The Experts below are selected from a list of 24912 Experts worldwide ranked by ideXlab platform
Heli Peltola - One of the best experts on this subject based on the ideXlab platform.
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impacts of climate change on timber production and regional risks of Wind induced Damage to forests in finland
Forest Ecology and Management, 2010Co-Authors: Heli Peltola, Velipekka Ikonen, Ari Venalainen, Harri Strandman, Hilppa Gregow, Antti Kilpelainen, Seppo KellomakiAbstract:Abstract In this work, we studied the impacts of climate change on timber production and regional risks of Wind-induced Damage to forests in Finland. The work employed: (i) national level forest inventory data, (ii) current baseline climate (1961–1990) and changing climate scenario (FINADAPT A2, 2001–2099), (iii) a forest ecosystem model (SIMA), (iv) a mechanistic Wind Damage model (HWind), and (v) currently applied forest management recommendations as a baseline. The results showed that the timber production will increase significantly towards the end of this century under the changing climate, and in a relative sense the most in Northern Finland. At the same time, the share of Norway spruce ( Picea abies L. Karst. ) is expected to decrease, especially in southernmost Finland, mainly favoring the presence of birch ( Betula spp.), but also Scots pine ( Pinus sylvestris L. ), when no species preference is given in management. As a result, the proportion of forest area in the two lowest critical Wind speed classes (i.e. Winds of 11–14 and 14–17 m s −1 ) will decrease in the autumn (birch without leaves) throughout Finland. However, in summertime (birch is in leaf) the proportion of forest area with such critical Wind speeds will even increase in southernmost Finland. Even though, in summertime the risk of Damage should be on average relatively low throughout Finland due to a lower occurrence of such Wind speeds compared to the Windiest time of the year (i.e. from autumn to early spring). The return period of critical Wind speeds of 11–17 m s −1 is today about every two years in southernmost Finland. In Northern Finland, the critical Wind speeds needed for Wind Damage are, on average, higher due to the larger share of Scots pine and on average lower height to breast height diameter ratios of trees compared to the south. To conclude, the climate change will affect clearly the forest growth and dynamics and, thus increase the need to manage forests more often and/or heavily (e.g. thinning, final felling), which in addition to species preference, will affect the risks of Damages. The consideration of the risk of Wind Damage is crucial especially in Southern Finland when adapting forest management to the changing climate. This is because the unfrozen soil period is expected to increase significantly in Finland, which decreases tree anchorage during the Windiest time of year.
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the effects of forest structure on the risk of Wind Damage at a landscape level in a boreal forest ecosystem
Annals of Forest Science, 2010Co-Authors: Hongcheng Zeng, Heli Peltola, Jordi Garciagonzalo, Seppo KellomakiAbstract:• The aim of this work was to analyze how the forest structure affects the risk of Wind Damage at the landscape level in a boreal forest. • This was done by employing: (i) Monte Carlo simulation technique for generating landscapes with different age class distributions, proportions of open areas (gaps), and tree species composition; and (ii) a mechanistic Wind Damage model, HWind, for predicting the critical Wind speeds at downWind stand edges of open areas (gaps) for risk consideration. The level of risk of Wind Damage observed at the landscape level was significantly affected by the presence of gaps and old stands. Even a slight increase in the proportion of gap areas or older stands had a significant impact on the total length of edges at risk. As a comparison, variation in species composition (Scots pine and/or Norway spruce) had much smaller impact on the risk of Damage. • In conclusion, the effects of forest structure on the risk of Wind Damage should especially be considered by forest managers in day-to-day forest planning in order to reduce the risk of Wind Damage both at the stand and landscape level.
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integrating the risk of Wind Damage into forest planning
Forest Ecology and Management, 2009Co-Authors: Tero Heinonen, Timo Pukkala, Velipekka Ikonen, Heli Peltola, Ari Venalainen, S DupontAbstract:Wind is the major abiotic risk factor in Finnish forests. Therefore, tools that help managers to assess the risk of Wind Damage are required. This study developed simple regression models for predicting the critical Wind speed needed to uproot Scots pine, Norway spruce and birch trees at the stand edges in Finnish conditions, using the characteristics of the retained forest both downWind and upWind stands as predictors. Using information on the prevailing Wind conditions in the region, the critical Wind speeds were converted into probabilities of Wind Damage, from which a mean risk index was calculated. The mean risk index was used as an objective variable in heuristic optimisation. The results of minimizing the mean risk index were compared to other objective variables such as minimal height differences between adjacent stands. The residuals of the regression models of critical Wind speeds were small, especially in Scots pine and birch. Increasing tree height of the downWind stand or area of the upWind stand (gap size) decreased the critical Wind speed regardless of tree species, whereas increases in the dbh/height ratio of the downWind stand increased the critical Wind speed. The shelter effect of upWind stand height was stronger in Norway spruce than in other tree species, whereas the effect of tree height of the downWind stand was larger in Scots pine and birch. Minimization of the mean risk of Wind Damage within forest landscapes led to smooth and non-fragmented landscape structures in terms of tree height. Incorporating even-flow constraints into the planning model led to a slight increase in the mean risk of Wind Damage. Of the surrogate methods for risk assessment minimization of height differences between adjacent stands performed well but not equally well as minimization of the mean risk index.
