The data file (Dendrometer_data_Pisy.xlsx) contains environmental records and dendrometer data, i.e., raw data as well as calculated mean daily radial variations of the xylem and inner bark, detrended radial variations of the xylem and inner bark, and daily xylem amplitudes. Data are documented in the following article: Oberhuber W, A Gruber, G Wieser (2023) Seasonal and daily xylem radius variations in Scots pine are closely linked to environmental factors affecting transpiration. Biology, 12, 1251; doi: 10.3390/ biology12091251 Summary Diurnal and seasonal radius variations of xylem and inner bark of mature Scots pine trees (Pinus sylvestris; stem diameter 27±2 cm) were determined at a drought prone inner alpine site (c. 750 m asl; Tyrol, Austria). Point dendrometers were mounted on xylem and on living phloem (i.e., inner bark) of four trees, and xylem radius variations (XRV) were continuously recorded throughout three growing seasons (April 2019–October 2021) and related to environmental factors including air temperature (T), vapour pressure deficit of the air (VPD), relative air humidity (RH), solar radiation (SR), precipitation (P) and soil water content (SWC). While inner bark width increased due to radial stem growth (c. 500 µm per year), radial xylem width consistently decreased by c. 50 µm during the growing seasons. Results of our study revealed that daily and seasonal radial variations of the xylem and inner bark were closely linked, indicating intensive water exchange between these tissues. Comparison of XRV with environmental variables affecting transpiration revealed a close coupling of XRV to VPD, T and SR, pointing to a strong dependence of stem water status on changes in atmospheric conditions. Because VPD increases exponentially with the increase in temperature and thus causes the water content in the stem to decrease especially under drought, tree growth and mortality will be increasingly affected by climate warming.

The research was funded by the Austrian Science Fund (FWF), project numbers P34706-B and P25643-B16.