The woodland and savanna portions of the Cross Timbers are mainly post oak and blackjack oak on coarse, sandy soils; fire suppression in recent years has increased forest density and allowed eastern redcedar to invade as well. The short, stout oaks that grow in the Cross Timbers were not usable as timber and those that were not cleared for farmland constitute one of the least disturbed forest types in the eastern United States (MADISON), with some of old-growth forest scattered throughout the region. These old-growth forests contain millions of post oak from 200 to 400 years old and red cedar over 500 years old. The prairie portions are chiefly tallgrass on finer, dry soils; overall, the Cross Timbers are not as arable as the surrounding ecoregions. Today, land use is a mixture of rangeland, pastures, and farmland. The area has also been an important site of oil extraction for over 80 years.