2024 Onward

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    Small area estimators in a simulation test
    (Canadian Science Publishing, 2024-10-08) Kangas, Annika; Myllymäki, Mari; Packalen, Petteri
    The Finnish National Forest Inventory produces municipality level results either with an indirect model-based K nearest neighbor estimator or a direct design-based post-stratification estimator. Design-based approach is unbiased, but not always feasible due to low number of field plots. The K nearest neighbor estimator is lacking an analytical estimator for the variance. A composite estimator combining the indirect and direct estimates could be an attractive solution. In this article, estimators for small-area estimation are analyzed in a simulation experiment with varying size small areas and quality auxiliary data. The potential of estimators is assessed based on the true standard errors and RMSEs in the simulation experiment. Direct estimators and composite estimators work reasonably well with varying quality models, but the performance of indirect estimators is dependent on the quality of the model used. The performance of different estimators also depends on the size of the small areas. Linear models in which the weight of plots outside the target domain is smaller than those within the target domain, performed better than an unweighted model, suggesting that localizing the models for the small areas is beneficial. EBLUP approach also performed well, both in connection of a KNN model and a linear model.
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    Effects of silicon application on Betula pendula seedlings
    (Canadian Science Publishing, 2024-10-08) Hassan, Md. Kamrul; Huitu, Otso; Aphalo, Pedro J.; Klemola, Tero; Leppänen, Tuomo; Tervahauta, Arja; Lehto, Tarja
    Silicon (Si) is a beneficial element for many plant species, conferring resistance to drought and herbivory, but its effects on trees are less known. We studied responses of silver birch (Betula pendula), grown in peat, to liquid Si supplementation (Si concentration 0.65 mM) on 1) growth, 2) water economy and 3) element accumulation plus 4) feeding preference of an insect, Epirrita autumnata and a mammalian herbivore, Microtus agrestis. Plant growth was not affected but control (Si–) plants shed their old leaves earlier. Detached Si+ leaves lost water 11%-units less than Si–, and the integrated water-use efficiency based on
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    Relative potential for stand persistence of riparian and upland aspen stands of a semi-arid montane landscape of the Southern Rocky Mountains
    (Canadian Science Publishing, 2024-10-16) Spei, Benjamin Adam; Goebel, P. Charles; Kashian, Daniel M.; Strand, Eva; Harley, Grant
    Several studies have predicted a loss of quaking aspen (Populus tremuloides) from many western landscapes, but other studies have suggested that aspen persistence is driven by local site factors. Increased frequency of acute drought has been implicated as an important factor driving overstory mortality and reduced regeneration densities in the region. We investigated the relationship between aspen regeneration and site moisture availability potential using ecosystem type as a proxy. We hypothesized that aspen stands growing along perennial-flowing streams would support higher aspen regeneration densities than upland aspen stands. We compared stand structure, groundcover composition, and regeneration densities of nine riparian aspen stands with nine paired upland aspen stands in the Caribou-Targhee National Forest. Aspen regeneration densities were significantly higher in the riparian aspen stands (845. 3 + 318.7 stems ha-1) compared to the upland aspen stands (249.1 + 74.1 stems ha-1) for regeneration shorter than one meter (p = 0.0391). Riparian stands also exhibited significantly higher forb (p
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    A comprehensive framework to evaluate the financial impacts of genetic improvement on wood products from planted forests
    (Canadian Science Publishing, 2024-10-16) Chagnon, Catherine; Moreau, Guillaume; Soro, André; Bombardier-Cauffopé, Christine; Baby-Bouchard, Emmanuelle; Chamberland, Vincent; Barrette, Julie; Gélinas, Nancy; Duchesne, Isabelle; Lenz, Patrick; Bousquet, Jean; Achim, Alexis
    Increasing the productivity of planted forests may efficiently provide an important part of the world’s growing demand for wood while protecting natural forests. In this study, we developed an integrated modelling framework to evaluate the financial impacts of improving productivity of planted forests by tree breeding. Using this framework, we compared three genetic improvement scenarios of white spruce plantations, a key reforestation species in North America, and evaluated the differences in the derived wood product assortments in terms of quantity, quality, and revenues. Favouring the production of wood volume appears as the best way to enhance financial gains from white spruce plantations in the current market. The scenario that focused on increasing tree height produced a greater volume of wood products and larger lumber pieces, which resulted in the greatest revenues. In comparison, favouring wood stiffness over volume led to poorer results, as the increased product quality was not sufficient to surpass the financial gain associated with greater wood volumes. While we successfully provided an evaluation of the product assortments derived from genetically improved plantations, the proposed framework would benefit from more data input to help maximize financial gains from a range of tree breeding strategies.
