I know someone who used to work for a paper forrester --the trees they plant are exclusively grown in managed timberlands for conversion to paper --no other use. They use fast growing varieties of trees[1]. The likes of Wayerhaeuser and others.
But they grow the pines for paper and then regrow them? Is the whole operation sustainable? According to Penn and Teller's "Bullshit", it is.
Yes, they use mostly young pines which are easily chipped. I think in about 6 years you can cut them for paper.
8-10 years. Most (~80%) of the power needed in a paper mill is generated from the bark of the tree which is converted into fuel using several chemical mixtures. Overall, the paper industry is actually very sustainable.
I am from western Canada, I guess it is not the same every where.