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  • Restricted English
    Authors: 
    Craig M.T. Johnston; G.C. van Kooten;
    Country: Netherlands

    Although wind, hydro and solar are the most discussed sources of renewable energy, countries will need to rely much more on biomass if they are to meet renewable energy targets. In this study, a global forest trade model is used to examine the global effects of expanded demand for wood pellets fired with coal in power plants. Positive mathematical programming is used to calibrate the model to 2011 bilateral trade flows. To assess the impact of increased demand for wood pellets on global forest products, we consider a scenario where demand for wood pellets doubles. Findings indicate that production of lumber and plywood is likely to increase in most of the 20 model regions, but outputs of fibreboard, particleboard and pulp will decline as these products must compete with wood pellets for residual fibre. Ultimately, policies promoting aggressive renewable energy targets cause wood pellet prices to more than double in our scenarios, which could increase the cost of generating electricity to such an extent that, in some regions, electricity producers will continue to use fossil fuels as their primary fuel, while some others might find it worthwhile to rely more on nuclear energy for base load power.

  • Restricted
    Authors: 
    Krystof Obidzinski; Ikuko Takahashi; Ahmad Dermawan; Heru Komarudin; A. Andrianto;
    Publisher: Elsevier BV
    Country: Netherlands

    This paper explores the impacts of large scale land acquisition for agro-development by analyzing the Merauke Integrated Food and Energy Estate (MIFEE) in Indonesia. It also examines the potential for MIFEE to meet sustainability requirements under RSPO, ISPO, and FSC. The plantation development plans are characterized by a lack of reliable official data and limited public disclosure. The available information paints a skewed picture of expected outcomes, where short-term economic benefits from forest clearing dominate and environmental impacts and social implications appear to be underestimated. Our analysis indicates that oil palm concessions under MIFEE can be RSPO compliant if they resist the short term windfall profits from conversion timber. ISPO certification is possible without any major overhaul. On the other hand, FSC certification for timber concessions is not possible. Because MIFEE plantation program is dominated by timber plantations, they weigh heavily on the program's poor sustainability prospects. In order to meet the Indonesian government's own objectives and improve the project's sustainability, the government needs to push for the implementation of oil palm certification and timber legality verification systems, reduce the size of plantations, target non-forestland, prioritize food crops, and secure local acceptance of plantation investments.

  • Restricted
    Authors: 
    Nicolás Talloni-Álvarez; U. Rashid Sumaila; Philippe Le Billon; William W. L. Cheung;
    Publisher: Elsevier BV
    Country: Germany

    Abstract Global warming is already affecting the oceans through changes in water temperature, acidification, oxygen content and sea level rise, amongst many others. These changes are having multiple effects on marine species worldwide, with subsequent impacts on marine fisheries, peoples' livelihoods and food security. This work presents a review of the recent literature on the current and projected impacts of climate change on Canada's Pacific marine ecosystem. We find that there is an increasing number of studies in British Columbia focusing on changes in ocean conditions and marine species responses under climate change, including an emerging literature on the socio-economic impacts of these changes considered to be a knowledge gap. According to the literature, it is well established that ocean temperatures are increasing over the long-term, especially, in southern areas of British Columbia. Warming trends are increasing in the spring and are strongest in summer. However, there are important uncertainties regarding other climate drivers, such as oxygen concentration and acidification, stemming mainly from the insufficiency of data. Pacific salmon, elasmobranchs, invertebrates and rockfishes are amongst the most vulnerable species groups to climate change in British Columbia. Also, shifts in stock distribution and fish abundance under climate change may have a significant impact on fish supply affecting the livelihoods and food security of some British Columbians. The magnitude of these impacts is likely to vary according to a latitudinal gradient, with southern coastal areas being more affected than northern and central areas; challenging multiple areas of governance, such as equity and fishing access amongst First Nations; and institutional arrangements for transboundary stocks between the U.S. and Canada.

  • Restricted
    Authors: 
    Frank Lam; S. Abayakoon; Staffan Svensson; C. Gyamfi;
    Publisher: Springer Science and Business Media LLC
    Country: Denmark

    Proof loading concept is a recognized quality control technique to improve the characteristics of the lower tail of strength distributions of structural timber products. Very few comprehensive studies are available to quantify the effectiveness on the use of proof loading relating to the choice of proof load level, the potential damage on the members resulting from the application of proof load, and the improvement of performance in the context of reliability based design methods. One of the difficulties is the need of a rather large sample size for an experimental-based study to develop statistically meaningful solutions. This paper illustrates the use of damage accumulation model and reliability based design analyses to quantify the effectiveness of proof loading. The performance of No. 2 and better Western Hemlock 38×140 mm dimension lumber in bending is considered. Damage accumulation laws are established to consider the residual strength of members that survived a proof load. Reliability analyses are conducted to compare the performance of proof-loaded and non-proof loaded members subject to snow load conditions in two locations in Canada. For a given reliability index (β), the improvement of performance can be quantified as characteristic strength adjustment factors for proof loading in terms of the ratio of the performance factors (φ) between the original and proof load material. Conversely the gain in reliability, β, for a given φ value is also apparent. The adjustment factors depend on the proof load level, the β level, and the distribution selected for fitting the strength data after proof loading.

  • Restricted English
    Authors: 
    Zehua Pan; Roy Brouwer;
    Country: Netherlands

    Green infrastructure for source water protection in the form of forest protection and afforestation is gaining interest worldwide. It is considered more sustainable in the long-term than traditional engineering-based approaches. This paper presents a theoretical model to support investment decisions in green and grey infrastructure to deliver safe drinking water. We first develop a static optimal control model accounting for the uncertainties surrounding green infrastructure. This model is then extended to factor in key characteristics surrounding investment decisions aimed at optimizing the stock of green and grey infrastructure. We first include dynamic forest growth, followed by the risk of wildfires and finally the potential offsetting effect of carbon sequestration on long-term climate change and the reduced risk of wildfires. We provide a numerical example to analyze the performance of the different model specifications, interpret their outcomes and draw conclusions to guide future investment decisions in green and grey infrastructure.

  • Restricted
    Authors: 
    Charoula Andreou; Derek Rogge; Benoit Rivard; Rupert Müller;
    Publisher: IEEE
    Country: Germany

    The traditional endmember extraction methods search for a fixed set of endmembers, each one assigned to a single material. However, in many real applications, the materials of interest may present spectral variability which is related to subtle absorption features crucial for their discrimination. Thus, extracting multiple spectra or bundles for different materials is considered a more effective approach for data analysis, accounting for intra-class spectral variability. In this work, a novel approach is introduced which aims at obtaining a full representation of materials in a given scene, specifically including those with low spectral contrast. The approach enables a traditional endmember extraction method, the N-FINDR, to extract image endmember bundles exploiting the original spectral bands through a spectral space splitting. Experiments were conducted using an airborne hyperspectral dataset for extracting endmembers of mafic and ultramafic lithological units and preliminary results show the potential usefulness of the new approach.

  • Restricted
    Authors: 
    A. Laeng; Daan Hubert; Tijl Verhoelst; T. von Clarmann; Bianca Maria Dinelli; Anu Dudhia; Piera Raspollini; Gabriele Stiller; Udo Grabowski; Arno Keppens; +6 more
    Publisher: Elsevier BV
    Country: Italy

