Proutsos et al. (2025) Impact of hydrometeorological factors and extreme events on black pine forests growth in the Mediterranean

Identification

• Journal: Acta Geophysica
• Year: 2025
• Date: 2025-12-16
• Authors: Nikolaos Proutsos, Dimitris Tigkas, Stefanos Stefanidis
• DOI: 10.1007/s11600-025-01747-7

Research Groups

• Institute of Mediterranean Forest Ecosystems, Hellenic Agricultural Organization - DIMITRA, Athens, Greece
• Centre for the Assessment of Natural Hazards and Proactive Planning & Laboratory of Reclamation Works and Water Resources Management, National Technical University of Athens, Athens, Greece
• Institute of Forest Research, Hellenic Agricultural Organization - DIMITRA, Thessaloniki, Greece

Short Summary

This study investigates the impact of hydrometeorological factors and extreme events on black pine (Pinus nigra) growth across 38 sites in the Mediterranean basin. It reveals that while warmer winters and summer precipitation positively influence growth, summer heat, high potential evapotranspiration, and droughts significantly limit it, with distinct regional differences between the Western and Eastern Mediterranean.

Objective

• To investigate the critical interactions between various hydrometeorological factors and the annual growth of black pine forests along the Mediterranean, including the particular impact of extreme events such as droughts.
• To identify the most influential factors determining tree growth in different regions across the longitudinal expansion of the Mediterranean basin.

Study Configuration

• Spatial Scale: 38 Pinus nigra forest sites across the Mediterranean basin, categorized into Western Mediterranean (19 sites in Spain and France) and Eastern Mediterranean (19 sites in Italy, Greece, Turkey, and Cyprus).
• Temporal Scale: Monthly gridded meteorological data from January 1901 to December 2018. Tree ring chronologies cover varying periods, with the analysis focusing on the common period with meteorological data.

Methodology and Data

• Models used: DrinC software for drought index calculation, Pearson's correlation coefficients for assessing growth response.
• Data sources:
  • Annual tree growth data: Tree ring composited Arstan chronologies (Standardized Growth Index, TRSGI) from 38 sites, obtained from the NOAA database.
  • Meteorological data: Monthly gridded data from the Climatic Research Unit Time-Series (CRU TS) dataset (Harris et al. 2020).
  • Climatic attributes: Mean, maximum, and minimum air temperatures (T mean, T max, T min), diurnal temperature range (DTR), frost day frequency (FRO), potential evapotranspiration (PET), precipitation (Prec.), vapor pressure (VP), wet day frequency (WET), and cloud cover (CC).
  • Drought indices: Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI), Agricultural Standardized Precipitation Index (aSPI), and Effective Reconnaissance Drought Index (eRDI).

Main Results

• Overall Mediterranean:
  • Positive correlations: Increased winter and early spring temperatures (T mean, T max, T min), summer precipitation (June-August, affecting up to 84% of sites), high precipitation to potential evapotranspiration (P/PET) ratio (June-July, 87% of sites), and wet day frequency (May-August, 71% of sites).
  • Negative correlations: Increased summer temperatures (June-July T max affecting 53% of sites), high potential evapotranspiration (PET) in summer (June-July, 74% of sites), and high frequency of frost days in late winter to early spring (February-April, 61% of sites).
  • Drought impact: Summer droughts (June-July) significantly limit tree growth, with all four drought indices showing strong positive correlations with annual growth in 87% of sites. Agriculturally adjusted indices (aSPI, eRDI) were more sensitive.
• Regional Differences:
  • Western Mediterranean (WM): Black pines show a stronger positive response to increasing winter and early spring temperatures and February vapor pressure. They are more negatively affected by late winter to early spring frosts (February-March FRO, 84% of sites), October temperatures, and June diurnal temperature range (DTR, 68% of sites). Summer droughts in July are highly impactful.
  • Eastern Mediterranean (EM): Black pines exhibit a stronger positive response to late spring to early autumn precipitation, P/PET ratio, and cloud cover (April-August, 74% of sites). They are more sensitive to summer heat (June-August T max, 58% of sites), summer PET (May-September, 84% of sites), and earlier onset of drought stress (May dryness, identified by aSPI).

Contributions

• Provides a comprehensive, basin-wide assessment of Pinus nigra growth responses to a wide range of hydrometeorological factors and extreme events, including novel insights into longitudinal variability.
• Highlights the critical importance of water-related factors (precipitation, PET, P/PET ratio, drought indices) during the summer growing season for black pine growth in the Mediterranean.
• Demonstrates the enhanced sensitivity of agriculturally adjusted drought indices (aSPI, eRDI) in detecting drought impacts on forest ecosystems.
• Offers region-specific findings that can inform tailored forest management strategies (e.g., selective thinning, water retention) to enhance the resilience of black pine forests to climate change.

Funding

No funding was received for conducting this study.

Citation

@article{Proutsos2025Impact,
  author = {Proutsos, Nikolaos and Tigkas, Dimitris and Stefanidis, Stefanos},
  title = {Impact of hydrometeorological factors and extreme events on black pine forests growth in the Mediterranean},
  journal = {Acta Geophysica},
  year = {2025},
  doi = {10.1007/s11600-025-01747-7},
  url = {https://doi.org/10.1007/s11600-025-01747-7}
}