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Stimulation of soil respiration by elevated CO 2 is enhanced under nitrogen limitation in a decade-long grassland study

Authors
  • Gao, Qun
  • Wang, Gangsheng
  • Xue, Kai
  • Yang, Yunfeng
  • Xie, Jianping
  • Yu, Hao
  • Bai, Shijie
  • Liu, Feifei
  • He, Zhili
  • Ning, Daliang
  • Hobbie, Sarah E.
  • Reich, Peter B.
  • Zhou, Jizhong
Type
Published Article
Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Publication Date
Dec 14, 2020
Volume
117
Issue
52
Pages
33317–33324
Identifiers
DOI: 10.1073/pnas.2002780117
PMID: 33318221
PMCID: PMC7777058
Source
PubMed Central
Keywords
Disciplines
  • Biological Sciences
  • Ecology
License
Unknown

Abstract

Whether and how CO2 and nitrogen (N) availability interact to influence carbon (C) cycling processes such as soil respiration remains a question of considerable uncertainty in projecting future C–climate feedbacks, which are strongly influenced by multiple global change drivers, including elevated atmospheric CO2 concentrations (eCO2) and increased N deposition. However, because decades of research on the responses of ecosystems to eCO2 and N enrichment have been done largely independently, their interactive effects on soil respiratory CO2 efflux remain unresolved. Here, we show that in a multifactor free-air CO2 enrichment experiment, BioCON (Biodiversity, CO2, and N deposition) in Minnesota, the positive response of soil respiration to eCO2 gradually strengthened at ambient (low) N supply but not enriched (high) N supply for the 12-y experimental period from 1998 to 2009. In contrast to earlier years, eCO2 stimulated soil respiration twice as much at low than at high N supply from 2006 to 2009. In parallel, microbial C degradation genes were significantly boosted by eCO2 at low but not high N supply. Incorporating those functional genes into a coupled C–N ecosystem model reduced model parameter uncertainty and improved the projections of the effects of different CO2 and N levels on soil respiration. If our observed results generalize to other ecosystems, they imply widely positive effects of eCO2 on soil respiration even in infertile systems.

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