Nutrient Dynamics and Growth Responses of Angelica glauca Edgew. to Elevated CO₂ and Temperature: A Three-Year Field Study

The present study aims to investigate the effect of elevated CO₂ (eCO₂) and increased temperature (eCO₂ + T) on the growth, biomass production and nutrient dynamics of a native alpine herb Angelica glauca. Open top chambers (OTCs) of 4.0 × 4.0 m (height×diameter) were established at 3400 m above sea level in Tungnath, India. Seed grown plants of A. glauca were treated with elevated CO₂ (eCO₂) and eCO₂ + temperature (eCO₂ + T) for three years, from 2018 to 2020, and compared to the plants grown in ambient conditions (control). Plant growth, biomass, macronutrients (nitrogen, phosphorus, and potassium) and organic carbon content from plants and soils were analyzed. Three years of CO₂ and temperature treatments showed decreased or slow growth in the eCO₂ and eCO₂ + T treatments. The plant morphology was either unaffected (in eCO₂) or inhibited (in eCO₂ + T). The biomass of both above and belowground parts, foliar and root N, as well as soil available N were all found decreased, whereas, the C: N ratio increased in CO₂ and temperature treatments. The variation in plant height and leaf area was significantly explained by soil available nitrogen, however, the variation in biomass production was significantly explained by the plant (leaf and root) nitrogen content. Elevated CO₂, a major driver as per IPCC, poses a 2°C temperature rise threat. Despite increased photosynthate from increased substrate availability, limiting nutrient concentrations hinder biomass translocation. Altered C:N ratios intensify nutrient dynamics, hindering plant productivity. The decline in growth and biomass may also result from an imbalance between increased respiration, photosynthesis, and water stress in a CO₂ enriched and warmer environment. Beyond A. glauca, this research offers insights into C3 alpine species’ responses to climate change, contributing to effective mitigation and adaptation plans for alpine ecosystems and their plants.