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<p>Riparian zones, situated where land and water environments intersect, rank among the richest and most functionally significant ecosystems on the planet. Yet, despite their importance, they are experiencing escalating deterioration due to human-driven pressures, particularly in Mediterranean landscapes subjected to intense urban and agricultural activities. This research explores the plant composition, biodiversity dynamics, and ecological responses of riparian vegetation along the upper stretch of the Medjerda River in north-eastern Algeria, an area influenced by untreated effluents and agricultural runoff. Field surveys were conducted at ten locations using standardized quadrat sampling to record woody and shrubby taxa. Concurrently, soil samples and <i>Populus alba</i> L. leaf tissues were assessed for concentrations of iron (Fe), zinc (Zn), and copper (Cu). Multiple biodiversity indices were applied, and vegetation community structure was interpreted through the Diversity Evenness and Rarity (DER) algorithm, Principal Component Analysis (PCA), Non-Metric Multidimensional Scaling (NMDS), and Hierarchical Cluster Analysis (HCA). The survey documented 20 species from 11 botanical families, with <i>P. alba</i> L., <i>Tamarix</i> species, and <i>Nerium oleander</i> L. emerging as the most prevalent. Substantial spatial variation was detected: Sites 8 and 9 exhibited diverse and well-balanced plant communities, while Sites 5 and 7 supported species-poor groups dominated by tolerant taxa, signalling ecological decline. PCA results revealed strong inverse relationships between Zn and Cu levels and biodiversity indicators, highlighting the suppressive influence of heavy metals on riparian vegetation. NMDS and DER identified three distinct ecological assemblages—degraded, transitional, and relatively stable—distributed along a continuum of human disturbance. These outcomes reveal pronounced ecological variability and heightened susceptibility of Mediterranean riparian environments to pollution stress. The study emphasizes the necessity of safeguarding biodiversity-rich areas and restoring impacted zones through sustainable management strategies within peri-urban river systems.</p> Graphical Abstract <p>The graphical abstract provides a visual synthesis of the multiscale ecological assessment conducted along the upper Medjerda River in northeastern Algeria. It highlights the integration of biodiversity surveys, heavy-metal quantification, and multivariate analyses used to characterize riparian ecosystem responses to anthropogenic pressures. The sampling design shows the studied sites along an urban effluent discharge point, with the presence of agricultural pressure nearby. The analysis of heavy metals indicates an elevated presence of zinc (Zn) and copper (Cu), and to a lesser extent, iron (Fe), in the environment. The specific plant species highlighted for study is Populus alba L. (white poplar). The vegetation response observed across the sampling sites varied significantly, reflecting the environmental stress: (i) Impoverished and stressed Tamarix spp assemblages indicate areas subjected to severe environmental stress. (ii) Intermediate assemblages were found in sites 2, 3, 4, 6, and 10. (iii) Stable high-diversity refugia were identified in sites 8 and 9, suggesting areas that are less impacted or more resilient. This pattern is summarized by the sequence: Anthropogenic disturbance → Community simplification → Biodiversity loss.The statistical analyses presented (PCA, NMDS, DER) support the hypothesis that heavy metal contamination (Cu, Zn) and urban/agricultural pressures drive a strong ecological filtering process. This filtering reduces riparian biodiversity by eliminating sensitive species, and instead promotes stress-tolerant species.</p>

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Riparian Vegetation Under Anthropogenic Stress: A Multivariate Approach To Biodiversity Decline along the Medjerda River (Algeria)

  • 期刊论文

  • 发表日期：

    2026年4月24日

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  • Imen Benradia,
  • Noureddine Guezgouz,
  • Choukri Barour,
  • Lassaad Ghreib,
  • Marwan Ghanem,
  • Rubina Vangone,
  • Valeria Guerretti,
  • Costantino Parisi,
  • Pasquale Napoletano,
  • Anna De Marco

摘要

Riparian zones, situated where land and water environments intersect, rank among the richest and most functionally significant ecosystems on the planet. Yet, despite their importance, they are experiencing escalating deterioration due to human-driven pressures, particularly in Mediterranean landscapes subjected to intense urban and agricultural activities. This research explores the plant composition, biodiversity dynamics, and ecological responses of riparian vegetation along the upper stretch of the Medjerda River in north-eastern Algeria, an area influenced by untreated effluents and agricultural runoff. Field surveys were conducted at ten locations using standardized quadrat sampling to record woody and shrubby taxa. Concurrently, soil samples and Populus alba L. leaf tissues were assessed for concentrations of iron (Fe), zinc (Zn), and copper (Cu). Multiple biodiversity indices were applied, and vegetation community structure was interpreted through the Diversity Evenness and Rarity (DER) algorithm, Principal Component Analysis (PCA), Non-Metric Multidimensional Scaling (NMDS), and Hierarchical Cluster Analysis (HCA). The survey documented 20 species from 11 botanical families, with P. alba L., Tamarix species, and Nerium oleander L. emerging as the most prevalent. Substantial spatial variation was detected: Sites 8 and 9 exhibited diverse and well-balanced plant communities, while Sites 5 and 7 supported species-poor groups dominated by tolerant taxa, signalling ecological decline. PCA results revealed strong inverse relationships between Zn and Cu levels and biodiversity indicators, highlighting the suppressive influence of heavy metals on riparian vegetation. NMDS and DER identified three distinct ecological assemblages—degraded, transitional, and relatively stable—distributed along a continuum of human disturbance. These outcomes reveal pronounced ecological variability and heightened susceptibility of Mediterranean riparian environments to pollution stress. The study emphasizes the necessity of safeguarding biodiversity-rich areas and restoring impacted zones through sustainable management strategies within peri-urban river systems.

Graphical Abstract

The graphical abstract provides a visual synthesis of the multiscale ecological assessment conducted along the upper Medjerda River in northeastern Algeria. It highlights the integration of biodiversity surveys, heavy-metal quantification, and multivariate analyses used to characterize riparian ecosystem responses to anthropogenic pressures. The sampling design shows the studied sites along an urban effluent discharge point, with the presence of agricultural pressure nearby. The analysis of heavy metals indicates an elevated presence of zinc (Zn) and copper (Cu), and to a lesser extent, iron (Fe), in the environment. The specific plant species highlighted for study is Populus alba L. (white poplar). The vegetation response observed across the sampling sites varied significantly, reflecting the environmental stress: (i) Impoverished and stressed Tamarix spp assemblages indicate areas subjected to severe environmental stress. (ii) Intermediate assemblages were found in sites 2, 3, 4, 6, and 10. (iii) Stable high-diversity refugia were identified in sites 8 and 9, suggesting areas that are less impacted or more resilient. This pattern is summarized by the sequence: Anthropogenic disturbance → Community simplification → Biodiversity loss.The statistical analyses presented (PCA, NMDS, DER) support the hypothesis that heavy metal contamination (Cu, Zn) and urban/agricultural pressures drive a strong ecological filtering process. This filtering reduces riparian biodiversity by eliminating sensitive species, and instead promotes stress-tolerant species.