Urszula Zajączkowska, Piotr Dąbrowski, Waldemar Kowalczuk, Grzegorz Tarwacki. (2022). Leaf photosynthetic capacity, trunk wood structure and stem xylem sap flow in 700-years old Quercus robur L.: a pilot study upon oak ‘Bartek’, a natural monument in Poland. Silva Fennica vol. 56 no. 3 article id 10561. https://doi.org/10.14214/sf.10561

Keywords: photosynthetic capacity; ‘Bartek’ oak; tree stem tomography; xylem sap flow

Highlights: Photosynthetic and hydraulic capacity of a 700-year-old Quercus robur is comparable to reference values from the literature measured in younger oak trees.

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Physiological studies of long-lived trees are particularly important at this time, especially in light of the need for trees to adapt to global climate change. The results of the present studies were obtained on an approximately 700-year-old Quercus robur L. – the ‘Bartek’ oak. The tree has to adapt to changing climatic conditions, starting from the transition between the Medieval Warm Period and the Little Ice Age, up to the present time of rapid global climate change. Tomograph imaging showed decay of the tree trunk interior and revealed that undamaged wood forms a thin layer around the trunk perimeter. Two series of experiments were carried out to assess the physiological state of the tree. The first concerned measurements related to photosynthetic capacity: chlorophyll a fluorescence, gas exchange (CO₂ assimilation, transpiration), stomatal conductance and leaf water potential. The second series concerned xylem sap flow velocity and anatomical studies of stem wood. Photosynthetic capacity was within the limits reported for young healthy trees. The diurnal pattern of velocity of xylem sap flow was also typical for young vigorous trees and flow velocity correlated positively with solar radiation and negatively with air relative humidity. Anatomical observations of the outermost wood showed relatively narrow annuals rings with large diameter earlywood vessels. The results indicate that the veteran tree does not show signs of water stress probably due to a good balance of water flow and that leaf area of the canopy needs only the current ring of wood to feed transpiration of the canopy.

Zajączkowska, Department of Forest Botany, Warsaw University of Life Sciences - SGGW, 159 Nowoursynowska Street, 02-776 Warsaw, Poland https://orcid.org/0000-0002-7119-7547 E-mail: urszula_zajaczkowska@sggw.edu.pl
Dąbrowski, Department of Environmental Development Warsaw University of Life Sciences - SGGW, Warsaw, Poland https://orcid.org/0000-0002-2867-8839 E-mail: piotr_dabrowski@sggw.edu.pl
Kowalczuk, Ekosystem Waldemar Kowalczuk Tomasz Kowalczuk, Otwock, Poland E-mail: ekosystem@ekosystem.waw.pl
Tarwacki, Forest Protection Department, Forest Research Institute, Sękocin Las, Poland https://orcid.org/0000-0001-5979-7788 E-mail: G.Tarwacki@ibles.waw.pl

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