1. 420 trees per acre, 12 inches in height, but less than 4 inches d.b.h. (10 feet average spacing).
2. 150 trees per acre, 4 to 6 inches d.b.h. (17 feet average spacing).
3. 75 trees per acre, 8 to 10 inches d.b.h. (24 feet average spacing).
4. 40 trees per acre, 12 inches d.b.h. or larger (31 feet average spacing).
(Added to NRS by 1971, 754)