In the conditions of dynamics of ecosystem, the flow of energy moves from one trophic level to the another. $50 \%$ events of sunlight on the earth, are in photosynthetically active radiation. Plants capture $2$ to $10$ per cent of the $PAR$ to form $GPP.$

Maximum gross primary productivity during respiration and other biotic processes is of $90 \%$. Gross net primary productivity is used in respiration by plants. Subtracting respiration loses plants use GPP for respiration which is used in second trophic level $C$ herbivores and decomposers.

Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.

Therefore to increase gross primary productivity in natural ecosystem, large amount of trees help in ecological system.

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

Human beings try to produce net primary productivity by producing other crops to fulfill their requirements, develop food.

$NPP$ (Formula to find net Primary productivity)

$\mathrm{NPP}-\mathrm{GPP}-\mathrm{R}$