For some purposes it is useful to express the contribution of individuals of one species in relation to the total. Dominance Dominance is a measure of the size, bulk, or weight of the vegetation. Weight measurements are often difficult and time consuming to obtain and the latter two measures are more often evaluated. Basal area is defined as the area of ground surface covered by the bases of plants, while canopy cover is the area of ground covered by the vertical projection of the canopy to the ground surface. Frequency Frequency is a measure of the commonness and distribution of a species within a study area.
Frequency is expressed as a percentage of sample plots in which a species occurs.
Number of samples in which a species occurs X 100 Total number of samples taken Frequency can also be expressed in relative terms, however, mathematically this is a poorly defined quantity. A Density, dominance, and frequency data can be obtained by many methods. One of the most widely used of all sampling methods is the area sample. This is ordinarily a square area of known size called a quadrat. These quadrats are distributed at random, on a grid pattern, or on some other pre-determined pattern throughout the stand being examined.