Continuous plant water potential measurement with PSY1 Psychrometer on a 23m-high Oak branch in Fontainebleau-Barbeau forest (France)

Continuous plant water potential measurement with PSY1 Psychrometer on a 23m-high Oak branch in Fontainebleau-Barbeau forest (France) Continuous measurement of water potential in megapascals (MPa) on a 3cm diameter oak (Quercus petraea) branch located at a height of 23m.These measurements were taken at the Barbeau forest research station : https://barbeau.ese.cnrs.fr/ Continuous measurements were made using a PSY1 Psychrometer from ICT International.Location : Fontaine-le-Port (France) 48.476319, 2.780154, 103 m a.s.l.Forest dominant height: 28mOak DBH : 84cmOak Height : 27m 2023Measurement frequency: 10 minutesMeasurement period start: June 29, 2023Measurement period end: October 10, 2023Last calibration (lab)* : 31 May 2023 2024 Measurement frequency: 10 minutesMeasurement period start: July 25, 2024Measurement period end: September 09, 2024Last calibration (lab)* : 03 July 2024 PSY1 Psychrometer (Stem & Leaf) for plant water potential : https://ictinternational.com/product/psy1-psychrometer-for-plant-water-potential/ The Fontainebleau-Barbeau site is located in the Paris area, near the Fontainebleau forest. The site has a gentle slope of 2 degree towards the Seine river which flows 750 m at the South-West of the flux tower. Sessile oak (Quercus petraea (Matt.) Liebl.) is the main species, accounting for 79\% of the basal area and dominating an understorey mostly occupied by hornbeam (Carpinus betulus L., 18\% of the basal area). The dominant height is 28 m. The soil is an endostagnic luvisol covered by an oligo-mull humus. It developed on a calcareous bedrock located at 5-10 m-depth and has a discontinuous buhrstone layer located between 60 to 90-cm depth, over which a perched water table develops in winter, usually till late spring. Mean annual air temperature and cumulated precipitation are 11.2 degC and 677 mm, respectively (1980–2010, Melun weather station, 12 km from the study site). The leaf area index (LAI) was on average 6.01 over the 2012–2018 period. In spring 2021, we established the root distribution at FR-Fon by counting roots according to diameter class in a 2-m wide and 150-cm deep trench dug 50 meters away from the flux tower. We noticed the presence of fine roots down to the bottom of the trench (-150 cm). In autumn 2021, we extracted one 5-m deep soil core, at a location that we consider broadly representative of the average soil conditions of the site, 80-m East from the flux tower. During the pedological description of this unique soil core of 10-cm diameter, we observed the presence of 1-mm diameter roots down to a depth of 4 meters, at the top of a dense green marl layer. We were not able to quantify the actual root distribution along this unique 5-m soil core, so our report of the presence of roots has a documentary, qualitative value. *calibration procedure following the manual ( https://ictinternational.com/wp-content/uploads/2023/08/PSY1-Manual-DOC-00087v2.pdf ) with 6 salinity points 0.1 /0.2/0.3/0.4/0.5/0.6 in a temperature chamber at 20°C maintained for 1 hour each In 2023 : Current Calibration Curve Slope = -4.366 ; Intercept = -1.145 ; R²=0.98535 In 2024 : Current Calibration Curve Slope = -3.004 ; Intercept = -1.130 ; R²=0.94360 Temperature Correction Constants : C1=0.0270 C2=0.3250