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Yves Bergeron - One of the best experts on this subject based on the ideXlab platform.
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Success Factors for Experimental Partial Harvesting in Unmanaged Boreal Forest: 10-Year Stand Yield Results
Forests, 2020Co-Authors: Louiza Moussaoui, Benoit Lafleur, Nicole J. Fenton, Alain Leduc, Miguel Montoro Girona, Annie Claude Bélisle, Yves BergeronAbstract:Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada’s boreal forest, especially in areas prone to organic matter accumulation (Paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to Paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands.
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Analysis of the Effect of Climate Warming on Paludification Processes: Will Soil Conditions Limit the Adaptation of Northern Boreal Forests to Climate Change? A Synthesis
Forests, 2020Co-Authors: Ahmed Laamrani, Osvaldo Valeria, Abdelghani Chehbouni, Yves BergeronAbstract:Northern boreal forests are characterized by accumulation of accumulation of peat (e.g., known as Paludification). The functioning of northern boreal forest species and their capacity to adapt to environmental changes appear to depend on soil conditions. Climate warming is expected to have particularly pronounced effects on paludified boreal ecosystems and can alter current forest species composition and adaptation by changing soil conditions such as moisture, temperature regimes, and soil respiration. In this paper, we review and synthesize results from various reported studies (i.e., 88 research articles cited hereafter) to assess the effects of climatic warming on soil conditions of paludified forests in North America. Predictions that global warming may increase the decomposition rate must be considered in combination with its impact on soil moisture, which appears to be a limiting factor. Local adaptation or acclimation to current climatic conditions is occurring in boreal forests, which is likely to be important for continued ecosystem stability in the context of climate change. The most commonly cited response of boreal forest species to global warming is a northward migration that tracks the climate and soil conditions (e.g., temperature and moisture) to which they are adapted. Yet, some constraints may influence this kind of adaptation, such as water availability, changes in fire regimes, decomposer adaptations, and the dynamic of peat accumulation. In this paper, as a study case, we examined an example of potential effects of climatic warming on future Paludification changes in the eastern lowland region of Canada through three different combined hypothetical scenarios based on temperature and precipitation (e.g., unchanged, increase, or decrease). An increase scenario in precipitation will likely favor peat accumulation in boreal forest stands prone to Paludification and facilitate forested peatland expansion into upland forest, while decreased or unchanged precipitation combined with an increase in temperature will probably favor succession of forested peatlands to upland boreal forests. Each of the three scenarios were discussed in this study, and consequent silvicultural treatment options were suggested for each scenario to cope with anticipated soil and species changes in the boreal forests. We concluded that, despite the fact boreal soils will not constrain adaptation of boreal forests, some consequences of climatic warming may reduce the ability of certain species to respond to natural disturbances such as pest and disease outbreaks, and extreme weather events.
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spatiotemporal evolution of Paludification associated with autogenic and allogenic factors in the black spruce moss boreal forest of quebec canada
Quaternary Research, 2019Co-Authors: Eloise Le Stumboivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering Paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along toposequences allowed us to understand the spatiotemporal dynamics of Paludification and its impacts on the vegetation dynamics over the Holocene.
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Spatiotemporal evolution of Paludification associated with autogenic and allogenic factors in the black spruce–moss boreal forest of Québec, Canada
Quaternary Research, 2019Co-Authors: Éloïse Le Stum-boivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering Paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along toposequences allowed us to understand the spatiotemporal dynamics of Paludification and its impacts on the vegetation dynamics over the Holocene.
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Soil data for mapping Paludification in black spruce forests of eastern Canada
Data in brief, 2018Co-Authors: Nicolas Mansuy, Ahmed Laamrani, Osvaldo Valeria, Yves Bergeron, Nicole J. Fenton, Luc Guindon, André Beaudoin, Sonia Légaré, Mohammed HennebAbstract:Abstract Soil data and soil mapping are indispensable tools in sustainable forest management. In northern boreal ecosystems, Paludification is defined as the accumulation of partially decomposed organic matter over saturated mineral soils, a process that reduces tree regeneration and forest growth. Given this negative effect on forest productivity, spatial prediction of Paludification in black spruce stands is important in forest management. This paper provides a description of the soil database to predict organic layer thickness (OLT) as a proxy of Paludification in northeastern Canada. The database contains 13,944 OLT measurements (in cm) and their respective GPS coordinates. We collected OLT measurements from georeferenced ground plots and transects from several previous projects. Despite the variety of sources, the sampling design for each dataset was similar, consisting of manual measurements of OLT with a hand probe. OLT measurements were variable across the study area, with a mean ± standard deviation of 21 ± 24 cm (ranging from a minimum of 0 cm to a maximum of 150 cm), and the distribution tended toward positive skewing, with a large number of low OLT values and fewer high OLT values. The dataset has been used to perform OLT mapping at 30-m resolution and predict the risk of Paludification in northeastern Canada (Mansuy et al., 2018) [1] . The spatially explicit and continuous database is also available to support national and international efforts in digital soil mapping.
