Effects of nitrogen loading on emission of carbon gases from estuarine tidal marshes with varying salinity

Minjie Hu; Josep Peñuelas; Jordi Sardans; Jiafang Huang; Dongdong Li; Chuan Tong

doi:10.1016/j.scitotenv.2019.02.429

Effects of nitrogen loading on emission of carbon gases from estuarine tidal marshes with varying salinity

Sci Total Environ. 2019 Jun 1:667:648-657. doi: 10.1016/j.scitotenv.2019.02.429. Epub 2019 Feb 28.

Authors

Minjie Hu¹, Josep Peñuelas², Jordi Sardans², Jiafang Huang³, Dongdong Li³, Chuan Tong⁴

Affiliations

¹ Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, China. Electronic address: mjhu@xmu.edu.cn.
² CSIC, Global Ecology CREAF-CSIC-UAB, Bellaterra, 08193 Barcelona, Catalonia, Spain; CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain.
³ Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China.
⁴ Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China. Electronic address: tongch@fjnu.edu.cn.

PMID: 30833263
DOI: 10.1016/j.scitotenv.2019.02.429

Abstract

Estuarine tidal marshes sequester significant quantities of carbon and are suffering from anthropogenic nitrogen (N) enhancement. However, the effects of this N loading on carbon gas emissions from freshwater-oligohaline tidal marshes are unknown. In this paper, we report on our evaluation of the effects of a N gradient (0, 24, 48 and 96 g NH₄NO₃-N m^-2 y^-1) on the methane (CH₄) and carbon dioxide (CO₂) emissions from freshwater and oligohaline tidal marshes in the Min River estuary, southeast China. On an annual scale, the oligohaline marsh has significantly higher CO₂ emissions, while it has slightly lower CH₄ emissions relative to freshwater marsh. The addition of N increased CH₄ emission from the freshwater marsh and decreased CH₄ emission from the oligohaline marsh, although there was no statistically significant difference in CH₄ emission between either of the two marshes and the control. The addition of 96 g NH₄NO₃-N m^-2 y^-1 significantly increased CO₂ emission from the freshwater marsh, while it did not significantly influence CO₂ emission from the oligohaline marsh. CH₄ and CO₂ emission levels were positively correlated with soil temperature under all conditions. The CH₄ flux resulting from both the control and the addition of N was negatively correlated with porewater SO₄^2- and Cl^- concentrations and soil EC in the oligohaline marsh. Overall, N addition significantly increased carbon gas emissions under freshwater conditions while slightly inhibiting carbon gas emissions from the oligohaline marsh. Our findings suggested that even under low salinity conditions, the effects of N loading on CH₄ and CO₂ emissions from freshwater and oligohaline tidal marshes can vary. We propose that the addition of N to estuarine tidal marshes has a significant effect on the carbon cycle and promotes soil carbon loss, phenomena which may be influenced by salinity.

Keywords: Carbon cycling; Estuarine tidal marsh; Flux; Greenhouse gases; Nitrogen addition; Saltwater intrusion.