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BOT 440/540 Field Methods in Vegetation Science

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Glossary

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Accuracy How close an estimate is to the parameter being estimated
Annual productivity Amount of living tissue created per year, less losses to respiration, per plant or per area; productivity is one of the best measures of a species's functional importance
Attribute A charactistic of an entity. For example, a tree (the entity) has a certain diameter (the attribute), or a species (the entity) has a certain cover (the attribute) within a community.
Basal area The cross-sectional area of the tree's trunk at breast height; stand basal area is the sum of tree basal area for the community
Baseline studies "Assessing existing conditions to provide a standard against which future change is measured" (Elzinga et al., 2001)
Bias Systematic error; the difference between the mean of all possible estimates given by an estimator and the parameter being estimated
Biomass Weight of living tissue, either per plant or per area. Biomass is the best single measure of a species's structural importance.
Completely random design (CRD) A design for manipulative experiments in which locations suitable for study are first identified, then treatments are assigned completely at random
Confidence interval A range of values intended to include a parameter
Confidence level The probability (or confidence) with which one makes a statement about an estimate
Cover Amount of the ground obscured by the aboveground portions of a species or group

Total cover

Cover of all plants, ignoring what leaf belongs to which species or group

Combined cover

Sum of the cover values for different plant species or groups.

Overall cover

Cover across the entire study area
Density Number of individuals per area
DBH Diameter of a tree trunk at breast height (1.37 m)
Efficiency The ability of a sampling design to produce precise estimates with moderate effort; precision per time
Error The difference between an estimated value and the true value
Estimate A statistic that is used as a guess of the value of a parameter
Experimental unit A single item subjected to an experimental treatment; units can be individuals or portions of area
Frequency The proportion of plots in which a species is found
Independence (of samples) The location of one sample does not affect the location of another
Inference The process of drawing conclusions about a statistical population based on sample observations
Interspersion The distribution of samples across the community
Leaf area index (LAI) Surface area of leaves per area of ground
Manipulative experiment Comparative study in which the investigator creates differences by imposing treatments
Measurement error The difference between the measured value of a single item and its true value
Mensurative experiment Comparative study in which the investigator exploits pre-existing differences; "natural experiment"
Monitoring "The collection and analysis of repeated observations or measurements to evaluate changes in condition and progress toward meeting a [scientific or] management objective." (Elzinga et al. 2001)
Net production Amount of organic matter created, less losses to respiration
Observational unit A single item being observed, also called a sampling unit; units can be individuals or portions of area, sometimes delimited by quadrat frames
Overall cover The cover of an entity over all observational units
Parameter A quantitative characteristic of the statistical population
Physiognomy Vertical and horizontal structure of a community
Precision The closeness of repeated measurements of the same quantity
Quadrat An area (of any shape) in which plant or vegetation attributes are recorded
Randomization A way to eliminate subjectivity
Randomized complete block design (RCB) A design for manipulative experiments in which all treatments are assigned at random to areas within blocks
Reliability When referring to data, reliability describes data with low variability.
Replication The repetition of equivalent measurements or treatments
Sample A part of a statistical population; a sample is usually taken to estimate something about the whole population
Sampling error Inaccuracy in an estimate causee by variability among observations
Sampling unit A single item being observed, also called an observation; units can be individuals or portions of area, sometimes delimited by quadrat frames
Sampling universe The whole group of items under investigation; all possible sampling units; sometimes called the statistical population
Simple random sample Sampling scheme in which each possible sample has the same probability of being selected
Statistic A quantitative characteristic of the sample
Statistical population The whole group of items under investigation; all possible sampling units; sometimes called the sampling universe
Stratified random sample Sampling scheme in which random samples are allocated to relatively uniform subunits within a population
Surveillance Measuring change in the absence of scientific or management objectives
Total cover (1) The cover of all plants considered as a group; (2) the combined (summed) cover of all species (#2 can be more than #1 if species overlap)
Variability The degree to which measurements differ from one another.
Zone of influence An imaginary boundary around a plant's crown, roughly representing the effects on the crown on the surrounding area, that fills in minute gaps within the crown and smooths its boundary.

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