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1.
We simulated how possible changes in wind and ground-frost climate and state of the forest due to changes in the future climate may affect the probability of exceeding critical wind speeds expected to cause wind damage within one northern and one southern study area in Sweden, respectively. The topography of the study areas was relatively gentle and the forests were dominated by Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). Using estimated changes in the net primary production (NPP) due to climate change and assuming a relative change in the site productivity equal to a relative change in NPP, we simulated possible future states of the forest under gradual adjustment of the site index in response to climate change using the model The Forest Time Machine. Global climate change scenarios based on two emission scenarios and one general circulation model were downscaled to the regional level. The modified WINDA model was used to calculate the sensitivity of the forest to wind and the probability of wind damage for individual forest stands for the periods 2011–2041 and 2071–2100 and for a control period 1961–1990. This was done while taking into account effects on stability of the forest from expected changes in the occurrence of ground frost. Increasing sensitivity of the forest to wind was indicated for both study areas when adhering to recommended management rules of today. Adding also a changed wind climate further increased the probability of wind damage. Calculated probabilities of wind damage were generally higher in the southern study area than in the northern one and were explained by differences in wind climate and the state of the forests, for example with respect to tree species composition. The indicated increase in sensitivity of the forest to wind under the current management regime, and possibly increasing windiness, motivate further analysis of the effects of different management options on the probability of wind damage and what modifications of Swedish forest management are possibly warranted. 相似文献
2.
3.
In Japan, coastal forests have been constructed along the seashore to prevent houses and fields from disasters caused by strong winds. A management method needs to be established to regulate the stand density. There is also the possibility that wind speed will increase in the future because of the increasing strength of tropical cyclones caused by climate change. We evaluated the current and future risk of wind damage associated with strip cutting of Japanese black pine forest based on moment work on sample trees. We established a research site consisting of three groups of trees: group A faced a 1.2-m cutting strip, group B faced a 5-m cutting strip, and group C was the control. Group B was vulnerable to strong winds because the normalized critical wind speed (CWSnml) was significantly smaller than that in the other groups. The damage risk was evaluated by comparing CWSnml with the criterion, a 50-year return period of wind speed. In the current conditions, 5-m cutting had a certain degree of risk, and 1.2-m cutting showed a low risk. Under the future wind conditions, 5-m cutting was found to show high risk so that most of the trees did not meet the criterion. The 1.2-m cutting showed a low risk even in the future conditions. Our results clearly reveal the significant changes in the stability of remaining trees against strong winds after strip cutting. This study suggests a method to quantify the risk involved in forest management. 相似文献
4.
Impacts of climate change on timber production and regional risks of wind-induced damage to forests in Finland 总被引：1，自引：0，他引：1
H. Peltola V.-P. Ikonen H. Gregow H. Strandman A. Kilpeläinen A. Venäläinen S. Kellomäki 《Forest Ecology and Management》2010
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. 相似文献
5.
风对林木的影响 总被引：7，自引：0，他引：7
风除对森林造成了危害外,还对树木的生长、形态以及森林生态等产生影响。随着全球气候变化的发展,更多和更强的暴风出现的危险性日益增加。为了更好地理解风害对树木、林分和森林生态系统的影响,为森林经营管理提供依据,本文对近10年来国际上有关风对林木影响内容进行归纳总结。结果表明,风对林木影响的研究主要在以下几个方面取得了重要的进展：1)风与林木的空气动力学关系;2)树木在风力荷载下其适应性的生长机理;3)树木对风的生理响应：4)森林风害的危险评估。所有这些研究大都在人工用材林中进行的。此外,本文还介绍了该研究领域需要开展的其它研究,如1)天然林或天然次生林的风害研究;2)风害形成的林窗和森林动态研究;3)风害对森林生态主要过程的影响研究;4)．风害与森林管理研究。图3参61。 相似文献
6.