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the effects of fragmentation on the susceptibility of a boreal forest ecosystem to Wind Damage
Forest Ecology and Management, 2009Co-Authors: Hongcheng Zeng, Heli Peltola, Hannu Vaisanen, Seppo KellomakiAbstract:Abstract The clear cuts and seedling stands can speed up Winds and may trigger blowdown at the edges of neighbour stands. Therefore, the height contrast of the neighbour stands and fragmentation at landscape level could be used to indicate the susceptibility of Windthrow. In this study, we studied how forest fragmentation affects the susceptibility of a boreal forest ecosystem to Wind Damage, both at patch and landscape level based on theoretical computations. For this purpose we generated, based on real stand inventory data of a Finnish forest ecosystem, different landscape configurations of Scots pine and Norway spruce forests using Monte Carlo simulation. Thereafter, we applied a mechanistic Wind Damage model to predict the Wind speeds needed for Wind Damage at forest edges. The fragmentation metrics of Contrast-Weighted Edge Density with three different height dissimilarity calculation methods were used to analyze the fragmentation at the landscape level. At the patch (stand) level, susceptibility of downWind stand to Wind Damage could be expressed in terms of a quadratic function, based on the tree height of upWind neighbouring stand or the height ratio between the neighbouring stands. At the landscape level, the relative risk of Wind Damage correlated linearly with the fragmentation despite of fragmentation metrics used. Both in single species and mixed forests, the metrics using empirical regression function based on patch level results (DS3) seemed more applicable in general than those using the ratio of tree heights between neighbouring stands (DS1) or constrained height contrast (DS2).
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a review of mechanistic modelling of Wind Damage risk to forests
Forestry, 2008Co-Authors: Barry Gardiner, Stephen J. Mitchell, Kana Kamimura, Heli Peltola, Kenneth E Byrne, Sophie E Hale, Jean Claude RuelAbstract:Summary This paper reviews the current status of mechanistic models for Wind Damage risk assessment, describing model structure, applicability, validation and current limitations. We focus particularly on the hybrid mechanistic/empirical models GALES and HWind, which have been designed for calculating Wind Damage risk at the stand level within uniform forests and which are the most widely adopted models within the research community. These models have been integrated with different methods for predicting the local Wind climate in order to calculate the probability of Wind Damage in a number of different countries. We also discuss ongoing modelling work and proposals for future development in order to deal with complex forest structures and to predict the Wind Damage risk of individual trees within stands through the integration of mechanistic risk models with forest growth and yield models within a geographical information system framework. This kind of model integration will enable spatial representation of tree lists and Damage propagation and allow managers to evaluate the effect of different harvesting and thinning scenarios on the risk of Windthrow of both stands and individual trees within a stand.
Seppo Kellomaki - One of the best experts on this subject based on the ideXlab platform.
