摘要:

not available

ISSN:0045-5067    

DOI:10.1139/x90-055

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Forest plantations in the early stages of establishment are considered as hierarchical biological systems, and some implications for the design of research projects and the education of regeneration foresters and scientists are discussed. Since less than optimum environmental conditions convey stress to seedlings, seedlings will in turn exhibit a strain response at either the biochemical, physiological, or morphological level. Environmental conditions in a clear-cut are contrasted with other regeneration niches, and implications for the performance of different plantation species are discussed. The important physiological and biochemical limitations on the absorption of water, nitrogen, and carbon by seedlings during their establishment phase are described. Methods of quantifying stress at the plantation site, including simple ways to separate seedling growth into its different physiological components, are shown. An example of an eastern white pine (PinusstrobusL.) plantation grown under different levels of soil temperature, fertilization, and brush control is presented to illustrate the concepts. An approach to silvicultural research is proposed that determines the effects of silvicultural treatment on the seedling environment and then relates these environmental conditions to seedling biochemistry, physiology, and growth.

ISSN:0045-5067    

DOI:10.1139/x90-056

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Impact of forest pests and fire on stand growth and timber yield is reviewed, with emphasis on spruce budworm (Choristoneurafumiferana(Clem.)). Damaging agents reduce tree growth, kill trees, destroy the commercial value of stands, and sometimes reduce yield in subsequent rotations. Sustainable harvest may be reduced by up to 60% by a severe spruce budworm outbreak and up to 40% by a 1% per annum loss to fire. Serious overestimation of future timber supply can therefore result from the failure to allow for catastrophic or continual small losses caused by fire or biotic agents. Current efforts in New Brunswick to explicitly incorporate effects of spruce budworm defoliation into forest management planning are described, including research studies into protection planning and delivery, damage detection, and defoliation-based growth forecasting. An improved understanding of the impact of insects, disease, and fire on stand yield and methods to incorporate this information into timber supply analyses are essential to reduce uncertainty about future timber supply.

ISSN:0045-5067    

DOI:10.1139/x90-057

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The level of silvicultural investment and area of forest land managed in Canada is rising dramatically. Although this will increase growth rates and help maintain the present level of harvest, it may well result in a reduction in the quality of the resource. The present paper illustrates the risk of ignoring this potential problem through examples of experience in utilizing plantation-grown trees in various parts of the world. Relying on technology to solve all resource quality problems may not necessarily make economic sense. Canada's future must lie in the production of "value-added" products that require a high quality resource, permitting the greatest flexibility in conversion options. Information relating silvicultural treatments to end-product quality is at present inadequate. Large integrated studies addressing these questions and the economics of silvicultural investments in terms of end-product value must be initiated for species that will be managed intensively. With relatively long rotations, Canada cannot afford to create a resource that does not match its future marketing strategy.

ISSN:0045-5067    

DOI:10.1139/x90-058

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Both the morphological and physiological characteristics of forest planting stock vary widely with nursery culture and environment. Through the control of environmentally determined variation in phenotype, stock can be adapted to both the stress of transplanting from nursery to forest site and the particular environmental conditions of the forest site. Evidence is discussed that indicates that the stress of transplanting is primarily water stress, resulting from (i) the confinement of roots to the planting hole, (ii) poor root–soil contact, and (iii) low root permeability. These deficiencies are overcome by root growth, which is thus a central process in plantation establishment. Root growth depends largely on current photosynthesis. Photosynthesis depends on the assimilation of carbon dioxide at the expense of lost water in transpiration. Transpiration is limited by water uptake and hence depends on root growth. Root growth and photosynthesis in newly planted trees are thus mutually dependent. Because of this relationship, plant water status immediately after planting, or as soon as conditions favorable to root growth occur, is a crucial factor in determining plantation establishment success. High plant tissue water status immediately after planting, or as soon as environmental conditions permit root growth, allows the onset of a positive cycle of root growth supported by photosynthesis and photosynthesis supported by root growth; whereas low tissue water potential immediately after planting can lead to the inhibition or root growth by a lack of photosynthesis and the inhibition of photosynthesis by a lack of root growth. Stock characteristics that enhance plant water status immediately after planting are reviewed and the scope for their control considered. Stock characteristics affecting adaptation to particular planting site conditions, or capable of affecting postestablishment plantation performance, are also discussed.

