The bare areas in this photo have been harvested recently; this is public land that is managed by the Department of Forestry. Timber is harvested when it has reached the necessary size to use for lumber.  The land is then reforested with seedlings. The money is used to maintain the land, fund schools and roads. In this photo you can see several reforested areas of different heights. 
Tillamook County is more than 80% Forest. Most of the forest land is owned by the public; the State of Oregon owns 48%, Federal ownership totals 22%, Private ownership totals 30%. Federal & State provide a full array of forest uses, including timber production, wildlife and fisheries habitat, watershed protection, outdoor recreation and scenic open space. 
I don't understand a lot about managing the forests; I just looked up a few facts on the internet. There is always controversy about how much land to harvest and how to harvest it.