Usually expressed as relative values, relative density is the number of a given species expressed as a percentage of all species present, relative frequency is the frequency of a given species expressed as a percentage of the sum of frequency values for all species present, and relative dominance is the basal area of a …
What is relative density in biodiversity?
Relative density is calculated by dividing the density by the sum of the densities of all species, multiplied by 100 (to obtain a percentage). Dominance is calculated as the total basal area of a species.
What is the relationship between density and frequency environmental science?
Remember that density measures how many of a species are present, while frequency measures how often that species occurs. Determining the frequency can help researchers define the distribution of species in a community.
How is ecological importance value calculated?
The importance value is calculated as the sum from (i) the relative frequency; (ii) the relative density; and (iii) the relative dominance. The importance value ranges between 0 and 300. Frequency is calculated as the number of plots where a species is observed divided by the total number of survey plots.
How do you find frequency in ecology?
Local frequency is easiest to measure if you have a gridded quadrat of 10 x 10 squares. For each species, count the number of squares which are at least half-occupied. The final figure (which will vary between 1 and 100) is the local frequency.
Why is relative abundance important?
The relative abundance of each species is more evenly distributed than Community 1. While both communities have the same species richness, Community 1 would have greater diversity due to the relative abundance of each species present.