Regeneration of desired species following a harvest is a key component of forest sustainability. Often undesirable trees, those of small diameter or larger non-commercial trees with little economic value after a harvest, if left, will ultimately compose the next forest. Site preparation is a silvicultural practice that removes these unwanted trees, as well as grasses and weeds, to encourage the regeneration of desirable species such as oaks. Site preparation can be performed before, during, or after a harvest or regeneration event.