199 Appendix B: Site Index Curves for Selected Tree Species Interpreting Site Index Curves Site index is the height to which trees will grow over a given period usually 50 years in the Lake States. Trees are expected to grow taller on good sites than on poor sites. Site index curves can be used to estimate relative site quality from the average age and average total height of dominant and codominant trees on a particular site. Each tree species has its own set of site index curves. To use the site index curves in this appendix, first measure the age and total height of several dominant and codominant trees of a single species on a site. Calculate the average total age and average total height of those same trees. Then refer to the site index curves for that species. For example, refer to the site index curves for quaking aspen in Appendix B-1. If the average age of aspen trees in your stand of interest is 40 years (horizontal axis) and the average total height is 62 feet (vertical axis), then those two lines converge closest to the site index curve for 70. This means that aspen trees in your stand are expected to be 70 feet tall when they are 50 years old. They are growing on a good site. B-1. Quaking Aspen B-2. Balsam Fir in the Lake States B-3. Black Spruce B-4. Black Walnut B-5. Green Ash B-6. Eastern Cottonwood B-7. Eastern White Pine B-8. Hardwood Comparisons B-9. Jack Pine B-10. Northern White-Cedar B-11. Red Pine B-12. Tamarack B-13. Northern Red Oak Woodland Stewardship
200 B-1: Quaking Aspen Note: Add 4 years to age at DBH to obtain total age. Folwell Avenue, St. Paul, MN 55108. p. 46. B-2: Balsam Fir in the Lake States Site Index: 20 30 40 50 60 70 Add Years: 15 13 11 10 9 8 Note: Curves are based on plots in the Lake States. Folwell Avenue, St. Paul, MN 55108. p. 70.
Appendix B: Site Index Curves for Selected Tree Species 201 B-3: Black Spruce Site Index: 20 30 40 50 60 70 80 90 Add Years: 15 13 11 10 9 8 7 6 Note: Curves are based on plots in northeastern Minnesota Superior National Forest. Folwell Avenue, St. Paul, MN 55108. p. 85. B-4: Black Walnut Note: Determine total age from stumps or planting records; do not damage trees by using an increment borer. Note: Curves are based on plots in southern Illinois. Folwell Avenue, St. Paul, MN 55108. p. 33. Woodland Stewardship
202 B-5: Green Ash Note: Add 2 years to age at DBH to obtain total age. Note: Curves are based on plots in Mississippi Valley alluvium in Louisiana, Mississippi, Arkansas, and Tennessee. Folwell Avenue, St. Paul, MN 55108. p. 30. B-6: Eastern Cottonwood Note: Add 2 years to age at DBH to obtain total age. Note: Curves are based on plots in Iowa bottomlands. Folwell Avenue, St. Paul, MN 55108. p. 45.
Appendix B: Site Index Curves for Selected Tree Species 203 B-7: Eastern White Pine Site Index: 40 50 60 70 80 Add Years: 12 12 10 8 6 Note: Curves are based on plots in northern Wisconsin. Jacobs. 1989. Site Index Curves for Forest Tree Species in the Eastern United States (General Technical Report NC-128). USDA Forest Service, North Central Forest Experimental Station, 1992 Folwell Avenue, St. Paul, MN 55108. p. 118. B-8: Hardwood Comparisons Note: If you know the site index for one species, you can determine the site index for another species on the same site by moving vertically up or down to the curve for each species of interest. For example, if you know the site index for aspen is 72, find that number on the aspen curve. Then read directly downward to the white ash curve to find the corresponding site index of 68 for white ash. Source: USDA, Forest Service. 1985. Northern Hardwood Notes (Note 4.02). U.S. Government Printing Office, Washington, DC 20402. Woodland Stewardship
204 B-9: Jack Pine Site Index: 30 40 50 60 70 80 90 Add Years: 9 8 7 6 5 4 4 Note: Curves are based on plots in the Lake States. Folwell Avenue, St. Paul, MN 55108. p. 89. B-10: Northern White-Cedar Site Index: 20 30 40 50 60 Add Years: 20 15 15 10 10 Note: Curves are based on plots in the Lake States. Jacobs. 1989. Site Index Curves for Forest Tree Species in the Eastern United States (General Technical Report NC-128). USDA Forest Service, North Central Forest Experimental Station, 1992 Folwell Avenue, St. Paul, MN 55108. p. 141.
Appendix B: Site Index Curves for Selected Tree Species 205 B-11: Red Pine Site Index: 40 50 60 70+ Add Years: 8 6 5 4 Note: Curves are based on plots in Minnesota. Jacobs. 1989. Site Index Curves for Forest Tree Species in the Eastern United States (General Technical Report NC-128). USDA Forest Service, North Central Forest Experimental Station, 1992 Folwell Avenue, St. Paul, MN 55108. p. 110. B-12: Tamarack Site Index: 20 30 40 50-90 Add Years: 12 10 7 5 Note: Curves are based on plots in Minnesota. Folwell Avenue, St. Paul, MN 55108. p. 75. Woodland Stewardship
206 B-13: Northern Red Oak Note: Add 4 years to age at DBH to obtain total age. Note: Curves are based on plots in southwestern Wisconsin. Folwell Avenue, St. Paul, MN 55108. p. 62.