Abstract
Aims
Vegetation in high-altitude regions is hypothesized to be more responsive to increasing atmospheric CO2 concentrations due to low CO2 partial pressure. However, the underlying mechanisms driving this response at an ecosystem scale are poorly understood. We aimed to explore the plant carbon (C) and nitrogen (N) relationships and biomass allocation in response to elevated CO2 and N addition in a Tibetan meadow.
Methods
A 5-year manipulation experiment was conducted in an alpine meadow (4585 m above sea level) to explore the responses of plant carbon (C), nitrogen (N), and biomass dynamics, as well as their allocation schemes, to elevated CO2 (from 380 ppm to 480 ppm) and N fertilization.
Results
Elevated CO2 alone significantly enhanced aboveground plant biomass by 98%, exhibiting a stronger CO2 fertilization effect than the global average level (20%) for grasslands. Elevated CO2 favored N accumulation in aboveground parts despite the declined concentration. Nitrogen fertilization alleviated the N constraints on CO2 fertilization effects, which strengthened C sequestration capacity for the aboveground plant tissues. Moreover, our results indicate a decoupling between C and N cycles in alpine ecosystems under elevated CO2, especially in the N-enrichment environments.
Conclusions
Overall, this study shows a high sensitivity of aboveground plant biomass and decoupled C-N relationships under elevated CO2 and N fertilization for high-elevation alpine ecosystems, highlighting the need to incorporate altitude effects into Earth System Models in predicting C cycle feedbacks to climate changes.
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Acknowledgements
This research was jointly supported by the National Natural Science Foundation of China (Grant No. 41725003), the National Key Research & Development Program of China (2019YFA0607302), the Strategic Priority Program of Chinese Academy of Science (Grant No. XDA20050102), the National Natural Science Foundation of China (Grant No. 41991234; 42101067) and the China Postdoctoral Science Foundation funded projected (Grant No. 2019M660781).
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Zhao, G., Chen, Y., Zhang, Y. et al. Decoupling of plant carbon and nitrogen under elevated CO2 and nitrogen addition in a typical alpine ecosystem. Plant Soil 474, 485–498 (2022). https://doi.org/10.1007/s11104-022-05354-z
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DOI: https://doi.org/10.1007/s11104-022-05354-z