Indirect regulation of topsoil nutrient cycling by groundwater depth: impacts on sand-fixing vegetation and rhizosphere bacterial communities

Lianyi Hao; Xiuhua Liu; Ruiqing Ji; Yandong Ma; Puxia Wu; Qingxi Cao; Yunling Xin

doi:10.3389/fmicb.2023.1285922

Indirect regulation of topsoil nutrient cycling by groundwater depth: impacts on sand-fixing vegetation and rhizosphere bacterial communities

Front Microbiol. 2023 Dec 5:14:1285922. doi: 10.3389/fmicb.2023.1285922. eCollection 2023.

Authors

Lianyi Hao^{1

2

3}, Xiuhua Liu^{1

2

3}, Ruiqing Ji^{1

2

3}, Yandong Ma⁴, Puxia Wu⁴, Qingxi Cao⁴, Yunling Xin⁴

Affiliations

¹ School of Water and Environment, Chang'an University, Xi'an, China.
² Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an, China.
³ Key Laboratory of Eco-hydrology and Water Security in Arid and Semi-arid Region of Ministry of Water Resources, Chang'an University, Xi'an, China.
⁴ Key Laboratory of State Forest Administration on Soil and Water Conservation & Ecological Restoration of Loess Plateau, Shaanxi Academy of Forestry, Xi'an, China.

Abstract

Introduction: The impact of groundwater table depth (GTD) on bacterial communities and soil nutrition in revegetated areas remains unclear.

Methods: We investigated the impacts of plant growth and soil physicochemical factors on rhizosphere bacterial communities under different GTD.

Results: The four plant growth indices (Pielou, Margalef, Simpson, and Shannon-Wiener indices) and soil water content (SWC) at the Artem and Salix sites all showed a decreasing trend with increasing GTD. Salix had a higher nutrient content than Artem. The response of plant rhizosphere bacterial communities to GTD changes were as follows. Rhizosphere bacteria at the Artem and Salix sites exhibited higher relative abundance and alpha diversity in SW (GTD < 5 m) compared than in DW (GTD > 5 m). Functional microbial predictions indicated that the rhizosphere bacterial communities of Artem and Salix promoted carbon metabolism in the SW. In contrast, Artem facilitated nitrogen cycling, whereas Salix enhanced both nitrogen cycling and phototrophic metabolism in the DW.

Discussion: Mantel test analysis revealed that in the SW of Artem sites, SWC primarily governed the diversity of rhizosphere and functional bacteria involved in the nitrogen cycle by affecting plant growth. In DW, functional bacteria increase soil organic carbon (SOC) to meet nutrient demands. However, higher carbon and nitrogen availability in the rhizosphere soil was observed in the SW of the Salix sites, whereas in DW, carbon nutrient availability correlated with keystone bacteria, and changes in nitrogen content could be attributed to nitrogen mineralization. This indicates that fluctuations in the groundwater table play a role in regulating microbes and the distribution of soil carbon and nitrogen nutrients in arid environments.

Keywords: groundwater table depth; plant diversity; rhizosphere functional bacteria; sand-fixing plant; soil nutrient.

Grants and funding

The author (s) declare financial support was received for the research, authorship, and/or publication of this article. This study was financially supported by grants from the National Natural Science Foundation of China (42372288, 41877179, and 42001033), the Central University Special Fund (300102292904), the Natural Science Basic Research Program of Shaanxi (2023-JC-YB-280), the Shaanxi Forest Science and Technology Innovation Team (SXLK2023-0301), and the Central Fiscal Forestry Science and Technology Extension Project (SLTG202303). The Forestry Science and Technology Innovation Project of Shaanxi Province (SXLK2022-06-3).