A silvicultural system in which felling and regeneration are distributed over the whole of the area and the resultant crop is so uneven-aged that trees of all ages are found mixed together over every part of the area. Such a crop is referred to as selection forest or all-aged forest. Regeneration operation is carried out throughout the life of crop.

Felling of trees all over the area of a forest is possible when the area is small but if the area is large it is not possible to fell the trees over the entire area annually. Therefore, Thus, felling is done in a coup after a certain number of years, which is equal to the number of coups. This interval is known as felling cycle, which is defined as the time between two successive main felling on the same area. The length of the felling cycle affects the silviculture of species, exploitation of forest, and the nature of crop produced.

Advantages

• It results in the production of all aged forest. Trees of all ages are mixed together on each unit of area. Then the growing space and site factors are fully utilized.
• By maintaining continuous leaf cover, the selection systems conserve soil and moisture to the fullest extent possible.
• The selection forest produced is most resistant to injuries by insect pests and adverse climate factors.
• It prevents invasion of grass and weeds.

Disadvantages

• Considerable skill is required in carrying out marking and felling to ensure regeneration to come up in the gaps. This requires knowledge of silviculture of spps.
• As mature trees to be removed are scattered, cost of logging and extraction is high.
• Felling, logging and extraction causes damage to the young crop.
• Seed is obtained from good as well as bad trees; there is genetic deterioration of future crop.
• There is much damage to regeneration by grazing.

Selection system may be of following two types:

1. Single tree selection system: Single tree selection removes individual trees of all size classes more or less uniformly throughout the stand to maintain an uneven-aged stand.
2. Group tree selection system: Group selection systems also promote uneven-aged stands with clumps of even-aged trees well distributed throughout the cutting unit.