Mostly hardwood trees such as Poplar trees are used for the fabrication of the pulp.
The higher quality pulp is used for fabrication of the copy paper. The remaining is used for books and mixed pulp paper
The trees are naturally grown and when a tree is cut down, another one is immediately planted in its place.
Poplar trees have an average age of 50 years and then they die out. The trees growth cycle is also one of the reasons it is used,