Watching the linked video does not show "electrical impulses" as the OP indicates. It seems to show DC voltage, but is difficult to tell what the meter switch is set to.
Be aware, the moisture and sugar and other chemicals in the sap of the tree makes it conductive. Trees have been used for vertical antennas for high frequency radio communications. Any tree near electrical power lines will also have a small induced voltage, just like a metal wire held vertically near a power line.
If the OP is interested in biologically generated voltage, not impulses, then stray voltages must be expected.
Paul