Upscaling xylem phenology: Sample size matters.

This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km 2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size while assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests.