In a temperate grassland the Gross Primary Production (GPP) is $6000{\text{kJm}}^{-2}{\text{d}}^{-1}$ and the ecosystem respiration is $2000{\text{kJm}}^{-2}{\text{d}}^{-1}$. Energy transfer efficiency from producers to primary consumers is 10% and from primary consumers to secondary consumers is 7%. Calculate the amount of energy (in ${\text{kJm}}^{-2}{\text{d}}^{-1}$) available to secondary consumers.

Step-by-step solution

1. First find Net Primary Production (NPP) = GPP – respiration.
2. NPP = $6000-2000=4000{\text{kJm}}^{-2}{\text{d}}^{-1}$.
3. Energy transferred to primary consumers = NPP × 10%.
4. Energy to primary consumers = $4000\times 0.10=400{\text{kJm}}^{-2}{\text{d}}^{-1}$.
5. Energy transferred to secondary consumers = (energy to primary consumers) × 7%.
6. Energy to secondary consumers = $400\times 0.07=28{\text{kJm}}^{-2}{\text{d}}^{-1}$.
7. Check calculation: 28 kJ is the correct amount.

Concept tested: Energy flow and ecological efficiency

Published 25 September 2026 · How this solution was prepared and checked