Dominant plants drive soil organic carbon storage in three gorges reservoir’s water-level fluctuation zone - Research Open Access

Sep 30, 2026

The water level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) is a distinctive ecotone whose reversed hydrological rhythms shape plant behavior and soil organic carbon (SOC) processes. Yet, the plant contribution to SOC storage after stable plant communities establish remains unclear. A 2023 field survey and soil sampling in the WLFZ assessed plant composition, diversity, soil and vegetation carbon/nitrogen contents, and stable carbon isotope ratios across mainstream and tributary areas at two elevation bands (155–165 m and 165–175 m). Results show elevation-associated increases in diversity, elevation-dependent SOC storage contrasts between regions, and SOC controls dominated by soil total nitrogen and C/N ratio.

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Abstract

Introduction

Liu et al. Carbon Balance and Management (2026) 21:4 [https://doi.org/10.1186/s13021-025-00351-y](https://doi.org/10.1186/s13021-025-00351-y) Carbon Balance and Management RESEARCH Open Access Dominant plants drive soil organic carbon storage in three gorges reservoir’s water-level fluctuation zone Xianglong Liu 1,2, Qiuhong Li3, Peng Xu4, Desheng Hong 1,2, Bin Yang 1,2, Hongyang Dong5, Xiaoguo Wang 1* and Bo Zhu 1 Abstract The water level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) represents a unique ecotone shaped by reversed hydrological rhythms that significantly influence plant dynamics and soil organic carbon (SOC) processes. However, the contribution of plants to SOC storage after the establishment of stable plant communities remains unclear. A field investigation and soil sampling were conducted in the WLFZ of the TGR in 2023, covering both the main stream and tributary regions in middle- (155–165 m) and high-elevation (165–175 m) zones. The plant composition, diversity, and carbon and nitrogen contents of soil and vegetation and the carbon stable isotope ratio signatures were analyzed. Results showed that plant diversity increased with elevation, while biomass allocation varied significantly between elevation zones. Cynodon dactylon (L.) Pers. had a significantly higher biomass than Xanthium strumarium L., both of which were identified as dominant species in the WLFZ based on their high importance values. The response of SOC storage to elevation differed between regions: in the mainstream, SOC storage was 23% higher in the middle-elevation than in the high-elevation zone, while in the tributary, SOC storage in the high-elevation zone exceeding that in the middle-elevation zone by 38% . Soil total nitrogen and the C/N ratio were the primary factors controlling SOC storage, explaining 68. 6% of the variance, while plant effects were relatively weak. Isotopic mixing model results indicated that X. strumarium contributed 34. 84% to SOC storage at 165–175m, whereas C. dactylon contributed 21. 06% at 155–165 m, but this difference occurred within the context of a minor overall plant contribution to SOC. These results highlight that SOC dynamics are primarily controlled by soil factors (soil nitrogen and the C/N ratio), with plants having a secondary effect. Keywords Water level fluctuation zone, Three gorges reservoir, Plant composition, Soil organic carbon, Stable carbon isotopes *Correspondence: Xiaoguo Wang [xgwang@imde.ac.cn](xgwang@imde.ac.cn) 1Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China 2University of Chinese Academy of Sciences, Beijing 100049, China 3PowerChina Chengdu Engineering Corporation Limited, Chengdu 611130, China 4Yangtze University, Jingzhou , Hubei 434023, China 5Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

FAQs

What makes the Three Gorges Reservoir water level fluctuation zone (WLFZ) ecologically distinct?

It is a unique ecotone formed by reversed hydrological rhythms that strongly influence plant dynamics and soil organic carbon (SOC) processes through frequent material and energy exchanges.

How were plants and SOC evaluated in the 2023 field investigation?

Plant composition and diversity were measured, and soil and vegetation carbon and nitrogen contents were analyzed alongside stable carbon isotope ratio signatures across elevation bands in mainstream and tributary regions.

What primarily controls SOC storage in the WLFZ according to the study findings?

Soil factors—especially soil total nitrogen and the C/N ratio—are the primary controls, explaining most of the SOC storage variance, while plant effects are comparatively weaker.

Sep 30, 2026

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