Context
A strategy widely proposed for increasing the resilience of forests against the impacts of projected climate change is to increase the number of species planted to spread and reduce the risks from a range of biotic and abiotic hazards.Aims
We tested this strategy in two case study areas in planted conifer forests in New Zealand and Scotland.Methods
The performance of the major tree species and an alternative was compared: radiata pine and Eucalyptus fastigata in New Zealand and Sitka spruce and Scots pine in Scotland. The process-based model 3-PG2S was used to simulate the effects of projected climate change at the end of this century, with and without CO2 fertilisation, upon productivity and financial returns. The effects of an abiotic hazard and two biotic hazards were considered.Results
Under the current climate, the major species outperform alternatives in nearly all circumstances. However, with climate change, their relative performance alters. In New Zealand, planting of E. fastigata becomes more attractive particularly when various hazards and elevated CO2 concentrations are considered. In Scotland, Scots pine becomes more attractive than Sitka spruce at lower interest rates.Conclusions
The major plantation species in both countries are well suited to the current climate, but deployment of alternative species and/or breeds can help to adapt these planted forests to the impacts of climate change. 相似文献7.
The famous “Faustmann” equation, which allows for identifying the most profitable tree species on a given unstocked piece of land, assumes constant timber prices. In reality, timber prices may fluctuate dramatically. Several authors have proven for monocultures that waiting for an acceptable timber price (reservation price) before harvesting (flexible harvest policy) increases the net present value of forest management. The first part of this paper investigates how efficient a flexible harvest strategy may be applied in mixed forests and whether the optimal species mixture is changed under such harvest policy. Mixtures of the conifer Norway spruce [Picea abies (L.) Karst] and the broadleaf European beech (Fagus sylvatica L.) were investigated. In order to evaluate mixed forests, the risks and the correlation of risks between tree species as well as the attitude towards risk of the decision-maker (risk-aversion is assumed) were considered according to the classical theory of optimal portfolio selection. In the second part we took up a recent critique on modern financial theory by Mandelbrot. Whether or not the assumption of normally distributed financial flows, which are supposed to occur under risk, would be appropriate to evaluate the risk of forest management was investigated. Market and hazard risks as well as their correlation were integrated in the evaluation of mixed forests by means of Monte-Carlo simulations (MCS). The risk of the timber price fluctuation was combined with the natural hazard risk, caused mainly by insects, snow and wind. Applying the μ-σ-rule, the mean net present value (NPV) from 1,000 simulations and their standard deviation were used for the optimisation. Given a low-return, risk-free interest rate to assess potential species mixtures of the Norway spruce and European beech, optimal proportions of European beech increased according to the theory of optimum portfolio selection with growing risk aversion from 0 (ignorance of risk) to 60% (great risk-aversion). In relation to a fixed harvest policy, the net present value of both, Norway spruce and European beech, could be increased significantly. Since the hazard risks of European beech were substantially lower compared with the Norway spruce (relation of susceptibility 1:4) beech benefited more from the flexible harvest policy. A comparison of simulated frequency distributions of the NPV with the expected density functions under the assumption of a normal distribution revealed significant differences. Only in the case of European beech was the general shape of the simulated frequency distribution similar to a normal distribution (bell-shaped curve). However, the density of NPV close to the mean was much greater than expected under the assumption of a normal distribution. Consequently, the frequency of a negative NPV for a European beech forest was greatly overestimated when applying the normal distribution. Though the shape of the simulated frequency distribution was rather different from a normal distribution for Norway spruce the simulated part of negative NPV was quite well approximated by the normal distribution. Therefore the simulated and expected frequencies of negative NPV were similar in case of Norway spruce; only a slight underestimation was seen in the assumption of a normal distribution. It can be concluded that actually simulated frequencies of negative NPV seem to be better measures for risk than computed probabilities of negative NPV, which assume normal distribution. As the risk for European beech was greatly overestimated by the conventional assumption of a normal distribution, the optimal proportions of European beech were surely rather underestimated according to the theory of portfolio. MCS on optimum mixtures derived by the classical portfolio theory seems necessary to test the robustness of such mixtures.
