This graph indicates:

• Yield capability classes are designated as:
  1. 121+ ft³/acre/year
  2. 86–120 ft³/acre/year
  3. 51–85 ft³/acre/year
  4. 21–50 ft³/acre/year
  5. 0–20 ft³/acre/year
• Abies grandis curve extends from a yield capability of 57 ft³/acre/year and a site index (50 year base) of 20 in a straight line (slope = 1.84) to a yield capability of 159 ft³/acre/year and a site index of 80.
• Pinus monticola curve extends from a yield capability of 50 ft³/acre/year and a site index (50 year base) of 20 in a straight line (slope = 1.84) to a yield capability of 152 ft³/acre/year and a site index of 80.
• Picea engelmannii curve extends from a yield capability of 12 ft³/acre/year and a site index (50 year base) of 20 in a straight line (slope = 1.84) to a yield capability of 122 ft³/acre/year and a site index of 80.
• Larix occidentalis and Pinus contorta curve is fairly close to the Picea engelmannii curve, but dips somewhat in the center of the curve as opposed to the Picea engelmannii curve which increases at a steady rate. It extends from a yield capability of 22 ft³/acre/year and a site index (50 year base) of 20 in a curved line to a yield capability of 121 ft³/acre/year and a site index of 80. At a site index of 50, the yield capability is 63 ft³/acre/year.
• Pinus ponderosa curve is fairly close to the Picea engelmannii curve, but dips somewhat in the center of the curve as opposed to the Picea engelmannii curve which increases at a steady rate. It extends from a yield capability of 19 ft³/acre/year and a site index (50 year base) of 20 in a curved line to a yield capability of 135 ft³/acre/year and a site index of 80. At a site index of 50, the yield capability is 57 ft³/acre/year.