Silviculture for old-growth attributes

Silviculture to maintain old-growth forest attributes appears to be an oxymoron since the late developmental phases of forest dynamics, described by the term old-growth, represent forests that have not experienced human intervention or timber removal for a long time. In the past, silvicultural systems applied to old-growth aimed to convert it into simplified, more productive regrowth forests substantially different in structure and composition. Now it is recognised that the maintenance of biodiversity associated with structural and functional complexity of late forest development successional stages cannot rely solely on old-growth forests in reserves. Therefore, in managed forests, silvicultural systems able to develop or maintain old-growth forest attributes are being sought. The degree to which old-growth attributes are maintained or developed is called “old-growthness”. In this paper, we discuss silvicultural approaches that promote or maintain structural attributes of old-growth forests at the forest stand level in (a) current old-growth forests managed for timber production to retain structural elements, (b) current old-growth forests requiring regular, minor disturbances to maintain their structure, and (c) regrowth and secondary forests to restore old-growth structural attributes. While the functions of different elements of forest structure, such as coarse woody debris, large veteran trees, etc., have been described in principle, our knowledge about the quantity and distribution, in time and space, of these elements required to meet certain management objectives is rather limited for most ecosystems. The risks and operational constraints associated with managing for structural attributes create further complexity, which cannot be addressed adequately through the use of traditional silvicultural approaches. Silvicultural systems used in the retention and restoration of old-growthness can, and need, to employ a variety of approaches for managing spatial and temporal structural complexity. We present examples of silvicultural options that have been applied in creative experiments and forestry practice over the last two decades. However, these largely comprise only short-term responses, which are often accompanied by increased risks and disturbance. Much research and monitoring is required still to develop and optimise new silvicultural systems for old-growthness for a wide variety of forest ecosystem types.     

Ecological strategies of forest insects: the need for a community-level approach to reforestation

The traditional, single-species approach to forest pest management is considered in light of the range of ecological strategies respresented in forest arthropod communities. Insect population growth and impact depend on host variables subject to silvicultural manipulation, especially during early stages of forest development, but silvicultural practices often induce undesirable responses from non-target insect populations. A suggested approach to forest pest management involves consideration of arthropod community structure, life history traits, and interactions among arthropod and plant species in order to anticipate insect responses and refine silvicultural recommendations accordingly.     

Monitoring managed forest structure at the compartment-level under different silvicultural heritages: An exploratory data analysis in Italy

ABSTRACT

The more and more diffused multifunctional role addressed nowadays to public forests, calls for targeted analysis aimed at highlighting the overall outcome of different practices implemented on the same forest compartment, according to the locally prevailing function. This study was carried out in four Italian beech forests across a latitudinal gradient representative of multiple management history, stand structure, and dominant stand age. We analyze forest structure at the compartment scale before and after silvicultural practices. We aim to explore relationships and similarities between 10 stand attributes (mensurational and structural variables) to identify relevant indicators for the monitoring and management of forest ecosystems. Results indicate changing patterns of correlation and similarity among mensurational variables following practice implementation. A sensitivity gradient to silvicultural practice was finally identified within the four sites investigated as a result of the diverging stand structure. Our approach suggests a way and provides an insight for the design of adaptive forestry management practices required to meet environmental targets, in addition to the already acknowledged supply of primary goods and services.     

The state of forest vegetation management in Europe in the 21st century

COST (COST is an intergovernmental framework for European cooperation in science and technology. COST funds network activities, workshops and conferences with the aim to reducing the fragmentation in European research) Action E47, European Network for Forest Vegetation Management??Towards Environmental Sustainability was formed in 2005 and gathered scientists and practitioners from eighteen European countries with the objective of sharing current scientific advances and best practice in the field of forest vegetation management to identify common knowledge gaps and European research potentials. This paper summarizes the work of the COST action and concludes that although diverse countries have by necessity adopted different means of addressing the challenges of forest vegetation management in Europe in the 21st century, some common themes are still evident. In all countries, there is a consensus that vegetation management is a critical silvicultural operation to achieve forest establishment, regeneration, growth and production. It appears that herbicides are still in use to some degree in all the countries reviewed, although at a lower intensity in many of the northern countries compared to other regions. The most common alternatives to herbicides adopted are the use of mechanical methods to cut vegetation and achieve soil cultivation; overstorey canopy manipulation to control vegetation by light availability; and in some instances the use of mulches or biological control. Any reductions in herbicide use achieved do not seem to have been driven solely by participation in forest certification schemes. Other factors, such as national initiatives or the availability of additional resources to implement more expensive non-chemical approaches, may be equally important. The development of more cost-effective and practical guidance for managers across Europe on non-chemical control methods can best be brought about by future collaborative research into more sustainable and holistic methods of managing forest vegetation, through the identification of silvicultural approaches to reduce or eliminate pesticide use and through gaining a better understanding of the fundamental mechanisms and impacts of competition.     

