In other cases, however, the vegetation might appear to be homogeneous when in fact it is not. For example, an area might appear to be juniper woodland, but in reality there could well be differences in various factors from one part of the area to another. Factors to be considered include among other things frequency, density, dominance or cover, height, and vigor. All of these can be measured in absolute or relative terms. The former involves all plants, the later only one species in relation to all others.
Frequency is the number of times a particular species is recorded in a sample area or transect.
Regardless, it is always measured as a percent of the sample area or transect. Height can be measured directly in the case of plants less than 2-3 meters tall, and estimated for those that are higher. Height of course reveals something about a plants age. Vigor is a qualitative estimation about the nature of a plant's, a specie's, or a community's growth. Sick or weak plants look different than healthy plants, and dead ones are certainly obvious.