Wang et al. (2025) Root zone storage capacity reveals ecohydrological turning points in Tibetan Plateau permafrost regions

Identification

• Journal: CATENA
• Year: 2025
• Date: 2025-12-04
• Authors: Yahui Wang, Hongkai Gao, Huijun Jin, Qiaojuan Xi, Peng Wang, Deliang Chen
• DOI: 10.1016/j.catena.2025.109716

Research Groups

• State Key Laboratory of Estuarine and Coastal Research, Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, China
• School of Ecology, China-Russia Joint Laboratory of Cold Regions Engineering and Environment, and Permafrost Institute, Northeast Forestry University, Harbin, China
• College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
• Department of Earth System Science, Tsinghua University, Beijing, China

Short Summary

This study estimates root zone storage capacity (SR) across the Tibetan Plateau using an observation-based water balance approach, revealing its spatial heterogeneity and identifying a critical ecohydrological turning point in permafrost regions linked to active layer thickness. The findings highlight how permafrost degradation restricts vegetation water access, providing a quantitative basis for assessing ecosystem vulnerability.

Objective

• To estimate root zone storage capacity (SR) across the Tibetan Plateau, defined as the maximum ecosystem-accessible water volume for plant use during drought periods, and to understand its spatial patterns and controlling factors.
• To identify ecohydrological turning points related to permafrost degradation and their implications for vegetation water use and ecosystem vulnerability under climate warming.

Study Configuration

• Spatial Scale: Tibetan Plateau (TP), focusing on permafrost and seasonal-frost regions.
• Temporal Scale: Analysis of spatial patterns of root zone storage capacity in the context of ongoing climate warming and permafrost degradation since the 1980s.

Methodology and Data

• Models used: Observation-based water balance approach.
• Data sources: Observation-based data, including original root zone storage capacity data for the Tibetan Plateau.

Main Results

• Root zone storage capacity (SR) across the Tibetan Plateau shows considerable heterogeneity, ranging from 24 mm to 278 mm (1st–99th percentiles), with a mean of 93 ± 12 mm.
• Permafrost regions exhibit significantly lower SR (67 ± 6 mm) compared to seasonal-frost regions (110 ± 15 mm).
• An ecohydrological turning point was identified at an active layer thickness (ALT) of 2.2–2.5 m, beyond which SR shifts from increasing to decreasing trends. This was determined using segmented regression combined with Davies’ supremum test.
• This transition coincides with marked declines in the evaporation ratio, Budyko-Fu’s ω parameter, and measured belowground phytomass, indicating restricted access of roots to supra-permafrost water.

Contributions

• Provides the first observation-based estimates of root zone storage capacity across the Tibetan Plateau, addressing the scarcity of direct observations in high-altitude permafrost environments.
• Identifies a critical ecohydrological turning point (ALT of 2.2–2.5 m) that quantitatively links permafrost degradation to vegetation water use.
• Offers a quantitative basis for understanding and predicting the coupled ecohydrological vulnerability of alpine/high-plateau ecosystems under ongoing climatic warming.

Funding

• Not specified in the provided text.

Citation

@article{Wang2025Root,
  author = {Wang, Yahui and Gao, Hongkai and Jin, Huijun and Xi, Qiaojuan and Wang, Peng and Chen, Deliang},
  title = {Root zone storage capacity reveals ecohydrological turning points in Tibetan Plateau permafrost regions},
  journal = {CATENA},
  year = {2025},
  doi = {10.1016/j.catena.2025.109716},
  url = {https://doi.org/10.1016/j.catena.2025.109716}
}