Hayashi et al. (2025) Efficient Estimation of the Number of Water Retention Curves Required for Applying a Scaling Technique to the Forest Soil

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Identification

• Journal: Agronomy
• Year: 2025
• Date: 2025-12-29
• Authors: Yuki Hayashi, Ken’ichirou KOSUGI
• DOI: 10.3390/agronomy16010089

Research Groups

Not explicitly mentioned in the provided text.

Short Summary

This study aimed to determine the minimum number of water retention curves (WRCs) required to effectively estimate reference parameters for a scaling approach on forest slopes. It found that a scaling approach could explain 78% of WRC spatial variability using reference parameters derived from eight samples, with stratified sampling considering slope direction being the most advantageous.

Objective

• To estimate the minimum number of water retention curves (WRCs) required to effectively determine the reference parameters (effective porosity, $\thetae$; matric pressure head corresponding to the median pore radius, $\psim$; and width of the pore-size distribution, $\sigma$) for a scaling approach simplifying spatial variability in WRCs on forest slopes.

Study Configuration

• Spatial Scale: A 25 meter forest slope.
• Temporal Scale: Not explicitly mentioned for the study's duration; WRCs represent static soil properties.

Methodology and Data

• Models used: LN model (for water retention curve scaling approach), Monte Carlo simulation (for random sampling).
• Data sources: 77 measured water retention curves (WRCs) from core samples collected from the 25 m forest slope.

Main Results

• The effect of scaling (EOS) increased with sample size, with the increase becoming small at approximately 20 samples.
• 78% (EOS = 0.78) of the spatial variability in WRCs could be explained at the 95% confidence level using reference parameters derived from eight samples.
• Stratified sampling was performed to reduce the required number of WRCs, with the sampling scheme considering variability only in the slope direction proving most advantageous.
• The geomorphological process, which influences spatial variability in reference parameters on forested slopes, is an important factor for their effective determination.

Contributions

• Provides a quantitative assessment of the minimum sample size required for water retention curve (WRC) determination using a scaling approach on forest slopes.
• Identifies an optimal stratified sampling strategy, specifically considering slope direction, to efficiently determine WRC reference parameters.
• Demonstrates that a scaling approach significantly reduces the number of samples needed for WRC characterization, explaining a substantial portion of spatial variability with a limited number of samples.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Hayashi2025Efficient,
  author = {Hayashi, Yuki and KOSUGI, Ken’ichirou},
  title = {Efficient Estimation of the Number of Water Retention Curves Required for Applying a Scaling Technique to the Forest Soil},
  journal = {Agronomy},
  year = {2025},
  doi = {10.3390/agronomy16010089},
  url = {https://doi.org/10.3390/agronomy16010089}
}