No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Flexibility in forest management: Managing uncertainty in Douglas-fir forests of the Pacific Northwest
Abstract
Long planning horizons generate substantial uncertainty in forest management, making management flexibility, the ability to choose between multiple options or opportunities, a desirable attribute of managed forests. Flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand. The wind stability of Pacific Northwest Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plantations is used to demonstrate the concept of management flexibility. Dense Douglas-fir plantations develop high height to diameter ratios (H/D same units) in the dominant trees making them unstable and prone to wind damage. The management of these plantations is inflexible, because without early and timely thinning, the stands do not contain stable trees that could be expected to survive long rotations or late thinnings. A combination of reduced planting densities and site-specific management reduces both the necessity and rigidity of intervention requirements (e.g., thinning) and expands the number of potential developmental pathways for these stands. The cost of greater management flexibility is reduced efficiency of wood volume production; however, greater adaptability to changing markets, labor conditions, and management objectives may be more important for many forest owners. While this approach to management is complex, it frees owners and managers from rigid management requirements and allows for a wider range of future stand conditions.
... This uncertainty has related to markets and prices, to the availability of human labor capacity, to the probability of biotic pests, etc. Thus, coping with uncertainty has some tradition in forestry, and forest science has developed strategies to deal with this kind of uncertainty, e.g., improving the flexibility to choose between different appropriate management options (Wilson and Baker 2001). However, the uncertainty associated with climate change adds a whole new and unparalleled dimension to the challenge of dealing with it. ...
... Consequently, here we expand the definition of resilience to " . . . the capacity of a social-ecological system to absorb shocks or perturbations and still retain its fundamental function, structure, identity, and feedbacks, often as a result of adaptive adjustment to changing conditions" (Chapin et al. 2006). Wilson and Baker (2001) have defined flexibility as: "The ability to choose between multiple options or opportunities". Thus "flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand" (Wilson and Baker 2001). ...
... Wilson and Baker (2001) have defined flexibility as: "The ability to choose between multiple options or opportunities". Thus "flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand" (Wilson and Baker 2001). Hence flexibility is strongly connected to the concept of adaptability. ...
... Lack of inclusion of trees with poor genetic growth potential may also be influential. In addition, H:D ratios will increase sooner on productive sites (Wilson and Oliver 2000;Wilson and Baker 2001). Carey and Curtis (1996) suggest that without early and timely thinning to reduce stem density many of these stands cannot be expected to survive long rotations or to thinnings at a later age, particularly on windy sites (Wilson and Baker 2001). ...
... In addition, H:D ratios will increase sooner on productive sites (Wilson and Oliver 2000;Wilson and Baker 2001). Carey and Curtis (1996) suggest that without early and timely thinning to reduce stem density many of these stands cannot be expected to survive long rotations or to thinnings at a later age, particularly on windy sites (Wilson and Baker 2001). In this regard, Wilson and Oliver (2000) Once a stand develops high H:D ratios thinning will not make them much more stable and vigorous immediately. ...
... Forests that developed at wider spacing and established wind-firm and snow-break resistant trees, are not limited to a single trajectory or endpoint (Wilson and Baker 2001 Moore 2002, unpublished). Well spaced trees or trees thinned early in development, also increase resistance to uprooting (Curtis and Marshall 1993), but usually not as rapidly as the rate of wind loading with increased spacing from thinning (Moore 2002, unpublished). ...
... This uncertainty has related to markets and prices, to the availability of human labor capacity, to the probability of biotic pests, etc. Thus, coping with uncertainty has some tradition in forestry, and forest science has developed strategies to deal with this kind of uncertainty, e.g., improving the flexibility to choose between different appropriate management options (Wilson and Baker 2001). However, the uncertainty associated with climate change adds a whole new and unparalleled dimension to the challenge of dealing with it. ...
... Consequently, here we expand the definition of resilience to " . . . the capacity of a social-ecological system to absorb shocks or perturbations and still retain its fundamental function, structure, identity, and feedbacks, often as a result of adaptive adjustment to changing conditions" (Chapin et al. 2006). Wilson and Baker (2001) have defined flexibility as: "The ability to choose between multiple options or opportunities". Thus "flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand" (Wilson and Baker 2001). ...
... Wilson and Baker (2001) have defined flexibility as: "The ability to choose between multiple options or opportunities". Thus "flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand" (Wilson and Baker 2001). Hence flexibility is strongly connected to the concept of adaptability. ...
The issue of rapid change in environmental conditions under which ecosystem processes and human interventions will take place in the future is relatively new to forestry, whereas the provision of ecosystem services, e.g., timber or fresh water, is at the very heart of the original concept of forest management. Forest managers have developed ambitious deterministic approaches to provide the services demanded, and thus the use of deterministic approaches for adapting to climate change seem to be a logical continuation.
However, as uncertainty about the intensity of climate change is high, forest managers need to answer this uncertainty conceptually. One may envision an indeterministic approach to cope with this uncertainty; but how the services will be provided in such a concept remains unclear. This article aims to explore the fundamental aspects of both deterministic and indeterministic approaches used in forestry to cope with climate change, and thereby point out trade-offs in service provisioning and adaptability. A forest owner needs to be able to anticipate these trade-offs in order to make decisions towards sustainable forest management under climate change.
... Tree stability against wind is strongly related to individual tree and stand characteristics, which interact with impact factors including climate, topography, soil type, soil water content, and silvicultural treatment (Nielsen 1995;Ruel 2000). Trees and stands are characterized by tree species (e.g., Gardiner and Quine 1994), root anchorage (e.g., Nielsen 1995) in relation to soil condition (e.g., Stathers et al. 1994), tree age (e.g., Lekes and Dandul 2000;Kuboyama et al. 2003), and the ratio of tree height to stem diameter (h/d ratio; e.g., Cremer et al. 1982;Wilson and Baker 2001). These characteristics reflect a tree's vulnerability to wind. 5 It is not easy to determine which factor is the most significant cause of wind damage in particular regions because the impact factors are usually inter-related. ...
... In addition, trees with tapered stems have a high risk not only of wind damage but also of snow damage. 11 The tapering Norway spruce and Scots pine are vulnerable to stem breakage caused by wind and snow Wilson and Baker 2001). ...
... 22 Changing the planting density, growth rate, and edge creation would significantly influence tree shapes, which relate to tree vulnerability (Gardiner and Quine 1994). Such changes would impact current and/or future wind damage risk (Wilson and Baker 2001). Therefore, it is essential to make suitable management plans so as to obtain maximum benefits without damage to forests. ...
Forest management for minimizing wind damage risk requires predicting future wind damage as accurately as possible. However,
previous studies carried out in Japan mostly focused on field observation and not on an extensive estimate of damage in various
regions. This paper, therefore, aims to understand better approaches to the assessment of wind damage in Japan. First, basic
descriptions of wind damage were reviewed including the process and types of tree and stand failures. Several factors relating
to wind damage were also described including biological factors and stand characteristics. Second, the current methods of
wind damage risk assessment were classified such as (1) observational/empirical, (2) statistical, and (3) mechanistic methods.
Of the current methods, the mechanistic methods were acceptable in terms of their prediction of wind damage using the mechanistic
behaviour of tree and stand as a result of wind pressure. Third, this paper reviewed previous case studies in Japan and showed
that most studies of wind damage focused on particular typhoon events. Their conclusions might be difficult to apply to other
settings for the estimation of future wind damage risk with the changes of stand condition (thinning, gap creation, etc.).
Therefore, the mechanistic methods would be one of the most powerful approaches to estimate the possibility of future wind
damage risk with changes of stand conditions. Further studies are required to develop the methods of wind damage risk assessment
in Japan including the mechanical behaviour of tree and stand as a result of wind (typhoon) phenomena.
... Spacing, either through initial planting or PCT, may be the best option for reducing future wind damage in stands. Spacing trees exposes them to wind early enough to stimulate root and cambial growth and develop favorable H/D ratios before the onset of competition (Wilson and Baker, 2001;Wilson and Oliver, 2000). For this reason PCT may be a more effective tool to increase windfirmness than commercial thinning. ...