Richard Tipping - One of the best experts on this subject based on the ideXlab platform.
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Storminess as an explanation for the decline of pine woodland ca. 7,400 years ago at Loch Tulla, western Scotland
Vegetation History and Archaeobotany, 2008Co-Authors: Richard TippingAbstract:Pinus wood remains some 7,400 years old are abundantly preserved near the base of eroding peat at Clashgour, west of Loch Tulla on Rannoch Moor in western Scotland. Measurements are presented of the orientations of root systems in 42 in situ stumps, the direction of fall in 27 fallen trunks and the orientation (where direction of fall cannot be defined) in 40 fallen trunks. There are statistically significant orientations in the root systems, which suggests that the root structure of the trees had responded to stress from westerly winds. However, despite this the orientations and directions of fall in tree trunks, also statistically significant, show that many trees were probably blown over by strong westerly winds. The data suggest that increased precipitation and accelerated Paludification are less likely explanations for tree loss at this site than a sudden demise through wind-throw.
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Storminess as an explanation for the decline of pine woodland ca. 7,400 years ago at Loch Tulla, western Scotland
Vegetation History and Archaeobotany, 2008Co-Authors: Richard TippingAbstract:Pinus wood remains some 7,400 years old are abundantly preserved near the base of eroding peat at Clashgour, west of Loch Tulla on Rannoch Moor in western Scotland. Measurements are presented of the orientations of root systems in 42 in situ stumps, the direction of fall in 27 fallen trunks and the orientation (where direction of fall cannot be defined) in 40 fallen trunks. There are statistically significant orientations in the root systems, which suggests that the root structure of the trees had responded to stress from westerly winds. However, despite this the orientations and directions of fall in tree trunks, also statistically significant, show that many trees were probably blown over by strong westerly winds. The data suggest that increased precipitation and accelerated Paludification are less likely explanations for tree loss at this site than a sudden demise through wind-throw.
Nicole J. Fenton - One of the best experts on this subject based on the ideXlab platform.
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Success Factors for Experimental Partial Harvesting in Unmanaged Boreal Forest: 10-Year Stand Yield Results
Forests, 2020Co-Authors: Louiza Moussaoui, Benoit Lafleur, Nicole J. Fenton, Alain Leduc, Miguel Montoro Girona, Annie Claude Bélisle, Yves BergeronAbstract:Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada’s boreal forest, especially in areas prone to organic matter accumulation (Paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to Paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands.
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spatiotemporal evolution of Paludification associated with autogenic and allogenic factors in the black spruce moss boreal forest of quebec canada
Quaternary Research, 2019Co-Authors: Eloise Le Stumboivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering Paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along toposequences allowed us to understand the spatiotemporal dynamics of Paludification and its impacts on the vegetation dynamics over the Holocene.
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Spatiotemporal evolution of Paludification associated with autogenic and allogenic factors in the black spruce–moss boreal forest of Québec, Canada
Quaternary Research, 2019Co-Authors: Éloïse Le Stum-boivin, Nicole J. Fenton, Gabriel Magnan, Michelle Garneau, Pierre Grondin, Yves BergeronAbstract:Paludification is the most common process of peatland formation in boreal regions. In this study, we investigated the autogenic (e.g., topography) and allogenic (fire and climate) factors triggering Paludification in different geomorphological contexts (glaciolacustrine silty-clayey and fluvioglacial deposits) within the Quebec black spruce ( Picea mariana )–moss boreal forest. Paleoecological analyses were conducted along three toposequences varying from a forest on mineral soil to forested and semi-open peatlands. Plant macrofossil and charcoal analyses were performed on basal peat sections (≤50 cm) and thick forest humus ( Sphagnum in microdepressions. Paludification resulted in the decline of some coniferous species such as Abies balsamea and Pinus banksiana . The paleoecological approach along toposequences allowed us to understand the spatiotemporal dynamics of Paludification and its impacts on the vegetation dynamics over the Holocene.
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Soil data for mapping Paludification in black spruce forests of eastern Canada
Data in brief, 2018Co-Authors: Nicolas Mansuy, Ahmed Laamrani, Osvaldo Valeria, Yves Bergeron, Nicole J. Fenton, Luc Guindon, André Beaudoin, Sonia Légaré, Mohammed HennebAbstract:Abstract Soil data and soil mapping are indispensable tools in sustainable forest management. In northern boreal ecosystems, Paludification is defined as the accumulation of partially decomposed organic matter over saturated mineral soils, a process that reduces tree regeneration and forest growth. Given this negative effect on forest productivity, spatial prediction of Paludification in black spruce stands is important in forest management. This paper provides a description of the soil database to predict organic layer thickness (OLT) as a proxy of Paludification in northeastern Canada. The database contains 13,944 OLT measurements (in cm) and their respective GPS coordinates. We collected OLT measurements from georeferenced ground plots and transects from several previous projects. Despite the variety of sources, the sampling design for each dataset was similar, consisting of manual measurements of OLT with a hand probe. OLT measurements were variable across the study area, with a mean ± standard deviation of 21 ± 24 cm (ranging from a minimum of 0 cm to a maximum of 150 cm), and the distribution tended toward positive skewing, with a large number of low OLT values and fewer high OLT values. The dataset has been used to perform OLT mapping at 30-m resolution and predict the risk of Paludification in northeastern Canada (Mansuy et al., 2018) [1] . The spatially explicit and continuous database is also available to support national and international efforts in digital soil mapping.
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Digital mapping of Paludification in soils under black spruce forests of eastern Canada
Geoderma Regional, 2018Co-Authors: Nicolas Mansuy, Ahmed Laamrani, Osvaldo Valeria, Yves Bergeron, Nicole J. Fenton, Luc Guindon, André Beaudoin, Sonia LégaréAbstract:Abstract In northern boreal ecosystems, Paludification is defined as the accumulation of partially decomposed organic matter over saturated mineral soils, a process that reduces tree regeneration and forest growth. Given this negative effect on forest productivity, spatial prediction of Paludification in black spruce stands is important in forest management. Here, we used the Random Forest approach to predict organic layer thickness (OLT) as a proxy of Paludification in northeastern Canada, where forests tend to paludify naturally. The RF approach involved regression and classification models using a suite of 20 environmental predictors derived from multiple sources. The performance of each model was evaluated using cross-validation and an independent dataset based on conventional ecological survey maps from a provincial forest inventory. Importance measures of the predictors indicated that slope, topographic position index, spectral bands 4 and 5 from Landsat, latitude, and PALSAR_HH were the most important variables explaining the spatial distribution of OLT for both models. Cross-validated relative root mean square error (± standard deviation) for the regression model was estimated at 20.66% ± 0.576, with R2 of 0.41 ± 0.020, whereas the average out-of-bag error for the classification model was estimated at 44.75%. However, both models performed better in predicting high risk of Paludification (OLT values >40 cm). With predicted OLT values averaging 44.07 ± 16.80 cm (range 4.25–104.58 cm), the spatial patterns were in accordance with the results of previous studies at the national and landscape scale. These results highlight that ecological types such as black spruce–sphagnum on thin-to-thick organic deposit, with ombrotrophic drainage, are particularly prone to Paludification (OLT depth > 40 cm) throughout the study area. Limitations of the models and applications for decision-making in forest management are discussed.
Martin Simard - One of the best experts on this subject based on the ideXlab platform.
