The rate of biomass production is called productivity in terms of gm-2yr-1 for an ecosystem, it can be divided in gross primary productivity (GPP) and net primary productivity (NPP). GPP of an ecosystem is the rate of production of organic matter during photosynthesis. NPP is the available biomass for the consumption of heterotrophs i.e., herbivores and decomposers. Secondary productivity is defined as the rate of formation of new organic matter by consumers.