摘要:

This paper presents an overview of the conclusions developed by 35 participating scientists and landmanagers at a scientific workshop held in Sun Valley, Idaho, November 14-20, 1993. The conclusions presented here are those of the authors, but reflect discussions of the entire group, and are based upon conclusions reached by those participants in working groups. The forests of the Inland West are, over wide regions, not healthy. Remedial, restorative, and preventative treatment and management particularly on the federal lands-is urgently needed. A brief window of opportunity, perhaps 15-30 years in length, exists. Without timely management intervention, the region is threatened by major ecological setbacks-pest epidemics and uncontrollable wildfires-that will damage resource values and convert large areas into new even-aged forest systems that set the stage for a repeat of the current problems far into the 21st Century. The scientific tools to understand these problems and mitigate them exist today, but are not being applied on the federal forests rapidly enough to meet the urgency of the situation. The current legal and procedural requirements on federal land management agencies impose time delays which, combined with public opposition to timber harvesting, prevent timely management, doom major forest areas to needless loss and damage, and impose large (and, perhaps, preventable) costs on both local and national economies.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_01

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Euro-American settlement of the Inland West has altered forest and woodland landscapes, species composition, disturbance regimes, and resource conditions. Public concern over the loss of selected species and unique habitats (e.g., old-growth) has caused us to neglect the more pervasive problem of declining ecosystem health. Population explosions of trees, exotic weed species, insects, diseases, and humans are stressing natural systems. In particular, fire exclusion, grazing, and timber harvest have created anomalous ecosystem structures, landscape patterns, and disturbance regimes that are not consistent with the evolutionary history of the indigenous biota. Continuation of historical trends of climate change, modified atmospheric chemistry, tree density increases, and catastrophic disturbances seems certain. However, ecosystem management strategies including the initiation of management experiments can facilitate the adaptation of both social and ecological systems to these anticipated changes. A fairly narrow window of opportunity-perhaps 15-30 years-exists for land managers to implement ecological restoration treatments.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_02

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

If forest health is to be approached scientifically, it must be defined and measured. Forest health is a condition of forest ecosystems that sustains their complexity while providing for human needs. We developed this broad definition becaue a wisely acceptable definition is lacking, and forest health is a focal point in discussions of how to sustain forest ecosystems in the United States. Steps for measuring forest health are: (1) select a representative set of indicators for a particular ecosystem; (2) establish baseline data, such as a historical range of variability; (3) develop standards against which to compare current conditions; and (4) establish a monitoring program to assess current conditions and modify baseline data as new trends develop.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_03

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The concept of historical range of variability in ecosystem structure or process is valuable in understanding and illustrating the dynamic nature of ecosystems; the processes that sustain and change ecosystems, especially disturbances; the current state of the system in relationship to the past; and the possible ranges of conditions that are feasible to maintain. Because ecosystems are structured hierarchically, historical range of variability must be characterized at multiple spatial scales and relevant time scales. Historical range of variability is a useful reference for determining a range of desired future conditions, and for establishing the limits of acceptable change for ecosystem components and processes.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_04

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

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.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_05

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Forests in the Inland West have been shaped by over a century of human migration and forest use. Relative forest health is still defined by human objectives in forest management. Economic analyses can help people understand the forest health implications of management choices between forest preservation, commodity production, or ecosystem management. Neo-classical microeconomics predictably casts the optimal forest health question as a cost-benefit trade-off even though valuation of forest health benefits must be inferred Alternative schools of thought, such as institutional economics, may reach different conclusions. Lack of public consensus on forest health objectives and acceptable remedies conflict with traditional deterministic analytic tools. An alternative planning approach that makes problem definition the focus of analysis may facilitate public forest health decisions.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_06

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Heavy livestock grazing, logging, and fire exclusion associated with Euro-American settlement has brought about substantial changes in forest conditions in western forests. Thus, old-growth definitions based on current forest conditions may not be compatible with the natural conditions prevalent throughout the evolutionary history of western forest types. Detailed analysis of data from two study areas in the southwestern ponderosa pine type suggests that average tree densities have increased from as few as 23 trees per acre in presettlement times to as many as 851 trees per acre today. Associated with these increases in tree density are increases in canopy closure, vertical fuel continuity, and surface fuel loadings resulting in fire hazards over large areas never reached before settlement. In addition, fire exclusion and increased tree density has likely decreased tree vigor (increasing mortality from disease, insect, drought, etc.), herbaceous and shrub production, aesthetic values, water availability and runoff, and nutrient availability, and also changed soil characteristics and altered wildlife habitat. To remedy these problems and restore these forest ecosystems to more nearly natural conditions, and maintain a viable cohort of old age-class trees, it will be necessary to thin out most of the postsettlement trees, manually remove heavy fuels from the base of large, old trees, and reintroduce periodic burning.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_07

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Forest health has become a major problem in much of the west and is closely linked to forest succession. Disturbances such as fire, flood, or windstorm periodically interrupt forest succession and recreate earlier seral conditions. The frequency and intensity of disturbance controls the extent of succession or the number of seral stages that may occur on a site. When the frequency of these disturbances is interrupted such as with fire control, succession can carry species composition and density beyond the historical range of seral stages. Historically, sites which were frequently disturbed are the first to get beyond their historical range and experience forest health problems when these disturbances are interrupted. Whereas, sites which, historically were less frequently disturbed may experience more complex successions that include outbreaks of insects and disease as part of the historical range of conditions.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_08

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper we present evidence supporting the premise that forest nutrition, nutrient cycling and nutrient management are critical factors for the health of Inland Western forests and for management of the ecosystems. The current state of knowledge suggests that inadequate tree nutrition, particularly potassium shortage, influences tree chemistry such that inadequate plant defensive compounds are produced. Pathogens and insects are unusually successful in attacking such trees. Forest managers have substantial influence on the forest nutritional environment through nearly all types of silvicultural treatments.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_09

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Forest ecosystems characterizing much of the Inland Western United States occupy precarious, changing environments that can be moisture, temperature, and/or nutrient limited. Rapid vegetative adaptations to inherent change are critical to both plant community stability and to the survival of individual species. Biological decomposition processes are often constrained and natural wildfires represent an important recycling agent Recycling of resources is critical. It is proposed that native insect, disease and other decomposer activities, plus natural wildfire, historically provided coordinated biological and physical processes that were integral to carbon, nitrogen, and other nutrient cycling, and to rapid evolution and adjustment of native conifers (and of their ecosystems) in this dynamic environment Current conditions, as imposed by traditional harvesting and fire control over the last 100 years, plus the introduction of white pine blister rust in the early 1930s, have changed many native vegetative and microbial systems. Endemic insects and diseases have responded to these changes by increasing activities. Their effects counter many of the destabilizing actions of site deterioration, fuel accumulation, changes in species and genetic compositions, increased stand densities and impairment of recycling processes. At least in the short term, many ecosystems are now highly vulnerable to potential damage from high fuel wildfire and perhaps to the momentum of alternative biological decomposition processes. Genetic resources and other diversity components may be at especially high risk. Many current trends place future values in increasing danger until the course is changed. Adjusting cycling processes, stand density and species composition will often be more important than controlling individual pests when managing forest health for this region in the future.

ISSN:1054-9811    

DOI:10.1300/J091v02n01_10

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor