Quantifying Dynamic Changes in Stem Storage-Water Use and Rehydration in Mature Trees: A Study on Pinus sylvestris Trees Exposed to Increased Atmospheric and Soil Drought.

Internal stem water storage in Pinus sylvestris increases from 10% to 55% of daily transpiration during drought conditions, highlighting its role in drought resilience.

• Why it matters: Understanding water fluxes within trees is crucial as forests face more frequent hot droughts with rising VPD and declining soil moisture, yet upstream fluxes like stem water storage are poorly quantified.
• What they did: The study combined high-resolution sap flow and dendrometer measurements over the 2024 growing season at the Pfynwald research platform, analyzing fluxes in relation to VPD and soil water potential.
• The result: Findings show that stem water storage sustains transpiration during drought, especially under dry conditions, and high nighttime VPD constrains tissue rehydration, emphasizing the importance of temporal water storage dynamics in tree water-use strategies.