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# Glossary

Accuracy - a measure of how close the sample estimator is to the true population value. It is impossible to measure accuracy directly without knowing the true population value. It is assumed that accuracy should be high if a sample estimator is unbiased and precise.

Bias - the difference between the expected value of a sample statistic (known as an estimator) and the population parameter (or true population value that the statistic is intended to estimate). Note: bias implies systematic distortion, as distinct from random error, which balances out on average; a sampling process involving such a distortion is said to be biased (Helms, 1998).

Biodiversity inventory - a list of biological entities from a particular site or area (Stork & Davis, 1996).

Biometric - the application of statistical methods to the measurement of biological objects (adapted from Shorter Oxford English Dictionary).

Enumeration - the listing of data. In forest inventory - the process of measuring the specific parameters required by the protocol. Enumeration data are the results of an enumeration (Helms, 1998).

Herbarium/Herbaria - a place where reference collections of plants are held, often associated with botanical gardens or natural history museums.

Forest inventory - 1) a set of objective sampling methods designed to quantify the spatial distribution, composition and rates of change of forest parameters within specified levels of precision for the purpose of management. 2) the listing (enumeration) of data from such a survey (Helms, 1998).

Life cycle - the successive stages through which an organism passes from fertilized ovum or spore to the fertilized ovum or spore of the next generation (Helms, 1998).

Life history - the continuous, descriptive account of an organisms habits and life cycle i.e. activities and duration (Helms, 1998).

Life table - an age-specific summary of the mortality and survivorship of a population, usually specifying the mortality agents (i.e. harvesting) operating (Helms, 1998).

Matrix models - mathematical models that predict future populations using probabilities to calculate the likelihood of individuals surviving, growing, dying or reproducing.

Mensuration - in forestry - the determination of dimensions, form, weight, growth, volume, age, etc., of trees, individually or collectively, and of the dimensions of their products (Helms, 1998).

Multi-disciplinary - from a broad range of disciplines, e.g. ethnobotany, agro-ecology, human ecology.

Phenology - the flowering and fruiting of plants.

Plot - derives from the physical unit of a plot of land. Its interpretation is now very much more general according to the subject matter of the particular survey (cf. sampling unit) (Marriott, 1990).

Population - the entire aggregate of individuals or items from which samples are drawn (Marriott, 1990).

Precision - a measure of the degree to which sample estimates cluster tightly together about their own average. A precise estimate has a small sampling error.

Protocol - the formal procedure for the implementation of a specific inventory. These are used at two levels: 1) field - concise, usually written, instructions which leave no ambiguity in how to deal with common field difficulties (i.e. where to measure a leaning tree, or how to measure distances on slopes) and used in training and for reference during the course of the work. 2) reporting - very concise description of sampling design which gives sufficient detail of field methods to enable replication of the study (Helms, 1998).

Qualitative data - descriptive data which is classified by type, i.e. grouped into low, medium, high, etc. (Porkess, 1988).

Quantitative data - data which is classified by some numeric value, i.e. the actual weight of an animal (Porkess, 1988).

Random selection - a sample selected from a finite population is said to be random if every possible sample has equal probability of selection (Marriott, 1990).

Recruitment - new individuals joining the population, i.e. through birth or germination.

Regression equation - the mathematical relationship between two variables, i.e. weight against length, usually a linear (straight line) relationship derived using a least squares method. The coefficient of determination r², is a measure of the strength of the relationship (Porkess, 1988). Regression equations are often used predictively, i.e. to estimate a characteristic (e.g. weight) using measurement of another, independent characteristic (e.g. diameter).

Replication - the execution of an experiment or survey more than once so as to increase precision and to obtain a closer estimation of the sampling error (Marriott, 1990).

Representative sample - in the widest sense, a sample which is representative of a population. Some confusion arises according to whether `representative' is regarded as meaning `selected by some process which gives all samples an equal chance of appearing to represent the population'; or, alternatively, whether it means `typical in respect of certain characteristics, however chosen'. On the whole, it seems best to confine the word `representative' to samples which turn out to be so, however chosen, rather than apply it to those chosen with the object of being representative (Marriott, 1990).

Sample - a part of a population which is provided by some process or other, usually by deliberate selection with the object of investigating the properties of the parent population (Marriott, 1990).

Sample design - used here to mean: a set of rules or specifications for the selecting of a sample in an unequivocal manner (Marriott, 1990).

Sampling error - the difference between the true value of a parameter of a parent population and that estimated from the sample. This error is due to the fact that the value has been calculated from a sample rather than from the whole parent population (Marriott, 1990). This is different from error due to imperfect selection, bias, and observational or recording errors. It is a measure of how much the estimates vary between different plots, and is usually given as a percentage of the overall mean.

Sample estimator - the population parameter value estimated through sampling a population, e.g. the mean.

Sampling units - units in which the population is divided or regarded as divided that are available to be selected in the sample. Each unit is regarded as an individual and indivisible when the selection is made. The definition of unit may be made on some natural basis, e.g. households, persons, units of product, etc., or upon some arbitrary basis, e.g. area of defined by grid co-ordinates on a map (Marriott, 1990). Sampling units can also be fixed units of time during which samples are taken.

Stratification - the division of a population into parts, known as strata; especially for the purpose of selecting a sample, an assigned proportion of the sample then being selected from each stratum (Marriott, 1990).

Sustainability - the capacity of forests, ranging from stands to ecoregions, to maintain their health, productivity, diversity and overall integrity, in the long run, in the context of human activity and use (Helms, 1998).

Sustainable yield - the use of living resources at levels of harvesting and in ways that allow these resources to supply products and services indefinitely. Sustainable yield means living off the interest, rather than the capital, of a resource base. It aims to: maintain essential ecological processes and life-supporting systems; to preserve genetic diversity; and to maintain and enhance environmental qualities relevant to productivity; it seeks not to disadvantage future generations (Gilpin, 1996).

Voucher specimens - botanical specimens collected during a survey for comparison with reference material in order to determine its identity.

Yield - the harvest of produce, actual or estimated, from plants or animals expressed by numbers or weight, or as a proportion of the standing crop, over a given period (modified from Helms, 1998).

Yield determination - the calculation of the amount of produce that may be harvested annually or periodically from a specified area over a stated period in accordance with the management objectives (modified from Helms, 1998).

Yield table - a table which can be used to estimate the yield based on a simple measure of size, i.e. a table which can be used to estimate the volume of timber from the diameter of a tree; the table is usually derived from a regression equation.

Glossary References:

Gilpin, A. 1996. Dictionary of environment and sustainable development. Wiley. 247 pp.

Helms, J.A. 1998. Dictionary of forestry. Society of American Foresters and CABI Publishing. 210 pp.

Marriott, F.H.C. 1990. A dictionary of statistical terms. Fifth edition. Longman. 223 pp.

Porkess, R. 1988. Dictionary of statistics. Collins. 267 pp.

Shorter Oxford English Dictionary.

Stork, N. & Davies J. 1996. Biodiversity inventories. pp. 1-34. In: HMSO. Biodiversity assessment. A guide to good practice. Field manual 1. Data and specimen collection of plants, fungi and microorganisms. HMSO, London. 82 pp.