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    Assessment of a probabilistic supervised machine learning method to estimate biomass expansion and conversion factors: A case study on cedar and pine trees.
    (Canadian Science Publishing, 2024-09-10) Diamantopoulou, Maria J.; KURNAZ, Emine; KALKANLI GENÇ, Şerife; GÜNER, Şükrü Teoman; ÇÖMEZ, Aydın; Özçelik, Ramazan
    Quantifying tree and forest biomass is crucial for formulating effective forest policy and management, given its role in human resource use and carbon storage. Forest biomass significantly contributes to environmental quality by absorbing carbon dioxide. Current research focuses on determining biomass factors for various tree species. This study employed both standard non-linear regression (NLR) and Gaussian process regression (GPR), a machine learning method using artificial intelligence, to estimate and predict biomass expansion and conversion factors accurately. The case study included plantation and naturally occurring cedar and pine trees in Türkiye's Western Anatolian Region and Göller Region. Non-linear regression used Levenberg-Marquardt optimization method, while Gaussian process regression employed radial basis function kernel. This dual approach allowed for assessing prediction uncertainties. The models constructed using GPR show superior performance compared to NLR models for both biomass factors and species within the datasets used. According to Furnival evaluation metric values, accuracy of the NLR models was 1.05 to 1.34 times lower than that of corresponding GPR models. Overall findings highlight the significant potential of Gaussian process regression for accurately estimating and predicting biomass factors with high variances. This emphasizes its utility in modeling scenarios that require high flexibility, such as tree biomass prediction.
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    Modeling stand fire probabilities with unobserved heterogeneity. Estimating stand age and climate change effects in Chilean radiata pine plantations
    (Canadian Science Publishing, 2024-09-16) Niklitschek, Mario E; Labbé, Rodrigo
    Evenly managed forest plantations are potentially vulnerable to fires because of their high fuel load build-up in each rotation. We use panel data analysis that considers the possible correlation between the observed covariates of interest with spatial unobserved heterogeneity. We compared two alternative approaches to estimate the stand burn probability function of the stand age: the average structural function (ASF) and the local average structural function (LASF). While our results show a significant positive effect of the stand age for the mature stage under both approaches, more differentiation in the stand burn probability for different ages is captured with the LASF. Also, under the LASF, the stand age functions are more sensitive to changes in site productivity. We predicted the burned area under the RCP 4.5 and RCP 8.5 climate scenarios considering adaptation in management regimes to site productivity changes. The largest impact is projected for the coastal areas where site productivity increases are combined with more suitable climate conditions for flammability. For the dryer hinterland, however, stand burn probabilities and the burned area are predicted to decline in the second period and the RCP 8.5 because of the dominant negative effect resulting from the site productivity reduction.
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    High genetic gains in growth and resistance to white pine weevil for the next Norway spruce breeding and propagation populations in Quebec, Canada
    (Canadian Science Publishing, 2024-08-29) Otis Prud'homme, Guillaume; DeBlois, Josianne; Pernot, Clémentine; Perron, Martin
    Genetic parameters for growth (height, diameter and volume) and resistance to the white pine weevil were estimated from 209 Norway spruce families aged 15 or 20 years old. Individual heritability values ranged from low to moderate, while family heritability values were moderate to high. This suggests that there is a genetic control for these variables. A selection index was developed to rank individuals on both volume growth and resistance to the white pine weevil. Opsel 2.0 software was used for selection to optimize genetic gain while keeping the level of relatedness between selected trees below an acceptable threshold. The selection of the best 70 individuals, i.e., the top 1% of the populations evaluated, resulted in volume gains of 15.5% and weevil resistance gains of 30.3% making it possible to create a new, more productive and weevil-resistant Norway spruce population. These new breeding and propagation populations will be planted in various locations in the province of Quebec and will be used for the operational deployment of this improved material.
