What is species richness?
Species richness is the number of species within a community or area. For example, if we have two plots of lands, A and B, and plot A has twenty four species of plants and plot B has eighty four species of plants, plot B has higher species richness.
Species richness does not take into account the distribution of species within the area or what is referred to as species evenness.
In the example above, if the majority of the individuals in plot B with eighty four different types of species all come from one or two different species, this plot would have low species evenness.
In the image below, both communities have identical species richness because they contain two species of trees. In terms of their evenness, community X is more even than community Z because there is an equal number of both tree species.