their size. Plot‐level inventory data provided through a collaborative network of federal, state, and private forest management groups were utilized to develop SDIMAX models for important Pacific Northwest conifers of western Washington and Oregon, USA. The influence of site‐specific climatic and environmental variables was explored within an ensemble learning model. Future climate projections based on global circulation models under different representative CO2 concentration pathways (RCP 4.5 and RCP 8.5) and timeframes (2050s and 2080s) were utilized in a space‐for‐time substitution to understand potential shifts in modeled SDIMAX. A majority of the region showed decreases in carrying capacity under future climate conditions. Modeled mean SDIMAX decreased 5.4% and 11.4% for Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) dominated forests and decreased 6.6% and 8.9% for western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Pacific silver fir (Abies amabilis), dominated forests under the RCP 4.5 in the 2050s and RCP 8.5 in the 2080s, respectively. Projected future conditions often fall outside the range of any contemporary climate profile, resulting in what may be referred to as extramural conditions. Within the study region, 45% and 46% of climate variables included in the final model were extramural for the Douglas‐fir and hemlock models, respectively, under RCP 8.5 in the 2080s. Although extrapolating beyond the range of input data is not appropriate and many unknowns remain regarding future climate projections, these results allow for general interpretations of the direction and magnitude of potential shifts in forest carrying capacity.

Yield and Toxin Analysis of Leaf Protein Concentrate from Common North American Coniferous Trees

In the event of an abrupt sunlight reduction scenario, there is a time window that occurs between when food stores would likely run out for many countries (~6 months or less) and ~1 year when resilient foods are scaled up. A promising temporary resilient food is leaf protein concentrate (LPC). Although it is possible to extract LPC from tree biomass (e.g., leaves and needles), neither the yields nor the toxicity of the protein concentrates for humans from the most common tree species has been widely investigated. To help fill this knowledge gap, this study uses high-resolution mass spectrometry and an open-source toolchain for non-targeted screening of toxins on five common North American coniferous species: Western Cedar, Douglas Fir, Ponderosa Pine, Western Hemlock, and Lodgepole Pine. The yields for LPC extraction from the conifers ranged from 1% to 7.5%. The toxicity screenings confirm that these trees may contain toxins that can be consumed in small amounts, and additional studies including measuring the quantity of each toxin are needed. The results indicate that LPC is a promising candidate to be used as resilient food, but future work is needed before LPCs from conifers can be used as a wide-scale human food.

Soil change and broadleaf tree growth 10 years after wood ash and brash co-application to a clearfelled lowland conifer site in Britain

Abstract Wood ash use, to raise pH and replace nutrients lost through forest harvesting, is well regulated in Scandinavia and Canada, but not yet in the UK. This experiment applied granulated wood ash from mixed tree thinnings to a lowland clay mineral soil at ~2.3 t ha−1 dose rate, after clearfell of western hemlock (Tsuga heterophylla (Raf.) Sarg.). With brash (~56 t ha−1 dry weight) as N resource, a 4 × 4 matrix of ash only, ash + brash, brash only and control treatments were planted with oak seedlings (Quercus robur L.). Soil survey was undertaken before ash application and followed over 10 years. By year 2, self-sown grass was dominant in the control and ash plots, and birch (Betula pendula, Roth.) was present across all treatments by year 4. In year 10, oak height was 25–29 per cent greater in brash and ash + brash plots, with DBH increased >20 per cent over the controls. Birch DBH was greater by 30 per cent in brash plots but was over 50 per cent in the ash + brash plots. Foliar concentrations of Ca, K and P significantly increased with ash addition in both oak and birch, as Al, Mn, Fe and Cr decreased. Soil pH (CaCl2) was reduced in all treatments in year 2 likely due to nitrification, during organic matter and needle breakdown, but recovered 8 years later to be significantly highest in ash and ash + brash plots. Mg, K, Ca, Na, Ba and S concentrations were higher in ash plot soils, but soil organic matter, total carbon and total nitrogen declined due to mineralization and uptake by grass and trees. Wood ash addition did not significantly increase heavy metal concentrations in either soil or foliage. In the long term, wood ash aided soil recovery and promoted tree growth in combination with the brash – it could be beneficial for tree growth after thinning/coppicing on heavy mineral soils, with the prerequisite of an existing ground cover. Aim To quantify the effects of wood ash and brash addition over time to soils and tree growth after conifer clearfelling on a lowland clay soil site.

