Most of China was deforested a long time ago in the interest of expanding farm fields. As another reply you received noted, much of the western territory of current China (which historically was sparsely populated and not part of China proper) has always been arid and has never had forests.
Xinjiang has beautiful gold pine trees on its border with kazhakistan. I was surprised, actually, I thought the whole place was a desert but it turned out to be more lush than much of northern China (at least for the northern part I visited).
