From fundamentals of ecology, Odum 2005:
... autogenic succession usually begins with an unbalanced community metabolism, where gross production, P, is either greater than or less than community respiration, R, and proceeds towards a more balanced condition, where P=R. The rate of biomass production (B/P ) increases during sucession until a stabilised system is achieved, in which a maximum of biomass (or high information content) and symbiosis between organisms are maintained per unit of available energy flow.
Isn't gross production (P) same as biomass (B) ? I can't tell them apart, given that Biomass is the amount of matter living organisms (usually of a specific trophic level) of a given area at a specific time is made up of.