Local flooding is not simply restricted to storm conditions, but can occur as a result of beavers building dams. Fires can be beneficial or highly damaging, depending on their intensity. A low intensity fire can effectively thin a stand by removing younger trees and species that are not fire resistant, such as grand fir and western hemlock. However, trees that remain after a fire may be stressed from charring. Pines that have been scorched are often attacked by red turpentine or other bark beetles, which can finish them off.
Wind can be a problem in stands that have recently been thinned or are adjacent to clearcuts.
Rather than thinning drastically once, a forest manager can thin regularly through the life of a stand, which will permit the trees to grow strong. When preparing to harvest, a forest manager can design small clearcuts that will not expose a great deal of the adjacent forest to the effects of wind. Insects and diseases . Airborne or waterborne pollutants can negatively impact the growth of a tree. Ozone, so scarce in the upper atmosphere, can be in a higher concentration near the ground.