Acre – An area of land that contains 43,560 square feet.
Advance regeneration (reproduction) – Seedling-size trees present in a stand before a harvest aimed at regenerating the stand.
Age class – A year or defined period of years within the life of a tree stand.
All-aged stand – A stand that contains trees of all, or almost all, age classes. Also called “uneven-aged” stand. Contrast with an “even-aged” stand.
Alluvial soil – Soil deposited when flowing water slows down and suspended sediment drops to the bottom.
Artificial regeneration (reproduction) – See regeneration.
Aspect – The compass direction toward which a slope faces.