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impacts of climate change on timber production and regional risks of Wind induced Damage to forests in finland
Forest Ecology and Management, 2010Co-Authors: Heli Peltola, Velipekka Ikonen, Ari Venalainen, Harri Strandman, Hilppa Gregow, Antti Kilpelainen, Seppo KellomakiAbstract:Abstract In this work, we studied the impacts of climate change on timber production and regional risks of Wind-induced Damage to forests in Finland. The work employed: (i) national level forest inventory data, (ii) current baseline climate (1961–1990) and changing climate scenario (FINADAPT A2, 2001–2099), (iii) a forest ecosystem model (SIMA), (iv) a mechanistic Wind Damage model (HWind), and (v) currently applied forest management recommendations as a baseline. The results showed that the timber production will increase significantly towards the end of this century under the changing climate, and in a relative sense the most in Northern Finland. At the same time, the share of Norway spruce ( Picea abies L. Karst. ) is expected to decrease, especially in southernmost Finland, mainly favoring the presence of birch ( Betula spp.), but also Scots pine ( Pinus sylvestris L. ), when no species preference is given in management. As a result, the proportion of forest area in the two lowest critical Wind speed classes (i.e. Winds of 11–14 and 14–17 m s −1 ) will decrease in the autumn (birch without leaves) throughout Finland. However, in summertime (birch is in leaf) the proportion of forest area with such critical Wind speeds will even increase in southernmost Finland. Even though, in summertime the risk of Damage should be on average relatively low throughout Finland due to a lower occurrence of such Wind speeds compared to the Windiest time of the year (i.e. from autumn to early spring). The return period of critical Wind speeds of 11–17 m s −1 is today about every two years in southernmost Finland. In Northern Finland, the critical Wind speeds needed for Wind Damage are, on average, higher due to the larger share of Scots pine and on average lower height to breast height diameter ratios of trees compared to the south. To conclude, the climate change will affect clearly the forest growth and dynamics and, thus increase the need to manage forests more often and/or heavily (e.g. thinning, final felling), which in addition to species preference, will affect the risks of Damages. The consideration of the risk of Wind Damage is crucial especially in Southern Finland when adapting forest management to the changing climate. This is because the unfrozen soil period is expected to increase significantly in Finland, which decreases tree anchorage during the Windiest time of year.
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the effects of forest structure on the risk of Wind Damage at a landscape level in a boreal forest ecosystem
Annals of Forest Science, 2010Co-Authors: Hongcheng Zeng, Heli Peltola, Jordi Garciagonzalo, Seppo KellomakiAbstract:• The aim of this work was to analyze how the forest structure affects the risk of Wind Damage at the landscape level in a boreal forest. • This was done by employing: (i) Monte Carlo simulation technique for generating landscapes with different age class distributions, proportions of open areas (gaps), and tree species composition; and (ii) a mechanistic Wind Damage model, HWind, for predicting the critical Wind speeds at downWind stand edges of open areas (gaps) for risk consideration. The level of risk of Wind Damage observed at the landscape level was significantly affected by the presence of gaps and old stands. Even a slight increase in the proportion of gap areas or older stands had a significant impact on the total length of edges at risk. As a comparison, variation in species composition (Scots pine and/or Norway spruce) had much smaller impact on the risk of Damage. • In conclusion, the effects of forest structure on the risk of Wind Damage should especially be considered by forest managers in day-to-day forest planning in order to reduce the risk of Wind Damage both at the stand and landscape level.
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the effects of fragmentation on the susceptibility of a boreal forest ecosystem to Wind Damage
Forest Ecology and Management, 2009Co-Authors: Hongcheng Zeng, Heli Peltola, Hannu Vaisanen, Seppo KellomakiAbstract:Abstract The clear cuts and seedling stands can speed up Winds and may trigger blowdown at the edges of neighbour stands. Therefore, the height contrast of the neighbour stands and fragmentation at landscape level could be used to indicate the susceptibility of Windthrow. In this study, we studied how forest fragmentation affects the susceptibility of a boreal forest ecosystem to Wind Damage, both at patch and landscape level based on theoretical computations. For this purpose we generated, based on real stand inventory data of a Finnish forest ecosystem, different landscape configurations of Scots pine and Norway spruce forests using Monte Carlo simulation. Thereafter, we applied a mechanistic Wind Damage model to predict the Wind speeds needed for Wind Damage at forest edges. The fragmentation metrics of Contrast-Weighted Edge Density with three different height dissimilarity calculation methods were used to analyze the fragmentation at the landscape level. At the patch (stand) level, susceptibility of downWind stand to Wind Damage could be expressed in terms of a quadratic function, based on the tree height of upWind neighbouring stand or the height ratio between the neighbouring stands. At the landscape level, the relative risk of Wind Damage correlated linearly with the fragmentation despite of fragmentation metrics used. Both in single species and mixed forests, the metrics using empirical regression function based on patch level results (DS3) seemed more applicable in general than those using the ratio of tree heights between neighbouring stands (DS1) or constrained height contrast (DS2).