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    Characterizing Diameter Distribution of Pinus nigra stands in Turkey with a Weibull Distribution
    (Canadian Science Publishing, 2024-09-26) Alkan, Onur; Cao, Quang V.; Özçelik, Ramazan
    The objective of this study was to identify the most effective system for predicting parameters of the Weibull function that characterize diameter distributions of black pine (Pinus nigra Arn.) stands in Turkey. We examined three Parameter Recovery methods: the Moment Recovery method, based on diameter moments (diameter variance and quadratic mean diameter), the Percentile Recovery method, relying on diameter percentiles (the 31st and 63rd percentiles), and the Hybrid method, which combines elements of both approaches. Within each of the three methods, we derived regression coefficients from four estimation approaches: Seemingly Unrelated Regression (SUR), Cumulative Distribution Function Regression (CDFR), Maximum Likelihood Estimator Regression (MLER), and Stand Table Regression (STR). Our findings demonstrated that the Moment Recovery method exhibited superior performance compared to the Percentile Recovery and Hybrid methods. Additionally, the MLER approach surpassed the other three estimation techniques. Notably, the Moment Recovery method, coupled with regression coefficients estimated through MLER, emerged as the top-performing combination overall. These results hold significant implications for the development of a diameter distribution growth and yield model tailored to black pine stands in Turkey.
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    La saison des feux de forêt 2023 au Québec : un aperçu des conditions extrêmes, des impacts, des leçons apprises et des considérations pour l'avenir
    (Canadian Science Publishing, 2024-09-11) Boulanger, Yan; Arseneault, Dominique; Bélisle, Annie Claude; Bergeron, Yves; Boucher, Jonathan; Boucher, Yan; Danneyrolles, Victor; Erni, Sandy; Gachon, Philippe; Girardin, Martin P.; Grant, Eliane; Grondin, Pierre; Jetté, Jean-Pierre; Labadie, Guillemette; Leblond, Mathieu; Leduc, Alain; Puigdevall, Jesus Pascual; St-Laurent, Martin-Hugues; Tremblay, Junior A.; Waldron, Kaysandra
    La saison des feux de forêt de 2023 au Québec, marquée par des conditions extrêmement chaudes et sèches, a établi de nouveaux records en brûlant 4,5 millions d'hectares. Cette situation est directement liée aux impacts persistants et en augmentation du changement climatique. Cette étude examine les conditions météorologiques exceptionnelles ayant mené aux feux et évalue leurs impacts significatifs sur le secteur forestier, la gestion des feux, les habitats du caribou boréal, et met particulièrement en lumière les répercussions profondes sur les communautés des Premières Nations. Les feux ont entraîné une baisse significative de la productivité des forêts et de l'approvisionnement en bois, submergeant les équipes de gestion des feux et nécessitant des évacuations massives. Le territoire et les communautés des Premières Nations ont été profondément affectés, confrontés à de graves problèmes de qualité de l'air et à des bouleversements considérables. Si l'impact sur l’habitat du caribou a été modeste dans l'ensemble de la province, les répercussions écologiques, économiques et sociales ont été considérables. Pour atténuer les impacts à venir des prochaines saisons de feux de forêt extrêmes, une avenue suggérée serait de modifier les pratiques d’aménagement forestier afin d'accroître la résilience et la résistance des forêts, d'adapter les structures industrielles aux nouvelles sources d'approvisionnement en bois et d'améliorer les stratégies de lutte contre les feux et la gestion des risques. De même, une approche globale
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    Stand composition and development stage affect fuel characteristics of quaking aspen forests in UT, USA
    (Canadian Science Publishing, 2024-09-10) Nesbit, Kristin A.; Yocom, Larissa; Trudgeon, Allison M.; Rogers, Paul C.; McAvoy, Darren J.; Lane, Emily; DeRose, R. Justin
    In western North America, quaking aspen stands (Populus tremuloides Michx.) have predominantly been described as low flammability, “fireproof” forests, but the specific relationship between aspen stand composition, fuel characteristics, and potential fire behavior is not fully understood. We investigated surface and canopy fuel characteristics in 80 aspen stands in Utah, U.S. that spanned gradients of tree species composition from aspen to conifer dominance and stand development from early to late stages. We quantified fuel type and load, measured fuel moisture content in representative stands across two summer seasons, and modeled flame lengths in each stand. Fuel type and load varied greatly across stands, though late development, conifer-dominated stands had significantly higher (~2-5 times) fine dead woody and litter load and significantly lower (~2-5 times) live understory herbaceous load compared to pure aspen stands. Fuel moisture content did not vary by stand type. Modeled flame lengths were lowest in pure aspen stands, and flame lengths increased linearly with decreasing aspen composition, suggesting that potential surface fire behavior increases as a seral aspen stand progresses through succession to conifer dominance.
