A considerable amount of gross primary productivity is utilized by...

Gross primary productivity (GPP) of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilized by plants in respiration (R).

The remaining biomass after respiratory losses is called net primary productivity (NPP).

$\text{NPP} = \text{GPP} - \text{R}$

Net primary productivity is the available biomass for the consumption to heterotrophs (herbivores and decomposers).

Answer: Net primary productivity