GPP of a temperate grassland is $7000{\text{kJ,m}}^{-2}{\text{d}}^{-1}$ and ecosystem respiration is $2500{\text{kJ,m}}^{-2}{\text{d}}^{-1}$. Energy transfer efficiencies are $10$ from producers to primary consumers and $8$ from primary to secondary consumers. What is the energy available to secondary consumers per square metre per day?

Step-by-step solution

1. Calculate Net Primary Production (NPP) by subtracting respiration from GPP: $NPP=7000-2500=4500$ kJ m⁻² d⁻¹. This represents the energy left after autotrophs lose energy in respiration.
2. Determine energy transferred to primary consumers by applying the 10 % efficiency: $E_{PC}=0.10\times 4500=450$ kJ m⁻² d⁻¹. This is the energy that primary consumers obtain.
3. Apply the 8 % efficiency from primary to secondary consumers: $E_{SC}=0.08\times 450=36$ kJ m⁻² d⁻¹. This is the final energy available to secondary consumers.

Concept tested: Energy flow through trophic levels

Published 28 September 2026 · How this solution was prepared and checked