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

Abstract

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.

Authors:
ORCiD logo; ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1543758
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Nature Climate Change
Additional Journal Information:
Journal Volume: 8; Journal Issue: 11; Journal ID: ISSN 1758-678X
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences

Citation Formats

Riley, W. J., Zhu, Q., and Tang, J. Y. Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods. United States: N. p., 2018. Web. doi:10.1038/s41558-018-0325-4.
Riley, W. J., Zhu, Q., & Tang, J. Y. Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods. United States. doi:10.1038/s41558-018-0325-4.
Riley, W. J., Zhu, Q., and Tang, J. Y. Mon . "Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods". United States. doi:10.1038/s41558-018-0325-4.
@article{osti_1543758,
title = {Weaker land–climate feedbacks from nutrient uptake during photosynthesis-inactive periods},
author = {Riley, W. J. and Zhu, Q. and Tang, J. Y.},
abstractNote = {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.},
doi = {10.1038/s41558-018-0325-4},
journal = {Nature Climate Change},
issn = {1758-678X},
number = 11,
volume = 8,
place = {United States},
year = {2018},
month = {10}
}