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    The 2023 wildfires in British Columbia, Canada: Impacts, drivers, and transformations to coexist with wildfire
    (Canadian Science Publishing, 2024-08-14) Daniels, Lori D; Dickson-Hoyle, Sarah; Baron, Jennifer N.; Copes-Gerbitz, Kelsey; Flannigan, Mike D; Castellanos Acuna, Dante; Hoffman, Kira M.; Bourbonnais, Mathieu; Wilkinson, Sophie L.; Roeser, Dominik; Harvey, Jill E.; Laflamme, Jocelyne; Tiribelli, Florencia; Whitehead, James; Leverkus, Sonja E.R.; Gray, Robert W
    In 2023, all regions of British Columbia (BC) experienced record-breaking fire weather and wildfires, with extreme behaviour and social-ecological effects. In total, 2,245 wildfires burned 2,840,545 hectares. Contemporary wildfires are the culmination of a century of altered human-forest-wildfire relationships, exacerbated by climate change. Transformative change is urgently needed for the ecosystems and communities to be resilient to wildfire. We present six interrelated strategies needed to amplify the pace and scale of change in response to recent wildfire extremes: (1) Immediately diversify wildfire response strategies and restore the ecological and cultural role of fire in BC’s ecosystems. (2) Invest in suppression capacity at local and national scales. (3) Support innovations to overcome the economic barriers for mitigating risk and building resilience within communities and the WUI. (4) Apply landscape fire management to drive a paradigm shift in forest management to increase ecological resilience to wildfire. (5) Transform wildfire governance to support collaborative and community-based solutions. (6) Strengthen expertise and capacity to uplift diverse ways of knowing, managing, and coexisting with fire. These strategies, combined with bold policy and governance changes and supported by sustained funding programs, provide a holistic approach to transform management and coexist with wildfire.
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    Nutrient Ratios, Foliar Vector Analysis, and Nutrient Use Efficiency of Four Conifer Stands Growing Under Contrasting Competing Vegetation Control Treatments in the Pacific Northwest of the United States.
    (Canadian Science Publishing, 2024-08-13) Gonzalez-Benecke, Carlos; Cannon, Callan F; Von Blon, Emily
    This study investigates competing vegetation effects on foliar and total plant derived nutrient ratios, nutrient use efficiency (NUE), and foliar nutrient content and concentration of ecosystem components using vector analysis for 19-year-old Douglas-fir (Pseudotsuga menzeisii Mirb. (Franco)), western hemlock (Tsuga hereophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Donn), and grand fir (Abies grandis (Dougl.) Lindl.) stands in Oregon’s Coast Range and for Douglas-fir and western redcedar in Oregon’s Cascade foothills. Treatments included the Control, which received no spring release herbicide applications, and vegetation management (VM), which received five years of spring release herbicide applications, reducing competing vegetation abundance. VM increased the NUE of N, P, Mg, S, and Cu across all species when calculated with total plant derived carbon and of all nutrients when calculated with stemwood carbon. VM often produced more harvestable and plant derived carbon per unit nutrient fixed, improving the NUE of stands managed for carbon sequestration and timber. Species showed different stand nutrient requirements, evident through foliar and plant derived nutrient ratios and their relationship with biomass production. Grand fir may obtain larger biomass increments for a given P:N ratio in plant derived tissue, and may be efficient in P-limited Coast Range sites.
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    Deep Learning Algorithms for Addressing Overfitting and Biological Realism in Tree Taper and Volume Predictions
    (Canadian Science Publishing, 2024-09-16) Ercanlı, İlker
    This study addresses the challenges of overfitting and maintaining biological realism in Deep Learning Algorithms (DLAs), for predicting individual tree taper using stem diameters outside bark (DOB) and total tree volume (TTV). To this end, DLAs were trained using two different approaches: a “hyperparameter-optimized DLA,” which customizes specific hyperparameters such as learning rate and momentum rate, and a “regularization-optimized DLA,” which incorporates optimization techniques like early stopping with Root Mean Square Error (RMSE), L1 and L2 regularization, and dropout. Although obtaining the deterioration in predictive capabilities statistics from the taring dataset to the validation dataset by standard DLA with adaptive learning processes without customizing the hyperparameters and regularization parameters, the hyperparameter-optimized DLA with a momentum of 0.8, and a 7 # hidden layer for the TTV and regularization-optimized DLA with a dropout ratio of 0.000001, a 3 # hidden layer for the DOB demonstrated comparable predictive capabilities statistics across both training and validation datasets with generating biologically plausible predictions. Our results support that these hyperparameter-optimized and regularization-optimized DLAs, by improving the "black-box" nature of artificial intelligence, offer significant potential for enhanced interpretability and performance by improving the problem of overfitting and the violations biological realism in forest biometrics applications.
