PUBLISHED: DECEMBER 2006

## Glossary

Allelopathic
Of or relating to allelopathy, the suppression of growth in one plant species due to chemicals produced by another.
Approximate Randomization Analysis
A randomization test involves the comparison of an observed test statistic with a distribution that is generated by randomly reordering the data values in some sense.
Bootstrapping
The essence of bootstrapping is that in the absence of any other information about a population, the values in a random sample are the best guide to the distribution, and that re-sampling the sample is the best guide to what can be expected from re-sampling the population. Much of the research on bootstrapping has been aimed at developing reliable methods for constructing confidence limits for population parameters (see Manly, 1997).
Climax species
The plant species that inhabit an area that has undergone the final stage of vegetational succession.
Confidence interval
The interval within which a parameter of a parent population is calculated (on the basis of the sampled data) in order to determine a stated probability of lying. The larger the sample size (n), the smaller the confidence interval and the more accurate the estimate of the parent mean.
Confidence limits
The upper and lower boundaries of the confidence interval.
Descriptive statistics
The general statistics of individual organisms or population (e.g. mean tree diameter or height).
Diameter at breast height (DBH)
The outside-bark diameter of a tree measured at 4.5 feet (1.37 meters) above the forest floor on the uphill side of the tree.
Frequency distribution
A set of frequencies or probabilities assigned to a set of events.
Gap-phase regeneration
The pioneer phase during which trees begin to colonize a site.
Importance value (IV)
An abundance estimate consisting of the sum of three relative values: relative density (the number of a given species/family expressed as a percentage of all species present), relative frequency (the frequency of a given species/family expressed as a percentage of the sum of frequency values for all species present), and relative dominance (the basal area of a given species expressed as a percentage of the total basal area of all species present (Oxford Dictionary of Ecology).
Knob-and-kettle topography
Also known as "sag and swell" topography, this is a landscape type sometimes associated with recent terminal moraine (debris and deposits laid down at the edge of a glacier). It consists of hummocky mounds (knobs) alternating with depressions (kettles).
Pioneer species
A species that is adapted to the early stages of vegetational succession.
Point estimate
The estimation of a parameter of a parent population as a single value. An arithmetic mean, such as mean density, is a single number called point estimate in statistics and must always be accompanied by some information upon which its usefulness as an estimate can be judged.
Quartiles
The value of a variable below which three quarters (1st or upper quartile) or one quarter (the 3rd or lower quartile) of a distribution lie. The median is the 2nd quartile.
Regression analysis (simple and multiple linear regression)
Simple linear regression and multiple linear regression are related statistical methods for modeling the relationship between two or more random variables using a linear equation. Simple linear regression refers to a regression on two variables while multiple regression refers to a regression on more than two variables. Linear regression assumes the best estimate of the response is a linear function of some parameters (though not necessarily linear on the predictors). See http://en.wikipedia.org/wiki/Regression_analysis.
Shannon-Wiener index (H')
One of several indices used to measure biodiversity. It takes into account the species evenness (relative abundance) of a population or community as well as the special richness (total number). For more information, visit http://en.wikipedia.org/wiki/Shannon-Wiener_Index.
Simpson's index
A simple mathematical measure of diversity in a community, devised by E.H. Simpson in 1949. See http://www.tiem.utk.edu/~gross/bioed/bealsmodules/simpsonDI.html.
Species richness
The total number of different species present.
Singleton
Occurring singly.
X, Y coordinates
The most common tools for identifying points in space are the Cartesian coordinates. The x-axis is the abscissa and y-axis is the ordinate. During vegetation surveys, Cartesian coordinates display the spatiality of individuals across a study plot and reveal the basic patterns of distribution—random, regular, and clumped.