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a gis based decision support system for risk assessment of Wind Damage in forest management
Environmental Modelling and Software, 2007Co-Authors: Hongcheng Zeng, Heli Peltola, Ari Talkkari, Seppo KellomakiAbstract:In this study a GIS-based decision support system (DSS) was built for assessing the short- and long-term risk of Wind Damage in boreal forests. This was done by integrating a forest growth model SIMA and a mechanistic Wind Damage model HWind into geographical information system software (ArcGIS 8.2) as a toolbar (DLL) using ArcObjects in ArcGIS and Visual Basic 6. In this DSS complex problems are solved within program so that forest gaps, edge stands and edges are automatically tracked when the forest structure changes over time as a result of forest growth dynamics and management. This DSS can be used to assess the risk of Wind Damage to Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula spp.) stands, regarding the number of stands and area at risk and length of vulnerable edges of these risk stands at certain critical Wind speed classes (i.e. corresponding the maximum Wind speed a tree/stand can resist). This DSS can helps forest managers to analyse and visualise (charts, maps) the possible effects of forest management, such as clear-cuts, on both the immediate and long-term risks of Wind Damage at both stand and regional level.
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influence of clear cutting on the risk of Wind Damage at forest edges
Forest Ecology and Management, 2004Co-Authors: Hongcheng Zeng, Heli Peltola, Ari Venalainen, Seppo Kellomaki, Ari Talkkari, Harri Strandman, Kaiyun WangAbstract:Abstract The objective was to predict the risk of Wind Damage at forest edges in Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and birch (Betula spp.) dominated stands in Central Finland. The method used here was to integrate a mechanistic Wind Damage model and an airflow model with forest database containing information at the tree, stand, and regional levels. Analyses were made for the current forest edges (Case I) and for situations in which new forest edges might be created through clear-cutting: (i) whenever a stand were to reach the minimum acceptable mean diameter and/or stand age (Case II); or (ii) whenever the stand age were to exceed 100 years (Case III). These case studies were used to analyse the number of stands and total area at risk, and length of vulnerable edges for different critical Wind speeds and risk probabilities. It was evident that new clear-cuttings did increase the high Wind speeds at forest edges, especially in Case II, as compared with the Wind speeds at current forest edges (Case I). This local effect was however compensated at regional level by the more intensive cuttings in Case II, since the old stands, which were more vulnerable, were cut and the average tree size at the regional level decreased relative to Case I or III. The overall risk of Wind Damage at the regional level therefore decreased in Case II in terms of the number of stands and the total area at risk, and also in terms of the length of vulnerable edges. On the other hand, the risk increased at the regional level in Case III relative to Case I or II, because there were still a lot of vulnerable old stands left at the newly created edges. The sensitivity analyses of Wind conditions also showed that Norway spruce was more vulnerable in overall than Scots pine under current conditions and birch the least vulnerable (i.e. Norway spruce has risks even in slow Wind speeds, while Scots pine and birch have risks at higher Wind speeds). Furthermore, Norway spruce was more sensitive than Scots pine under more Windy conditions.
Barry Gardiner - One of the best experts on this subject based on the ideXlab platform.
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Agent-based modelling of Wind Damage processes and patterns in forests
Agricultural and Forest Meteorology, 2019Co-Authors: Kana Kamimura, Sylvain Dupont, Barry Gardiner, John FinniganAbstract:Powerful storms, consisting of strong gusts and Winds, Damage forests. Therefore, foresters need forest management strategies to reduce the Damage risk. This paper focused on the Damage patterns within the forest as the final results of multiple tree-Wind dynamic interactions in time and space during a storm. Recent developments in computer technology allow for the possibility of simulating the complex and dynamic phenomena of Damage during a storm but are extremely time consuming. To simplify the simulations without losing the crucial aspects of Wind Damage in forests, we introduced a computer simulation model using the agent-based modelling (ABM) technique, which capture the phenomena and interactions of individuals called ‘agents’. We created an ABM for forest Wind Damage simulation, coupling together an accepted understanding of Wind gusts in forests, tree bending moments, and Damage propagation. The model was tested with variations in three conditions: trees acclimated and unacclimated to their Wind environment; three levels of gust strength; and three tree planting densities. The ABM was able to replicate Damage patterns and demonstrate Damage propagation within the forest and the effects of forest edges. The difference in the rate of Damage in the forest between acclimated and unacclimated edges became similar with an increase in the gust intensity, and a decrease in tree density through a reduction in the shelter effect of the forest. The ABM could be improved in the future by parametrizing the variation in individual tree resistance, and the variation in gust and Wind strength, as well as adding more information on local environmental conditions such as topography and soil variation, and storm characteristics such as duration and intensity.
