Life table vs secondary production analyses—relationships and usage in ecology

Abstract.  The life table is a well known approach for understanding populations and has appeared in general ecology textbooks for >60 y. Secondary production is associated with energy flow, but methods rarely appear in texts. Our objectives were to: 1) demonstrate conceptual/analytical relationships between secondary production and life tables, 2) use a real example of pond-breeding salamanders to illustrate how the 2 approaches can be integrated, and 3) use publication frequency analysis to determine trends and biases for each approach within ecological (particularly aquatic) subdisciplines. The example illustrated that both approaches incorporate age- or stage-specific survivorship. The main difference is that life tables are used to calculate production of offspring with age-specific fecundity, and production analyses are used to calculate production of biomass with mass-specific increments. Publication frequency analysis over 12 y demonstrated that 78% more papers used life tables (698) than production (393) overall, but 50% more papers used production (353) than life tables (236) in basic research. Furthermore, production was studied primarily in aquatic (98%), mostly benthic (77%), environments. Life tables were used primarily in terrestrial environments (65%). Recognizing the relatedness of these concepts and usage biases may explain philosophical differences and help bridge gaps between terrestrial–aquatic and population–ecosystem ecologists.