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

Journal Article · Mon Oct 29 00:00:00 EDT 2018 · Nature Climate Change

DOI:https://doi.org/10.1038/s41558-018-0325-4· OSTI ID:1563979

Riley, W. J.  ^[1]; Zhu, Q.  ^[1]; Tang, J. Y.  ^[1]

---

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Terrestrial carbon–climate feedbacks depend on two large and opposing fluxes—soil organic matter decomposition and photosynthesis—that are tightly regulated by nutrients. Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 5 represented nutrient dynamics poorly, 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%). Furthermore, 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.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1563979
• Journal Information: Nature Climate Change, Vol. 8, Issue 11; ISSN 1758-678X
• Publisher: Nature Publishing Group
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES