Depending on the distance between your arboretum and humus, you may want to use both - a normal gate to check for resources and an autarchic gate to pulse (read: pull) whenever it's below a certain value. I think the gate at the arboretum will show a setting like "<25% resources" or similar. Let it give off a pipewire signal leading to your autarchic gate, which, whenever "pipe signal = on" will "energy pulse", thus sending the humus on its way.
And Moezso is right - the "energy pulse" can only be done by all of the autarchic gates.