Pepelnik et al. (2026) Isotopic Composition of Precipitation and Its Role in Forest Hydrology Under Climate Change: Insights from Slovenian Lowland Forests

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Identification

• Journal: Water
• Year: 2026
• Date: 2026-03-23
• Authors: Katja Koren Pepelnik, Mitja Janža, Matjaž Čater, Barbara Čenčur Curk, Polona Vreča
• DOI: 10.3390/w18060760

Research Groups

Not explicitly stated, but research was conducted in two Slovenian lowland forests: Murska šuma and Krakovski gozd.

Short Summary

This study systematically analyzed 65 years of air temperature and precipitation changes in two Slovenian lowland forests, combining it with throughfall isotopic composition. It found that rising temperatures and altered precipitation patterns are reflected in throughfall isotopes, confirming extreme events and aiding in estimating groundwater residence time and tree water origin.

Objective

• To conduct the first systematic analysis of air temperature and precipitation changes over the past 65 years in two Slovenian lowland forests (Murska šuma and Krakovski gozd), in combination with isotopic composition research of throughfall (δ18O, δ2H).

Study Configuration

• Spatial Scale: Two Slovenian lowland forests: Murska šuma and Krakovski gozd.
• Temporal Scale: 65 years (long-term climate analysis), with specific focus on the last 35 years for precipitation patterns, and extreme events in 2022 (drought) and 2023 (flood).

Methodology and Data

• Models used: Standardized Precipitation Index (SPI), Local Meteoric Water Lines (LMWL).
• Data sources: Monitoring of stable isotopes in throughfall (δ18O, δ2H) and meteorological parameters (air temperature, precipitation).

Main Results

• Air temperature increased by approximately 2.5 °C over the last 65 years.
• Total annual precipitation amounts remained relatively stable, but the last 35 years show a notable decrease in growing season precipitation and an increase during the dormant season, influenced by air masses of Mediterranean origin.
• Extreme drought in 2022 and flood in 2023 were confirmed by the Standardized Precipitation Index and isotopic variations in throughfall due to fractionation processes.
• Annual variability in throughfall isotopes appears as seasonal changes, with sine-curve amplitudes of 3.71‰ in Krakovski gozd and 3.61‰ in Murska šuma.
• These patterns, together with Local Meteoric Water Lines, support estimates of groundwater mean residence time and the origin of water used by trees.

Contributions

• Presents the first systematic, long-term (65 years) analysis of air temperature and precipitation changes in specific Slovenian lowland forests combined with throughfall isotopic composition.
• Demonstrates how long-term climate shifts and extreme events (droughts, floods) are reflected in the isotopic composition of throughfall.
• Utilizes isotopic data and Local Meteoric Water Lines to support estimations of groundwater mean residence time and the origin of water utilized by trees.

Funding

Not explicitly stated in the provided text.

Citation

@article{Pepelnik2026Isotopic,
  author = {Pepelnik, Katja Koren and Janža, Mitja and Čater, Matjaž and Curk, Barbara Čenčur and Vreča, Polona},
  title = {Isotopic Composition of Precipitation and Its Role in Forest Hydrology Under Climate Change: Insights from Slovenian Lowland Forests},
  journal = {Water},
  year = {2026},
  doi = {10.3390/w18060760},
  url = {https://doi.org/10.3390/w18060760}
}