Silicon Effects on Biomass Carbon and Phytolith-Occluded Carbon in Grasslands Under High-Salinity Conditions

Linan Liu; Zhaoliang Song; Changxun Yu; Guanghui Yu; Rob M Ellam; Hongyan Liu; Bhupinder Pal Singh; Hailong Wang

doi:10.3389/fpls.2020.00657

Silicon Effects on Biomass Carbon and Phytolith-Occluded Carbon in Grasslands Under High-Salinity Conditions

Front Plant Sci. 2020 May 26:11:657. doi: 10.3389/fpls.2020.00657. eCollection 2020.

Authors

Linan Liu^{1

2}, Zhaoliang Song², Changxun Yu³, Guanghui Yu², Rob M Ellam^{2

4}, Hongyan Liu⁵, Bhupinder Pal Singh^{6

7}, Hailong Wang^{8

9}

Affiliations

¹ School of Environmental Science and Engineering, Tianjin University, Tianjin, China.
² Institute of Surface-Earth System Science, Tianjin University, Tianjin, China.
³ Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden.
⁴ Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom.
⁵ College of Urban and Environmental Sciences, Peking University, Beijing, China.
⁶ School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
⁷ NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW, Australia.
⁸ School of Environmental and Chemical Engineering, Foshan University, Foshan, China.
⁹ Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University, Hangzhou, China.

Abstract

Changes in climate and land use are causing grasslands to suffer increasingly from abiotic stresses, including soil salinization. Silicon (Si) amendment has been frequently proposed to improve plant resistance to multiple biotic and abiotic stresses and increase ecosystem productivity while controlling the biogeochemical carbon (C) cycle. However, the effects of Si on plant C distribution and accumulation in salt-suffering grasslands are still unclear. In this study, we investigated how salt ions affected major elemental composition in plants and whether Si enhanced biomass C accumulation in grassland species in situ. In samples from the margins of salt lakes, our results showed that the differing distance away from the shore resulted in distinctive phytocoenosis, including halophytes and moderately salt-tolerant grasses, which are closely related to changing soil properties. Different salinity (Na⁺/K⁺, ranging from 0.02 to 11.8) in plants caused negative effects on plant C content that decreased from 53.9 to 29.2% with the increase in salinity. Plant Si storage [0.02-2.29 g Si m^-2 dry weight (dw)] and plant Si content (0.53 to 2.58%) were positively correlated with bioavailable Si in soils (ranging from 94.4 to 192 mg kg^-1). Although C contents in plants and phytoliths were negatively correlated with plant Si content, biomass C accumulation (1.90-83.5 g C m^-2 dw) increased due to the increase of Si storage in plants. Plant phytolith-occluded carbon (PhytOC) increased from 0.07 to 0.28‰ of dry mass with the increase of Si content in moderately salt-tolerant grasses. This study demonstrates the potential of Si in mediating plant salinity and C assimilation, providing a reference for potential manipulation of long-term C sequestration via PhytOC production and biomass C accumulation in Si-accumulator dominated grasslands.

Keywords: carbon cycle; grassland species; phytolith-occluded carbon; salinity stress; silicon cycle.