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<p>High-altitude treelines in western Himalaya are highly sensitive to climate variability and atmospheric circulations, which influences regional temperature and moisture. We measured leaf-level ecophysiological responses-gas exchange, photosynthetic pigments (chl<sub>a</sub>, chl<sub>b</sub>), chlorophyll fluorescence, photosynthetic rate (Pn), water use efficiency (WUE), vapor pressure deficit (VPD) between the co-occurring seedlings and trees in <i>Rhododendron campanulatum</i> D. Don and <i>Quercus semecarpifolia</i> Sm. growing at 3200–3450&#xa0;m a.s.l. (treeline). Also, ERA5 climate datasets were analysed to understand how these tree species adjust to physiological stresses at treeline. <i>Quercus semecarpifolia</i> showed higher chl<sub>a</sub>, chl<sub>b</sub> and chl<sub>a+b</sub> content, specific leaf area (SLA), WUEi, Amass and Fv/Fm. Also, Fv/Fm values remained close to optimal threshold (~ 0.80), indicating stable photosystem-II functioning, whereas lower values in <i>R. campanulatum</i> indicate greater susceptibility to photo-inhibition at treeline. <i>Rhododendron campanulatum</i> showed significantly higher VPD than <i>Q. semecarpifolia</i>, reflecting greater atmospheric dryness and evaporative demands. Principal component analysis (PCA) explained 37.2% and 26.9% variations in the first two components in ecophysiological traits respectively highlighting key functional attributes influencing treeline performance. Overall, <i>Q. semecarpifolia</i> demonstrates greater climate resilience at treeline due to its efficient water<b>-</b>use and stable photosynthetic function under variable climatic stress. Trait’s response to climate warming suggests likely treeline advance. Stress tolerant conservative species (<i>R. campanulatum</i>) may expand their distribution under warmer and drier conditions. However, acquisitive species (<i>Q. semecarpifolia</i>) may show reduced growth and recruitment, leading to species-specific and asymmetric treeline response under future climate change. These findings underscore adaptive strategies employed by high-altitude treeline species in response to climatic constraints.</p>

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Leaf ecophysiological responses to climate variabilities revealed its sensitivity and adaptive strategies of treeline ecotone species in the western Himalaya, India

  • 期刊论文

  • 发表日期：

    2026年7月19日

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  • Rajman Gupta,
  • Ambuj Mishra,
  • Rajendra Kr. Joshi,
  • Ramesh Kumar Yadav,
  • Satish Chandra Garkoti,
  • Shreyasi Upadhyay

摘要

High-altitude treelines in western Himalaya are highly sensitive to climate variability and atmospheric circulations, which influences regional temperature and moisture. We measured leaf-level ecophysiological responses-gas exchange, photosynthetic pigments (chla, chlb), chlorophyll fluorescence, photosynthetic rate (Pn), water use efficiency (WUE), vapor pressure deficit (VPD) between the co-occurring seedlings and trees in Rhododendron campanulatum D. Don and Quercus semecarpifolia Sm. growing at 3200–3450 m a.s.l. (treeline). Also, ERA5 climate datasets were analysed to understand how these tree species adjust to physiological stresses at treeline. Quercus semecarpifolia showed higher chla, chlb and chla+b content, specific leaf area (SLA), WUEi, Amass and Fv/Fm. Also, Fv/Fm values remained close to optimal threshold (~ 0.80), indicating stable photosystem-II functioning, whereas lower values in R. campanulatum indicate greater susceptibility to photo-inhibition at treeline. Rhododendron campanulatum showed significantly higher VPD than Q. semecarpifolia, reflecting greater atmospheric dryness and evaporative demands. Principal component analysis (PCA) explained 37.2% and 26.9% variations in the first two components in ecophysiological traits respectively highlighting key functional attributes influencing treeline performance. Overall, Q. semecarpifolia demonstrates greater climate resilience at treeline due to its efficient water-use and stable photosynthetic function under variable climatic stress. Trait’s response to climate warming suggests likely treeline advance. Stress tolerant conservative species (R. campanulatum) may expand their distribution under warmer and drier conditions. However, acquisitive species (Q. semecarpifolia) may show reduced growth and recruitment, leading to species-specific and asymmetric treeline response under future climate change. These findings underscore adaptive strategies employed by high-altitude treeline species in response to climatic constraints.