Realistic rates of nitrogen addition increase carbon flux rates but do not change soil carbon stocks in a temperate grassland

Megan E. Wilcots, Katie M. Schroeder, Lang C. DeLancey, Savannah J. Kjaer, Sarah E. Hobbie, Eric W. Seabloom, Elizabeth T. Borer

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Changes in the biosphere carbon (C) sink are of utmost importance given rising atmospheric CO2 levels. Concurrent global changes, such as increasing nitrogen (N) deposition, are affecting how much C can be stored in terrestrial ecosystems. Understanding the extent of these impacts will help in predicting the fate of the biosphere C sink. However, most N addition experiments add N in rates that greatly exceed ambient rates of N deposition, making inference from current knowledge difficult. Here, we leveraged data from a 13-year N addition gradient experiment with addition rates spanning realistic rates of N deposition (0, 1, 5, and 10 g N m−2 year−1) to assess the rates of N addition at which C uptake and storage were stimulated in a temperate grassland. Very low rates of N addition stimulated gross primary productivity and plant biomass, but also stimulated ecosystem respiration such that there was no net change in C uptake or storage. Furthermore, we found consistent, nonlinear relationships between N addition rate and plant responses such that intermediate rates of N addition induced the greatest ecosystem responses. Soil pH and microbial biomass and respiration all declined with increasing N addition indicating that negative consequences of N addition have direct effects on belowground processes, which could then affect whole ecosystem C uptake and storage. Our work demonstrates that experiments that add large amounts of N may be underestimating the effect of low to intermediate rates of N deposition on grassland C cycling. Furthermore, we show that plant biomass does not reliably indicate rates of C uptake or soil C storage, and that measuring rates of C loss (i.e., ecosystem and soil respiration) in conjunction with rates of C uptake and C pools are crucial for accurately understanding grassland C storage.

Original languageEnglish (US)
Pages (from-to)4819-4831
Number of pages13
JournalGlobal change biology
Volume28
Issue number16
DOIs
StatePublished - Aug 2022

Bibliographical note

Funding Information:
Coordination and data management for this study have been supported by funding to ETB and EWS from the National Science Foundation Research Coordination Network (NSF‐DEB‐1042132) and the Long‐Term Ecological Research (NSF‐DEB‐1234162 and NSF‐DEB‐1831944 to Cedar Creek LTER) programs, and the Institute on the Environment (DG‐0001‐13). Soil analyses were supported, in part, by USDA‐ARS grant 58‐3098‐7‐007 to ETB. SJK was supported by NSF Ecosystems Studies Program NSF‐DEB‐1556529, KMS was supported by the Cedar Creek LTER REU Program, and MEW was supported by an NSF‐GRFP fellowship. We would like to thank the interns at Cedar Creek Ecosystem Science Reserve who clipped, sorted, dried, and weigh all aboveground plant biomass used in this study, the Gutknecht lab members at the University of Minnesota who processed the MBC data, and two anonymous reviewers whose comments greatly improved the manuscript.

Funding Information:
Coordination and data management for this study have been supported by funding to ETB and EWS from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and the Long-Term Ecological Research (NSF-DEB-1234162 and NSF-DEB-1831944 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13). Soil analyses were supported, in part, by USDA-ARS grant 58-3098-7-007 to ETB. SJK was supported by NSF Ecosystems Studies Program NSF-DEB-1556529, KMS was supported by the Cedar Creek LTER REU Program, and MEW was supported by an NSF-GRFP fellowship. We would like to thank the interns at Cedar Creek Ecosystem Science Reserve who clipped, sorted, dried, and weigh all aboveground plant biomass used in this study, the Gutknecht lab members at the University of Minnesota who processed the MBC data, and two anonymous reviewers whose comments greatly improved the manuscript.

Publisher Copyright:
© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Keywords

  • carbon cycling
  • grasslands
  • net ecosystem exchange
  • nitrogen deposition
  • soil respiration

PubMed: MeSH publication types

  • Journal Article

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