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Silviculture to sustain productivity in black spruce paludified forests
Forest Ecology and Management, 2016Co-Authors: Benoit Lafleur, Martin Simard, David Pare, Nelson Thiffault, Nicole J. Fenton, Sébastien M. Renard, Cécile Leroy, Sylvie Gauthier, Alain Leduc, Yves BergeronAbstract:Abstract Fire is considered the major disturbance in boreal forests. Nonetheless, in several areas logging has become the primary driver of forest dynamics. In many areas of the boreal forest, stands may undergo Paludification (i.e. the accumulation of thick, poorly decomposed organic layers over the mineral soil) in the prolonged absence of fire, which reduces forest productivity. Whereas high-severity fires (HSF) may restore forest productivity by burning the soil organic layer (SOL), low-severity fires (LSF) mainly burn the soil surface and do not significantly reduce SOL thickness. In the Clay Belt region of eastern Canada, an area prone to Paludification, forest stands have historically been harvested by clearcutting (CC), but concerns about the protection of soils and tree regeneration lead to the replacement of CC by careful logging (CL). Whereas CC disturbs the SOL and is thought to favor tree growth, CL has little impact on the SOL. Furthermore, it has been suggested that prescribed burning after clearcut (CCPB) could also be used to control Paludification. Using a retrospective approach, this study sought to understand how CC, CL, and CCPB compare to LSF and HSF with respect to soil properties, SOL thickness, vegetation ground cover, tree nutrition, and stand height in paludified black spruce stands of the Clay Belt region. HSF led to significantly taller trees than CL and LSF, but did not differ from CC and CCPB. Foliar N was significantly higher in HSF and CCPB sites relative to CL and LSF, with an intermediate value in CC sites. Ground cover of Rhododendron groenlandicum was significantly lower in HSF and CC sites relative to LSF, with intermediate values in CL and CCPB sites. Sphagnum spp. ground cover was significantly lower in HSF and CCPB sites relative to CL, with intermediate values in CC and LSF sites. High-severity fire sites had a significantly thinner SOL than the four other disturbances. Finally, regression tree analysis showed that SOL thickness represented the best predictor of tree height, whereas segmented regression showed that tree height was negatively correlated to SOL thickness and revealed a cut-off point circa 23 cm, which suggests that tree growth is impeded beyond this threshold. These results support the idea that management strategies intending to regenerate paludified forests should primarily aim at reducing organic layer thickness, either through mechanical disturbance or combustion.
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Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada.
Silva Fennica, 2010Co-Authors: Benoit Lafleur, Martin Simard, David Pare, Nicole J. Fenton, Yves BergeronAbstract:Lafleur, B., Fenton, N.J., Pare, D., Simard, M. & Bergeron, Y. 2010. Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada. Silva Fennica 44(5): 799–813. It has been suggested that without sufficient soil disturbance, harvest in boreal forested peatlands may accelerate Paludification and reduce forest productivity. The objectives of this study were to compare the effects of harvest methods (clearcutting vs. careful logging) and season (summer vs. winter harvest) on black spruce regeneration and growth in boreal forested peatlands of eastern Canada, and to identify the soil variables that favour tree growth following harvest. Moreover, we sought to determine how stand growth following harvest compared with that observed following fire. The average tree height of summer clearcuts was greater than that of summer carefully logged stands and that of all winter harvested sites. Summer clearcutting also resulted in a higher density of trees > 3 m and > 4 m tall and in a 50% reduction in Rhododendron groenlandicum cover, a species associated with reduced black spruce growth. Height growth of sample trees was related to foliar N and P concentrations, and to soil total N, pH and available Ca and Mg but not to harvest method or season. Our results also indicate that summer clearcutting could produce stand productivity levels comparable to those observed after high-severity soil burns. These results suggest that summer clearcutting could be used to restore forest productivity following harvest in forested peatlands, and offer further support to the idea that sufficient levels of soil disturbance may be required to restore productivity in ecosystems undergoing Paludification.
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Paludification dynamics in the boreal forest of the James Bay Lowlands: effect of time since fire and topography
Canadian Journal of Forest Research, 2009Co-Authors: Martin Simard, Yves Bergeron, Pierre Y. Bernier, David Pare, Lakhdar Guérinel. GuérineAbstract:In many northern forest ecosystems, soil organic matter accumulation can lead to Paludification and forest pro- ductivity losses. Paludification rate is primarily influenced by topography and time elapsed since fire, two factors whose in- fluence is often confounded and whose discrimination would help forest management. This study, which was conducted in the black spruce (Picea mariana (Mill.) BSP) boreal forest of northwestern Quebec (Canada), aimed to (1) quantify the ef- fect of slope and time since fire on Paludification rates, (2) determine whether soil organic layer depth could be estimated by surface variables that can potentially be remotely sensed, and (3) relate the degree of Paludification to tree productivity. In this study, soil organic layer depth was used as an estimator of the degree of Paludification. Slope and postfire age strongly affected Paludification dynamics. Young stands growing on steep slopes had thinner organic layers and lower or- ganic matter accumulation rates compared with young stands growing on flat sites. Black spruce basal area and Sphagnum cover were strong predictors of organic layer depth, potentially allowing mapping of Paludification degree across the land- scape. Tree productivity was negatively related to organic layer depth (R 2 = 0.57). The equations developed here can be used to quantify forest productivity decline in stands that are undergoing Paludification, as well as potential productivity re- covery given appropriate site preparation techniques.