相似文献
| Thomas KnokeEmail: Phone: +49-8161-714700Fax: +49-8161-714616 |
8.
海岸林风害危险率评价的理论推导 总被引：2，自引：0，他引：2
本文在对间伐和风害之间关系的讨论和以往有关研究结果的基础上,确定了一种林木风害危险率的估计方法,用于评价间伐对林木风害的影响。这种对单株黑松及整个黑松林分的风害危险率估计,是根据风速廓线、枝条分布和透光分层疏透度(OSP)系数推导出来的。结果表明:如果枝条分布模型中的参数β等于单株树冠中风速廓线模型的衰减系数αs,参数H/D1.33可用于比较和评价对单株树木的风害危险率。这一原理也同样适用于整个林分,即用林分内风速廓线衰减系数α和透光分层疏透度(OSP)的分布中的衰减系数ν,结合D1.33估计和比较林分风害危险率。文中对间伐与非间伐单株黑松风害危险率进行了估计,得出了间伐两年后可以降低单株黑松风害危险率的结论;同时给出了确定林分风害危险率估计的过程图。图3参45。 相似文献
9.
Rolf Lidskog Johanna Johansson Daniel Sjödin 《Scandinavian Journal of Forest Research》2019,34(4):319-328
Wildfires present a growing risk to many countries, and climate change is likely to exacerbate this risk. This study analyzes how people directly affected by a wildfire understand its causes and consequences, as well as the future risk of wildfires. The point of departure is that social understanding of wildfires has an important influence on the consequences that emerge in the wake of a wildfire. The empirical case analyzed here is the largest forest fire in modern Swedish history, and the material basis of the study is a postal survey to all individuals directly affected by the fire. The results revealed a complex picture of the respondents’ understanding of the wildfire. Even if the fire was human caused, there was little blame toward forest companies and fire departments. Many positive consequences, such as a long-term increase in biodiversity, were attached to the disaster, and there was a belief that organizations will learn from it and take action to limit wildfires in the future. Simultaneously, the majority of the respondents believed that climate change may lead to an increased risk of forest fires in the future. These findings illustrate the complexity of people's perceptions of the fire and its aftermath. 相似文献
10.
《Journal of Sustainable Forestry》2013,32(2-3):201-212
Abstract Active risk management is central to the implementation of sustainable forestry, yet a fairly unexplored field of research. This study attempts to present some components of an analytical framework for risk management centred on the decision situation. Within this framework, a systems analysis approach to providing decision support for risk management is presented with an example dealing with outcome risk. The approach covers identification of risk factors for which decision support could be useful for the problem holders, presentation of how one such risk factor, wind damage, can be characterised in terms of a computer model, and how this computer model can be used for providing decision support. In addition to outcome risk, there is risk due to knowledge uncertainty and uncertainty related to valuation. The implications of these uncertainties for active risk management are discussed. Furthermore, communicative criteria for making the decision support useful are discussed. Since the work on the concept is still under way, this is too early to evaluate. So far, however, our results have been met with interest not only from representatives of forestry but also from mass media. 相似文献
11.
T. Heinonen T. PukkalaV.-P. Ikonen H. PeltolaH. Gregow A. Venäläinen 《Forest Ecology and Management》2011,261(3):710-719
Forest planning needs to assess various risks that may cause economic or other losses to forest owners. This study aimed at developing a wind risk assessment method, which considers the occurrence and directional distribution of strong winds, and the effect of snow loads and support by neighbouring trees on the expected wind damage. For this purpose, regression models were developed for predicting the critical wind speeds needed to uproot Scots pine, Norway spruce and birch trees at the downwind stand edges in Finnish conditions under unfrozen soil conditions, based on the characteristics of both downwind and upwind stand, and additional snow load on tree crowns. Furthermore, a risk index was developed for the forest landscape, based on the critical wind speeds of stands, occurrence of strong winds and their directional distribution, and the prevailing snow loading in the region. Thereafter, the mean risk index was used as an objective variable in heuristic optimization in forest planning to demonstrate how the optimal cuttings and the spatial layout of the landscape may change depending on the wind and snow conditions and the support that trees provide to each other. Our results show that the directional distribution of strong winds shape the optimal forest landscape structure markedly. Consideration of snow loading in the calculation of critical wind speeds increased the mean risk clearly and produced slightly more aggregated landscape structures in terms of tree height. The consideration of support that neighbouring trees provide to each other had minor effects. To conclude, the consideration of risk of wind induced damages in forest planning calculations clearly affects the selected cutting strategies and impacts the spatial layout of the landscape. 相似文献
12.