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Modelling Wind risk to Eucalyptus globulus (Labill.) stands
Forest Ecology and Management, 2016Co-Authors: Tommaso Locatelli, Barry Gardiner, Stefano Tarantola, Bruce Nicoll, Jean-marc Bonnefond, Didier Garrigou, Kana Kamimura, Genevieve PatenaudeAbstract:Wind Damage to commercial plantations and natural forests is a serious concern for forest owners and managers all over the world, with notable losses having been reported in the last few decades in Europe, the Americas, and Oceania. Wind-risk models such as ForestGALES allow for a good understanding of the dynamics involved in Wind Damage, and for calculations of risk to be made, therefore providing vital information on the best practices to minimise such risk. In this paper we parameterise ForestGALES for Eucalyptus globulus (Labill.), arguably one the most widespread and commercially important species for pulp and biomass production, with tree-pulling data obtained in Asturias, Spain. Despite the scarce data on tree and stand characteristics available for Wind Damaged stands of Eucalyptus spp., we provide an evaluation of our model’s performance under different stocking densities by comparing our simulations with real Wind Damage data acquired from the literature. We show that ForestGALES is able to accurately model the critical Wind speeds responsible for Eucalypts stand Damage, hence extending the model’s applicability to this important commercial genus. In line with good modelling practice, we present the results of a sensitivity analysis of the model, performed with a Global variance-based method. Our sensitivity analysis confirmed the main role of Dbh, stocking density, and tree height in driving the model outputs, and highlighted the importance of accurately knowing the size of any upWind gaps adjacent to a stand to reduce uncertainty in model predictions.
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mechanistic and statistical approaches to predicting Wind Damage to individual maritime pine pinus pinaster trees in forests
Canadian Journal of Forest Research, 2016Co-Authors: Kana Kamimura, Sylvain Dupont, Barry Gardiner, Dominique Guyon, Celine MeredieuAbstract:Maritime pine (Pinus pinaster Aiton) forests in the Aquitaine region, southwestern France, suffered catastrophic Damage from storms Martin (1999) and Klaus (2009), and more Damage is expected in the future due to forest structural change and climate change. Thus, developing risk assessment methods is one of the keys to finding forest management strategies to reduce future Damage. In this paper, we evaluated two approaches to calculate Wind Damage risk to individual trees using data from different Damage data sets from two storm events. Airflow models were coupled either with a mechanistic model (GALES) or a bias-reduced logistic regression model to discriminate between Damaged and unDamaged trees. The mechanistic approach was found to successfully discriminate the trees for different storms but only in locations with soil conditions similar to where the model parameters were obtained from previous field experiments. The statistical approach successfully discriminated the trees only when applied to similar...
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Review: Wind impacts on plant growth, mechanics and Damage
Plant Science, 2016Co-Authors: Barry Gardiner, Peter Berry, Bruno MouliaAbstract:Land plants have adapted to survive under a range of Wind climates and this involve changes in chemical composition, physical structure and morphology at all scales from the cell to the whole plant. Under strong Winds plants can re-orientate themselves, reconfigure their canopies, or shed needles, leaves and branches in order to reduce the drag. If the Wind is too strong the plants oscillate until the roots or stem fail. The mechanisms of root and stem failure are very similar in different plants although the exact details of the failure may be different. Cereals and other herbaceous crops can often recover after Wind Damage and even woody plants can partially recovery if there is sufficient access to water and nutrients. Wind Damage can have major economic impacts on crops, forests and urban trees. This can be reduced by management that is sensitive to the local site and climatic conditions and accounts for the ability of plants to acclimate to their local Wind climate. Wind is also a major disturbance in many plant ecosystems and can play a crucial role in plant regeneration and the change of successional stage.
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a review of mechanistic modelling of Wind Damage risk to forests
Forestry, 2008Co-Authors: Barry Gardiner, Stephen J. Mitchell, Kana Kamimura, Heli Peltola, Kenneth E Byrne, Sophie E Hale, Jean Claude RuelAbstract:Summary This paper reviews the current status of mechanistic models for Wind Damage risk assessment, describing model structure, applicability, validation and current limitations. We focus particularly on the hybrid mechanistic/empirical models GALES and HWind, which have been designed for calculating Wind Damage risk at the stand level within uniform forests and which are the most widely adopted models within the research community. These models have been integrated with different methods for predicting the local Wind climate in order to calculate the probability of Wind Damage in a number of different countries. We also discuss ongoing modelling work and proposals for future development in order to deal with complex forest structures and to predict the Wind Damage risk of individual trees within stands through the integration of mechanistic risk models with forest growth and yield models within a geographical information system framework. This kind of model integration will enable spatial representation of tree lists and Damage propagation and allow managers to evaluate the effect of different harvesting and thinning scenarios on the risk of Windthrow of both stands and individual trees within a stand.
Jean Claude Ruel - One of the best experts on this subject based on the ideXlab platform.
