Preprints
https://doi.org/10.5194/egusphere-2024-332
https://doi.org/10.5194/egusphere-2024-332
20 Feb 2024
 | 20 Feb 2024

Root zone in the Earth system

Hongkai Gao, Markus Hrachowitz, Lan Wang-Erlandsson, Fabrizio Fenicia, Qiaojuan Xi, Jianyang Xia, Wei Shao, Ge Sun, and Hubert Savenije

Abstract. The concept of “root zone” is widely used in hydrology, agronomy, and land surface process studies. However, the root zone still lacks a precise definition. More essentially, the importance of root zone in the Earth system science is largely under explored. Furthermore, the methodology to estimate root zone is still controversial. In this study, we firstly attempted to clarify the definition of the root zone by comparing with various “similar” terms, such as rooting depth, soil depth, vadose zone, rhizosphere, and critical zone, to bridge the gaps within and between traditional disciplinary boundaries. Secondly, we found that, from a hydrological and thus water-centric perspective, the root zone holds profound implications across all the spheres of the Earth system, including biosphere (living organisms), hydrosphere (water), pedosphere (soil), lithosphere (rock), and atmosphere (air), through various exchange fluxes of mass and energy. The role of the root zone in the Anthropocene is elaborated as well, including the intensifying impacts of climate change and agriculture, along with implications for nature-based solutions and planetary stewardship. Thirdly, for root zone estimation, we underscore that the theoretical foundation of the traditional reductionist approach to understand and model the root zone is problematic due to the complex and dynamic nature of root zone functions. We advocate for a shift towards a holistic ecosystem-centered perspective, which offers a more realistic, simplified, and dynamic representation of the root zone in Earth system science.

Hongkai Gao, Markus Hrachowitz, Lan Wang-Erlandsson, Fabrizio Fenicia, Qiaojuan Xi, Jianyang Xia, Wei Shao, Ge Sun, and Hubert Savenije

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-332', Anonymous Referee #1, 21 Mar 2024
    • AC1: 'Reply on RC1', Hongkai Gao, 17 Apr 2024
  • RC2: 'Comment on egusphere-2024-332', Anonymous Referee #2, 26 Mar 2024
  • CC1: 'Comment on egusphere-2024-332', H. Jochen Schenk, 28 Mar 2024
    • AC2: 'Reply on CC1', Hongkai Gao, 17 Apr 2024
  • RC3: 'Comment on egusphere-2024-332', Anonymous Referee #3, 01 Apr 2024
  • RC4: 'Comment on egusphere-2024-332', Anonymous Referee #4, 07 Apr 2024
Hongkai Gao, Markus Hrachowitz, Lan Wang-Erlandsson, Fabrizio Fenicia, Qiaojuan Xi, Jianyang Xia, Wei Shao, Ge Sun, and Hubert Savenije
Hongkai Gao, Markus Hrachowitz, Lan Wang-Erlandsson, Fabrizio Fenicia, Qiaojuan Xi, Jianyang Xia, Wei Shao, Ge Sun, and Hubert Savenije

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Short summary
The concept of root zone is widely used, but still lacks a precise definition. Moreover, its importance in Earth system science is not well elaborated. Here, we clarified its definition with several similar terms, to bridge the multi-disciplinary gap. We underscore the key role of root zone in Earth system, which links biosphere, hydrosphere, lithosphere, atmosphere, and anthroposphere. To better represent root zone, we advocate a paradigm shift towards ecosystem-centered modelling.