Density effects on growth and dominance in pure and mixed stands of red alder and western hemlock in western Oregon

Maintaining diversity of conifer and hardwood species in riparian and upland areas is of increasing interest to forest managers. For example, having conifer and hardwood inputs into streams increases structural diversity and influences assemblages of aquatic and terrestrial organisms, and the presence of both components in stands may be beneficial in resiliency after disturbances. To examine the impacts of density and weeding on the establishment of red alder (Alnus rubra Bong.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.), combination Nelder and replacement series plots were established on three sites in western Oregon. Species ratios of hemlock:alder were 100:0, 75:25, 50:50, 25:75, and 0:100, with densities ranging from 988 to 85,400 tph. Measurements were available for two sites after 24 years, and one site for 14 years. Weeding increased heights and diameters at lower densities, especially in the early years. As crowns closed, the impacts of weeding decreased through time, but were still evident in some plots after 24 years. Increasing density of red alder resulted in lower survival and growth of both species. Hemlock density did not impact red alder growth through 24 years. Although mixed stands resulted in greater volume in early years, that did not continue in later years. Greater juvenile growth rates of red alder compared to western hemlock resulted in dominance of alder over hemlock in early years, especially at higher densities and ratios of alder. Hemlock growing with lower alder density have maintained co-dominance with alder and will become dominant as alder growth rates decline. Alder density needs to be low enough for hemlock to survive and grow. Density, site, species ratio, animal damage, and presence of other competing vegetation resulted in different scenarios of hemlock and alder dominance, making long-term outcomes difficult to predict with precision.

Conifer performance, stand productivity, and understory cover in varying densities of mixed conifer-broadleaf stands in southwestern British Columbia

There is an increasing interest in mixed conifer-broadleaf stands as a way to increase the diversity and productivity of managed forests. This study examined the impacts of varying densities of planted broadleaf trees on conifer performance, total stand productivity, and understory plant cover 20 years after stand establishment. The study took place in the Malcolm Knapp Research Forest in Maple Ridge, British Columbia. It used a randomized complete block design to compare treatments containing low, moderate, or high broadleaf densities added to a constant conifer density. Each block contained a conifer-only plot as a control. Conifers were composed of equal amounts of western hemlock, western redcedar, and Douglas-fir. Broadleaves were composed of either red alder or paper birch. We found that conifer volume was significantly lower in most broadleaf treatments relative to the control, due to lower hemlock and redcedar volumes. Douglas-fir, on the other hand, had a higher volume—albeit not significant—in the broadleaf treatments. There were no significant differences in total stand volume between any of the treatments and the control. Shrub cover was significantly higher in the low and high alder treatments relative to the control, but there were no differences in shrub cover between birch treatments and the control. The results suggest that low alder density provides a good balance of conifer yield and understory development.

Asymmetric synthesis of sex pheromone of the western hemlock looper, Lambdina fiscellaria lugubrosa (Hulst)

The western hemlock looper is an economically important defoliator of coniferous trees. Its sex pheromone has been synthesized in 36–50% total yield using the enantiomers of 2-methyloxiraneoxide as chiral sources. The key steps of this strategy involved CuI catalyzed ring-opening of chiral 2-methyloxiraneoxide, stereospecific inversion of secondary tosylate and Wittig coupling of the aldehyde with chiral phosphonium salt. The synthetic pheromones would be used to monitor and control this pest.

The Role of Drying Schedule and Conditioning in Moisture Uniformity in Wood: A Machine Learning Approach.

