I am surprised by the weight they mention in the article (and on Wikipedia). 6600 tons for more than 40 000 trunks, considering that Populus tremuloides are us

I am surprised by the weight they mention in the article (and on Wikipedia). 6600 tons for more than 40 000 trunks, considering that Populus tremuloides are usually 20–25m tall at maturity (again, according to wikipedia), seems very low.