Observations based on single points, such as the step point method, tend to take less time to record and give a more precise estimate of cover than do the same number of points sampled as a group, such as the point frame method.
Many different attributes describing plant dimensions can be used to determine plant biomass. Measurements on plant height, plant basal area, twig length and diameter, trunk diameter, canopy cover, or canopy volume, are all used as indirect methods to estimate biomass.
Values that summarize properties of the population are known as parameters. Commonly expressed parameters are the population mean (
) and the population variance (
2).
16 September 1997 (Draft for Review)
This is not an index to every page in this section, but most of the higher-level ones. It is designed to give an overview of the subject matter the chapter covers and access to most parts.
Normal distributions are sampling distributions generated when an attribute possessing a continuous, and typically unbounded, range of outcomes is recorded from a series of sample units. Sample units should be independent and selected by random sampling. Normal distributions follow a symmetrical form, characterized as a bell-shaped curve.
Nested quadrats are a special sample unit that includes a series of different sized quadrats all placed at the same location. They are usually positioned so that all have a common corner point, causing the area sampled by smaller quadrats to be included in the progressively larger ones.
Mean area, or the average space available to each plant, is another way to consider density. Mean area is the mathematical reciprocal of density, and is the basis of the various distance methods developed to estimate plant density.
Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Sons, New York, NY. pp 148.