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INTRODUCTION

In the first widely available book on Forest Mensuration in North America, Henry S. Graves (1906) wrote: “Forest mensuration deals with the determination of the volume of logs, trees, and stands, and with the study of increment and yield.” The Dictionary of Forestry (Helms, 1998) states that “Forest mensuration is the determination of dimensions, form, weight, growth, volume, and age of trees, individually or collectively, and of the dimensions of their products.” This definition is essentially a paraphrase of the 1906 definition given by Henry S. Graves. Although some foresters feel this definition is still adequate, this text considers that mensuration should embrace new measurement problems that have arisen or have been recognized as the horizons of forestry have expanded.

If we accept the challenge of a broader scope, we must ask: “To what degree should mensuration be concerned with measurement problems of wildlife management, recreation, watershed management, and the other aspects of multiple–use forestry?” One might argue that it is unrealistic to imagine that forest mensuration can take as its domain such a diverse group of subjects. The objection becomes irrelevant if we recognize forest mensuration, not as a collection of specific techniques, but as a subject of study that provides principles applicable to a wide range of measurement problems. We view the measurement and quantification of all aspects of forest vegetation as within the domain of forest mensuration. Moreover, many ideas, approaches, and techniques have been developed within the context of traditional forest mensuration that have broad applicability for forest ecology, wildlife habitat, recreation, and watershed management. This book, in addition to a treatment of the traditional product‐oriented measurement problems of forestry, will also provide a unified foundation of principles for solving measurement problems in other aspects of forestry.

During the latter half of the twentieth century, the application of statistical theory and the use of computers, electronics, and lasers wrought a revolution in the solution of forest measurement problems. Consequently, mensurationists must have a degree of competence in their use as well as in basic mathematics and statistics. Knowledge of calculus is also desirable. In addition, familiarity with systems analysis and operational research, approaches to problem solving that depend on model building and techniques that include simulation and mathematical programming, will also be valuable, especially in advanced and more sophisticated treatments of forest mensurational problems. We do not presume that all readers of this text will have such a deep and broad background, and have tried to present forest mensuration in a way that is accessible to new students but provides a comprehensive overview of the possibilities of the field.

1.1. ROLE OF FOREST MENSURATION IN FOREST MANAGEMENT

Forest mensuration is one of the cornerstones in the foundation of forestry. Forestry in the broadest sense is a management activity involving forest land, the plants and animals on the land, and humans as they use the land. Much of the forest land in North America and in other parts of the world is under active forest management. In many jurisdictions, foresters are required to complete detailed long‐term forest management plans, especially on public lands. These plans require foresters to make detailed predictions about the growth and yield of forest resources, and how harvesting and other forest management activities influence the flow of timber and other resources. Based on the outputs from these models, forest managers make decisions about where, when, how, and how much forest land should be treated. Elsewhere, management planning may reflect shorter time horizons, but the decisions are no less critical. Good forest management decisions require good tools to analyze the impacts of management activities on the quantities and flows of the various forest resources and on the state of the forest itself. These tools require good models and, ultimately, these models require good data. The acquisition of this data is the subject of this book.

Foresters are faced with many decisions in the management of a forest. The following questions are examples of the problems that must be solved for a particular forest:

1. What silvicultural treatment will result in best regeneration and growth?
2. What species is most suitable for reforestation?
3. Is there sufficient timber to supply a forest industry and for an economical harvesting operation?
4. What is the value of the timber and land?
5. What is the recreational potential?
6. What is the wildlife potential?
7. What is the status of biodiversity on the area?
8. What is the status of the forest as a carbon sink?

A forester needs information to answer these and countless other questions and to make intelligent decisions or recommendations to a client. This information often is needed in quantifiable terms. In most situations, the axiom holds, “You can’t efficiently make, manage, or study anything you don’t locate and measure.” At the same time, resources for measurement are usually limited, so information must be acquired efficiently. In this sense, forest mensuration is the application of measurement principles to obtain quantifiable information for forest management decision‐making.

To summarize, forest mensuration is concerned with obtaining information about forest resources and conditions. The ultimate objective of forest mensuration is to provide quantitative information about the forest and its resources that will allow making reasonable decisions on its destiny, use, and management.

1.2. FOREST MENSURATION AS A TOOL FOR MONITORING FORESTS

To many, a forest, if not affected by cutting, fire, or some other calamity, is a stable, unchanging entity. Actually, a forest is a dynamic system that is continuously changing. Although this may not be evident over a short term, such as a few years, change is always present: some trees increase their dimensions, others die, and new trees germinate and enter the forest. Consequently, the information obtained about the status of a forest area at a given time is only valid for a length of time that depends on the vegetation itself, and on environmental and external pressures affecting the forest. This means that the mensurational information regarding the forest must be updated periodically by monitoring procedures so that the appropriate management and policy decisions may be taken.

Throughout the twentieth century, the demand on forest resources increased worldwide (Westoby, 1987). In the opening decades of the twenty‐first century, this increase is expected to continue. During the last 40 years, not only have the demands for timber increased, foresters also have been required to manage for other resources including wildlife habitat, water quality, recreational opportunities, and biodiversity. An increase in the public awareness of the influence of human activities on the environment has resulted in the development of a number of forest certification procedures to ensure that forest management activities are sustainable both economically and environmentally. These procedures require forest managers to document and monitor the impacts of forest management activities on a wide range of forest resources, not just timber.

Monitoring must consider changes in composition, structure, size and health of forests (Max et al., 1996). To be effective, monitoring must be comprehensive. In these situations, foresters must increase the scope of their inventories, and the models they use, to include information on multiple aspects of forest structure, not just timber‐producing trees. To be cost effective, forest managers will be required to design and implement new sampling strategies and measurement procedures to meet the demand for increased information.

In the early 1900s, as professional forestry was beginning in North America, the need to use the quantitative tools forest mensuration and forest inventory offered to monitor forest resources was quickly recognized (Bates and Zon, 1922). Zon (1910), in one of the first attempts to assess global forest resources, recognized the need for systematic monitoring of forest resources on both a national and global basis. The Scandinavian countries (Norway in 1919, Finland in 1920, and Sweden in 1923) were the first countries to implement systematic national forest inventories (NFIs) based on modern statistical principles (Tokola, 2006; Tomppo, 2006). The United Kingdom began NFIs in 1924 and the United States in 1930. The Food and Agricultural Organization of the United Nations began compiling global assessments of forest resources in 1947. Many other European and Asian countries began NFIs in the 1960s and 1970s. In the late 1980s and early 1990s, many countries, including the United States and Sweden, redesigned their NFIs, adopting a systematic‐grid‐based sample design and consistent plot designs and remeasurement intervals. A number of countries around the world have redesigned or adopted similar protocols for their NFIs. Although most NFIs began with a focus on timber and related resources, nearly all are actively broadening to address the full range of economic, conservation, and environmental challenges faced by regional and national policymakers. Most countries have also integrated remote sensing, aerial photography, and/or LiDAR data into the analyses of...