    Abstract The MIPAS spectrometer onboard the Envisat platform observed infrared emission from the Earth's limb between 2002 and 2012. It recorded high-resolution spectra during day and night, from pole to pole and between 6 and 70 km altitude in the nominal measurement mode or up to 170 km in special measurement modes, producing daily more than 1000 vertical profiles of various trace gases. The operational Level-2 data are processed by ESA/DLR but there exist three other, independent research Level-2 processors that are hosted by ISAC-CNR/University of Bologna, Oxford University, and KIT IMK/IAA. All four Level-2 processors rely on the same Level-1b data provided by ESA but their retrieval schemes differ. As part of ESA's Ozone Climate Change Initiative project, an intercomparison of the four MIPAS processors took place, in which vertical ozone profiles retrieved by these four processors from MIPAS nominal mode measurements were compared for 2007 and 2008. We present the results of this comparison exercise, which consisted of five parts: an information content study of the vertical averaging kernels, an intercomparison of zonal seasonal means and spreads, a determination of biases through comparison to ozonesonde and lidar measurements, a comparison to other satellite records (bias estimation and precision assessment with respect to ACE-FTS and Aura-MLS data), and a geophysical validation of the provided error bars using MIPAS–MIPAS collocations. The four processors demonstrate similar performance. All processors use the same Level-1b data from ESA, apply global fits, and use microwindows instead of the full spectrum. The main differences in the processing schemes include the choice of microwindows, the regularization approach, the treatment of negative retrieved values, and the cloud detection threshold. The different regularization schemes lead to a different trade-off between noise and resolution, but without a clear average advantage for any particular data set. The vertical resolution is typically 3–5 km and the single profile precision is about 2–3%. In the middle and upper stratosphere, at 25–45 km, all four MIPAS processors clearly show a high bias of 2 to 5% relative to all reference instruments. The similarity of the structure and magnitude of the bias among the MIPAS data sets indicates that the bias is most likely linked to the use of microwindows of the MIPAS AB band. The satellite intercomparisons show furthermore that for the KIT dataset, the onset of the high bias starts at a somewhat higher altitude (only above 35 km) than for the other three datasets. This is likely due to the more restrictive use of the AB band by the KIT processor, which comes at the cost of a coarser vertical resolution near the ozone volume mixing ratio (vmr) peak. In the troposphere, the Level-2 algorithms that suppress negative ozone values in the iterative retrieval process produce a larger positive bias than the algorithm that does not follow such a strategy. Our main conclusion is that the four MIPAS processors are more similar to each other than to any other reference instrument. This indicates that the observed biases are very likely instrument-related.

  • Restricted
    Authors: 
    Zia Mehrabi; Verena Seufert; Navin Ramankutty;
    Publisher: Elsevier BV
    Country: Netherlands

    Garibaldi et al. [1] provide a much-needed discussion on the state of our knowledge on the socioecological impacts of different farming choices. They highlight a lack of data on comparisons of different farming choices, and recommend a research program for comparing alternative versus conventional systems as a way to solve this problem. We discuss here some of the ongoing challenges the scientific community faces in making conventional and alternative system comparisons. Although we see value in categorizing farming systems, we contend that our classifications are never black and white in their outcomes – there can be environmentally sound and socially just conventional systems, and alternative systems that are environmentally and socially detrimental.

  • Publication . Article . 2000
    Restricted English
    Authors: 
    Maria Nijnik; G.C. van Kooten;
    Country: Netherlands

    The economy of the Ukraine is in transition from a communist command-and-control to a capitalist system. In this paper, we describe the current state of its forest resources, the structure of its forestry and wood processing sectors, and the problems facing policy makers. While the forest sector should be, and still has the potential to become, an engine for economic growth, the combination of past exploitation and the slow pace of economic reform are major obstacles to implementing rational forest policies. Given the right economic incentives and appropriate forest policies, it may still be possible for the Ukraine to improve its future timber supply while enjoying environmental benefits from its forests. However, this requires economic and institutional reforms beyond the forest sector.

  • Restricted English
    Authors: 
    M D Piercey-Normore; J A Bérubé;
    Country: Canada

    Armillaria ostoyae (Romagnesi) Herink causes root disease in conifers of the northern hemisphere. Pathogenicity tests of established conifer trees with A. ostoyae, has never been done in the boreal forest. Seven forest plots were selected in Newfoundland; a black spruce (Picea mariana (Mill.) BSP) plantation, a naturally regenerated black spruce stand, a balsam fir (Abies balsamea (L.) Mill.) stand with hemlock looper (Lambdina fiscellaria (Guen.)) defoliation, two balsam woolly adelgid (Adelges piceae (Ratz.)) infested balsam fir stands (thinned and unthinned sites), a balsam fir sawfly (Neodiprion abietis Harris) defoliated balsam fir stand, and an artificially defoliated black spruce stand. Roots of fir and spruce trees were inoculated with two isolates of A. ostoyae and re-examined after 2 years. The purpose of this study was to compare differences in root infection within plots for different types of host stress to examine the response of trees to controlled inoculations of A. ostoyae. There was a statistically significant difference in number of infected roots between the two isolates used as inoculum. There was significantly more root response with severity of infection within all sites except both adelgid plots. A marginally significant relationship between tree health and root infection was present in the balsam fir sawfly plot. There was a significantly larger number of infected roots associated with rhizomorphs in the naturally regenerated black spruce stand and the artificially defoliated balsam fir stand. These results suggest that stress prediposes the host tree to root infection by A. ostoyae.