... Numerous factors, some of which cannot be controlled, are continually interacting with the forest resource, introducing risk to management, and making consistent predictable management outcomes uncertain (Birot and Gollier, 2001;Wilson and Baker, 2001). This uncertainty includes product markets and non-market forest values. ...
The likelihood of windthrow or windsnap occurring in a forest stand includes numerous factors; however, past research suggests that these factors can be grouped into four broad categories: regional climate, topographic exposure, soil properties and stand characteristics (Mitchell, 1995). Of the three categories, stand characteristics are most commonly and easily modified through forest management. Vulnerability to wind damage in Maine may increase in the future because of three trends influencing stand conditions. One, Maine forests contain a considerable amount of balsam fir and red spruce, tree species that are considered particularly susceptible to wind damage. Two, extensive areas regenerated after the 1970's and 1980's era spruce budworm outbreak are maturing. Three, partial removals currently account for over 74 percent of the area harvested annually in the state (McWilliams et al. 2005). Two approaches to augment our understanding of the interaction between forest management and wind damage vulnerability in Maine forests were developed The first approach combined information from the base of scientific wind disturbance literature with more localized information from Maine's forest resource managers. Forest resource professionals were surveyed through phone calls and professional meetings to gather information about wind damage over their careers. The second approach developed a general vulnerability to wind damage model that reflects topographic exposure (distance limited TOPEX (Ruel et al. 1997), restricted rooting depth, elevation, and stand characteristics (height, density, edge, treatment history, and species composition). Results of the first approach reveal serious limitations in information about wind damage statewide. However, numerous patterns and trends were identified. Damage differs by storm type and storms impact the state on a continuum of storm intensity, frequency, and scale. Numerous factors influence the damage potential of these wind events on forests. These factors include topographic exposure, soil conditions and stand characteristics. Damaging storms appear to originate from the southwest most frequently and impact softwoods more severely than hardwoods. Frequent low-intensity winds tend to eliminate softwoods from hardwood dominated stands. The general vulnerability to wind damage model is based on Mitchell's (1998) conceptual windthrow triangle and is built from eight component variables describing stand, soil, and topographic characteristics. The model is built and calibrated from composite variables which combine the component variables into distinct site and stand components. The model was tested on a 40,800 hectare forest area in northern Maine with spatially explicit wind damage records. To avoid problems with spatial autocorrelation ten random samples were drawn from the study area and evaluated individually with a Mann-Whitney non-parametric comparison of means test (alpha 0.05). Results from the ten samples were pooled, and a one sample comparison of means t-test was used to analyze the consistency of the results from the ten individual samples (alpha 0.05). The final model identifies significant and consistent differences between damaged and undamaged areas (p-value 0.000). When evaluated individually, not all model components were significantly different (e.g., density, edge, exposure and species composition). Variables describing thinning, stand height, and elevation had the greatest differences between means of the populations of damaged and undamaged stands in the study area. The general model developed proved useful on the study area and by design should be transferable to diverse regions throughout the state.
... The problem with the sensitivity of Douglas-fir of damage by abiotic factors (wind, snow)-high H/D ratio and the suggestions to resolve it by conducting of felling are subject to a number of publications [27][28][29]. ...
... Wilson and Baker [28] emphasized that later thinnings may not be effective in promoting stability, since there was no lower H/D values appeared. In the studied Douglas-fir plantations, silvicultural interventions are late and the intervention should be conducted very carefully. ...
The aim of the article was to study the growth of Douglas-fir plantations in the region of the Training Experimental Forest Enterprise, Yundola (Central South Bulgaria). The study sites were three Douglas-fir plantations, ranging between 50 and 55 years of age at altitudinal range between 1,400 m and 1,600 m above sea level (masl). The mean height, diameter at breast height, site class, stem volume as well as the mechanical resistance (H/D ratio) of Douglas-fir were measured for each plantation. The results showed that Douglas-fir had the best height growth of the studied plantations on slope facing South at altitude 1,600 masl and Douglas-fir with age 55 years old reached a mean height of 32.4 m. The average diameter at breast height of the studied plantations reaches approximately 30 cm, which shows that they are suitable for large scale wood harvesting. The average stem volume of Douglas-fir in the observed plantations up to age of 55 is within the range of 400-600 m 3 /ha, with an average annual volume increment from 7 m 3 /ha to 12 m 3 /ha each year. The high index of mechanical resistance (H/D ratio) indicated a risk for abiotic damages, which implicated the need for the immediate implementation of felling.
... Most restoration activities in the redwood region have focused on older stands, but studies elsewhere in the Pacific Northwest forests have demonstrated that early-stage thinning enhances tree growth and vigor, expediting the growth of large trees, height differentiation, and development of late-successional forest structure [3,11]. Early-stage thinning has also been demonstrated to improve tree resistance to wind and snow damage [9,12,13]. ...
... Declines in vigor (measured using live crown ratio) and growth (measured using the 10-year radial growth increment) negatively affect a stand's ability to respond to future thinnings and compromise a stand's potential developmental pathways [13]. In this study, thinning resulted in 27% greater live crowns ( Figure 5), apparently due to slowed crown recession which permitted trees to accrete crown length. ...
Among forested parks and reserves of the Pacific Coast of the United States, the restoration of late-successional conditions to second-growth stands is a management priority. Some traditional silvicultural treatments may help achieve this objective. We evaluated early-stage thinning as a restoration treatment to facilitate the growth and development of young (33- to 45-year old), homogeneous, and second-growth stands of coast redwood (Sequoia sempervirens) and Douglas-fir (Pseudotsuga menziesii). Targeting both stand-level responses and dominant (focal) tree responses for analysis, we compared structural attributes of adjacent thinned and unthinned stands, 12–17 years after thinning. Thinned stands displayed enhanced metrics of tree vigor, growth, and mechanical stability, thereby improving response to future restoration treatments and broadening the range of potential stand conditions. We conclude that early-stage thinning has been successful as a preliminary restoration treatment because it accomplished many initial goals of forest restoration, while retaining sufficient tree numbers to buffer against possible attrition from future disturbances.
... Thinning should start early, ideally before 20 years of age (de Champs and Demarq 1996; Kohnle 2008). Delayed early thinning can result in stand instability and make Douglas-fir susceptible to windthrow (Wilson and Baker 2001). The first thinning should be heavy, removing 20% − 25% of trees (Romania: Liubimirescu 1973) up to 30% − 35% (France: CRPF 1999) to fully utilize the growth potential of the species. ...
Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), one of the most commercially important tree species in western North America and one of the most valuable timber trees worldwide, was introduced to Europe in 1827. It became a major species for afforestation in Western Europe after WWII, currently grows in 35 countries on over 0.83 million ha and is one of the most widespread non-native tree species across the continent. A lower sensitivity to drought makes Douglas-fir a potential alternative to the more drought-sensitive Norway spruce so its importance in Europe is expected to increase in the future. It is one of the fastest growing conifer species cultivated in Europe, with the largest reported dimensions of 2.3 m in diameter and 67.5 m in height. Pure stands have high productivity (up to 20 m3 ha-1a-1) and production (over 1000 m3 ha-1). The species is generally regenerated by planting (initial stocking density from less than 1000 seedlings ha-1 to more than 4000 ha-1), using seedlings of European provenance derived from seed orchards or certified seed stands. As the range of end-uses of its wood is very wide, the rotation period of Douglas-fir is highly variable and ranges between 40 and 120 years. When the production of large-sized, knot-free timber is targeted, thinnings are always coupled with pruning up to 6 m. There is an increasing interest in growing Douglas-fir in mixtures and managing stands through The online version is available at
... Sobre o tópico das oportunidades, o mais evidente e que se aplica em ambas as regiões (Norte e Centro Sul), é o facto de estas serem bastante isoladas, não só em comparação com o restante país, mas também em relação a quem lhes pretende aceder, o que claramente pode ser uma oportunidade, especialmente se considerarmos que o consumidor é cada vez mais exigente e procura cada vez mais a autenticidade e criatividade Wilson, 2001) algo que certamente poderá encontrar na Patagónia devido á pouca presença humana na região, mais, no período pós COVID-19, é expectável que locais mais isolados onde o contacto entre pessoas seja bastante reduzido venham a ter um aumento na procura turística, algo que a região beneficia e terá tudo a ganhar. ...
