Wang et al. (2025) Discriminating the impact of soil moisture and vapor pressure deficit on vegetation greening over multiple time scales

Identification

• Journal: Global and Planetary Change
• Year: 2025
• Date: 2025-10-10
• Authors: Zijun Wang, Rong Wu, Jiazheng Li, Yangyang Liu, Chenfeng Cui, Junrong Liu
• DOI: 10.1016/j.gloplacha.2025.105111

Research Groups

• College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi, China
• Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas of Ministry of Education, Northwest A&F University, Yangling, Shaanxi, China
• Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, China
• College of Grassland Agriculture, Northwest A&F University, Yangling, Shaanxi, China
• China Coal Aerial Survey and Remote Sensing Group Co., Ltd, Xi’an, Shaanxi, China

Short Summary

This study investigated the latent time scales and nonlinear characteristics of global vegetation greening from 1982 to 2020, examining the sensitivity and response mechanisms of Leaf Area Index (LAI) to soil moisture (SM), vapor pressure deficit (VPD), and their interactions across multiple time scales. The findings indicate that LAI and its multi-temporal components are more sensitive to SM than to VPD or their interaction, with these influences exhibiting scale dependence.

Objective

• To investigate the latent time scales and nonlinear characteristics of global vegetation greening from 1982 to 2020, and to examine the sensitivity and response mechanisms of Leaf Area Index (LAI) to soil moisture (SM), vapor pressure deficit (VPD), and their interactions (SM × VPD) across multiple time scales.

Study Configuration

• Spatial Scale: Global
• Temporal Scale: 1982 to 2020 (39 years), analyzed across multiple intrinsic time scales (interannual, interdecadal, and long-term trend).

Methodology and Data

• Models used: Ensemble Empirical Mode Decomposition (EEMD), Structural equation modeling.
• Data sources: Leaf Area Index (LAI), Soil Moisture (SM), and Vapor Pressure Deficit (VPD) data from 1982 to 2020.

Main Results

• LAI was decomposed into four intrinsic mode functions (IMFs) and a Residual trend, capturing interannual fluctuations (IMF1, IMF2), interdecadal variations (IMF3, IMF4), and a long-term greening trend (Residual).
• IMF1 (35 %) and the Residual (33 %) accounted for the largest variance contributions, dominating 49.0 % and 40.8 % of vegetated areas, respectively.
• LAI exhibited nonlinear and nonstationary characteristics, with 8.5 % of vegetated regions showing a significant ‘greening to browning’ transition and 31.5 % undergoing a significant ‘browning to greening’ transition, mostly before 2002.
• LAI and its multi-temporal components (LAImt) were more sensitive to soil moisture (SM) than to vapor pressure deficit (VPD) or their interaction (SM × VPD).
• The influences of SM, VPD, and SM × VPD on LAImt exhibited scale dependence, with strong effects on interannual fluctuations but weaker effects on interdecadal variations and long-term trends.
• The study analyzed the sensitivity of LAImt to SM, VPD, and SM × VPD across different vegetation types and aridity gradients.
• Structural equation modeling elucidated distinct mechanisms by which water stress factors influence LAImt.

Contributions

• Provides valuable insights into the role of soil and atmospheric water constraints in regulating vegetation greenness through a comprehensive multi-temporal scale analysis.
• Addresses the gap in understanding the relationships between vegetation dynamics and water stress factors (SM, VPD, SM × VPD) across multiple, latent time scales using EEMD.
• Reveals the nonlinear and nonstationary characteristics of global greening trends over the past four decades.
• Quantifies the scale-dependent influences of SM, VPD, and their interaction on LAI, highlighting their varying importance across different temporal scales.

Funding

Not specified in the provided text.

Citation

@article{Wang2025Discriminating,
  author = {Wang, Zijun and Wu, Rong and Li, Jiazheng and Liu, Yangyang and Cui, Chenfeng and Liu, Junrong},
  title = {Discriminating the impact of soil moisture and vapor pressure deficit on vegetation greening over multiple time scales},
  journal = {Global and Planetary Change},
  year = {2025},
  doi = {10.1016/j.gloplacha.2025.105111},
  url = {https://doi.org/10.1016/j.gloplacha.2025.105111}
}