Trophic structure and productivity

Biomass is the total organic mass of all living organisms in an ecosystem at a given moment (dry matter; g/m², kg/ha, or per unit volume in water bodies); plant biomass is phytomass, animal biomass is zoomass. Productivity is the amount of biomass formed per unit of time (day, year), that is, the rate of growth: biomass and productivity are not the same – a forest has large biomass but relatively small annual growth; the phytoplankton of a pond has small biomass but multiplies within days and gives high productivity. The mass formed by producers in photosynthesis or chemosynthesis is primary production; if the part spent on respiration is subtracted, net primary production remains (NPP = gross primary production − respiration), and it is what herbivores and others consume. What consumers and reducers form is secondary production. On average about 1 % of the solar energy reaching the surface is converted to biomass energy (the «1 % rule»; 0.1–2 % in different ecosystems). Tropical forests and productive ponds have high productivity, deserts and tundra low; oceans, because of their area, provide about half of global photosynthesis.