Sophie E. Hale Barry A. Gardiner Axel Wellpott Bruce C. Nicoll Alexis Achim 《European Journal of Forest Research》2012,131(1):203-217
Wind damage to forests is an important ecological disturbance factor. At the same time, it can have serious economic consequences
due to a reduction in timber production. Current models for predicting the risk of wind damage are useful, but generally only
focus on the “mean” tree within uniform stands. This paper presents measurements made of wind loading on trees of different
sizes within four forest stands of different structure and management history, but all well-acclimated to current wind conditions.
Each tree demonstrated a linear relationship between the maximum hourly turning moment and the square of the average hourly
wind speed at the canopy top; we defined this ratio (the gradient of the line M
max vs. u
2) as the turning moment coefficient (T
C). T
C was correlated with tree size, in a relationship that differed little between the four forest sites despite the differences
between the stands. The relationship between T
C and individual tree competition within each stand was investigated, using both distance-independent and distance-dependent
competition indices. All sites showed decreasing T
C with increasing competition. However, the relationships differed between sites and would also be expected to change through
time for a single site. The distance-dependent indices offered no improvement over the simpler, non-spatial indices that required
only a diameter distribution. We suggest how, subject to further work, the results presented could be applied to calculate
the risk of wind damage to trees of different sizes within a forest stand, and how the risk of wind damage to individual trees
might change in response to thinning. 相似文献
13.
Based on paper of “Theoretical derivation of risk-ratios for assessing wind damage in coastal forest“,wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in “Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest“.The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(7):598-606
ABSTRACTPotential risk for disruption to supply of raw materials for bio-based industrial sites from natural disasters has received little attention in site evaluations even though these risks may be significant. Biomass supply in the form of roundwood, forest and agricultural residues, or dedicated short rotation plantations are especially subject to disruptions from meteorological disturbances such as floods, wind and ice storms. The objective of this study was to account for risk from natural disasters in assessing the economic supply of biomass for the Eastern United States in a geospatial context, at the sub-county level (5-digit ZIP Code Tabulation Area). The Presidential Disaster Declaration database was used to identify risk zones where natural disasters frequently exceeded the response capability of State and local governments. Risk levels were estimated from exposure (the combination of the extent of natural hazards and the biomass assets at risk) and adaptive capacity (comprised of economic, social, and environmental factors). Of the 25,044 geospatial polygons in the 33-state study region, 43.8% were located in low risk regions, 26.8% were considered at moderate risk for disruption, and 29.4% were considered at high risk for disruption. The lowest risk locations were in southern Georgia, South Carolina, and Texas. 相似文献
15.