Sustainable Management of biodiversity and Fisheries Based on EO Data
... Forest management plays a fundamental role in that it can reduce a priori vulnerability, within certain limits, or minimize the impacts caused by extreme extratropical cyclones (Wilson and Baker, 2001;Cucchi and Bert, 2003;Schelhaas et al., 2003;Mason and Valinger, 2013). Such management is complex, and success may sometimes not be guaranteed, for example, when a particular stand is in the path of an extreme storm, as it happened with the Lothar, Martin, and Klaus (Mason and Valinger, 2013). ...
In European forests, extreme wind events associated with severe extratropical cyclones are considered the main abiotic agent of forest vulnerability, leading to high economic losses in forests due to damage caused by the uprooting of trees and trunk breaks. Despite the importance recognized to severe cyclones and associated extreme phenomena, the impact on forest stocks is not always properly reported, leading to underestimation in the perception of losses, with direct consequences on forest governance decisions. This is particularly true in countries where other agents traditionally have a high impact, such as the countries under the influence of the Mediterranean, where wildfire is a recurrent menace with devastating effects. This work characterizes the situation observed in Portugal and presents the methodology followed to obtain information about forest damages and the procedure to identify the extreme extratropical cyclones responsible for those damages. As an example, available information and the recording of damage occurring in the Portuguese forest in winter 2017–2018 are presented and discussed. The study shows how difficult and demanding it is to obtain past information about the damage. In addition, there is high uncertainty about the precise identification of the event that caused the damage, as field records often occur several days or even weeks after the storm. To reduce the constraints, it is proposed to use a model whose skeleton of information has been designed to obtain useful information from traditional registries. The proposed model is useful for the characterization of losses and to support national policies to reduce the impact of damage associated with extreme wind events. The design of the catalogue can be used for recording information at the stand scale level by stakeholders and ensure compatibility with international databases for updating information purposes.
... Mangrove community structure can also provide wind protection during storms (Das and Crépin, 2013). In contrast, the dense Douglas fir plantation forms a height diameter ratio in the dominant trees that makes it unstable and vulnerable to wind damage (Wilson and Baker, 2001). ...
Rubber (Hevea brasiliensis Müll. Arg.) trees have been commercialized for several decades in Asia, notably in China and form a typical plantation ecosystem in tropical areas. Although rubber trees have been planted successfully as commercial crops in many places, adapting rubber plantations to sub-optimal environments remains a challenge. Especially in young rubber plantations, populations are often not stable or sustainable because tree breakage and death are common due to frequent strong storms. Intercropping to optimize group structure has been proposed as a method to improve the overall stability of rubber plantations. The objective of our study is to explore the wind resistance and growth of individual rubber trees in an intercropped system that utilizes native tree species Michelia macclurei and Mytilaria laosensis. The density of rubber trees was the same in the monoculture and the intercrop, with additional native trees added in the intercrop. The effects of the wind resistance and growth of the system to three different planting patterns namely, the monoculture of Hevea brasiliensis, Hevea brasiliensis intercropping with Michelia macclurei, and Hevea brasiliensis intercropping with Mytilaria laosensis were analyzed using observation data from the field plots. The results show that both the maximum and average wind speeds were lower in intercropped rubber plantations than in monoculture rubber plantations, the average maximum wind speeds were lower in Hevea-Michelia and Hevea-Mytilaria intercropping systems than in the Hevea monocrop system by 8.4% and 19.6%, respectively. The average wind speeds were also lower in Hevea-Michelia and Hevea-Mytilaria intercropping systems than in the Hevea monocrop system, with daily average wind speeds 21.2% and 36.0% lower, respectively. The proportion of rubber trees showing Grade 6 wind damage in monoculture, intercropping with Michelia and intercropping with Mytilaria were 9.5%, 2.3% and 1.9%, respectively. There was a competition between the intercropping Michelia / macclurei and Hevea in soil nutrient absorption and utilization, and the competition of soil nutrient further decreased the height growth and formed small crown area opposing wind loading. This indicates that the pattern of intercropping rubber with native tree species may reduce wind speed and average wind speed in intercropped rubber systems, thereby reducing the wind damage on rubber trees and improving their health. The biomass of intercropping with Michelia and intercropping with Mytilaria systems is significantly higher than Hevea monocrop system. This result shows that the intercropping patterns of Hevea-Michelia and Hevea-Mytilaria enhance the total productivity. This indicates that intercropping rubber with native trees may construct an environment that buffers wind effects and benefits tree growth to the extent that it could also improve ecosystem stability in rubber plantations. Healthier and stronger rubber trees may lead to a more sustainable and possibly increased yield of rubber from plantations in the future. These results also enrich tropical protection science and provide a valuable reference for the sustainable management of agricultural system or other plantation.
... In most developed countries with a long tradition in forestry, forest managers and owners have developed strategies to deal with this kind of uncertainty, e.g., improving the flexibility to choose between different appropriate management options (Wilson and Baker 2001). In Ireland, the situation is quite different. ...
In Ireland the political consensus to expand forest cover has not been really questioned for the last five decades, neither by policy‐makers nor by forest owners’ representatives. However, in 2014, Irish private forest owners experienced for the first time in their life a catastrophic windstorm. A qualitative survey, conducted among the forest owners affected by the storm, shows that beyond the economic losses this disaster deeply shook their convictions about the real benefits of afforestation programmes. Using the theoretical concept of relational expectations, we show that Storm Darwin deconstructed a significant part of their identity as their status switched from audacious pioneer to forestry loser overnight. The political and socio‐economic structures outweighed the agency of individuals and their initial desire not to reforest. While the reconstitution scheme gave them the direction to follow, it reduced the risk of desertion. However, our study also shows that landowners may be a lot more cautious before signing up for afforestation programmes in the future.
... For example, this is the case for biodiversity, carbon sequestration, oxygen production, improvement of local wind climate and soil preservation. Furthermore, the review observed only few investigations of the real impacts of biotic hazards on forest utilisation (5%), and the economics of biotic risk in forest management was emphasised by only Wilson and Baker (2001) and Xu et al. (2009). ...
... Option pricing models focus on the desirable part of uncertainty (i.e., positive deviations from the expected value). They assume that decisions may be adjusted during the considered time horizon and hence quantify the "value" of flexibility (Wilson and Baker 2001;Yemshanov et al. 2015). For instance, Yemshanov et al. (2015) demonstrated the differences in opportunity costs of land-use change when calculated conventionally and when calculated by an option pricing model. ...
Keymessage: Non-stochastic portfolio optimization of forest stands provides a good alternative to stochastic mean variance optimization when available statistical data is incomplete. The suggested approach has a theoretical background in the areas of robust optimization, continuous multicriteria decision-making, and fuzzy theory.
Context: Economic optimization addressing diversification in mixed uneven-aged forest stands is a useful tool for forest planners.
Aims: The study aims to compare two approaches for optimizing rotation age cohort portfolios under risk. Rotation age cohorts emerge from age-based regeneration-harvesting operations simulated for two tree species: Picea abies and Fagus sylvatica.
Methods: The first optimization approach is a stochastic mean-variance approach. The second is a non-stochastic optimization approach, which has rarely been applied to optimize tree species composition and the distribution of harvested timber over many periods. It aims at relatively good solutions, even if the deviation from the initially assumed return is very high. The objective function for both approaches is sensitive to the selection of various harvesting periods for different parts of the stand. For the stochastic approach, the objective function maximizes the annuitized net present value (economic return) for specific levels of risk by allocating area proportions to harvesting periods and tree species. In the non-stochastic approach, the allocation of area proportions instead minimizes the maximum deviation from the greatest possible economic
return among many uncertainty scenarios (non-stochastic approach).
Results: Portfolios from both approaches were diverse in rotation age cohorts. The non-stochastic portfolios were more diverse when compared with portfolios from the efficient frontier, which showed the same standard deviation. However, P. abies clearly dominated the non-stochastic portfolios, while stochastic portfolios also integrated beech to a greater extent, but only in very low risk portfolios. The economic losses of the non-stochastic portfolios compared to the efficient frontier of the mean-variance approach lay between 1 and 3% only for different levels of accepted risk.