search
Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
185 Research products, page 1 of 19
  • Restricted English
    Authors: 
    Craig M.T. Johnston; G.C. van Kooten;
    Country: Netherlands

    Although wind, hydro and solar are the most discussed sources of renewable energy, countries will need to rely much more on biomass if they are to meet renewable energy targets. In this study, a global forest trade model is used to examine the global effects of expanded demand for wood pellets fired with coal in power plants. Positive mathematical programming is used to calibrate the model to 2011 bilateral trade flows. To assess the impact of increased demand for wood pellets on global forest products, we consider a scenario where demand for wood pellets doubles. Findings indicate that production of lumber and plywood is likely to increase in most of the 20 model regions, but outputs of fibreboard, particleboard and pulp will decline as these products must compete with wood pellets for residual fibre. Ultimately, policies promoting aggressive renewable energy targets cause wood pellet prices to more than double in our scenarios, which could increase the cost of generating electricity to such an extent that, in some regions, electricity producers will continue to use fossil fuels as their primary fuel, while some others might find it worthwhile to rely more on nuclear energy for base load power.

  • Restricted
    Authors: 
    Krystof Obidzinski; Ikuko Takahashi; Ahmad Dermawan; Heru Komarudin; A. Andrianto;
    Publisher: Elsevier BV
    Country: Netherlands

    This paper explores the impacts of large scale land acquisition for agro-development by analyzing the Merauke Integrated Food and Energy Estate (MIFEE) in Indonesia. It also examines the potential for MIFEE to meet sustainability requirements under RSPO, ISPO, and FSC. The plantation development plans are characterized by a lack of reliable official data and limited public disclosure. The available information paints a skewed picture of expected outcomes, where short-term economic benefits from forest clearing dominate and environmental impacts and social implications appear to be underestimated. Our analysis indicates that oil palm concessions under MIFEE can be RSPO compliant if they resist the short term windfall profits from conversion timber. ISPO certification is possible without any major overhaul. On the other hand, FSC certification for timber concessions is not possible. Because MIFEE plantation program is dominated by timber plantations, they weigh heavily on the program's poor sustainability prospects. In order to meet the Indonesian government's own objectives and improve the project's sustainability, the government needs to push for the implementation of oil palm certification and timber legality verification systems, reduce the size of plantations, target non-forestland, prioritize food crops, and secure local acceptance of plantation investments.

  • Restricted
    Authors: 
    Nicolás Talloni-Álvarez; U. Rashid Sumaila; Philippe Le Billon; William W. L. Cheung;
    Publisher: Elsevier BV
    Country: Germany

    Abstract Global warming is already affecting the oceans through changes in water temperature, acidification, oxygen content and sea level rise, amongst many others. These changes are having multiple effects on marine species worldwide, with subsequent impacts on marine fisheries, peoples' livelihoods and food security. This work presents a review of the recent literature on the current and projected impacts of climate change on Canada's Pacific marine ecosystem. We find that there is an increasing number of studies in British Columbia focusing on changes in ocean conditions and marine species responses under climate change, including an emerging literature on the socio-economic impacts of these changes considered to be a knowledge gap. According to the literature, it is well established that ocean temperatures are increasing over the long-term, especially, in southern areas of British Columbia. Warming trends are increasing in the spring and are strongest in summer. However, there are important uncertainties regarding other climate drivers, such as oxygen concentration and acidification, stemming mainly from the insufficiency of data. Pacific salmon, elasmobranchs, invertebrates and rockfishes are amongst the most vulnerable species groups to climate change in British Columbia. Also, shifts in stock distribution and fish abundance under climate change may have a significant impact on fish supply affecting the livelihoods and food security of some British Columbians. The magnitude of these impacts is likely to vary according to a latitudinal gradient, with southern coastal areas being more affected than northern and central areas; challenging multiple areas of governance, such as equity and fishing access amongst First Nations; and institutional arrangements for transboundary stocks between the U.S. and Canada.