Chidiebere Ofoegbu Paxie W Chirwa Joseph Francis Folarannmi D Babalola 《Southern Forests》2017,79(2):109-116
In most African countries, forest-based climate change intervention initiatives such as nationally appropriate mitigation actions (NAMAs) and national adaptation programmes of action (NAPAs) are widely accepted. This is mainly due to the fact that they are relevant in addressing multiple challenges associated with rural development, mitigation and adaptation to climate change, and sustainable forest management. However, there are concerns about the implications of strategic and practical steps taken in this context on forest-dependent communities. Thus, there is need to reconcile local socio-economic vulnerabilities and forest-based climate change intervention initiatives. In the current study, socio-economic factors influencing households’ dependence on forest resources and associated implications on climate change interventions were investigated. Proportionate stratified random sampling was used to select 366 households from forest-based rural communities in Vhembe District of South Africa. A structured questionnaire was administered to household heads in 21 villages. The Pearson’s chi-square test was used to analyse the factors that influence household dependence on forest. The effects of household socio-economic characteristics on households’ forest dependence influencing factor were determined using the binary logit model. Up to 97% of the respondents depended on the forest resources predominantly because of low costs associated with using them. It was observed that socio-economic characteristics of households such as farm husbandry skills, years of residence (53–65) in the community and age of respondents (≤38–65) significantly (P < 0.05) influenced use of the forest resources. Thus, effectiveness and sustainability of forest-based climate change intervention initiatives can be promoted if the socio-economic conditions prevailing within households in areas next to forests are improved. 相似文献
16.
T. Heinonen T. Pukkala V.-P. Ikonen H. Peltola A. Venlinen S. Dupont 《Forest Ecology and Management》2009,258(7):1567-1577
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. 相似文献
17.
《Scandinavian Journal of Forest Research》2012,27(6):651-660
A set of hypotheses was formulated on the basis of available knowledge about non-industrial private forest (NIPF) owners' risk preferences. The empirical material used for testing the hypotheses was gathered in telephone interviews with 130 randomly selected NIPF owners. The results confirm that direct economic risks such as price and cost changes are seen by this group as much more important than indirect economic risks such as biological damage. The forest owners regarded forest holdings as a safer investment than stocks or bank savings. The results on risk attitudes were ambiguous. However, when larger amounts of money were at stake, the forest owners could be considered risk averters and a decrease in absolute and relative risk aversion could be confirmed. 相似文献
18.
《Scandinavian Journal of Forest Research》2012,27(6):574-584
Abstract Climate change effects such as storms and droughts are leading to increased risk of forest damage in central Europe. The aim of this paper was to evaluate forest fuel sourcing models including climate change-induced risks on forest fuel supply. Stochastic risk events, such as storms and bark beetle infestations, were modelled by means of a Monte Carlo simulation, and the economic performance was evaluated for two fuel-sourcing models supplying a single combined heat and power plant (CHP). The first sourcing model depicted a common sourcing model for Austrian CHPs, where only forest chips provided by long- and short-term suppliers were stored. The second sourcing model additionally enabled the storage of salvaged pulpwood to supply forest fuel from the plant's own inventory during shortage periods. Simulation results showed that storing salvage pulpwood as feedstock considerably reduced supply chain risks and resulted in lower procurement costs (1–3% less than normal delivered cost without storing salvaged pulpwood). 相似文献
19.
Elias Andersson E. Carina H. Keskitalo Sabina Bergstén 《Scandinavian Journal of Forest Research》2018,33(8):800-808
With a changing climate, storm and wind throw is becoming an increasing risk to forest. However, Swedish forest management practices have so far involved relatively little consideration of adaptation to climate change. This study examined resistance and alternatives to “business as usual” forest management, drawing upon material obtained in interviews with individual forest owners who spontaneously identified and discussed storm and wind throw as a risk to their forest. They thereby expressed a logic differing from that of the forest industry in Sweden, which has largely normalised storm risk rather than considering it in climate change adaptation work. The present analysis illustrates the broad and largely concerned position of individual forest owners, in contrast with a more established industry position on storm as an accepted and existing risk. Overall, the study highlights the diversity, agency and power relations within Swedish forestry and the forested landscape – aspects that are vital to better understanding processes relevant to forest and climate change adaptation. 相似文献
20.
The effects of forest structure on the risk of wind damage at a landscape level in a boreal forest ecosystem 总被引：1，自引：0，他引：1
Hongcheng Zeng Jordi Garcia-Gonzalo Heli Peltola Seppo Kellomäki 《Annals of Forest Science》2010,67(1):111-111