ISSN:0045-5067    

DOI:10.1139/x90-059

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Articicial intelligence is a new science that deals with the representation, automatic acquisition, and use of knowledge. Artificial intelligence programs attempt to emulate human thought processes such as deduction, inference, language, and visual recognition. The goal of artificial intelligence is to make computers more useful for reasoning, planning, acting, and communicating with humans. Development of artificial intelligence applications involves the integration of advanced computer science, psychology, and sometimes robotics. Of the subfields that artificial intelligence can be broken into, the one of most immediate interest to forest management is expert systems. Expert systems involve encoding knowledge usually derived from an expert in a narrow subject area and using this knowledge to mimic his decision making. The knowledge is represented usually in the form of facts and rules, involving symbols such as English words. At the core of these systems is a mechanism that automatically searches for and pieces together the facts and rules necessary to solve a specific problem. Small expert systems can be developed on common microcomputers using existing low-cost commercial expert shells. Shells are general expert systems empty of knowledge. The user merely defines the solution structure and adds the desired knowledge. Larger systems usually require integration with existing forestry data bases and models. Their development requires either the relatively expensive expert system development tool kits or the use of one of the artificial intelligence development languages such as lisp orPROLOG. Large systems are expensive to develop, require a high degree of skill in knowledge engineering and computer science, and can require years of testing and modification before they become operational. Expert systems have a major role in all aspects of Canadian forestry. They can be used in conjunction with conventional process models to add currently lacking expert knowledge or as pure knowledge-based systems to solve problems never before tackled. They can preserve and accumulate forestry knowledge by encoding it. Expert systems allow us to package our forestry knowlege into a transportable and saleable product. They are a means to ensure consistent application of policies and operational procedures. There is a sense of urgency associated with the integration of artificial intelligence tools into Canadian forestry. Canada must awaken to the potential of this technology. Such systems are essential to improve industrial efficiency. A possible spin-off will be a resource knowledge business that can market our forestry knowledge worldwide. If we act decisively, we can easily compete with other countries such as Japan to fill this niche. A consortium of resource companies, provincial resource agencies, universities, and federal government laboratories is required to advance this goal.

ISSN:0045-5067    

DOI:10.1139/x90-060

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

In view of the possible applications of ectomycorrhizae to forestry, this paper discusses the important functions of ectomycorrhizae, the conditions affecting their formation, and methods for the production and application of inoculum. A rationale for selecting appropriate ectomycorrhizal fungi and considerations in selecting sites where ectomycorrhizal seedlings should be planted are presented. Suggestions are also made on encouraging the use of ectomycorrhizal technology. A cost–benefit analysis of inoculation is done.

ISSN:0045-5067    

DOI:10.1139/x90-061

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Time is a major constraint in the progress of tree improvement programs. Four ways in which time influences the tree improvement process are (i) evolutionary time, (ii) time to harvest, (iii) time to achieve phenotypic stability, and (iv) time to reach reproductive maturity. The ways in which each of these affects the three phases of a tree improvement program (conservation, selection and breeding, and propagation) are identified and discussed. How biotechnological techniques, as well as other enabling technologies, address the time constraint problem is also discussed. The biotechnological approaches include tissue culture, molecular genetics, and genetic engineering; the enabling technologies include early testing and flower induction. Through tissue culture it is possible to increase genetic gain per unit time and increase total genetic gain by using more of the total genetic variation. Development of high-resolution linkage maps, through application of molecular genetics technology, will provide new approaches to early screening, testing, and selection. Additionally, molecular probes will be useful in improving methods that genetically fingerprint germ plasm. Genetic engineering has considerable potential to reduce time constraints. However, because of the diverse breeding and production populations typically employed, much basic work needs to be done to integrate genetically engineered materials into tree improvement programs. Early selection and flower induction address the time constraints imposed by age-stable performance and reproductive maturity. When used in combination with the previously described biotechnologies, a powerful system is created that can dramatically reduce the time required to integrate genetically improved material into forest regeneration programs. An example of integrating tree improvement, clonal forestry, and biotechnology is described for an existing black spruce regeneration program.

ISSN:0045-5067    

DOI:10.1139/x90-062

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Canadian forest management has had a long history of developing and implementing remote sensing technology and is a major user of remote sensing. Despite difficulties in developing and implementing new digital remote sensing techniques, several key developments in Canadian forest management and in remote sensing and computer technology make the development and implementation of new remote sensing techniques at this time feasible and appropriate. Integration of different remote sensing technologies, remote sensing data with other information sources through geographic information systems, and remote sensing interpretations with forest management systems and practices are critical. Current capabilities and new advances in remote sensing technology for forest survey (excluding forest damage assessment) are discussed. Satellite imagery is a cost-effective tool for broad forest type mapping. New satellite systems improve this capability, but their major impact will be in inventories for new clear-cut and burned areas. Advances in linear array imager technology and lidar systems may lead to development of an end to end inventory mapping system. This system would provide an alternative to aerial photography and current mapping methods and could revolutionize the way forests are inventoried. Imaging spectrometry is a new technology with applications in damage assessment, but as yet has limited potential for assisting in other forest surveys. Spaceborne imaging radar systems are being developed for the 1990s. These systems can produce imagery under cloudy conditions. Their major impact on forestry will be to provide an alternative to visible-infrared satellite data for inventory update.

ISSN:0045-5067    

DOI:10.1139/x90-063

出版商:NRC Research Press    

年代:1990

数据来源: NRC