Monitoring the moisture content (MC) of wood and avoiding large MC variation is a crucial task as a large moisture spread after drying significantly devalues the product, especially in species with high green MC spread. Therefore, this research aims to optimize kiln-drying and provides a predictive approach to estimate and classify target timber moisture, using a gradient-boosting machine learning model. Inputs include three wood attributes (initial moisture, initial weight, and basic density) and three drying parameters (schedule, conditioning, and post-storage). Results show that initial weight has the highest correlation with the final moisture and possesses the highest relative importance in both predictive and classifier models. This model demonstrated a drop in training accuracy after removing schedule, conditioning, and post-storage from inputs, emphasizing that the drying parameters are significant in the robustness of the model. However, the regression-based model failed to satisfactorily predict the moisture after kiln-drying. In contrast, the classifying model is capable of classifying dried wood into acceptable, over-, and under-dried groups, which could apply to timber pre- and post-sorting. Overall, the gradient-boosting model successfully classified the moisture in kiln-dried western hemlock timber.

Postglacial vegetation and fire history with a high-resolution analysis of tephra impacts, High Cascade Range, Oregon, USA

The postglacial history of vegetation, wildfire, and climate in the Cascade Range (Oregon) is only partly understood. This study uses high-resolution macroscopic charcoal and pollen analysis from a 13-m, 14,500 years sediment record from Gold Lake, located in a montane forest, to reconstruct forest vegetation and fire history. The occurrence of three tephra layers, including a 78-cm airfall Mazama tephra, as well as highly laminated segments, allows one to study tephra impacts on vegetation at a fine temporal resolution. From the Late Glacial through the Younger Dryas, pollen spectra vary little. The early Holocene is marked by a sudden increase in Pseudotsuga, indicating warmer conditions, while the late Holocene is marked by increasing Tsuga heterophylla and Tsuga mertensiana, indicating the onset of moist conditions in the region. High-resolution charcoal data show periods of large peaks during the Late Glacial, pre-, and post-Mazama eruption and since 4 ka (thousands of years before present). Low fire during the early Holocene is unexpected, given regional evidence of warmer and drier summers, but it may be the result of fuel limitation. After the Mazama tephra deposition (7.63 ka), the non-arboreal pollen composition was changed, with some taxa disappearing or reduced in abundance for 300 years. Arboreal taxa were little affected by the tephra, showing only a 20% increase in Pinus pollen and no discernible impact on the pollen accumulation rate (PAR).In contrast, the Mazama tephra was followed by ca. 70 years of very low charcoal input, followed by a large peak, consistent with the burial of surface fuels and decades of fuel accumulation. There was also increased fire frequency and peak magnitude at 1.5 ka, followed by very little fire after 0.4 ka, consistent with the current old-growth forest surrounding the lake. This detailed and high-resolution record adds significantly to understanding the impacts of climate change and the singular effect of the Mazama eruption, impacting watershed vegetation, and fire for centuries but with minimal impact on the regional forest composition.

A novel method and validation for obtaining the optimal interference fit of round-end mortise-and-tenon joint

ABSTRACT To determine the optimal interference fit of mortise-and-tenon (M&T) a novel method is proposed. To validate its effectiveness, compression tests were conducted considering the effects of wood species (beech and western hemlock), tenon widths (30, 40, 50 mm), and grain orientations (radial, diagonal, and tangential) to obtain the optimal interference fit and contact force (CF). Furthermore, the mounting force (MF) and withdrawal force capacity (WFC) of T-shaped M&T joints constructed by the control and optimal interference fit were evaluated by compression and withdrawal tests, respectively. The results indicated that (1) all three evaluated factors had significant effects on the tenon compression behavior and CF; (2) the derived optimal fits showed that the tenon with a larger width required a higher fit value based on regression equations; (3) the MF and WFC were significantly affected by the three evaluated factors and proportional to the tenon fit; (4) the maximum WFC occurred at the M&T joints made of western hemlock with 50-mm tenon width in tangential orientation with 0.99-mm interference fit, and the beech with 30-mm tenon width in diagonal orientation with 0.78-mm interference fit. The proposed method will assist the wood product manufacturers to design M&T joints rationally.