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Windthrow dynamics in boreal ontario a simulation of the vulnerability of several stand types across a range of Wind speeds
Forests, 2017Co-Authors: Kenneth A Anyomi, Stephen J. Mitchell, Ajith H Perera, Jean Claude RuelAbstract:In Boreal North America, management approaches inspired by the variability in natural disturbances are expected to produce more resilient forests. Wind storms are recurrent within Boreal Ontario. The objective of this study was to simulate Wind Damage for common Boreal forest types for regular as well as extreme Wind speeds. The ForestGALES_BC Windthrow prediction model was used for these simulations. Input tree-level data were derived from permanent sample plot (PSP) data provided by the Ontario Ministry of Natural Resources. PSPs were assigned to one of nine stand types: Balsam fir-, Jack pine-, Black spruce-, and hardwood-dominated stands, and, Jack pine-, spruce-, conifer-, hardwood-, and Red and White pine-mixed species stands. Morphological and biomechanical parameters for the major tree species were obtained from the literature. At 5 m/s, predicted Windthrow ranged from 0 to 20%, with Damage increasing to 2 to 90% for Winds of 20 m/s and to 10 to 100% for Winds of 40 m/s. Windthrow varied by forest stand type, with lower vulnerability within hardwoods. This is the first study to provide such broad simulations of Windthrow vulnerability data for Boreal North America, and we believe this will benefit policy decisions regarding risk management and forest planning.
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a review of mechanistic modelling of Wind Damage risk to forests
Forestry, 2008Co-Authors: Barry Gardiner, Stephen J. Mitchell, Kana Kamimura, Heli Peltola, Kenneth E Byrne, Sophie E Hale, Jean Claude RuelAbstract:Summary This paper reviews the current status of mechanistic models for Wind Damage risk assessment, describing model structure, applicability, validation and current limitations. We focus particularly on the hybrid mechanistic/empirical models GALES and HWind, which have been designed for calculating Wind Damage risk at the stand level within uniform forests and which are the most widely adopted models within the research community. These models have been integrated with different methods for predicting the local Wind climate in order to calculate the probability of Wind Damage in a number of different countries. We also discuss ongoing modelling work and proposals for future development in order to deal with complex forest structures and to predict the Wind Damage risk of individual trees within stands through the integration of mechanistic risk models with forest growth and yield models within a geographical information system framework. This kind of model integration will enable spatial representation of tree lists and Damage propagation and allow managers to evaluate the effect of different harvesting and thinning scenarios on the risk of Windthrow of both stands and individual trees within a stand.
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modelling the vulnerability of balsam fir forests to Wind Damage
Forest Ecology and Management, 2005Co-Authors: Alexis Achim, Jean Claude Ruel, Barry Gardiner, G Laflamme, S MeunierAbstract:Abstract Wind causes significant Damage to forests in central Quebec, and with the current move to more refined silvicultural practices, concerns are increasing. This study investigates the mechanisms of Windthrow resistance in stands dominated by balsam fir ( Abies balsamea (L.) Mill.) with a minor component of white spruce ( Picea glauca (Moench) Voss.), representing the dominant feature of a large section of the Eastern Canadian boreal forest. The aim was to compare the stability of trees of both species on mesic and rich mesic sites and then to compare the Windthrow vulnerability of the entire stands on the same sites. Stability was measured by static tree-pulling tests. The resulting critical turning moments were calculated at the base of the stem and were related to a series of tree descriptors. Stem mass and tree mass were the variables showing the highest correlation coefficients. The effects of the site and the species on the critical turning moments were non-significant (P > 0.05). Influence diagnostics did not reveal the need for separating the stability of the pulled trees from their mode of failure. A similar analysis also showed that the amount of rot at the base of the stem did not affect significantly the vulnerability to Windthrow in this study. Windthrow vulnerability was modelled using the methodology developed for the British GALES model. By using the relationship between the drag of the air on a surface and its aerodynamic roughness, the Wind speed over a forest canopy was transformed into a resulting turning moment at the base of the stem. Critical Wind speeds at which trees would overturn or snap could then be inferred for typical balsam fir stands growing on two site indices corresponding to those where the tree-pulling study was conducted. The immediate effect of a thinning operation was simulated by reducing the number of stems in the stands. The critical Wind speeds were invariably higher for stem breakage than for overturning. In the later case, they were close to 20 m s−1 on both sites before declining at senescence. A thinning treatment removing 30% of the basal area would reduce this speed by approximately 4 m s−1.
