Biomass refers to the amount or weight of living biological material or organic matter present in an organism, community, or biome in a given area or ecosystem at a particular time. It refers to the mass of living organisms.

Sere or seral communities are the intermediate stages in ecological succession. Seral stages represent the entire sequence of development stages of biotic succession from pioneer to a climax community in a given ecosystem.

The gradual and predictable change in the species composition in an area is called ecological succession. Sere is the series of succession starting from the pioneer stage to the climax stage. Hydrosere can be defined as a succession that develops over time from a water body into the woodland. Example includes: Phytoplankton stage; Rooted submerged stage ( Vallisneria ); floating stage; Reed swamp stage ( Typha ); Meadow stage ( Gallium ), Woodland stage ( Salix ), Forest stage.