First report of Phytophthora pluvialis causing needle lesions on Pinus pinea in New Zealand

During routine surveillance in October 2020, needle lesions and necrosis were observed in two 42-year-old stone pines (Pinus pinea) situated in an amenity planting within an infected Pinus radiata plantation in Nelson, New Zealand. Symptoms were widespread across the foliage of infected trees and samples were sent to Scion's Forest Health Reference Laboratory. Approximately fifteen needles displaying yellow and red bands (Fig. 1) tested positive for Phytophthora using a Phytophthora ImmunoStrip® (Agdia, USA), and PCR and subsequent DNA sequencing with Ypap2F/Ypap2R primers (McDougal et al., 2021), indicated Phytophthora pluvialis. A Phytophthora species was isolated from diseased tissue. Morphological characteristics were consistent with those described by Reeser et al. (2013) for P. pluvialis. This identification was confirmed by sequencing the internal transcribed spacer region (White et al., 1990). The isolate was deposited in the National Forest Culture Collection (NZFS 5280) and symptomatic needles were lodged into the National Forest Mycological Herbarium (NZFRI 5931). Foliage symptoms caused by P. pluvialis on other conifers, including Pinus radiata, Pseudotsuga menziesii and Tsuga heterophylla, typically express as distinct khaki/red lesions and black resinous bands (Dick et al., 2014), rather than the yellow and red bands observed on the stone pines (Fig. 2). Pathogenicity testing was done by inoculating stone pine needles with P. pluvialis zoospores using a needle dip assay according to Dick et al. (2014). Stone pine needles from young healthy seedlings were placed in sterile pond water inoculated with P. pluvialis zoospores and incubated in darkness at 17°C for 24 hours. Control needles were placed in sterile pond water. Needles were then lain on moist paper towels in a sealed tray and incubated at 17°C at a 14-hour photoperiod. After ten days, olive/yellow lesions were observed on needles (Fig. 3). These lesions were lighter than those observed on field samples, however, this is common in detached needle assays of other species, such as P. pluvialis infection of Pinus radiata (Dick et al., 2014). Sporangia were observed near the lesion margin of needles (Fig. 4). Sections of symptomatic needles were surface sterilised and plated onto a Phytophthora-selective media (10% carrot agar + ampicillin, pimaricin, rifampicin, nystatin and hymexazol). The resultant cultures displayed morphological features of P. pluvialis, fulfilling Koch's postulates (Fig. 5). Control needles remained healthy (Fig. 3). To our knowledge, this is the first report of P. pluvialis causing needle disease on stone pine. Stone pine is an economically important species due to the production of high value pine nuts and timber. Although stone pine accounts for a small proportion (<1%) of New Zealand's forests, continued monitoring is recommended to assess the impact of disease on the growth and yield of these plantations. Forest Growers Levy Trust funded surveillance and diagnosis through the Forest Biosecurity Surveillance system.

Air permeability of thermally modified hemlock wood

Western hemlock (Tsuga heterophylla) is a prevalent coastal species in British Columbia (BC). Its wood has a high potential for thermal modification, a process that can affect numerous physical properties, including air permeability. The current study investigates the longitudinal air permeability of hemlock wood modified at three temperature levels, 170 °C, 212 °C, and 230 °C, and a two-hour treatment length. Permeability values obtained using Darcy’s law and the water-falling volume displacement method were positively correlated with treatment temperature up to 212 °C, after which the permeability decreased slightly. ANOVA followed by the Duncan test revealed that thermal treatment at 212 °C and 230 °C significantly increased air permeability, whereas it was insignificant at 170 °C.

Mapping the presence and distribution of tree species in Canada's forested ecosystems