Conclusion: The non-stochastic portfolio optimization over a large uncertainty space is so far uncommon in forest science, yet provides a viable alternative to stochastic optimization, particularly when available data is scarce. However, further research should consider ecological effects, such as increased resistance against hazards of conifers in mixed stands. Resulting robust portfolios only show slight economic losses compared to the efficient frontier of a stochastic optimization.
... The downside of this strategy is, however, sacrificing optimality for less sensitivity to false assumptions and hoping for partial safeguarding of forest resources and services under any future conditions (Lempert and Collins 2007). Other approaches are recommended in the literature, e.g., an option-oriented (i.e., "flexibility") management (Wilson and Baker 2001), a "complex adaptive system" to improve resilience of forest resources (Puettmann et al. 2013), and analyzing trade-offs between service provisioning and adaptability applying deterministic decision-making (Wagner et al. 2014) containing implicitly some notions of robustness. We recommend making robust and active adaptation strategies and the development of related frameworks and modeling systems to guarantee sustainable provisioning of forest goods and services. ...
Key message: Pertinence of alternative adaptation strategies to business as usual, namely reactive, active, and robust adaptation strategies, can be evaluated by incorporating the expected costs and benefits of adaptation, climate change uncertainty, and the risk attitudes of decision-makers. Context: Forest management is used to coping with risky and uncertain projections and estimates. However, climate change adds a major challenge and necessitates adaptation in many ways. Aims: This paper highlights the dependency of the decisions on adaptation strategies to four aspects of forest management: (i) the costs of mitigating undesirable climate change impacts on forests, (ii) the value of ecosystem goods and services to be sustained, (iii) uncertainties about future climate trajectories, and (iv) the attitude of decision-makers towards risk (risk aversion level). Methods: We develop a framework to evaluate the pertinence of reactive, active, and robust adaptation strategies in forest management in response to climate change. Results: Business as usual may still be retained if the value of the forest and cost of climate impacts are low. Otherwise, it is crucial to react and facilitate the resilience of affected forest resources or actively adapt in advance and improve forest resistance. Adaptation should be robust under any future climate conditions, if the value of the ecosystem, the impacts from climatic changes, and the uncertainty about climate scenarios are very high. Conclusion: The decision framework for adaptation should take into account multiple aspects of forest management under climate change towards an active and robust strategy.
... Above this tree height, unstable trees will not regain stability for many years and the probable result of thinning will be windthrow of some or all of the remaining trees; and the window for successful thinning will have been missed. Efforts to restore stand structural diversity at the broader landscape scale may be impeded by silvicultural prescriptions that sacrifice operational flexibility (i.e., larger windows of opportunity) for operational efficiency (Wilson and Baker 2001). ...
... The ratio of mean dominant tree height to mean diameter (H:D) in a stand increases as stand stocking rates increase over time (Cremer et al. 1982). Ratios greater than 100 have been noted as unstable and susceptible to wind damage (Stathers et al. 1994, Wang et al. 1998, Harrington 2001, although ratios as low as 80 have often been associated with high stocking and increased potential wind damage (Wilson and Baker 2001, Wonn and O'Hara 2001, Roberts et al. 2007. This ratio has also been suggested as a measure of competitive stress (Opio et al. 2000). ...
Foresters have come to rely on growth-and-yield simulators when making management decisions extending decades into the future. The importance of obtaining reliable estimates of growth-and-yield projections is apparent, hence evaluating and selecting an appropriate simulator can be challenging. One way to evaluate growth-and-yield models for prospective applications is by examining how model predictions adhere to basic expectations of biological growth. We compared five computer growth-and-yield simulators for loblolly pine (Pinus taeda L.) using relationships depicted in Leary's 1997 lower triangular matrix of stand property interdependence. The graphical comparison of common loblolly pine growth-and-yield simulators indicates how model predictions adhere to current conventional wisdom concerning biological growth in forest stands. The basic principles of property interdependence are generally evident in the computer growth-and-yield simulators with, however, notable differences because some model results deviate from the expected "biological behavior".
... On the other side, some of the cost savings when using wide initial spacing may be offset (or more than offset) by the larger branches and thus lower quality wood at time of harvest (Johansson, 1992). However, starting with lower density plantings will allow for future management flexibility (Wilson and Baker, 2001) and better allow foresters to take advantage of the variation in species, size and spatial patterns found in advanced regeneration (Smith, 1992). Switching assessment scales in this context means acknowledging the uncertainty of future conditions and using caution accordingly in management decisions. ...
Foresters influence short- and long-term development of plant neighbourhoods, stands and landscapes by their management practices. In the past, most of these practices have aimed to homogenize the composition and structure of stands for efficient wood production. This publication provides an overview of and guidance on how to recognize and efficiently utilize opportunities to modify silvicultural practices, with the goal of increasing species diversity and spatial variability within stands and landscapes at minimum cost. We suggest a procedure for selecting candidate treatments that might be used in this way. We further suggest that multi-scale evaluations (e.g. different objectives, such as economic vs ecological goals; different time frames from short-term to rotation lengths; and longer, different spatial scales from plant neighbourhoods to landscapes) can highlight opportunities to increase species diversity and spatial variability during implementations of standard forest management practices. For example, opportunities may derive from situations where management practices did not achieve their intended goals or where natural disturbances can be viewed as stimuli that initiate opportunities to increase heterogeneity. With modifications, silvicultural responses to such conditions can provide efficient, low-cost (or even cost saving) means to increase species diversity and spatial variability. Using replanting, treatment of minority species, variable spacing guidelines, and other examples, we show how varying the spatial and time scales of evaluations for such modified treatments can influence conclusions about costs and ecological impacts. Consequently, the choice of evaluation scales can be a deciding factor in whether treatment modifications are considered as economically justifiable ways to achieve a suite of diverse objectives.
... They are mainly found under the elevation of 600 m and facing north. Thinning early is advisable in high productive sites so that the fast growth in hdom can be compensated by diameter growth and thus, promote robustness of individual trees (Nivert, 2001;Wilson and Baker (2001). Maintaining H/D values under 75 should keep stands in a moderately stable situation. ...
... Above this tree height, unstable trees will not regain stability for many years and the probable result of thinning will be windthrow of some or all of the remaining trees; and the window for successful thinning will have been missed. Efforts to restore stand structural diversity at the broader landscape scale may be impeded by silvicultural prescriptions that sacrifice operational flexibility (i.e., larger windows of opportunity) for operational efficiency (Wilson and Baker 2001). ...
... Some authors suggest that irregular stands should be more windfi rm because individual trees have greater wind exposure and generally have lower height: diameter ratios and this ratio has been reported as an important predictor of tree stability (e.g. Savill, 1983 ;Wang et al. , 1998 ;Wilson and Baker, 2001 ;Mason, 2002 ). Our hypothesis therefore was that trees in irregular stands would be more resistant to windthrow. ...
A tree winching experiment was conducted, simulating wind action and resulting damage, in order to assess mechanical resistance of black spruce (Picea mariana (Mill.) B.S.P.) trees in stands of regular and irregular structures. The critical bending moment (M(c)) of winched trees was determined and the relationship between M(c) and tree and stand characteristics was investigated through statistical analyses. Stem mass (SW), average spacing between trees (S) and height:diameter ratio (H/d.b.h.) were initially selected by a screening procedure to predict M(c). Potential differences between stand structures were tested in mixed models using different subsets of the data. Included fixed effects varied between the different models. SW was the most useful and significant variable in all models and H/d.b.h. was significant only when snapped trees were included in the analysis. When decayed samples were excluded, resistance to uprooting was higher in irregular stands. Decay seemed to play an important role in irregular stands and should be investigated further. Since no difference was observed in the relationship between stem mass and critical turning moment between distant sites, relationships should be applicable across wide regions. This study provides some of the basic relationships required to model windthrow risk in irregular stands. However, the effects of stand structure on wind load for individual trees will also need to be considered.
... In short, our results demonstrate that individual koa trees for which growth had stagnated are capable of significant, rapid, and sustained growth responses to crown release. This is an important and encouraging result for landowners who currently manage koa stands as well as those interested in establishing new koa stands, because it shows that the timing of thinning operations can be relatively flexible (sensu Wilson and Baker 2001) without compromising the ability of koa to respond. ...
We examined the growth response of Acacia koa Gray (koa) in dense (10 000 trees/ha), ~25-year-old, second-growth stands on Hawai‘i to crown release (thinning) and grass control. Koa diameter increment increased within 2 months of thinning across the range of residual densities (200–900 trees/ha). After 3 years, diameter increment in the most intense thinning treatment was 180% greater than in the control treatment (1.4 vs. 0.5 cm/year); in the least intense thinning treatment diameter increment was 100% greater than the control (1.0 vs. 0.5 cm/year). Koa’s growth response was independent of all measures of tree size (diameter at breast height, height, and leaf area) across the range of tree sizes sampled. A grass control treatment to determine if reduced competition for soil water would improve koa growth showed no improvement in growth response. Koa phyllode δ13C values, which represent an integrated measure of tree water status, showed no evidence of tree water stress (mean δ13C = –28.3‰) and were not significantly different between the grass removal and control treatments. These results demonstrate that koa is capable of responding quickly and positively to crown release despite years of suppressed growth and suggest that landowners interested in managing koa forests may have considerable flexibility in the timing and application of thinning treatments to koa stands.
... Floodplain forests are highly productive ecosystems, producing timber, storing substantial amounts of carbon and sustaining high biodiversity. Managing forests for multiple benefits involves compromises as well as substantial uncertainty, given long planning horizons (Wilson and Baker, 2001). The benefits of silvicultural thinning on timber production are well known (Anon, 1930;Alam et al., 2008). ...
Forest ecosystems are increasingly expected to produce multiple goods and services, such as timber, biodiversity, water flows, and sequestered carbon. While many of these are not mutually exclusive, they cannot all be simultaneously maximised so that management compromise is inevitable. We used a 42-year dataset from a naturally regenerating floodplain forest of the river red gum (Eucalyptus camaldulensis) to investigate the effects of pre-commercial thinning on long-term patterns in habitat quality, forest structure and rates of carbon storage (i.e. standing aboveground carbon). Estimates of habitat quality were based on the density of hollow-bearing trees because hollows are ecologically important to many species of vertebrates and invertebrates in these forests. Thinning improved habitat value by producing 20 (±8) hollow-bearing trees per ha after 42 years, while the unthinned treatment produced none. Unthinned (highest density) stands were dominated by many slender trees, mostly < 25 cm in diameter, whereas thinned stands produced negatively skewed size distributions with higher median and maximum stem diameters. Moderately thinned stands (560 trees ha−1) had the highest aboveground carbon storage rate (4.1 t C year−1) and the highest aboveground carbon stocks (200.2 ± 9.6 t C ha−1) after 42 years, while the unthinned treatment had the lowest carbon storage rate (1.6 t C year−1) and an intermediate level of aboveground standing carbon (165.1 ± 31.1 t C ha−1). Our results highlight the importance of early stand density as a determinant of long-term forest structure, habitat quality and carbon storage rates. We recommend that thinning be considered as one component of a broader strategy for enhancing the structure, habitat value and aboveground carbon storage of developing floodplain forests.
... Thinning decreased horizontal canopy heterogeneity by lowering the incidence of storm-related canopy gaps (Dave Perry, unpublished data). Significant numbers of trees in steep unthinned areas toppled as a result of snow loads in the winter of 1996, an effect that has been observed in other regions (Nykanen et al., 1997;Wilson and Baker, 2001). The higher incidence of treefall gaps in unthinned stands may have reduced the contrast in understory composition between thinned and unthinned stands. ...
We compared the understory herb and shrub communities of pre-commercially thinned and unthinned young- and old-growth Douglas-fir (Pseudotsuga menziesii) stands. Sites were located in the Cascade Mountains of western Oregon. Young stands were approximately 40 years old at the time of sampling; thinning occurred 20 years earlier. Although tree spacing was wider in thinned than in unthinned stands, faster tree growth in thinned stands meant that thinning had no long-term effect on basal area of P. menziesii. The very large, widely spaced P. menziesii individuals in old-growth stands contributed similar basal area as the smaller trees in young stands; however, old stands had much higher basal area of shade-tolerant conifers. Although low shrubs responded positively to thinning, the difference in cover between thinned and unthinned stands was too small to be statistically significant. Ordination of sample plots in terms of their understory shrub and herb species composition identified a strong gradient in community composition from young to old-growth stands. Understory species associated with old growth included both gap specialists and those that may be dependent on the litter depth and mycorrhizal fungi of old-growth forest floors. Although both thinned and unthinned young stand composition were quite distinct from that of old-growth stands, thinned stands were more similar to old growth than were unthinned stands. Thinned stands had higher frequency of late-seral herbs than did unthinned stands. Forest generalist and release species showed mixed responses to thinning. We conclude that pre-commercial thinning may be a useful management tool to encourage old growth associated understory herbs without precipitating dominance of the understory by low shrubs and weedy species. Although thinning did accelerate tree growth, changes in the understory appear to have been precipitated by the transient increase in resource levels following thinning rather than by any long-term changes in stand structure.
The increased understanding of how forests grow—forest stand dynamics Forest stand dynamics will not be in italics when referring to the subject (e.g., forest stand dynamics), but will
be in italics when referring to the book (e.g., Forest Stand Dynamics) is both changing our perceptions of forests and enabling us to provide more commodity and non-commodity values from forests sustainably. This understanding has occurred over many decades and generations of academicians, students, and practicing foresters, with the authors within this festschrift playing major roles. Within recent decades, the realization that forests can be thought of as complex adaptive systems (CAS) offers more opportunities for understanding forest stand dynamics—provided CAS behaviors are not blindly accepted as governing forests. Key CAS concepts include hierarchies, emergent properties, initial conditions, tipping points, feedbacks, and outliers among others. Our increased understanding will enable us to increase the abundance of forest non-commodity and commodity values since we will be able to manage—or not manage—with more accuracy and use emerging technical tools. This understanding will also lead to our next opportunity for increasing the abundance of forest values: managing across a landscape of many stands.KeywordsEmergent propertiesInitial conditionsLandscape agentsLandscape management
This chapter describes the scientific basis for managing wildlife and other values across forested landscapes, and discusses the organization of the Landscape Management System (LMS) and how its modularity allows it to be improved and integrated with other systems. Managing landscapes can enhance their value to humans by providing appropriate habitats for desired wildlife species. The habitat management is an important determinant of wildlife presence and abundance in addition to hunter harvest of the target species, its prey, or its predators. The overall management system consists of two sets of tools: the Landscape Management System containing the LMS tool and the Decision Analysis System (DAS) Tools containing the "Scope & Group" and "Toggle" tools. The Landscape Management System coordinates the activities of approximately 50 computer programs to facilitate the evaluation of alternative management approaches. The LMS software package uses a point-and-click graphical user interface (GUI) with dropdown menus to interact with information for a specific landscape. A portfolio in LMS consists of a group of stands that are combined into a larger planning unit or landscape. Any user can create a portfolio by using minimal inventory and stand attribute information about individual stands or polygons. Menus within LMS facilitate the performance of functions such as growth, stand treatments, and visualization of stands, and landscapes.
