Vertical distribution of gas exchanges and their integration throughout the entire canopy in a maize field

Abstract

Fluxes of carbon and water along a vertical profile within a canopy, particularly the associations between canopy and ecosystem levels, are not well studied. In this study, gas exchange along the vertical profile in a maize canopy was examined. The relationships between leaf- and ecosystem-level carbon and water fluxes were compared. The results from research conducted over two growing seasons showed that during vegetative growth, the top and middle leaf layers in the canopy contribute most to the carbon and water fluxes of the entire canopy. During the grain-filling stage, gas exchange processes were performed mostly in the middle leaves with and near the ears. Significant relationships were observed between the net ecosystem CO2 exchange rate (NEE) plus soil respiration and the assumed canopy levels (Acanopy) and between evapotranspiration rates at the ecosystem (ET) and assumed canopy levels (Ecanopy). This highlights the close associations between these parameters by integrating the leaf gas exchange rates measured in a conventional leaf cuvette and those at the ecosystem level via the eddy covariance technique. These results improve our understanding of how carbon assimilation varies vertically within a canopy, highlighting the critical role of ear leaves.

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Acknowledgements

We are grateful to Chunqiao Shi, Hongyan Qi, Tao Liang, Yang Yang, and Jingli Liu for their great help during this study.

Funding

The study was funded by National Key Research and Development Program of China (2016YFD0300106), and China Special Fund for Meteorological Research in the Public Interest (GYHY201506001-3).

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ZX and GZ conceived and designed the study. ZX and QH analyzed the data and wrote the draft manuscript. The three authors read and approved the final manuscript.

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Correspondence to Zhenzhu Xu or Guangsheng Zhou.

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Xu, Z., Zhou, G. & He, Q. Vertical distribution of gas exchanges and their integration throughout the entire canopy in a maize field. Photosynth Res (2021). https://doi.org/10.1007/s11120-020-00817-9

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Keywords

  • Vertical distribution
  • Carbon exchange
  • Eddy covariance
  • Stomatal conductance
  • Evapotranspiration
  • Maize canopy