Total biomass refers to the combined weight or mass of all living organisms within a specific ecosystem or area. It includes all plants, animals, microorganisms, and other living beings present in that particular environment. Full definition
This is expected to shift biomass generation to winter but only raise total biomass output by perhaps 1 %. (carbonbrief.org)
For biofuels, you might think about recent research (from University of Minnesota, IIRC) showing that a mixed native prairie produces more total biomass than any monoculture. (green.blogs.nytimes.com)
Land use for biomass production is one of the most important stressors on biodiversity, while total biomass use has continued to grow and demand is expected to continue growing over the next few decades [25]. (academic.oup.com)