In a temperate grassland ecosystem, the gross primary productivity (GPPGPPGPP) is measured as 3.6×104 kJ m−2 yr−13.6 \times 10^4 \text{ kJ m}^{-2} \text{ yr}^{-1}3.6×104 kJ m−2 yr−1. The primary producers (grasses) lose 60% of this energy as heat during respiration. A population of primary consumers (sheep) grazing on this grassland ingests 15% of the net primary productivity (NPPNPPNPP). Of the energy ingested by these sheep, 55% is lost in faeces and urine (FFF), and 35% is lost through respiration (RRR). Calculate the net secondary productivity (NNN) of this sheep population in kJ m−2 yr−1\text{kJ m}^{-2} \text{ yr}^{-1}kJ m−2 yr−1.
216 kJ m−2 yr−1216 \text{ kJ m}^{-2} \text{ yr}^{-1}216 kJ m−2 yr−1
540 kJ m−2 yr−1540 \text{ kJ m}^{-2} \text{ yr}^{-1}540 kJ m−2 yr−1
1944 kJ m−2 yr−11944 \text{ kJ m}^{-2} \text{ yr}^{-1}1944 kJ m−2 yr−1
324 kJ m−2 yr−1324 \text{ kJ m}^{-2} \text{ yr}^{-1}324 kJ m−2 yr−1