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    Tree Species Diversity in Managed Acadian Forests of Eastern Canada
    (Canadian Science Publishing, 2024-06-21) White, Timothy L.; Adams, Gregory W; Taylor, Anthony Robert; Gagnon, Rolland; Sherrill, Josh; McCartney, Andrew
    Maintaining forest diversity is an important value in long range management planning. This study was conducted in the ecologically diverse Acadian Forest Region in the Province of New Brunswick, Canada across 1.65 million hectares of publicly owned (Crown) and privately owned (Freehold) land. Tree species diversity using Hill numbers was evaluated across 21 forest type/age class combinations (Groups) using 1,691 sample plots to assess tree species richness (
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    Six year efficacy of silvicultural treatments to control American beech regeneration in stands affected by beech bark disease in Ontario, Canada
    (Canadian Science Publishing, 2024-06-21) Searle, Eric; Jones, Trevor A.; Yietagesu, Aklilu A.; Mallory, Elaine C.; Trerise, Bridget; Bein, Aliya S.
    High beech regeneration density is a concern in northern shade tolerant hardwood forests. High densities of beech (Fagus grandifolia Ehrh) regeneration can crowd out other desirable species, such as sugar maple (Acer saccharum Marsh.), and jeopardize long-term sustainability since beech is under threat from beech bark disease (Cryptococcus fagisuga/Neonectria spp. Complex). We examined the efficacy of three tending (no tending, brush saw, and basal bark herbicide) and two timing and harvesting (deferred 5 years post-single tree selection harvest, concurrent with uniform shelterwood harvest) treatments on reducing beech regeneration density and promoting sugar maple regeneration density over 6 years. Six years after tending we found that large beech regeneration density was reduced, medium beech regeneration density had recovered to pre-tending levels in most treatments, and small beech regeneration density remained unaffected. Tending treatments had no effect on any size class of sugar maple regeneration density but the uniform shelterwood harvest promoted medium sugar maple density more than the single-tree selection harvest. Despite this increase, in all treatment combinations sugar maple regeneration densities remained below stocking targets. Our results suggest that while tending treatments can temporarily reduce beech regeneration densities, sugar maple is unable to take advantage of the increased growing space.
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    On the characterization of patterning in spruce budworm time-series data
    (Canadian Science Publishing, 2024-05-29) Cooke, Barry
    I outline the “definitional problem” in forest insect outbreak analytics and show how it is related to the “counting problem” in dendroentomology and the “forecasting problem” in forest insect population dynamics, through the ubiquitous presence of non-stationary complex periodicity. Using real-world examples from the spruce budworm (Choristoneura fumiferana Clem.) system, I show that regardless how outbreak patterning is characterized – whether by peak impact, cycle frequency, interval duration, or interval severity – the distribution in pattern attributes appears to be extremely variable, regardless how the data are processed through definitional filters. I show that this extreme variability is an unavoidable and key feature of the system’s dynamics and argue that it needs to be viewed as an object of study, instead of a nuisance problem to be swept under the rug. The single biggest opportunity for rapid gains in spruce budworm predictive ecology is determining the environmental and ecological factors that separate high-intensity from low-intensity outbreak cycling.
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    Below ground chemical and microbial community responses of wood ash addition to a hardwood forest in central Ontario
    (Canadian Science Publishing, 2024-07-03) Smith, Edward Philip; Basiliko, Nathan; Eimers, Catherine; Munford, Kimber E.; Hazlett, Paul; Watmough, Shaun A.
