Soil water status modulates the temperature dependence of stem CO2 efflux in Quercus ilex and Quercus faginea trees
Researcher:
Ferrio Díaz, Juan Pedro
Congress:
XVI Simposio Internacional Hispano-Portugués de Relaciones Hídricas en Plantas
Participation type:
Póster
Other authors:
López-Ballesteros A (speaker), Peguero-Pina JJ., dos Santos-Silva JV., Martín-Sánchez R., Sancho-Knapik D., Gil-Pelegrín E., Ferrio JP
Year:
2024
Location:
Zaragoza
Publication:
López-Ballesteros A (speaker), Peguero-Pina JJ., dos Santos-Silva JV., Martín-Sánchez R., Sancho-Knapik D., Gil-Pelegrín E., Ferrio JP 2024. Soil water status modulates the temperature dependence of stem CO2 efflux in Quercus ilex and Quercus faginea trees. Póster presentado en XVI Simposio Internacional Hispano-Portugués de Relaciones Hídricas en Plantas. 14-16 Feb 2024.
The contribution of stem respiration to the overall forest carbon balance is currently uncertain due to the difficulty to directly measure it. Recent research has demonstrated that not all the CO2 produced by respiration in woody tissues escapes immediately to the atmosphere. Instead, it can be partially stored inside the tree or dissolved and transported within the xylem. Furthermore, the CO2 respired within the soil by heterotrophs can even move upwards and contribute to the measured CO2 efflux at a given height of the tree stem. To disentangle this complex process, we have developed an automated system to quantify and trace the metabolic origin of stem CO2 efflux. This system is composed by dynamic steady-state stem chambers where the CO2 efflux and its stable isotope composition (δ13C and δ18O) are measured in real time together with plant transpiration, photosynthetic active radiation, vapor pressure deficit, and soil, stem, and air temperature. In this work, we present a mesocosm experiment where we monitored stem respiratory fluxes of two Quercus species with contrasting traits that are extensively distributed across the Iberian Peninsula, Quercus ilex subsp. rotundifolia and Quercus faginea. Given that the CO2 transport within and outside the stem depends on xylem sap velocity and morphology of woody tissues, we hypothesize that both the magnitude and isotope signal of stem CO2 efflux will differ between species as well as its relationship with ambient variables. Preliminary results show that Q. ilex has a greater stem CO2 efflux compared with Q. faginea, especially during nightime. Additionally, moderate soil drought (in terms of soil water potential) reduced the temperature dependence of stem CO2 efflux for both species. Under moderate drought, the efflux increased in Q. ilex but decreased in Q. faginea. Similarly, δ13C and δ18O of CO2 efflux also varied depending on the stem temperature and soil water status.
The contribution of stem respiration to the overall forest carbon balance is currently uncertain due to the difficulty to directly measure it. Recent research has demonstrated that not all the CO2 produced by respiration in woody tissues escapes immediately to the atmosphere. Instead, it can be partially stored inside the tree or dissolved and transported within the xylem. Furthermore, the CO2 respired within the soil by heterotrophs can even move upwards and contribute to the measured CO2 efflux at a given height of the tree stem. To disentangle this complex process, we have developed an automated system to quantify and trace the metabolic origin of stem CO2 efflux. This system is composed by dynamic steady-state stem chambers where the CO2 efflux and its stable isotope composition (δ13C and δ18O) are measured in real time together with plant transpiration, photosynthetic active radiation, vapor pressure deficit, and soil, stem, and air temperature. In this work, we present a mesocosm experiment where we monitored stem respiratory fluxes of two Quercus species with contrasting traits that are extensively distributed across the Iberian Peninsula, Quercus ilex subsp. rotundifolia and Quercus faginea. Given that the CO2 transport within and outside the stem depends on xylem sap velocity and morphology of woody tissues, we hypothesize that both the magnitude and isotope signal of stem CO2 efflux will differ between species as well as its relationship with ambient variables. Preliminary results show that Q. ilex has a greater stem CO2 efflux compared with Q. faginea, especially during nightime. Additionally, moderate soil drought (in terms of soil water potential) reduced the temperature dependence of stem CO2 efflux for both species. Under moderate drought, the efflux increased in Q. ilex but decreased in Q. faginea. Similarly, δ13C and δ18O of CO2 efflux also varied depending on the stem temperature and soil water status.