I like trees because they seem more resigned to the way they have to live than other things do.
(Willa Cather "O Pioneers!")
Except in limited areas where there is enough advance regeneration, establishment of forest cover on harvested lands continues to depend on seedling planting programs or on natural regeneration by seeds. Whereas successful plantation programs depend primarily on plant competition and site variables at the time of planting, successful natural regeneration depends not only on the availability of seeds, but on favourable environmental conditions throughout the processes of seed production, dispersal, germination, and seedling establishment.
Site preparation and other silvicultural treatments can improve the suitability of the seedbed and its micro-environment, but there is still much we do not understand about how various factors contribute to successful forest establishment. We have gained some insights, under controlled conditions, about the influence of major factors such as light and temperature, but we have limited experience with biological responses under actual conditions in the field.
Anyone who has conducted research in the field quickly comes to realize the complexity of the systems chosen for study. An immense number of external and internal factors that affect living organisms must be taken into account-with limited possibilities to control these factors. A major constraint, particularly in a forest environment, is the difficulty inherent in conducting field studies involving seeds. Infrequent seed production, prediction by animals, difficulty locating small seeds, estimating the numbers of buried seeds, measuring germination, and monitoring survival pose myriad challenges for the field researcher. Added to these difficulties is the lack of information about effective methods for conducting field studies of tree seeds. A recent assessment of ecosystem management needs stressed the importance of standardized sampling and monitoring techniques, and the lack of consistent methods for archiving, accessing, and updating databases (U.S. Dep. Agric. For. Serv. 1996 a). Techniques gleaned from agriculture literature are generally not applicable, and traditional ecological studies (e.g., of seed banks) tend to be primarily descriptive with little emphasis on experimental approaches.
The primary objective of this manual is to detail methods that have been gleaned from the literature and from personal experience of the authors. It is a manual of methods with some general guidelines and interpretation. Relevant background papers are cited where appropriate, but it is not a literature review. The manual is intended for use by researchers in public and private forest resource management agencies, universities, and colleges. Although specifically directed to tree seed research in forested ecosystems, many of the methods described can be used to study seeds of graminoid, herb, and shrub species in both forest and non-forest plant communities. The extensive background information included in the text also provides valuable reference material for many who have an interest in tree seeds, but who are not directly involved in research activities. The detailed examples from previous studies are included, not to prescribe how such studies should be done, but to assist in planning by providing reference values on which to base measurements, sample sizes, and other experimental details.
Since the manual is directed primarily to re-searchers working in the province of British Columbia (B.C.), Canada, many examples (forest types, species, research topics), procedures (the biogeoclimatic ecosystem classification system), and regulatory policies are specific to this geographic and political jurisdiction. Nevertheless, it is hoped that the underlying principles are self-evident and will be generally applicable to the conduct of field research elsewhere.
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Updated April 27, 2007