Nature-based forest management—Where are we going?: Elaborating forest development types in and with practice

The decision to transform “classical” age-class forests (plantation forestry) into more nature-based forest stand structures implied a paradigmatic shift in the Danish state owned forests and their management. In order to facilitate this process of change, scientists were employed by the Danish Forest and Nature Agency which enabled interactions with the professionals in the forest over a nearly 2-year period. Very soon it became evident that the main questions were not so much related to the process of shifting from age-class forests to nature-based management, but more to the evident lack of settled long-term goals in terms of stand structure and dynamics of the “future” forests. Realizing this constraint, forest development types (FDT) and their illustration by means of profile diagrams were elaborated in an adaptive, participatory process involving people both inside and outside the organisation. FDT describes long-term goals for forest development on a given locality (climate and soil conditions) in order to accomplish specific long-term aims of functionality. It is based upon an analysis of the silvicultural possibilities in combination with the aspirations of future forest functions. It will serve as a guide for future silvicultural activities in order to “channel” the actual forest stand in the desired direction.Looking through the lens of “social learning” this paper reflects on and discusses the participatory, bottom-up process in which the knowledge of professionals and scientists was mixed in the development of long-term goals for stand structures and dynamics in nature-based forest management. Specifically, the use of FDT scenarios and their illustration by means of profile diagrams as tools to organise and ease communication in this learning process is addressed and presented as an integrative, flexible and easily comprehensible concept for communicating long-term goals for stand development in nature-based forest management.     

Representing uncertainty in silvicultural decisions: an application of the Dempster–Shafer theory of evidence

Forest management decisions often must be made using sparse data and expert judgment. The representation of this knowledge in traditional approaches to decision analysis implies a precise value for probabilities or, in the case of Bayesian analysis, a precisely specified joint distribution for unknown parameters. The precision of this specification does not depend on the strength or weakness of the evidence on which it is based. This often leads to exaggerated precision in the results of decision analyses, and obscures the importance of imperfect information. Here, I suggest an alternative based on the Dempster–Shafer theory of evidence, which differs from conventional approaches in allowing the allocation of belief to subsets of the possible outcomes, or, in the case of a continuous set of possibilities, to intervals. The Dempster–Shafer theory incorporates Bayesian analysis as a special case; a critical difference lies in the representation of ignorance or uncertainty. I present examples of silvicultural decision-making using belief functions for the case of no data, sparse data, and adaptive management under increasing data availability. An approach based on the Dempster–Shafer principles can yield not only indications of optimal policies, but also valuable information about the level of certainty in decision-making.     

Perspectives on Community-Based Forest Management in Oaxaca,Mexico

Abstract

This compilation of papers explores various aspects related to community-based natural resource management in a comparative analysis of two communities located in different regions of Oaxaca, Mexico: the Chimalapas and the Sierra Norte. The contrasting histories, cultures, and forest ecosystems in the two communities have led to diverse approaches to managing their natural resources. Our analysis highlights the existence of underlying principles driving participatory management approaches, as well as the importance of adapting these approaches to site-specific local conditions. One theme addressed in these papers is the development of appropriate silvicultural techniques that incorporate both the local peoples' needs and experiences with the ecological characteristics of the forest ecosystem. Other land use activities are then discussed that affect management decisions in the regions such as cattle ranching and the collection of medicinal plants within the context of managing for sustainable forest and human ecosystems in the two regions. Finally, the role of community organization and the formation of partnerships with external institutions in strengthening local management and conservation initiatives are also considered. Together, these papers provide a commentary on the potentials and constraints of emerging participatory approaches to managing high priority conservation areas, and which are providing new alternatives where previous models have often failed.     

Forest science and forest policy in the Americas: building bridges to a sustainable future

Making forest policies that help bridge from the current situation to a sustainable future requires sound scientific information. Too often, scientific information is available, yet policy makers do not use it. At a workshop in Costa Rica, attendees from the Americas reviewed 16 case studies where forest science influenced forest policies and identified six reasons. Two reasons related to the content of research programs and four to personal characteristics of researchers. Research programs that practice continuous innovation and adaptive management retained their relevancy to policy makers. Market-based and incentive approaches work better than regulatory ones, so economic and social sciences are critical parts of the research portfolio. Key attributes of influential scientists include an understanding of the policy process and how it differs from the science process; a willingness to engage in the policy arena and bear the associated risks; an adeptness at communicating early and often, matching the means and message to various audiences; and a penchant for collaboration that builds the trust essential to influence policy.     

