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<p>The subtropical–temperate habitats of the Himalayas form a transition between lowland subtropical forests and mid-elevation temperate zones. These areas are both highly diverse and heavily impacted by human disturbance. Lichens, symbiotic organisms of fungi and algae, serve as established bioindicators of heavy metal pollution. Although lichen-based studies on metal pollution exist in the Himalayas, subtropical–temperate zones remain underexplored. This study examines the biomonitoring potential of Physcioid lichens at two contrasting sites in Champawat, India: a reserve forest (PRF) and a highway-exposed location (ETC). The study assessed interspecific and site-level variability in heavy metal accumulation by physcioid lichens and its relation to land use. Epiphytic lichens were collected from tree trunks and analysed for metal concentrations using atomic absorption spectrophotometry (AAS). Heavy metal data were analysed using one-way ANOVA, Welch’s t-test, Pearson correlations, and principal component analysis (PCA). Visualisations included species-level boxplots and PCA biplots generated using R and Python. Five Physcioid lichens were recorded, with <i>Dirinaria applanata</i>, <i>D. consimilis</i>, and <i>Pyxine sorediata</i> common to both sites. Metal concentrations varied widely: iron (Fe) was most abundant, followed by aluminium (Al), magnesium (Mg), and zinc (Zn), while chromium (Cr) was below detection limits. Lichens at the highway site (ETC) accumulated nearly twice the total metal load compared to the reserve forest (PRF), likely due to vehicular emissions. Cumulative metal loads (ΣM<sub>10</sub>) were significantly higher in ETC lichens, with <i>D. consimilis</i> and <i>D. aegialita</i> showing particularly elevated Fe and Al levels. PCA showed that PC1 (78.9% variance) was driven by traffic-related metals (Fe, Al, Pb, Zn, Cu), clearly separating ETC from PRF samples. These results affirm that Physcioid lichens effectively capture both geogenic and anthropogenic pollution gradients and can serve as reliable tools for long-term ecological monitoring of Himalayan ecotones.</p>

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Physcioid lichens as indicators of spatial variation in heavy metal deposition in the subtropical-temperate habitat of the Himalayas

  • 期刊论文

  • 发表日期：

    2025年10月19日

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  • Pramod Nag,
  • Rajan Kumar Gupta,
  • Afroz Alam

摘要

The subtropical–temperate habitats of the Himalayas form a transition between lowland subtropical forests and mid-elevation temperate zones. These areas are both highly diverse and heavily impacted by human disturbance. Lichens, symbiotic organisms of fungi and algae, serve as established bioindicators of heavy metal pollution. Although lichen-based studies on metal pollution exist in the Himalayas, subtropical–temperate zones remain underexplored. This study examines the biomonitoring potential of Physcioid lichens at two contrasting sites in Champawat, India: a reserve forest (PRF) and a highway-exposed location (ETC). The study assessed interspecific and site-level variability in heavy metal accumulation by physcioid lichens and its relation to land use. Epiphytic lichens were collected from tree trunks and analysed for metal concentrations using atomic absorption spectrophotometry (AAS). Heavy metal data were analysed using one-way ANOVA, Welch’s t-test, Pearson correlations, and principal component analysis (PCA). Visualisations included species-level boxplots and PCA biplots generated using R and Python. Five Physcioid lichens were recorded, with Dirinaria applanata, D. consimilis, and Pyxine sorediata common to both sites. Metal concentrations varied widely: iron (Fe) was most abundant, followed by aluminium (Al), magnesium (Mg), and zinc (Zn), while chromium (Cr) was below detection limits. Lichens at the highway site (ETC) accumulated nearly twice the total metal load compared to the reserve forest (PRF), likely due to vehicular emissions. Cumulative metal loads (ΣM10) were significantly higher in ETC lichens, with D. consimilis and D. aegialita showing particularly elevated Fe and Al levels. PCA showed that PC1 (78.9% variance) was driven by traffic-related metals (Fe, Al, Pb, Zn, Cu), clearly separating ETC from PRF samples. These results affirm that Physcioid lichens effectively capture both geogenic and anthropogenic pollution gradients and can serve as reliable tools for long-term ecological monitoring of Himalayan ecotones.