Regional Sustainability >

2026 , Vol. 7 >Issue 2: 100328

DOI: https://doi.org/10.1016/j.regsus.2026.100328

Research article

Nonlinear carbon-water coupling in terrestrial ecosystems: Insights from China’s Three-North Shelterbelt Forest region

  • CHEN Xuanhao ,
  • LI Chao ,
  • ZHANG Shiqiang
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  • aCollege of Urban and Environmental Science, Northwest University, Xi’an, 710127, China
    bSchool of Land Engineering, Shaanxi Key Laboratory of Land Consolidation, Chang’an University, Xi’an, 710054, China
* E-mail address: lichaomic@chd.edu.cn (LI Chao).

Received date: 2025-03-24

  Revised date: 2025-09-17

  Accepted date: 2026-01-28

  Online published: 2026-03-17

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Abstract

Understanding the coupling between carbon and water in terrestrial ecosystems is essential for achieving sustainable development. Net primary productivity (NPP), carbon use efficiency (CUE), and water use efficiency (WUE) are key indicators for assessing carbon balance and carbon-water interactions. However, knowledge gaps remain regarding how these indicators respond to climate change and interact with one another. This study examined the spatial and temporal dynamics of NPP, CUE, and WUE, as well as their interrelationships, within the Three-North Shelterbelt Forest region of China. Furthermore, the study investigated the driving mechanisms of these indicators using Extreme Gradient Boosting (XGBoost), SHapley Additive exPlanations (SHAP), and Partial Least Squares Structural Equation Modeling (PLS-SEM). The results revealed that from 2000 to 2020, both NPP (2.69 g C/(m2•a); P<0.010) and WUE (0.004 g C/(kg H2O•a); P<0.010) increased significantly, while CUE exhibited a non-significant decline (-5.40×10-4/a; P>0.050) across different climatic zones (arid, semi-arid, humid, and sub-humid) and vegetation types (cropland, forest, grassland, shrubland, and wetland). The correlation between WUE and NPP (correlation coefficient of 0.70) was stronger than that between CUE and NPP (correlation coefficient of 0.15). NPP and WUE were primarily influenced by leaf area index, whereas CUE was most strongly affected by elevation. The relationships between the key drivers and the three indicators were largely nonlinear, with stronger driver contributions corresponding to more pronounced nonlinear interactions. Moreover, these nonlinear relationships were modulated by differences in dry versus wet climatic conditions. Geographical factors (e.g., longitude, latitude, and elevation) further shaped vegetation characteristics (e.g., fractional vegetation cover and leaf area index) by regulating climatic variables such as temperature, precipitation, and evapotranspiration, ultimately influencing NPP, WUE, and CUE. This study advances the understanding of vegetation carbon-water coupling and provides a scientific basis for ecosystem management and sustainable development policy-making in various climatic zones.

Key words： Carbon use efficiency (CUE); Water use efficiency (WUE); Net primary productivity (NPP); Climate change; Machine learning method; Three-North Shelterbelt Forest

Cite this article

CHEN Xuanhao , LI Chao , ZHANG Shiqiang . Nonlinear carbon-water coupling in terrestrial ecosystems: Insights from China’s Three-North Shelterbelt Forest region[J]. Regional Sustainability, 2026 , 7(2) : 100328 . DOI: 10.1016/j.regsus.2026.100328

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