Pedunculate oak (Quercus robur L.) silviculture in natural stands of NW Spain: Environmental conditioners

Forest management is often carried out in different ways, without any appropriate environmental restrictions. Stands of pedunculate oak (Quercus robur L.) in Galicia (NW Spain) have been harvested by alternating high forest and, mainly, coppice forest. However, some totally inappropriate silvicultural treatments have been used, such as thinning of the best trees and inadequate pruning. The objective of the present study was to analyse how environmental characteristics affect the management of oak forests in Galicia. For this, a botanical inventory was carried out in 39 selected stands of Q. robur and a total of 42 parameters were measured, 4 of which were physiographical, 12 climatic, 19 edaphic and 7 silvicultural. In order to analyse the possible relationships among these variables, the silvicultural data were compared with the other data, by canonical correlation analysis. All parameters were correlated with the silvicultural regime, although the correlation was weak for the floristic data. It is therefore evident that the environmental conditions affect how forest stands should be managed, although this does not imply that more profitable use of the stands cannot be achieved than at present, and alternative silvicultural methods must be found to enable appropriate management and conservation of oak stands.     

Forest responses to climate change in the northwestern United States: Ecophysiological foundations for adaptive management

Climate change resulting from increased concentrations of atmospheric carbon dioxide ([CO₂]) is expected to result in warmer temperatures and changed precipitation regimes during this century. In the northwestern U.S., these changes will likely decrease snowpack, cause earlier snowmelt, increase summer evapotranspiration, and increase the frequency and severity of droughts. Elevated [CO₂] and warmer temperatures may have positive effects on growth and productivity where there is adequate moisture or growth is currently limited by cold. However, the effects of climate change are generally expected to reduce growth and survival, predispose forests to disturbance by wildfire, insects, and disease; and ultimately change forest structure and composition at the landscape scale. Substantial warming will likely decrease winter chilling resulting in delayed bud burst, and adversely affect flowering and seed germination for some species. The extent of these effects will depend on the magnitude of climate change, the abilities of individual trees to acclimate, and for tree populations to adapt in situ, or to migrate to suitable habitats. These coping mechanisms may be insufficient to maintain optimal fitness of tree populations to rapidly changing climate. Physiological responses to climatic stresses are relatively well-understood at the organ or whole-plant scale but not at the stand or landscape scale. In particular, the interactive effects of multiple stressors is not well known. Genetic and silvicultural approaches to increase adaptive capacities and to decrease climate-related vulnerabilities of forests can be based on ecophysiological knowledge. Effective approaches to climate adaptation will likely include assisted migration of species and populations, and density management. Use of these approaches to increase forest resistance and resilience at the landscape scale requires a better understanding of species adaptations, within-species genetic variation, and the mitigating effects of silvicultural treatments.     

Disturbances and structural development of natural forest ecosystems with silvicultural implications,using Douglas-fir forests as an example

Forest managers need a comprehensive scientific understanding of natural stand development processes when designing silvicultural systems that integrate ecological and economic objectives, including a better appreciation of the nature of disturbance regimes and the biological legacies, such as live trees, snags, and logs, that they leave behind. Most conceptual forest development models do not incorporate current knowledge of the: (1) complexity of structures (including spatial patterns) and developmental processes; (2) duration of development in long-lived forests; (3) complex spatial patterns of stands that develop in later stages of seres; and particularly (4) the role of disturbances in creating structural legacies that become key elements of the post-disturbance stands. We elaborate on existing models for stand structural development using natural stand development of the Douglas-fir—western hemlock sere in the Pacific Northwest as our primary example; most of the principles are broadly applicable while some processes (e.g. role of epicormic branches) are related to specific species. We discuss the use of principles from disturbance ecology and natural stand development to create silvicultural approaches that are more aligned with natural processes. Such approaches provide for a greater abundance of standing dead and down wood and large old trees, perhaps reducing short-term commercial productivity but ultimately enhancing wildlife habitat, biodiversity, and ecosystem function, including soil protection and nutrient retention.     

