I like to pet and water each tree I interact with before I harvest from it. (I found in the past that this occasionally increases the output when harvesting.) I've noticed that the order of actions on the paper trees is unlike the other trees, in that the "Harvest" option is right at the top (rather than at the bottom as with the others), so by accident and when not paying attention, I end up harvesting paper before being kind to the tree. I'd recommend consistency in menu ordering.