EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest     

Gabriela U. Neves1, Vanessa R. Ferrer1, Sabrina Garcia1, Vinicius F. de Souza2, Tomas Domingues3, Izabela Aleixo1, Henrique Tozzi4, Pedro A. C. L. Pequeno5, Nathielly P. Martins1, Alacimar Guedes1, Iokanam S. Pereira1, Juliane C. G. Menezes1, Amanda R. M. Damasceno1, Yago R. Santos1, Maquelle N. Garcia1, Anna C. M. Moraes1, Ana Caroline M. Pereira1, Bart Kruijt6, Carlos A. N. Quesada1, and the AmazonFACE Team*
Gabriela U. Neves et al.
  • 1National Institute of Amazonian Research
  • 2Estonian University of Life Sciences, Tartu, Estonia
  • 3University of São Paulo, São Paulo, Brazil
  • 4São Paulo State University, São Paulo, Brazil
  • 5Federal University of Roraima, Boa Vista, Brazil
  • 6Wageningen University & Research, Wageningen, Netherlands
  • *A full list of authors appears at the end of the abstract

The increase in atmospheric CO2 concentration positively affects plant carbon assimilation and carbon stock in different biomes. However, there are uncertainties regarding how plants in tropical forests, especially in the Amazon rainforest, will respond to this increase, since a large part of the soils in the region present natural low phosphorus (P) availability, which could constrain positive effects of elevated CO2. Here, we investigated if P addition would interfere on leaf primary carbon metabolism and aboveground development responses under elevated CO2. For that, we used 46  seedlings of Inga edulis Mart., a native leguminous nitrogen-fixing species, exposed for 10 months (November 2019 - September 2020) to CO2 and P treatments. Plants grew in pots - half with natural P availability (-P) and half with P addition (+P) -, inside CO2 enrichment chambers - half with ambient CO2 (aCO2) and half with elevated CO2 (aCO2 + 200 ppm; eCO2), - in the understory of a primary forest in Central Amazonia, Manaus, Brazil.  A factorial experimental design was used, with 11-12 plants for each treatment: aCO2-P (control), aCO2+P, eCO2-P and eCO2+P. To assess the carbon metabolism, we measured light-saturated net CO2 assimilation (Asat), leaf respiration in the light (Rlight), leaf respiration in the dark (Rdark) and photorespiration (PR). To assess aboveground development, we measured plant height and diameter, crown height and diameter,  number of leaves and total leaf area. We found that eCO2, regardless of P availability, significantly increased Asat and Rlight, while decreasing Rdark and Asat:Rdark ratio, but it did not affect PR . Those results suggest that seedlings indeed assimilated more carbon under eCO2. However, irrespective of CO2 treatment, +P significantly increased aboveground responses. Under P addition, plants showed greater height and greater crown development (higher crown height and diameter and larger leaves) compared to control or eCO2-only. Plant diameter and number of leaves did not respond to any treatment. We did not find differences between +P seedlings under different CO2 treatments (aCO2+P and eCO2+P), indicating that only P had an effect on these responses. Still, there were substantial changes on some of the aboveground responses between these treatments, particularly in total leaf area which increased 60% (aCO2+P) and 126% (eCO2+P) compared to control. Overall, we observed a distinguished pattern, in which eCO2 mainly affected physiological responses, while P addition consistently affected aboveground development. The lack of response of aboveground components under eCO2 suggests that the extra carbon assimilated was not necessarily used to aboveground development as shown by many studies. Our findings indicate that, in the short-term, eCO2 is highly important in determining changes in plant metabolism whereas it has little impact on growth, even when nutrient limitation is alleviate. However there is still need to understand if such responses will persist in the long-term and in other species, as these processes are key factors in determining forest responses to climate change.  

AmazonFACE Team:

From the National Institute of Amazonian Research: Bruno T. T. Portela¹. From University of Campinas: David M. Lapola

How to cite: U. Neves, G., R. Ferrer, V., Garcia, S., F. de Souza, V., Domingues, T., Aleixo, I., Tozzi, H., A. C. L. Pequeno, P., P. Martins, N., Guedes, A., S. Pereira, I., C. G. Menezes, J., R. M. Damasceno, A., R. Santos, Y., N. Garcia, M., C. M. Moraes, A., M. Pereira, A. C., Kruijt, B., and A. N. Quesada, C. and the AmazonFACE Team: Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest     , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8975,, 2022.

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