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Forest productivity decline caused by successional Paludification of boreal soils
Ecological Applications, 2007Co-Authors: Martin Simard, Nicolas Lecomte, Yves Bergeron, Pierre Y. Bernier, David PareAbstract:Long - term forest productivity decline in boreal forests has been extensively studied in the last decades , yet its causes are still unclear . Soil conditions associated with soil organic matter accumulation are thought to be responsible for site productivity decline . The objectives of this study were to determine if Paludification of boreal soils resulted in reduced forest productivity , and to identify changes in the physical and chemical properties of soils associated with reduction in productivity . We used a chronosequence of 23 black spruce stands ranging in postfire age from 50 to 2350 years and calculated three different stand productivity indices , including site index . We assessed changes in forest productivity with time using two complementary approaches : (1) by comparing productivity among the chronosequence stands and (2) by comparing the productivity of successive cohorts of trees within the same stands to determine the influence of time independently of other site factors . Charcoal stratigraphy indicates that the forest stands differ in their fire history and originated either from high - or low - severity soil burns . Both chronosequence and cohort approaches demonstrate declines in black spruce productivity of 50 – 80% with increased Paludification , particularly during the first centuries after fire . Paludification alters bryophyte abundance and succession , increases soil moisture , reduces soil temperature and nutrient availability , and alters the vertical distribution of roots . Low - severity soil burns significantly accelerate rates of Paludification and productivity decline compared with high - severity fires and ultimately reduce nutrient content in black spruce needles . The two combined approaches indicate that Paludification can be driven by forest succession only , independently of site factors such as position on slope . This successional Paludification contrasts with edaphic Paludification , where topography and drainage primarily control the extent and rate of Paludification . At the landscape scale , the fire regime (frequency and severity) controls Paludification and forest productivity through its effect on soil organic layers . Implications for global carbon budgets and sustainable forestry are discussed .
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Effects of fire severity and initial tree composition on understorey vegetation dynamics in a boreal landscape inferred from chronosequence and paleoecological data
Journal of Vegetation Science, 2005Co-Authors: Nicolas Lecomte, Martin Simard, Yves Bergeron, Alayn C. Larouche, Hans Asnong, Pierre J. H. RichardAbstract:Abstract Question and Location: How does soil burn severity and early post-fire tree composition affect long-term understorey vegetation dynamics in the coniferous forests of eastern Canada? Method: Vegetation dynamics were assessed using paleoecological methods and a chronosequence analysis of extant stands. The relation between environmental factors and succession was evaluated using ordination techniques on the chronosequence data. Understorey succession was studied by regression analysis on the chronosequence data and through within-site Markovian transition probabilities between successive 1-cm layers of plant macroremains from soil organic matter profiles. Results: Initial tree composition (Picea mariana and Pinus banksiana) had little effect on understorey composition. Soil burn severity (measured as the thickness of the residual forest floor humus) significantly affected temporal changes in understorey species. Following fires of high severity, stands underwent a gradual Paludification with a net ...
David Pare - One of the best experts on this subject based on the ideXlab platform.