  • Restricted
    Authors: 
    Frank Lam; S. Abayakoon; Staffan Svensson; C. Gyamfi;
    Publisher: Springer Science and Business Media LLC
    Country: Denmark

    Proof loading concept is a recognized quality control technique to improve the characteristics of the lower tail of strength distributions of structural timber products. Very few comprehensive studies are available to quantify the effectiveness on the use of proof loading relating to the choice of proof load level, the potential damage on the members resulting from the application of proof load, and the improvement of performance in the context of reliability based design methods. One of the difficulties is the need of a rather large sample size for an experimental-based study to develop statistically meaningful solutions. This paper illustrates the use of damage accumulation model and reliability based design analyses to quantify the effectiveness of proof loading. The performance of No. 2 and better Western Hemlock 38×140 mm dimension lumber in bending is considered. Damage accumulation laws are established to consider the residual strength of members that survived a proof load. Reliability analyses are conducted to compare the performance of proof-loaded and non-proof loaded members subject to snow load conditions in two locations in Canada. For a given reliability index (β), the improvement of performance can be quantified as characteristic strength adjustment factors for proof loading in terms of the ratio of the performance factors (φ) between the original and proof load material. Conversely the gain in reliability, β, for a given φ value is also apparent. The adjustment factors depend on the proof load level, the β level, and the distribution selected for fitting the strength data after proof loading.

  • Restricted English
    Authors: 
    Zehua Pan; Roy Brouwer;
    Country: Netherlands

    Green infrastructure for source water protection in the form of forest protection and afforestation is gaining interest worldwide. It is considered more sustainable in the long-term than traditional engineering-based approaches. This paper presents a theoretical model to support investment decisions in green and grey infrastructure to deliver safe drinking water. We first develop a static optimal control model accounting for the uncertainties surrounding green infrastructure. This model is then extended to factor in key characteristics surrounding investment decisions aimed at optimizing the stock of green and grey infrastructure. We first include dynamic forest growth, followed by the risk of wildfires and finally the potential offsetting effect of carbon sequestration on long-term climate change and the reduced risk of wildfires. We provide a numerical example to analyze the performance of the different model specifications, interpret their outcomes and draw conclusions to guide future investment decisions in green and grey infrastructure.

  • Restricted
    Authors: 
    Charoula Andreou; Derek Rogge; Benoit Rivard; Rupert Müller;
    Publisher: IEEE
    Country: Germany

    The traditional endmember extraction methods search for a fixed set of endmembers, each one assigned to a single material. However, in many real applications, the materials of interest may present spectral variability which is related to subtle absorption features crucial for their discrimination. Thus, extracting multiple spectra or bundles for different materials is considered a more effective approach for data analysis, accounting for intra-class spectral variability. In this work, a novel approach is introduced which aims at obtaining a full representation of materials in a given scene, specifically including those with low spectral contrast. The approach enables a traditional endmember extraction method, the N-FINDR, to extract image endmember bundles exploiting the original spectral bands through a spectral space splitting. Experiments were conducted using an airborne hyperspectral dataset for extracting endmembers of mafic and ultramafic lithological units and preliminary results show the potential usefulness of the new approach.

  • Restricted
    Authors: 
    A. Laeng; Daan Hubert; Tijl Verhoelst; T. von Clarmann; Bianca Maria Dinelli; Anu Dudhia; Piera Raspollini; Gabriele Stiller; Udo Grabowski; Arno Keppens; +6 more
    Publisher: Elsevier BV
    Country: Italy

