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Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods


Terrestrial carbon–climate feedbacks depend on two large and opposing fluxes—soil organic matter decomposition and photosynthesis—that are tightly regulated by nutrients1,2. Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 5 represented nutrient dynamics poorly1,3, rendering predictions of twenty-first century carbon–climate feedbacks highly uncertain. Here, we use a new land model to quantify the effects of observed plant nutrient uptake mechanisms missing in most other ESMs. In particular, we estimate the global role of root nutrient competition with microbes and abiotic processes during periods without photosynthesis. Nitrogen and phosphorus uptake during these periods account for 45 and 43%, respectively, of annual uptake, with large latitudinal variation. Globally, night-time nutrient uptake dominates this signal. Simulations show that ignoring this plant uptake, as is done when applying an instantaneous relative demand approach, leads to large positive biases in annual nitrogen leaching (96%) and N2O emissions (44%). This N2O emission bias has a GWP equivalent of ~2.4 PgCO2 yr−1, which is substantial compared to the current terrestrial CO2 sink. Such large biases will lead to predictions of overly open terrestrial nutrient cycles and lower carbon sequestration capacity. Both factors imply over-prediction of positive terrestrial feedbacks with climate in current ESMs.

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Fig. 1: ELMv1-ECA accurately represents observed short-term nutrient uptake patterns.
Fig. 2: Photosynthesis-inactive period nutrient uptake is a large proportion of annual uptake globally.
Fig. 3: Ignoring photosynthesis-inactive-period nitrogen uptake has large effects on nitrogen leaching and gaseous losses.

Data availabilty

The data that support the findings of this study are available from the corresponding author upon request.


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This research was supported as part of the Energy Exascale Earth System Model project, funded by the US Department of Energy, Office of Sciences, Office of Biological and Environmental Research under contract number DE-AC02-05CH11231 to the Lawrence Berkeley National Laboratory. This research used resources of the National Energy Research Scientific Computing Center, a Department of Energy Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract number DE-AC02-05CH11231.

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Authors and Affiliations



All authors contributed intellectually to this work. W.J.R. and Q.Z. designed the numerical experiments. Q.Z. performed the simulations and synthesized the nutrient uptake observational benchmark, and W.J.R. analysed the results. Q.Z. and J.Y.T. implemented the numerical model. W.J.R. wrote the manuscript, and Q.Z. and J.Y.T. contributed extensively to its content.

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Correspondence to W. J. Riley.

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Supplementary tables 1–3, Supplementary figures 1–4, Supplementary references

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Riley, W.J., Zhu, Q. & Tang, J.Y. Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods. Nature Clim Change 8, 1002–1006 (2018).

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