    The use of wood ash as a soil amendment remains restricted in many parts of Canada. To better understand belowground biogeochemical responses to wood ash, soil solution chemistry was measured over three years following the application of wood ash (0, 2.5, 5.0, 7.5 Mg·ha-1) at a hardwood stand in Ontario, after which soil microbial response was assessed using 16S rRNA gene and ITS sequencing. Metal concentrations in the locally sourced wood ash were below provincial regulatory limits. Significant increases in soil solution pH were observed within the forest floor in the first year of the trial, and significant increases in calcium and magnesium were also observed in later years of the trial. Concentrations of most metals in soil water either decreased or exhibited no significant change in response to wood ash. There was an increase in diversity and richness of soil prokaryotic groups in the FH horizon at the highest wood ash treatment that is most likely linked to the large increase in pH. This study indicates that wood ash has a strong ameliorative effect on soil and soil water chemistry without major changes to soil microbial communities and is a viable amendment to forest soils at dosages below 5 Mg·ha-1.
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    Effects of silvicultural release on artificial oak regeneration in bottomland hardwood forests in northern Missouri
    (Canadian Science Publishing, 2024-06-21) Hayford, Isaac; Knapp, Benjamin; Wood, Jeffrey D; Argerich, Alba; Kabrick, John M; Elliott, Grant P; Olson, Matthew
    In bottomland forests, managing oak regeneration is challenging due to competition with other species. Low understory light levels in mature stands favor more shade-tolerant tree species, whereas harvest often results in release of fast-growing competitors. In the late 1990s, a study was initiated in northeastern Missouri to evaluate the effects of overstory harvests on stand development of bottomland forests, with particular interest in oak regeneration. Canopy removal resulted in rapid growth of undesired soft-mast species without increasing the abundance of oak reproduction. In 2017, bare-rooted pin oak (Quercus palustris Muenchh.) and swamp white oak (Quercus bicolor Willd.) seedlings were planted, to increase the oak component through enrichment planting in the stands that had previously been harvested and underplanting in the stands that had received no regeneration harvest. For all planted seedlings, three levels of midstory release treatments were applied after planting in 2017, including a control (no release), and light release, and a heavy release. This study tested the effects of the original overstory harvests and the subsequent midstory release on survival and development of planted oak advance reproduction over 5 years. Our results suggest that establishing oak advance reproduction prior to overstory harvest is more efficient than enrichment planting after overstory harvest. A prior midstory release is important to develop competitive oak advance reproduction before a later overstory harvest to ensure successful oak regeneration.
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    Model-assisted estimation of domain totals, areas, and densities in two-stage sample survey designs
    (Canadian Science Publishing, 2024-07-25) Andersen, Hans-Erik; Ståhl, Göran; Cook, Bruce; Morton, Douglas; Finley, Andrew
    Model-assisted, two-stage forest survey sampling designs provide a means to combine airborne remote sensing data, collected in a sampling mode, with field plot data to increase the precision of national forest inventory estimates, while maintaining important properties of design-based inventories, such as unbiased estimation and quantification of uncertainty. In this study, we present a comprehensive set of model-assisted estimators for domain-level attributes in a two-stage sampling design, including new estimators for densities, and compare the performance of these estimators with standard poststratified estimators. Simulation was used to assess the statistical properties (bias, variability) of these estimators, with both simple random and systematic sampling configurations, and indicated that 1) all estimators were generally unbiased. and 2) the use of lidar in a sampling mode increased the precision of the estimators at all assessed field sampling intensities, with particularly marked increases in precision at lower field sampling intensities. Variance estimators are generally unbiased for model-assisted estimators without poststratification, while model-assisted estimators with poststratification were increasingly biased as field sampling intensity decreased. In general, these results indicate that airborne remote sensing data, collected as an intermediate level of sampling, can be used to increase the efficiency of national forest inventories in remote regions.
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    Differences in the intensity of past forest fire events inferred from stable oxygen isotope analysis of charred bark.
    (Canadian Science Publishing, 2024-06-19) McWhirter, Tegan; Webb, Elizabeth; Dech, Jeffery P
    Understanding past fire regimes requires reliable proxy data that record fire conditions and preserve them over time. The objective of this study was to determine if the oxygen isotope composition of charred bark samples (pyrogenic organic matter) could be used as proxy data to differentiate wildfires based on burn intensity. We collected charred and uncharred bark samples from three fire sites in northern Ontario, Canada that represented a gradient of fire intensity as depicted by Fire Weather Index (FWI) data. We hypothesized that the mean Δ18Obark-char (the difference between δ18O of uncharred bark and a charred sample) would be greater for fires with higher intensities. Analysis of variance of Δ18Obark-char indicated a significant effect of fire event (F=73.6, p