Ice-snow damage is a common natural disaster, and it often caused huge damage to forests. The frequency of ice storms may increase in response to climate change. Typically, warm, moist air overruns a shallow body of cold air, rain from warm air may become supercooled when it falls from the warmer clouds, causing it to freeze immediately upon contact. Ice-snow damage occurs when the ice loaded on crown exceeds the maximum bending moment for a tree of given size and species. Ice-snow damage of forests dependents on ice accumulation. Accumulation ice can cause tree damage ranged from the loss of tissues to structural failure. Ice-snow damage to trees can range from mere breakage of a few twigs, to bending stems to the ground, to moderate crown loss, to outright breakage of the trunk. There is a close relationship between ice- snow damage and forest characteristics, such as stand density and species composition as well as tree characteristics, such as diameter at breast height, tree height, stem taper, leaf area, crowns symmetry, root system and stand age, etc. The stands with the highest density are the most vulnerable to ice-snow damage, especially for a few years after thinning. Softwoods suffer less damage from the same degree of ice loading than do hardwoods. Trees with branches that droop or have pliable stems and limbs are better withstand ice-snow damage. Dominant canopy trees incur more ice-snow damage than sub-canopy trees. Moreover, ice-snow damage is affected by some external factors, such as topography and soil conditions, including elevation, slope grade, slope aspect, slope position, soil type, soil thickness and soil water content. Higher elevations are more prone to freezing rain. Elevation and aspects increasing exposure to stronger winds result in higher damage. Ice-snow damage also exerts an impact on forest understory light, soil, litter, disease fungi and wildlife. The understory light condition that followed ice-snow damages has great significance to species regeneration, forest dynamic and recovery. A transient increase in understory light following an ice-snow damage may accelerate the conversion of early successional stands to more shade-tolerant species. The rapid decrease in understory light following an ice-snow damage is likely a result of the recovery of both the overstory and understory vegetation. An ice-snow damage indirectly impacts natural plant regeneration by its impact on fruit and seed production. Wildlife first must endure the perils of the ice-snow storm-low temperatures, ice buildup, falling debris, and reduced mobility. Birds are especially vulnerable. Wounds caused by ice-snow damages permit infection by a wide array of disease fungi and become breeding grounds for bark beetles or other pests, especially when the injuries are large and do not heal rapidly. Ice damages also increase potential fire risk by elevating fuel loads. Future research in the field of ice-snow damage to forests should focus on effects of ice-snow damage on natural forests and the long-term research of nutrient cycling and soil, especially microorganism, wildlife, forest dynamics and forest understory light, and reducing the risk of ice-snow damage through forest management.
Expert knowledge of forest succession is used widely in forest management planning, but its level of uncertainty is unknown. Using boreal Ontario as an example, we examined the level of uncertainty in expert knowledge of forest succession and explored possible sources of this uncertainty. Overall, the level of uncertainty associated with expert knowledge was high for all aspects of forest succession, except for post-fire species establishment. Higher levels of uncertainty were associated with knowledge of forest succession for mixed forest types and moderate site conditions, as opposed to coniferous or non-coniferous forest types and extreme dry/wet or poor/rich sites. We hypothesize that uncertainty in expert knowledge is highest when vegetation dynamics are highly stochastic as with complex species assemblages, environmental controls on succession are weak, and effects of disturbances are less drastic. Awareness about the degree of uncertainty in expert knowledge of forest succession could be incorporated into forest management decision processes. It could also help researchers to identify critical knowledge gaps to guide further studies.
• Context
This review paper provides an overview of approaches to which we may resort for handling the complex decision problems involving uncertainty and risk that climate change implies for forest managers. Modelling approaches that could support adaptive management strategies seem to be called for, not only as climate change denotes increased economic uncertainty but also because new and more reliable information becomes available as time passes and climate changes.
• Aims
The paper (1) provides a broad overview of state-of-the-art methods for optimal decision making under risk and uncertainty in forestry and (2) elaborates on the possible use of these methods in adaptive forest management under climate change.
• Method
A survey of the current literature is carried out to identify approaches and developments that may prove most promising in relation to different challenges to the adaptive management of forest ecosystems under climate change.
• Results
Most studies focusing on changing, typically increasing, risks in forest management under climate change tend to build on existing approaches about changes in risk levels contingent on climate change scenarios.
• Conclusion
Finally, we discuss what to emphasise in future studies to improve the understanding of adaptive forest management and decision support tools needed to cope with climate change.
Increasing severity of recent wildfires, storms, pest outbreaks, and biological invasions has intensified concern among governmental agencies, private enterprises, and the general public regarding the future of forest resources. Economic analysis can help decision-makers understand the causes and consequences of forest disturbances, as well as evaluate trade-offs, and set priorities. It is the premise of this book that similarities existing among forest disturbances permit the development of a unified framework for economic analysis. This book sketches out how this framework could be constructed, provides an overview and summary of current research in the economics of forest disturbances, and illustrates how economic theory and empirical methods can be applied to address specific disturbances.
To motivate subsequent analysis, the following section presents a broad characterization of various classes of forest disturbances and describes how specific disturbance characteristics constrain the set of management interventions that can be employed to mitigate economic impacts. Section 3 then provides an overview of the major lessons learned and presented throughout the remainder of the book. The chapter concludes in section 4 by offering suggestions for future research.
The effects of periodic gales on Nothofagus (southern beech) stand development and landscape dynamics were studied in a 10.4-km2 study area in the Sierra de las Pinturas, part of the Andes in Argentine Tierra del Fuego. We reconstructed blowdown history (patch sizes, dates of origin, return intervals) since the late 1700s to assess how periodic large-scale wind disturbance influenced landscape pattern in a relatively simple system. Most previous studies have focused on single storms in more diverse forests and in landscapes influenced by several disturbance types and human activities. Boundaries of post-blowdown stands were digitized from aerial photographs and analyzed within a geographic information system. Ages of blowdowns and return intervals were determined from scars, growth releases, and maximum tree ages. Discrete blowdown patches (0.1 to >100 ha) covered two-thirds of the study area and ranged from 19 to ≃200 yr of age, with 20-30 yr between major events. The meteorology of these storms was unknown, but we suspect they were caused by intense low-pressure systems originating in Antarctica. The mean return interval for 34 sites was 145 yr, with a range of 103-218 yr. Based on treefall size distributions, most stands blown over in the past 100 yr were even-aged, with mean tree dbh (diameter at breast height) between 20 and 32 cm. Aerial photographs taken in 1970 were used for before-and-after comparisons of a 1972 blowdown. Seventy-one percent of the area blown over in 1972 was even-aged, and 35% of the boundaries from this storm exactly coincided with previous stand boundaries. Damage patterns from storms in 1924 and 1972 suggested that forests located on valleys parallel to the wind, windward side slopes, and possibly upper leeward slopes were most vulnerable to blowdown, but few landscape positions escaped being hit by repeated storms. Return intervals were not significantly related to slope, elevation, or aspect; but surprisingly, shorter return intervals were associated with deeper soils. The landscape pattern of blowdown and recovery shifted over time because of variation among individual storms and because a small proportion of old-growth stands were converted to blowdowns and vice versa. Browsing by guanacos (Lama guanaco), a large native camelid, has severely inhibited tree regeneration during the past 75 yr in small blowdowns and the perimeters of larger ones, converting some stands to open meadows and incipient alpine communities. In the relatively simple Nothofagus forests of Tierra del Fuego, periodic gales are the main determinants of forest structure and pattern across a range of scales from small patches to entire landscapes.
A landscape approach to forest management must consider the implications of alternative scenarios across stands and through time. The Landscape Management System, a computer program, facilitates implementation of this approach by integrating forest inventories, spatial information, growth models, visualization, summarization, and analysis. A case study with three scenarios--no harvest, clearcut, and thinning--exposes the complex tradeoffs inherent in forest management and highlights the need for comparative analysis tools.
A potential vegetation classification system is presented for the Olympic National Forest. It is based on a sample of 1046 Reconnaissance and 408 Intensive plots. The hierarchical classification includes sixvegetation series and 64 plant associations. Diagnostickeys are presented to aid in the identification of series and associations. Descriptions are presented for each series and association which are oriented toward the application of this classification for land management objectives. Association descriptions include information about plant species occurrences, including mosses and lichens, mammals, birds, insect pests and diseases. Most descriptions include information on timber productivity and soils. Background information is also presented on the ecology, geology, soils and history of the Olympic Mountains. Key words: vegetation classification, climax vegetation, climax plant communities, plant association, vegetation series, plant community ecology, forest ecology, mosses, lichens, birds, mammals, forest diseases, timber productivity, soil, Olympic Mountains. no
A model for the mechanism of windfall and stem breakage was constructed for single Scots pine ( L.) at the stand edge. The total turning moment arising from the wind drag and from the bending of stem and crown was calculated along with the breaking stress of the stem. Similarly, the support given by the root -soil plate anchorage was calculated. Windspeed variation within the crown and the vertical distribution of stem and crown weight were taken into account. Model computations showed that trees having a large height to diameter ratio were subjected to greater risk of falling down or breaking than trees with a small height to diameter ratio. The windspeed required to blow down a tree or break the stem of a tree decreased if the height to diameter ratio or the crown to stem ratio of trees increased. The PDF includes an abstract in Finnish.Pinus sylvestris
Winds over topography and inside forests produce mechanical reactions in trees, and eventually failure in stems and roots when stressed by storms. The mechanics of these reactions and the physiological responses to wind in leaves, stems and root systems, and the important ecological consequences of wind-throw are described in this book. Management techniques of forests in windy climates are detailed, including the use of models predicting risk of wind damage. It is clear that the whole field of wind effects on trees has benefited from recent multi-disciplinary research, and significant advances in knowledge of most parts of the subject have been made in the last decade. This book brings the up-to-date theories, methodologies and results together, and gives the reader a sense of coherence in this complex but fascinating field.
