Understory ejections are distinct turbulent features emerging in prime tall-forest ecosystems. We share a method to isolate understory ejections based on H₂O–CO₂ anomaly quadrants. From these, we calculate the flux contributions of understory ejections and all flux quadrants. In addition, we show that a distinctly depleted isotopic composition can be found in the ejected water vapour. Finally, we explored the role of clouds as a potential trigger for understory ejections.