Count annuals if dry or green if still rooted in quadrat. Annuals are grouped only as grasses or forbs. Shrubs are counted if rooted in quadrat or any woody part of plant overhangs the quadrat. Record which species occur in the frame. The number of occurrences divided by the total number of frames is the frequency.
Frequency means the probability of finding a species within a particular area.
The probability is based on the occurrence of that species in a series of sample units. Frequency is a simple vegetation attribute to measure because it only requires identification of the species in each quadrat, and does not require that individuals are distinguished, measured, or counted. Therefore, data collection is usually a more rapid procedure than for other vegetation attributes such as biomass, cover, or density, which involve counting or subjective quantification. This advantage is most apparent in rangeland vegetation characterized by a relatively low species richness, but diminishes in vegetation with complex species composition. Frequency values are determined for individual species because an overall frequency for the entire vegetation cannot be obtained, in contrast to other attributes such as biomass, cover, or density.