Winds over topography and inside forests produce mechanical reactions in trees, and eventually failure in stems and roots when stressed by storms. The mechanics of these reactions and the physiological responses to wind in leaves, stems and root systems, and the important ecological consequences of wind-throw are described in this book. Management techniques of forests in windy climates are detailed, including the use of models predicting risk of wind damage. It is clear that the whole field of wind effects on trees has benefited from recent multi-disciplinary research, and significant advances in knowledge of most parts of the subject have been made in the last decade. This book brings the up-to-date theories, methodologies and results together, and gives the reader a sense of coherence in this complex but fascinating field.
Windthrow is a damaging agent that can be of paramount importance in silviculture. Windthrow depends on a number of factors interacting with each other. This paper tries to incorporate windthrow concerns into the silvicultural decision making process by understanding the windthrow process and its interaction with silviculture. The forces involved in the windthrow process are reviewed. The effects of natural factors on these forces are examined and the potential impact of silviculture on these factors is discussed. Some available hazard rating systems are reviewed, trying to underline their applicability in the Eastern Canadian context. Climate affects the severity and frequency of storms. However, wind speed in a particular stand is influenced strongly by local topography. Soil and root characteristics determine the sturdiness of the anchoring system. Many stand-related factors, such as stand height, age, density and stem form, can also exert an influence on the resistance to uprooting. Silviculture can modify the vulnerability to windthrow by acting on these factors. In stands at risk, stripcutting, thinning or the creation of new margins can cause important losses. The impact of stem form also indicates the need for an early control of stand density. Among the hazard rating systems available, the British system seems the most complete but would require some adjustments for use in the Eastern Canadian context. Key words: windthrow, uprooting, blowdown, wind
Wind is a major cause of damage in North American forests. Salvaging windthrow is costly and may disrupt silvicultural and management plans. Non-salvaged windthrown trees provide bark beetle habitat, increase fuel loading, and limit the mobility of wildlife and recreationists. Freshly exposed stand edges and recently partially cut stands are particularly prone to wind damage. Windthrow results from complex interactions of many environmental factors, which can be grouped into three broad components of hazard: topographic exposure, soil properties, and stand characteristics. These three component groups form the three sides of the Windthrow Triangle. This simple model can be used to evaluate the relative windthrow hazard of forested sites. The evaluation will assist managers with the formulation of treatment prescriptions designed to reduce losses from endemic windthrow. The model incorporates stand level attributes and is not intended to replace existing methods for individual hazard tree assessment. Key w...
(1) The effect of catastrophic hurricane wind on forest vegetation in central New England was examined at the species and stand level. (2) Species susceptibility to wind is largely explained by canopy position: fast-growing, pioneer species that form overstorey dominants (Pinus strobus, P. resinosa, Populus spp. and Betula papyrifera) suffered much greater damage than slower growing, or tolerant species occurring primarily in codominant, intermediate and suppressed canopy positions (Carya spp., Acer rubrum, Quercus alba, Q. velutina and Tsuga canadensis). Uprooting was much more important than breakage as the primary form of damage. This result, which contrasts with the findings of most studies of wind damage, may perhaps be explained by the very high levels of precipitation that accompanied the storm, saturating the soil and loosening the roots. (3) Damage to forest stands exhibits a positive, linear relationship with stand age and height and negative relationship with density. Conifer forests are significantly more susceptible than hardwood forests. Pinus strobus and P. resinosa stands are susceptible to wind at 15 years of age and are completely destroyed at 30 years; hardwood stands exhibit increasing damage from age 20 years, but are not completely blown down until age 80-100 years. (4) Within stands, damage shifts progressively from the dominant trees in young stands to include trees in the codominant, intermediate and suppressed layers in older forests. Parallel changes with age in the type of damage include a decline in the number of leaning trees and increase in uprooting. (5) Damage to species and stands from a catastrophic windstorm occurs quite predictably and specifically within the forests studied. This discriminating impact of wind has profound consequences on the vegetation at a range of spatial scales and is largely mediated by historical factors and structural and compositional aspects of the vegetation mosaic.
Windthrow impacts are negative if stand or forest level management objectives are compromised. Consideration of the impact of expected damage on management objectives enables mitigative actions to be prescribed where necessary. The level of damage along recent cutblock boundaries from endemic peak winds depends on biophysical and management factors. A diagnostic framework is presented in which windthrow patterns in harvested areas are observed, and site indicators and management regimes are compared with areas proposed for harvesting. Topographic exposure, soils and stand components of biophysical hazard are separately assessed and then integrated. The orientation and placement of the proposed boundaries relative to damaging wind directions is considered and integrated with biophysical hazard to yield an estimate of expected damage. Practitioners are guided through the assessment process by a series of simple diagnostic questions.
The most destructive windstorm of recorded history in the Pacific Northwest occurred on October 12, 1962. With a method between that of mesoanalysis and ordinary synoptic analysis, detailed reanalysis was made of the structure of the storm over Oregon and Washington, including isobaric patterns and frontal positions at I-hr. intervals. The significant features of the storm are described. Comparison is made with other notable windstorms in the region. The pressure pattern is used to determine location and magnitude of maximum winds.
The pattern of vertical stratification in mixed Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and western hemlock (Tsugaheterophylla (Raf.) Sarg.) stands was documented by observing tree interaction patterns on temporary plots in stands between 35 and 80 years old. It was found that Douglas-fir predictably dominated the hemlock. Several possible causes of the stratification were studied. They were differences in ages between species, differences in mortality patterns, and differences in growth rates. Increment borings of trees on sample plots in the 35- to 80-year stands with the observed stratification revealed the overtopping Douglas-firs and suppressed hemlocks to be essentially of the same age. Searches for dead or dying Douglas-fir in groups of mixed stands of 35 to 80 years, 22 to 35 years, and less than 12 years revealed very little Douglas-fir mortality by suppression. Therefore, the possibility of death of intermediate and suppressed Douglas-firs was not an important factor leading to Douglas...
In 1981 a storm caused windthrow of 3 million cubic meters of softwood in Denmark, equal to the normal removals of three years. The object of the present analysis is to determine the way in which the probability of windthrow depends on parameters that can be affected by forest management, viz. rotation age, thinning programme, choice of species, spatial distribution of stands and drainage. An empirical data set from 612 stands is used in the estimations. It is found that the windthrow probability is negatively affected by tree diameter, drainage, the time since last thinning and the protection from other stands. The probability increases with tree height, age and relative thinning volume in the latest thinning. Picea is more stable than Abies and Pseudotsuga.
Summarizes and consolidates ecological and silvicultural knowledge of spruce-fir forests. Describes the biological and environmental values, stand regeneration, stand management, and growth and yield.
Thesis (Ph.D.)--University of Washington, 1998 Risk of wind damage is an important factor influencing forest management throughout the world. Managed forest landscapes of the coastal Pacific Northwest are undergoing a transition from dominance by naturally regenerated second-growth stands to Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantations. This analysis evaluates the impacts of the managed forest transition on risk of wind damage. Experimental plot data are used to compare tree size variability and stand stability between naturally regenerated and planted stands. In addition, a landscape-scale wind risk rating system is developed to evaluate the impact of stand and management transitions at both stand and larger spatial scales.Naturally regenerated stands tend to develop greater variation of tree sizes compared to plantations. Limited size variation in plantations makes them more susceptible to developing high height to diameter ratios (H/D same units) in the dominant trees. The H/D of a tree is a relative measure of stability under wind and snow loads. H/D can be lowered in plantations through reduced planting densities or early thinning. The higher the initial density the shorter the period during which thinning can effectively lower future H/D values. Thinning requirements in dense plantations make their management inflexible. The flexibility with which a stand can be managed describes the rigidity of intervention requirements and/or potential range of stand development pathways.Shorter rotations in plantations compared to naturally regenerated stands offset much of the increased risk of wind damage caused by higher H/D values. The transition from naturally regenerated to planted stands typically increases the diversity of stand ages within a landscape. Even-aged landscapes have distinct periods of high and low risk, as all stands in the landscape move through susceptibility stages together. Uneven-aged landscapes never reach the same levels of landscape risk; however, some portion of the landscape is typically at high risk. As the transition from naturally regenerated to planted stands continues wind damage may be more common but have a reduced potential for devastating a landscape.
In this work both conical and paraboloidal conifer stems are taken to bend along curves calculated to produce uniform strain in the outer wood. Such curvature has been observed in wind tunnel tests. From these curves for various displacements the resistive bending moment produced by the elasticity of the stem may be calculated. The maximum value of this is related to the breaking stress of the timber. The bending moments applied by the weights of stem, crown and snowload are calculated by obtaining the appropriate lever arms from the stem bending curves. Applied and resistive bending moments are compared for 20m-high trees of various types. Densely grown trees of low taper are least stable. Open grown trees with conical stems and high taper are most stable. The effects on tree stability of wind, a leaning stem, an asymmetrical crown and basal bowing are also investigated.
L'étude de couples de peuplements contigus ayant réagi différemment à la tempête de novembre 1982, a permis de mettre en évidence l'effet conjugué du facteur d'élancement (H/D) et de la hauteur dominante sur la stabilité des peuplements. A partir de ces deux caractéristiques, il est possible de classer un peuplement dans une « plage de stabilité », qui conditionne les interventions à y envisager. Inversement, le gestionnaire, en jouant sur la sylviculture, peut influer sur la stabilité ; en effet, l'évolution des caractéristiques des peuplements d'Epicéa décrites par les tables de production françaises et anglaises montre que, même si la sylviculture actuelle présente des risques importants de chablis, il doit être possible de les réduire sensiblement par l'adoption de techniques appropriées : abaissement des densités de plantation, dépressages éventuels et éclaircies précoces. Il est également possible de maintenir les peuplements stables, sans les éclaircir, à condition de les planter à des densités inférieures à 1 300 voire 1 000 tiges par hectare. The study of contiguous pairs of stands which reacted differently to the storm of November 1982 made it possible to show the combined effects of the rapid growth factor (H/D) and dominant height on stand stability. From these two characteristics it is possible to classify a stand in a « stability band », which determines the silvicultural operations to be contemplated. On the other hand, by manipulating the silvicultural treatment the manager can affect the stability ; in fact, the development of the characteristics of Norway spruces stands described by French and English yield tables shows that even if the present silviculture gives serious risks of windthrows, it should be possible to reduce them considerably by adopting appropriate techniques : reduction of planting density, possible thinning out and early thinning. It is also possible to keep stands stable without thinning them by planting them at densities of less than 1 300 or even 1 000 stems per hectare.
Gone with the wind, Forest Service mulls over miles of toppled trees in the Rockies
- T Kenworthy
Kenworthy, T., 1998. Gone with the wind, Forest Service mulls
over miles of toppled trees in the Rockies. The Washington
Post, 2 February.
Detailed analysis of the 1962 Columbus Day windstorm in Oregon and Washington. Monthly Weather Rev Landscape management through integration of existing tools and emerging technologies
- R E Lynott
- O P Cramer
- ±
- J M Mccarter
- J S Wilson
- P J Baker
- J L Moffett
- C D Oliver
Lynott, R.E., Cramer, O.P., 1966. Detailed analysis of the 1962 Columbus Day windstorm in Oregon and Washington. Monthly Weather Rev. 94, 105±117. McCarter, J.M., Wilson, J.S., Baker, P.J., Moffett, J.L., Oliver, C.D., 1998. Landscape management through integration of existing tools and emerging technologies. J. For. 96, 17±23.
Windthrow and Windsnap in Forest Plantations
- M J Kennedy
Kennedy, M.J., 1974. Windthrow and Windsnap in Forest
Plantations, Northern Ireland. Michigan Geographical Publication No. 11, University of Michigan, Ann Arbor. 164 pp.
Thinning regime in stands of Norway spruce subjected to snow and wind damage Wind and Trees Graphical summaries and data on the UBC Research Forest spacing trials (57-5) to age 26 and evaluations of results to date
- M Slodicak
Slodicak, M., 1995. Thinning regime in stands of Norway spruce subjected to snow and wind damage. In: Coutts, M.P., Grace, J. (Eds.), Wind and Trees. Cambridge University Press, Cam-bridge, 485 pp. Smith, J.H.G., 1983. Graphical summaries and data on the UBC Research Forest spacing trials (57-5) to age 26 and evaluations of results to date. Dept. of Forest Resource Management. Faculty of Forestry, 79 pp.
Effects of the 12 October 1962 windstorm on permanent growth plots in southwest Washington
- K N Wiley
Wiley, K.N., 1965. Effects of the 12 October 1962 windstorm on
permanent growth plots in southwest Washington. Weyerhaeuser Forestry Paper No. 7, 13 pp.
BC Nelder plot data. Numbers to the right of legend lines represent initial Douglas-fir density (tph) in particular arcs (data from Smith
- H Early
- Haney
Early H/D trends from Haney, BC Nelder plot data. Numbers to the right of legend lines represent initial Douglas-fir density (tph) in particular arcs (data from Smith, 1983; Reukema and Smith, 1987).
Ecology, silviculture, and management of Engelmann spruce and subalpine fir type in central and southern Rocky Mountains USDA Forest Service Agricultural Handbook No. 659 L'existence de zones de stabilite des peuplements. Consequences sur la gestion
- R R Alexander
- J Becquey
- P Riou-Nivert
Alexander, R.R., 1987. Ecology, silviculture, and management of Engelmann spruce and subalpine fir type in central and southern Rocky Mountains. USDA Forest Service Agricultural Handbook No. 659. Becquey, J., Riou-Nivert, P., 1987. L'existence de zones de stabilite des peuplements. Consequences sur la gestion. Revue Forstiere Francaise 39, 323±334. Cremer, K.W., Borough, C.J., McKinnell, F.H., Carter, P.R., 1982. Effects of stocking and thinning on wind damage in plantations. NZ J. For. Sci. 12, 244±268.
Blowdown history and landscape patterns in the Andes of Tierra Del Fuego, Argentina Development over 25 years of Douglas-fir, western hemlock, and western redcedar planted at various spacings on a very good site in British Columbia
- A J Rebertus
- T Kitzberger
- T T Veblen
- L M Roovers
Rebertus, A.J., Kitzberger, T., Veblen, T.T., Roovers, L.M., 1997. Blowdown history and landscape patterns in the Andes of Tierra Del Fuego, Argentina. Ecology 78, 678±692. Reukema, D.L., Smith, J.H.G., 1987. Development over 25 years of Douglas-fir, western hemlock, and western redcedar planted at various spacings on a very good site in British Columbia. USDA Forest Service Research Paper, PNW-381, 46 pp.
Site index curves and tables for British Columbia: Coastal species. BC Ministry of Forests
- K J Mitchell
- K R Polsson
Mitchell, K.J., Polsson, K.R., 1988. Site index curves and tables for
British Columbia: Coastal species. BC Ministry of Forests,
FRDA Report 037, 29 pp.
Graphical summaries and data on the UBC Research Forest spacing trials (57-5) to age 26 and evaluations of results to date. Dept. of Forest Resource Management. Faculty of Forestry
- J H G Smith
Smith, J.H.G., 1983. Graphical summaries and data on the UBC
Research Forest spacing trials (57-5) to age 26 and evaluations
of results to date. Dept. of Forest Resource Management.
Faculty of Forestry, 79 pp.
Detailed analysis of the 1962 Columbus Day windstorm in Oregon and Washington. Monthly Weather Rev
- R E Lynott
- O P Cramer
Lynott, R.E., Cramer, O.P., 1966. Detailed analysis of the 1962
Columbus Day windstorm in Oregon and Washington. Monthly
Weather Rev. 94, 105±117.
Detailed analysis of the 1962 Columbus Day windstorm in Oregon and Washington
- Lynott