The rate at which plants produce biomass is known as primary productivity.
Which of the following is a suitable unit with which to measure the primary productivity of a terrestrial grassland ecosystem?
kg year−1 m−3\text{kg year}^{-1}\text{ m}^{-3}kg year−1 m−3
kg year−1 m−2\text{kg year}^{-1}\text{ m}^{-2}kg year−1 m−2
kg year m−2\text{kg year m}^{-2}kg year m−2
m2 kg−1 year−1\text{m}^2\text{ kg}^{-1}\text{ year}^{-1}m2 kg−1 year−1
