That's interesting. We raise cattle (grass fed with a daily grain supplement) for our own use
Our pasture is located partially in a poplar forest, but after 20 years the cattle have destroyed about half of the poplars
What happens is - the cows like to rub themselves on the trees, and they eat all the lower leaves. Eventually, they rub off enough bark & decomposition sets in.
It seemed like a good idea when we first built a pasture there...maybe a different species of tree is needed? I don't know.