You are studying plant physiology and want to compare the energy used during cellular respiration for plants in tundras at varying longitudes. However, you do not have the funding to travel to multiple tundras and actually measure plant respiration. Instead, you decide to gather previously published data in order to arrive at an accurate average. You find very few data on plant respiration in tundra, but lots of data on their gross primary production. What would be the most logical next step towards estimating the energy used in cellular respiration?