Fig. 4.

Empirical data for the residence time of carbon and nitrogen for diverse organisms and ecosystem types. Symbol color and shape as in Fig. 2A. Solid black lines are GLM regression fits (gray shading is the 95% confidence band), and black dotted lines are our predicted relationships from our theory. (A) Within individual organisms the half-life of carbon and nitrogen increases with body mass with a slope of 0. 23 ± 0.03 95% CI (this includes our predicted slope of 0.25, see prediction 1 in main text). These data have been temperature corrected to 15°C and include a large diversity of tissue types (Materials and Methods and SI Appendix, Table S2). As we also predict, in entire ecosystems, carbon residence times increase with (B) increasing body size of the primary producers (slope is 0.21 ± 0.02 95% CI; expected slope is <0.25 depending on the network, see prediction 3 in main text), data replotted from Allen et al. (10), and (C) the ratio of total biomass to primary production (slope is 0.85 ± 0.17 95% CI, see prediction 2 in main text). Production is GPP, determined by doubling NPP values in ref. 12 as per ref. 45. For terrestrial systems, biomass = plant and herbivore biomass. For freshwater pelagic systems, biomass = 3 × producer mass (46).