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modelling the vulnerability of balsam fir forests to Wind Damage
Forest Ecology and Management, 2005Co-Authors: Alexis Achim, Jean Claude Ruel, Barry Gardiner, G Laflamme, S MeunierAbstract:Abstract Wind causes significant Damage to forests in central Quebec, and with the current move to more refined silvicultural practices, concerns are increasing. This study investigates the mechanisms of Windthrow resistance in stands dominated by balsam fir ( Abies balsamea (L.) Mill.) with a minor component of white spruce ( Picea glauca (Moench) Voss.), representing the dominant feature of a large section of the Eastern Canadian boreal forest. The aim was to compare the stability of trees of both species on mesic and rich mesic sites and then to compare the Windthrow vulnerability of the entire stands on the same sites. Stability was measured by static tree-pulling tests. The resulting critical turning moments were calculated at the base of the stem and were related to a series of tree descriptors. Stem mass and tree mass were the variables showing the highest correlation coefficients. The effects of the site and the species on the critical turning moments were non-significant (P > 0.05). Influence diagnostics did not reveal the need for separating the stability of the pulled trees from their mode of failure. A similar analysis also showed that the amount of rot at the base of the stem did not affect significantly the vulnerability to Windthrow in this study. Windthrow vulnerability was modelled using the methodology developed for the British GALES model. By using the relationship between the drag of the air on a surface and its aerodynamic roughness, the Wind speed over a forest canopy was transformed into a resulting turning moment at the base of the stem. Critical Wind speeds at which trees would overturn or snap could then be inferred for typical balsam fir stands growing on two site indices corresponding to those where the tree-pulling study was conducted. The immediate effect of a thinning operation was simulated by reducing the number of stems in the stands. The critical Wind speeds were invariably higher for stem breakage than for overturning. In the later case, they were close to 20 m s−1 on both sites before declining at senescence. A thinning treatment removing 30% of the basal area would reduce this speed by approximately 4 m s−1.
Hongcheng Zeng - One of the best experts on this subject based on the ideXlab platform.
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the effects of forest structure on the risk of Wind Damage at a landscape level in a boreal forest ecosystem
Annals of Forest Science, 2010Co-Authors: Hongcheng Zeng, Heli Peltola, Jordi Garciagonzalo, Seppo KellomakiAbstract:• The aim of this work was to analyze how the forest structure affects the risk of Wind Damage at the landscape level in a boreal forest. • This was done by employing: (i) Monte Carlo simulation technique for generating landscapes with different age class distributions, proportions of open areas (gaps), and tree species composition; and (ii) a mechanistic Wind Damage model, HWind, for predicting the critical Wind speeds at downWind stand edges of open areas (gaps) for risk consideration. The level of risk of Wind Damage observed at the landscape level was significantly affected by the presence of gaps and old stands. Even a slight increase in the proportion of gap areas or older stands had a significant impact on the total length of edges at risk. As a comparison, variation in species composition (Scots pine and/or Norway spruce) had much smaller impact on the risk of Damage. • In conclusion, the effects of forest structure on the risk of Wind Damage should especially be considered by forest managers in day-to-day forest planning in order to reduce the risk of Wind Damage both at the stand and landscape level.
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the effects of fragmentation on the susceptibility of a boreal forest ecosystem to Wind Damage
Forest Ecology and Management, 2009Co-Authors: Hongcheng Zeng, Heli Peltola, Hannu Vaisanen, Seppo KellomakiAbstract:Abstract The clear cuts and seedling stands can speed up Winds and may trigger blowdown at the edges of neighbour stands. Therefore, the height contrast of the neighbour stands and fragmentation at landscape level could be used to indicate the susceptibility of Windthrow. In this study, we studied how forest fragmentation affects the susceptibility of a boreal forest ecosystem to Wind Damage, both at patch and landscape level based on theoretical computations. For this purpose we generated, based on real stand inventory data of a Finnish forest ecosystem, different landscape configurations of Scots pine and Norway spruce forests using Monte Carlo simulation. Thereafter, we applied a mechanistic Wind Damage model to predict the Wind speeds needed for Wind Damage at forest edges. The fragmentation metrics of Contrast-Weighted Edge Density with three different height dissimilarity calculation methods were used to analyze the fragmentation at the landscape level. At the patch (stand) level, susceptibility of downWind stand to Wind Damage could be expressed in terms of a quadratic function, based on the tree height of upWind neighbouring stand or the height ratio between the neighbouring stands. At the landscape level, the relative risk of Wind Damage correlated linearly with the fragmentation despite of fragmentation metrics used. Both in single species and mixed forests, the metrics using empirical regression function based on patch level results (DS3) seemed more applicable in general than those using the ratio of tree heights between neighbouring stands (DS1) or constrained height contrast (DS2).