    Abstract The MIPAS spectrometer onboard the Envisat platform observed infrared emission from the Earth's limb between 2002 and 2012. It recorded high-resolution spectra during day and night, from pole to pole and between 6 and 70 km altitude in the nominal measurement mode or up to 170 km in special measurement modes, producing daily more than 1000 vertical profiles of various trace gases. The operational Level-2 data are processed by ESA/DLR but there exist three other, independent research Level-2 processors that are hosted by ISAC-CNR/University of Bologna, Oxford University, and KIT IMK/IAA. All four Level-2 processors rely on the same Level-1b data provided by ESA but their retrieval schemes differ. As part of ESA's Ozone Climate Change Initiative project, an intercomparison of the four MIPAS processors took place, in which vertical ozone profiles retrieved by these four processors from MIPAS nominal mode measurements were compared for 2007 and 2008. We present the results of this comparison exercise, which consisted of five parts: an information content study of the vertical averaging kernels, an intercomparison of zonal seasonal means and spreads, a determination of biases through comparison to ozonesonde and lidar measurements, a comparison to other satellite records (bias estimation and precision assessment with respect to ACE-FTS and Aura-MLS data), and a geophysical validation of the provided error bars using MIPAS–MIPAS collocations. The four processors demonstrate similar performance. All processors use the same Level-1b data from ESA, apply global fits, and use microwindows instead of the full spectrum. The main differences in the processing schemes include the choice of microwindows, the regularization approach, the treatment of negative retrieved values, and the cloud detection threshold. The different regularization schemes lead to a different trade-off between noise and resolution, but without a clear average advantage for any particular data set. The vertical resolution is typically 3–5 km and the single profile precision is about 2–3%. In the middle and upper stratosphere, at 25–45 km, all four MIPAS processors clearly show a high bias of 2 to 5% relative to all reference instruments. The similarity of the structure and magnitude of the bias among the MIPAS data sets indicates that the bias is most likely linked to the use of microwindows of the MIPAS AB band. The satellite intercomparisons show furthermore that for the KIT dataset, the onset of the high bias starts at a somewhat higher altitude (only above 35 km) than for the other three datasets. This is likely due to the more restrictive use of the AB band by the KIT processor, which comes at the cost of a coarser vertical resolution near the ozone volume mixing ratio (vmr) peak. In the troposphere, the Level-2 algorithms that suppress negative ozone values in the iterative retrieval process produce a larger positive bias than the algorithm that does not follow such a strategy. Our main conclusion is that the four MIPAS processors are more similar to each other than to any other reference instrument. This indicates that the observed biases are very likely instrument-related.

  • Restricted
    Authors: 
    Zia Mehrabi; Verena Seufert; Navin Ramankutty;
    Publisher: Elsevier BV
    Country: Netherlands

    Garibaldi et al. [1] provide a much-needed discussion on the state of our knowledge on the socioecological impacts of different farming choices. They highlight a lack of data on comparisons of different farming choices, and recommend a research program for comparing alternative versus conventional systems as a way to solve this problem. We discuss here some of the ongoing challenges the scientific community faces in making conventional and alternative system comparisons. Although we see value in categorizing farming systems, we contend that our classifications are never black and white in their outcomes – there can be environmentally sound and socially just conventional systems, and alternative systems that are environmentally and socially detrimental.

  • Publication . Article . 2000
    Restricted English
    Authors: 
    Maria Nijnik; G.C. van Kooten;
    Country: Netherlands

    The economy of the Ukraine is in transition from a communist command-and-control to a capitalist system. In this paper, we describe the current state of its forest resources, the structure of its forestry and wood processing sectors, and the problems facing policy makers. While the forest sector should be, and still has the potential to become, an engine for economic growth, the combination of past exploitation and the slow pace of economic reform are major obstacles to implementing rational forest policies. Given the right economic incentives and appropriate forest policies, it may still be possible for the Ukraine to improve its future timber supply while enjoying environmental benefits from its forests. However, this requires economic and institutional reforms beyond the forest sector.

  • Restricted English
    Authors: 
    M D Piercey-Normore; J A Bérubé;
    Country: Canada

    Armillaria ostoyae (Romagnesi) Herink causes root disease in conifers of the northern hemisphere. Pathogenicity tests of established conifer trees with A. ostoyae, has never been done in the boreal forest. Seven forest plots were selected in Newfoundland; a black spruce (Picea mariana (Mill.) BSP) plantation, a naturally regenerated black spruce stand, a balsam fir (Abies balsamea (L.) Mill.) stand with hemlock looper (Lambdina fiscellaria (Guen.)) defoliation, two balsam woolly adelgid (Adelges piceae (Ratz.)) infested balsam fir stands (thinned and unthinned sites), a balsam fir sawfly (Neodiprion abietis Harris) defoliated balsam fir stand, and an artificially defoliated black spruce stand. Roots of fir and spruce trees were inoculated with two isolates of A. ostoyae and re-examined after 2 years. The purpose of this study was to compare differences in root infection within plots for different types of host stress to examine the response of trees to controlled inoculations of A. ostoyae. There was a statistically significant difference in number of infected roots between the two isolates used as inoculum. There was significantly more root response with severity of infection within all sites except both adelgid plots. A marginally significant relationship between tree health and root infection was present in the balsam fir sawfly plot. There was a significantly larger number of infected roots associated with rhizomorphs in the naturally regenerated black spruce stand and the artificially defoliated balsam fir stand. These results suggest that stress prediposes the host tree to root infection by A. ostoyae.