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Silviculture to sustain productivity in black spruce paludified forests
Forest Ecology and Management, 2016Co-Authors: Benoit Lafleur, Martin Simard, David Pare, Nelson Thiffault, Nicole J. Fenton, Sébastien M. Renard, Cécile Leroy, Sylvie Gauthier, Alain Leduc, Yves BergeronAbstract:Abstract Fire is considered the major disturbance in boreal forests. Nonetheless, in several areas logging has become the primary driver of forest dynamics. In many areas of the boreal forest, stands may undergo Paludification (i.e. the accumulation of thick, poorly decomposed organic layers over the mineral soil) in the prolonged absence of fire, which reduces forest productivity. Whereas high-severity fires (HSF) may restore forest productivity by burning the soil organic layer (SOL), low-severity fires (LSF) mainly burn the soil surface and do not significantly reduce SOL thickness. In the Clay Belt region of eastern Canada, an area prone to Paludification, forest stands have historically been harvested by clearcutting (CC), but concerns about the protection of soils and tree regeneration lead to the replacement of CC by careful logging (CL). Whereas CC disturbs the SOL and is thought to favor tree growth, CL has little impact on the SOL. Furthermore, it has been suggested that prescribed burning after clearcut (CCPB) could also be used to control Paludification. Using a retrospective approach, this study sought to understand how CC, CL, and CCPB compare to LSF and HSF with respect to soil properties, SOL thickness, vegetation ground cover, tree nutrition, and stand height in paludified black spruce stands of the Clay Belt region. HSF led to significantly taller trees than CL and LSF, but did not differ from CC and CCPB. Foliar N was significantly higher in HSF and CCPB sites relative to CL and LSF, with an intermediate value in CC sites. Ground cover of Rhododendron groenlandicum was significantly lower in HSF and CC sites relative to LSF, with intermediate values in CL and CCPB sites. Sphagnum spp. ground cover was significantly lower in HSF and CCPB sites relative to CL, with intermediate values in CC and LSF sites. High-severity fire sites had a significantly thinner SOL than the four other disturbances. Finally, regression tree analysis showed that SOL thickness represented the best predictor of tree height, whereas segmented regression showed that tree height was negatively correlated to SOL thickness and revealed a cut-off point circa 23 cm, which suggests that tree growth is impeded beyond this threshold. These results support the idea that management strategies intending to regenerate paludified forests should primarily aim at reducing organic layer thickness, either through mechanical disturbance or combustion.
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Paludification of boreal soils reduces wood decomposition rates and increases wood-based carbon storage
Ecosphere, 2015Co-Authors: Jenna M. Jacobs, David Pare, Timothy T. Work, Yves BergeronAbstract:Over long time periods, Paludification reduces aboveground productivity resulting in forest retrogression. Paludified forests are typified by intense accumulation of the soil organic layer and a reduction in soil temperatures and nutrient availability. En route to Paludification, early successional forests experience large inputs of deadwood biomass during the senescence of the post-fire cohort, much of which may be entombed in this rapidly growing soil organic layer. Here we examined the effects of Paludification across a >2000-year chronosequence of black spruce forests on wood decomposition using three complementary approaches. We (1) repeatedly measured wood density of logs through time, (2) utilize a time-series of logs that varied in time since death, and (3) estimate woody biomass at the stand level as it progresses from live trees to snags, logs and ultimately to buried or decomposed deadwood. Together these approaches demonstrated a 6–7-year delay before the onset of rapid decomposition. We also found strong evidence that Paludification results in a large proportion of logs becoming buried in the soil organic layer. Stand level modeling indicates that the rates of accumulation of buried deadwood were greatest following the senescence of the post-fire cohort when both soil organic layer build-up and creation of deadwood peaked. Following this period of high deadwood creation, stands enter a retrogressive state whereby productivity continues to decline albeit more slowly. Continued losses in woody carbon biomass from trees during this retrogressive state are offset by lower wood decomposition rates and a high biomass of accumulated buried deadwood, essentially stabilizing the wood based carbon budget in these ecosystems. We recommend that partial cutting be conducted prior to or near the senescence of the post-fire cohort to improve emulation of natural forest succession in terms of both live tree and deadwood biomass. Furthermore, deadwood during this period has an extremely short residence time and the dynamics of deadwood should recover much quicker than if harvesting is conducted later in succession when there is less live tree biomass and deadwood has longer residence times.
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Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada.
