Note: I think you mean mass of all plants and.
Answer: total biomass in a region is quantified by measuring the dry mass of all plants and animals in population, habitat, or region.
Biomass is the total mass of all living material within a certain area. This includes all plants, animals and other organisms found there. The area is defined by a scientist so that it can be a specific habitat or region.
As all organisms contain water and the amount varies largely between species, the total biomass is calculated as a dry mass.