EGU21-6430
https://doi.org/10.5194/egusphere-egu21-6430
EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Combining branch-scale COS/CO2 exchange and canopy-scale SIF measurements to disentangle the effects of high VPD and low soil moisture in mature pine trees under field conditions

Rafat Qubaja, Rafael Stern, Itay Oz, Amnon Cochavi, Jonathan Muller, and Dan Yakir
Rafat Qubaja et al.
  • Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel 76100 (rafat.qubaja@weizmann.ac.il; dan.yakir@weizmann.ac.il)

During the regular seasonal drought conditions in our semi-arid pine forest, soil water content decrease below the 16% threshold of no transpirable soil water availability, and VPD increase to values of >5 kPa. Soil drought in one forest plot was eliminated by using supplemental drip irrigation during summer. We used automatic branch chambers to measure CO2/H2O exchange together with laser-based COS exchange, and retrieving canopy sun induced fluorescence (SIF) using a high-resolution spectrometer above the canopy that was moved between the control and irrigated plots on a weekly basis. Using these research tools, we investigated the ecophysiological response (including rates of gas exchange, conductances, and photochemical response) of the mature pine trees to the differential effects of soil and atmospheric droughts. Leaf relative uptake (LRU) ratio of COS to CO2 fluxes was used to constrain estimates of carbon assimilation (An) and changes in the An/gl ratio (where gl is leaf conductance), and leaf COS and H2O exchange fluxes were also used to partition leaf conductance. We will report on the first seasonal cycle of COS and CO2 fluxes, LRU and SIFA of mature pine trees under field conditions in the semi-arid forest, which includes the summer dry stress period, the recovery during the transition to the winter wet season, and the spring peak activity period.

How to cite: Qubaja, R., Stern, R., Oz, I., Cochavi, A., Muller, J., and Yakir, D.: Combining branch-scale COS/CO2 exchange and canopy-scale SIF measurements to disentangle the effects of high VPD and low soil moisture in mature pine trees under field conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6430, https://doi.org/10.5194/egusphere-egu21-6430, 2021.

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