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a gis based decision support system for risk assessment of Wind Damage in forest management
Environmental Modelling and Software, 2007Co-Authors: Hongcheng Zeng, Heli Peltola, Ari Talkkari, Seppo KellomakiAbstract:In this study a GIS-based decision support system (DSS) was built for assessing the short- and long-term risk of Wind Damage in boreal forests. This was done by integrating a forest growth model SIMA and a mechanistic Wind Damage model HWind into geographical information system software (ArcGIS 8.2) as a toolbar (DLL) using ArcObjects in ArcGIS and Visual Basic 6. In this DSS complex problems are solved within program so that forest gaps, edge stands and edges are automatically tracked when the forest structure changes over time as a result of forest growth dynamics and management. This DSS can be used to assess the risk of Wind Damage to Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula spp.) stands, regarding the number of stands and area at risk and length of vulnerable edges of these risk stands at certain critical Wind speed classes (i.e. corresponding the maximum Wind speed a tree/stand can resist). This DSS can helps forest managers to analyse and visualise (charts, maps) the possible effects of forest management, such as clear-cuts, on both the immediate and long-term risks of Wind Damage at both stand and regional level.
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the use of heuristic optimization in risk management of Wind Damage in forest planning
Forest Ecology and Management, 2007Co-Authors: Hongcheng Zeng, Timo Pukkala, Heli PeltolaAbstract:In this work heuristic techniques were used with a forest growth model (SIMA), mechanistic Wind Damage model (HWind) and GIS software (ArcGIS) in order to manage the risk of Wind Damage in forest planning. The study optimized clear-cut regimes taking into account the risk of Wind Damage and timber harvest over a 30-year simulation (planning) period in a forest located in central Finland. To demonstrate the effect of management goals related to Wind Damage, the amount of stand edges at risk was either minimized or maximized with or without even-flow targets of harvested timber. The three heuristic techniques included in the preliminary tests (simulated annealing, tabu search, and genetic algorithms) produced rather similar results for the planning problems. Tabu search performed slightly better than simulated annealing and genetic algorithms, and was therefore used in the subsequent analyses. The optimizations showed that the risk of Wind Damage could be decreased by aggregating clear-cuts and avoiding clear-cuts at the edge of stands with a high possibility of being Damaged. The even-flow timber harvesting objective limited the possibilities of minimizing the risk of Wind Damage. In addition, the optimization of clear-cut regimes was sensitive to the criterion of critical Wind speed that bisected the stands into risky and non-risky ones.
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influence of clear cutting on the risk of Wind Damage at forest edges
Forest Ecology and Management, 2004Co-Authors: Hongcheng Zeng, Heli Peltola, Ari Venalainen, Seppo Kellomaki, Ari Talkkari, Harri Strandman, Kaiyun WangAbstract:Abstract The objective was to predict the risk of Wind Damage at forest edges in Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and birch (Betula spp.) dominated stands in Central Finland. The method used here was to integrate a mechanistic Wind Damage model and an airflow model with forest database containing information at the tree, stand, and regional levels. Analyses were made for the current forest edges (Case I) and for situations in which new forest edges might be created through clear-cutting: (i) whenever a stand were to reach the minimum acceptable mean diameter and/or stand age (Case II); or (ii) whenever the stand age were to exceed 100 years (Case III). These case studies were used to analyse the number of stands and total area at risk, and length of vulnerable edges for different critical Wind speeds and risk probabilities. It was evident that new clear-cuttings did increase the high Wind speeds at forest edges, especially in Case II, as compared with the Wind speeds at current forest edges (Case I). This local effect was however compensated at regional level by the more intensive cuttings in Case II, since the old stands, which were more vulnerable, were cut and the average tree size at the regional level decreased relative to Case I or III. The overall risk of Wind Damage at the regional level therefore decreased in Case II in terms of the number of stands and the total area at risk, and also in terms of the length of vulnerable edges. On the other hand, the risk increased at the regional level in Case III relative to Case I or II, because there were still a lot of vulnerable old stands left at the newly created edges. The sensitivity analyses of Wind conditions also showed that Norway spruce was more vulnerable in overall than Scots pine under current conditions and birch the least vulnerable (i.e. Norway spruce has risks even in slow Wind speeds, while Scots pine and birch have risks at higher Wind speeds). Furthermore, Norway spruce was more sensitive than Scots pine under more Windy conditions.