Knowledge of tree species is required to inform management, planning, and monitoring of forests as well as to characterize habitat and ecosystem function. Remotely sensed data and spatial modeling enable mapping of tree species presence and distribution. Following an assessment of tree species identified in the sample-based National Forest Inventory (NFI), we mapped 37 tree species over the 650-Mha, forest-dominated ecosystems of Canada representing 2019 conditions. Landsat imagery and related spectral indices, geographic and climate data, elevation derivatives, and remote sensing-derived phenology are used as predictor variables trained with calibration samples from Canada's NFI using the Random Forests machine learning algorithm. Based upon prior knowledge of tree species distributions, classification models were implemented on a regional basis, meaning only the tree species that are expected in a given mapping region were modeled using local calibration samples. Modeling resulted in class membership probabilities values for each regionally eligible tree species for all treed pixels as well as an indicator of attribution confidence derived from the distance in feature space between the two leading classes. Accuracy assessment was conducted using independent validation data also drawn from the NFI following the same selection rules and indicated an overall accuracy of 93.1% ± 0.1% (95%-confidence interval). Predictor variables informing on geographic, climatic and topographic conditions had the largest importance on the classification models. Nationally, the most common leading tree species were black spruce (Picea mariana; 203 Mha or 57.3% of the treed area), trembling aspen (Populus tremuloides; 34.7 Mha, 9.8%), and lodgepole pine (Pinus contorta; 21.1 Mha, 5.9%). Regionally, there was ecozone-level dominance of other tree species, including subalpine fir (Abies lasiocarpa; Montane Cordillera), western hemlock (Tsuga heterophylla; Pacific Maritime), and balsam fir (Abies balsamea; Atlantic Maritime). Based upon the per-pixel class membership probabilities, species assemblages akin to those in forest inventories can also be produced. Further, given the calibrated reflectance of Landsat imagery, the methods presented herein can be implemented over a time series of images. The approach uses open data as predictor variables, making the method portable to other areas given availability of tree species training data.

An analysis of conifer experiments in Britain to identify productive alternatives to Sitka spruce

Abstract As the climate changes there is a need to reduce the reliance on Sitka spruce (Picea sitchensis (Bong) Carr.) in upland British forestry and increase species diversity to lower the risk of damage or loss of production due to biotic or abiotic events. An analysis of relevant species trials was carried out to assess the productivity of potential alternative conifer species on upland site types in Britain. Data from 87 forest experiments planted between 1929 and 1995 were analysed to compare long-term performance of 52 species with that of Sitka spruce under the same conditions and site type. Sites were broadly categorized using soil and climatic factors, which were used as primary factors in models predicting General Yield Class (GYC, the maximum mean annual increment in m3 ha−1 year−1) of the potential alternative species and of Sitka spruce. No species had significantly higher GYC estimates than Sitka spruce, but grand fir (Abies grandis (Douglas ex D. Don) Lindl.), noble fir (Abies procera (Rehder)), western hemlock (Tsuga heterophylla (Raf.) Sarg.), Lutz’s spruce (Picea x lutzii (Little)), maritime pine (Pinus pinaster (Aiton)), Lawson cypress (Chamaecyparis lawsoniana (A. Murray bis) Parl.), Scots pine (Pinus sylvestris (L.)), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata (Donn ex D.Don)) all had GYC estimates which were not significantly lower than that of Sitka spruce under certain soil and climate conditions. A further 26 species, particularly Abies species, had GYC within 3 m3 ha−1 year−1 of Sitka spruce but were present on too few sites for inclusion in statistical models. The results of the analysis provide objective evidence for the planting of a wider range of species where Sitka spruce may currently be first choice. In the absence of any major pest or disease affecting Sitka spruce, it is still a good choice for many upland sites, however, a wider range of options with equivalent productivity exist, allowing forest managers to diversify and reduce the risk of damage or loss of production due to biotic or abiotic events.

Development and wildfire dynamics of dry coastal temperate forests, BC, Canada

The vegetation and fire history at the Coastal Douglas-fir (CDF) and Coastal Western Hemlock (CWH) boundary on east-central Vancouver Island was reconstructed. A basal non-arboreal assemblage at the most inland site likely represents an open parkland community during the cold early late-glacial interval. Widespread Pinus woodland followed under cold, dry climate, yielding to closed-canopy mixed conifer forest as climate moistened. While fire disturbance was initially rare, it increased in the late-glacial mixed conifer forest. In the early-Holocene, dry coastal temperate forest replaced the mixed-conifer assemblage. Fire disturbance was widespread, characterized by frequent, possibly lower severity burns. These CDF-like forests expanded northward and westward under warm, dry conditions, attaining maximum extent 9500 – 10 500 calendar years before present, retreating thereafter towards the modern CDF–CWH boundary, which established ∼6000 years ago as climate moistened. Quercus garryana communities were scattered along the coast at this time, maintained by surface fire. Throughout the remainder of the record, the forest canopy closed as modern forests developed and a mixed-severity fire regime developed. The extended early-Holocene range of CDF-like forest suggests that the existing CWHxm biogeoclimatic subzone may be replaced by CDF stands with climate change.