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<p>Cork oak woodlands (<i>Quercus suber</i> L.), known as montado, are multifunctional ecosystems in the western Mediterranean region providing critical ecosystem services. Climate change, particularly intensifying drought, poses a significant threat to these systems. This study analyzes long-term (1984–2015) interannual NDVI dynamics and their relationship with precipitation, temperature, and drought across two cork oak-dominated sites in Portugal using Landsat satellite data. Drought was assessed using the Standardized Precipitation-Evapotranspiration Index (SPEI) at 12- and 24-month timescales. Three vegetation functional types were defined: closed cork oak woodland, open cork oak woodland, and herbaceous vegetation. Mann–Kendall trend analysis assessed temporal NDVI trends, Kendall correlation quantified relationships between NDVI and climate variables, and ANOVA assessed differences among sites, vegetation functional types, and seasons. Results reveal a clear seasonal structure in NDVI across all vegetation functional types. Precipitation emerged as the dominant climatic driver of interannual NDVI variability, with significant associations during winter for herbaceous and open woodland vegetation, and during summer for closed cork oak woodland. Temperature and multi-month SPEI showed no significant relationships with NDVI. A contrasting climate sensitivity was observed between vegetation layers: herbaceous vegetation responds strongly to short-term precipitation variability, while cork oak maintains relatively stable greenness during summer drought, acting as a structural buffer for ecosystem resilience. These findings highlight the value of long-term remote sensing for monitoring vegetation responses to climate variability in Mediterranean woodlands and provide an empirical basis for environmental instruments such as Portugal’s PEPAC, which supports maintaining minimum cork oak cover thresholds in agroforestry systems.</p>

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NDVI seasonal trends and climate drivers in two Portuguese Cork Oak Woodland

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月20日

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  • Cristina Soares,
  • Sílvia Carvalho,
  • João Neves Silva,
  • Sofia Cerasoli

摘要

Cork oak woodlands (Quercus suber L.), known as montado, are multifunctional ecosystems in the western Mediterranean region providing critical ecosystem services. Climate change, particularly intensifying drought, poses a significant threat to these systems. This study analyzes long-term (1984–2015) interannual NDVI dynamics and their relationship with precipitation, temperature, and drought across two cork oak-dominated sites in Portugal using Landsat satellite data. Drought was assessed using the Standardized Precipitation-Evapotranspiration Index (SPEI) at 12- and 24-month timescales. Three vegetation functional types were defined: closed cork oak woodland, open cork oak woodland, and herbaceous vegetation. Mann–Kendall trend analysis assessed temporal NDVI trends, Kendall correlation quantified relationships between NDVI and climate variables, and ANOVA assessed differences among sites, vegetation functional types, and seasons. Results reveal a clear seasonal structure in NDVI across all vegetation functional types. Precipitation emerged as the dominant climatic driver of interannual NDVI variability, with significant associations during winter for herbaceous and open woodland vegetation, and during summer for closed cork oak woodland. Temperature and multi-month SPEI showed no significant relationships with NDVI. A contrasting climate sensitivity was observed between vegetation layers: herbaceous vegetation responds strongly to short-term precipitation variability, while cork oak maintains relatively stable greenness during summer drought, acting as a structural buffer for ecosystem resilience. These findings highlight the value of long-term remote sensing for monitoring vegetation responses to climate variability in Mediterranean woodlands and provide an empirical basis for environmental instruments such as Portugal’s PEPAC, which supports maintaining minimum cork oak cover thresholds in agroforestry systems.