Silva Fennica, 2010Co-Authors: Benoit Lafleur, Martin Simard, David Pare, Nicole J. Fenton, Yves BergeronAbstract:Lafleur, B., Fenton, N.J., Pare, D., Simard, M. & Bergeron, Y. 2010. Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada. Silva Fennica 44(5): 799–813. It has been suggested that without sufficient soil disturbance, harvest in boreal forested peatlands may accelerate Paludification and reduce forest productivity. The objectives of this study were to compare the effects of harvest methods (clearcutting vs. careful logging) and season (summer vs. winter harvest) on black spruce regeneration and growth in boreal forested peatlands of eastern Canada, and to identify the soil variables that favour tree growth following harvest. Moreover, we sought to determine how stand growth following harvest compared with that observed following fire. The average tree height of summer clearcuts was greater than that of summer carefully logged stands and that of all winter harvested sites. Summer clearcutting also resulted in a higher density of trees > 3 m and > 4 m tall and in a 50% reduction in Rhododendron groenlandicum cover, a species associated with reduced black spruce growth. Height growth of sample trees was related to foliar N and P concentrations, and to soil total N, pH and available Ca and Mg but not to harvest method or season. Our results also indicate that summer clearcutting could produce stand productivity levels comparable to those observed after high-severity soil burns. These results suggest that summer clearcutting could be used to restore forest productivity following harvest in forested peatlands, and offer further support to the idea that sufficient levels of soil disturbance may be required to restore productivity in ecosystems undergoing Paludification.
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Paludification dynamics in the boreal forest of the James Bay Lowlands: effect of time since fire and topography
Canadian Journal of Forest Research, 2009Co-Authors: Martin Simard, Yves Bergeron, Pierre Y. Bernier, David Pare, Lakhdar Guérinel. GuérineAbstract:In many northern forest ecosystems, soil organic matter accumulation can lead to Paludification and forest pro- ductivity losses. Paludification rate is primarily influenced by topography and time elapsed since fire, two factors whose in- fluence is often confounded and whose discrimination would help forest management. This study, which was conducted in the black spruce (Picea mariana (Mill.) BSP) boreal forest of northwestern Quebec (Canada), aimed to (1) quantify the ef- fect of slope and time since fire on Paludification rates, (2) determine whether soil organic layer depth could be estimated by surface variables that can potentially be remotely sensed, and (3) relate the degree of Paludification to tree productivity. In this study, soil organic layer depth was used as an estimator of the degree of Paludification. Slope and postfire age strongly affected Paludification dynamics. Young stands growing on steep slopes had thinner organic layers and lower or- ganic matter accumulation rates compared with young stands growing on flat sites. Black spruce basal area and Sphagnum cover were strong predictors of organic layer depth, potentially allowing mapping of Paludification degree across the land- scape. Tree productivity was negatively related to organic layer depth (R 2 = 0.57). The equations developed here can be used to quantify forest productivity decline in stands that are undergoing Paludification, as well as potential productivity re- covery given appropriate site preparation techniques.
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Forest productivity decline caused by successional Paludification of boreal soils
Ecological Applications, 2007Co-Authors: Martin Simard, Nicolas Lecomte, Yves Bergeron, Pierre Y. Bernier, David PareAbstract:Long - term forest productivity decline in boreal forests has been extensively studied in the last decades , yet its causes are still unclear . Soil conditions associated with soil organic matter accumulation are thought to be responsible for site productivity decline . The objectives of this study were to determine if Paludification of boreal soils resulted in reduced forest productivity , and to identify changes in the physical and chemical properties of soils associated with reduction in productivity . We used a chronosequence of 23 black spruce stands ranging in postfire age from 50 to 2350 years and calculated three different stand productivity indices , including site index . We assessed changes in forest productivity with time using two complementary approaches : (1) by comparing productivity among the chronosequence stands and (2) by comparing the productivity of successive cohorts of trees within the same stands to determine the influence of time independently of other site factors . Charcoal stratigraphy indicates that the forest stands differ in their fire history and originated either from high - or low - severity soil burns . Both chronosequence and cohort approaches demonstrate declines in black spruce productivity of 50 – 80% with increased Paludification , particularly during the first centuries after fire . Paludification alters bryophyte abundance and succession , increases soil moisture , reduces soil temperature and nutrient availability , and alters the vertical distribution of roots . Low - severity soil burns significantly accelerate rates of Paludification and productivity decline compared with high - severity fires and ultimately reduce nutrient content in black spruce needles . The two combined approaches indicate that Paludification can be driven by forest succession only , independently of site factors such as position on slope . This successional Paludification contrasts with edaphic Paludification , where topography and drainage primarily control the extent and rate of Paludification . At the landscape scale , the fire regime (frequency and severity) controls Paludification and forest productivity through its effect on soil organic layers . Implications for global carbon budgets and sustainable forestry are discussed .