Managing Ecosystems for Forest Health

Forest health is most appropriately based on the scientific paradigm of dynamic, constantly changing forest ecosystems. Many forests in the Inland West now support high levels of insect infestations, disease epidemics, fire susceptibilities, and imbalances in stand structures and habitats because of natural processes and past management practices. Impending, potentially catastrophic fires can be avoided or modified through proactive forest health management-protecting, creating, and maintaining stand structures, processes, and species populations at viable levels across substantial landscapes. Proactive management will be less costly than fire fighting and associated rehabilitation, especially if done jointly with environmentally sound production of commodities. Management to achieve a fluctuating balance of patterns, processes, and species can begin while better information-based tools and scientific knowledge are being developed. A wider array of silvicultural and other management tools will be required for forest health management than has traditionally been used for commodity management. Specific changes that will allow forest health management include: recognizing the extent and consequences of present imbalances, decentralizing management decisions, adopting management techniques, coordinating with various landowners through incentives, funding forest health management activities, and supporting appropriate research.     

藜蒴大面积人工造林技术初报

文章介绍了藜蒴大面积人工造林技术,包括种子的采集贮藏方法、播种育苗的一系列措施、造林抚育的一整套技术。     

Forest soils research and changing societal needs and values

The 10th North American Forest Soils Conference was held in Sault Ste. Marie, Canada, 20–24 July 2003. These conferences, held at 5-year intervals since 1958, are intended to provide a forum to discuss and summarize the state of knowledge on selected topics related to forest soils. Approximately 60 papers were presented on a variety of topics related to understanding and managing soils that support forests with particular emphasis given to field research, soil carbon, and site management/classification. We discuss the topics of this conference in relation to earlier ones and conclude that advances are made unevenly and that there is a need for new approaches to investigating many of the topics. We note the change in forest management that has occurred since the first of these conferences and the resulting changes needed in our approach to research and management. The need for interaction of scientists and clientele groups is noted as necessary for development of sound management and research policy. The interaction of scientific disciplines is needed to attack problems that have been difficult to elucidate. The challenge to forest soil scientists is to mesh their scientific interests with the needs of society to obtain the resources needed to advance science and provide information that will improve forest management.     

Stand-landscape integration in natural disturbance-based management of the southern boreal forest

Forest ecosystem management, based partly on a greater understanding of natural disturbance regimes, has many variations but is generally considered the most promising approach to accommodating biodiversity concerns in managed forested regions. Using the Lake Duparquet Forest in the southeastern Canadian boreal forest as an example, we demonstrate an approach that attempts to integrate forest and stand-level scales in biodiversity maintenance. The concept of cohorts is used to integrate stand age, composition and structure into broad successional or stand development phases. Mean forest age (MFA), because it partly incorporates historic variability of the regional fire cycle, is used as a target fire cycle. At the landscape level, forest composition and cohort objectives are derived from regional natural disturbance history, ecosystem classification, stand dynamics and a negative exponential age distribution based on a 140 year fire cycle. The resulting multi-cohort structure provides a framework for maintaining the landscape in a semi-natural age structure and composition. At the stand level, the approach relies on diversifying interventions, using both even-aged and uneven-aged silviculture to reflect natural stand dynamics, control the passage (“fluxes”) between forest types of different cohorts and maintain forest-level objectives. Partial and selective harvesting is intended to create the structural and compositional characteristics of mid- to late-successional forest types and, as such, offers an alternative to increasing rotation lengths to maintain ecosystem diversity associated with over-mature and old-growth forests. The approach does not however supplant the necessity for complementary strategies for maintaining biodiversity such as the creation of reserves to protect rare, old or simply natural ecosystems. The emphasis on maintaining the cohort structure and forest type diversity contrasts significantly with current even-aged management in the Canadian boreal forest and has implications for stand-level interventions, notably in necessitating a greater diversification of silvicultural practices including more uneven-aged harvesting regimes. The approach also presents a number of operational challenges and potentially higher risks associated with multiply stand entries, partial cutting and longer intervals between final harvests. There is a need for translating the conceptual model into a more quantitative silvicultural framework. Silvicultural trials have been established to evaluate stand-level responses to treatments and operational aspects of the approach.     

恒被林及其育林体系

恒被林很早就被提出来了,但其育林体系直到现在才得到推行,这个育林体系不包括皆伐,要求林冠永远地覆盖林地,而不使土壤裸露。这个育林体系既能维护森林环境,不影响森林景观和森林结构的变化,又能培育与收获木材,很符合现代的森林经营观念。英国的恒被育林体系包括:群状与单株择伐,渐伐,带状与群状渐伐,有计划的群状采伐,伐块范围不超过0.25hm2,采用人工栽植或天然更新或两者结合以形成复层异龄混交林。对于同龄纯林可采用上述育林体系进行改造。