What site index values indicate good, average, and poor sites for upland hardwoods in Illinois?

What site index values indicate good, average, and poor sites for upland hardwoods in Illinois?

• A. Good sites = site index 75+, Average sites = site index 55-75, Poor sites = site index 40-54.
• B. Good: 60+, Average: 40-60, Poor: below 40.
• C. Good: 90+, Average: 70-90, Poor: 50-69.
• D. Good: 85+, Average: 65-85, Poor: 45-64.

Answer: (A)

Site index measures a site’s productivity for a forest type by the height that dominant trees reach at a standard reference age; higher values indicate more productive sites. For upland hardwoods in Illinois, the commonly used classification is good if the site index is 75 or higher, average if it falls between 55 and 75, and poor if it is 40 to 54. This set of thresholds aligns with Illinois forestry guidelines, reflecting how soil, moisture, and other site conditions translate into height growth and potential timber yield. The option that uses Good: 75+, Average: 55-75, Poor: 40-54 is the one that matches those established categories.

Site index measures a site’s productivity for a forest type by the height that dominant trees reach at a standard reference age; higher values indicate more productive sites. For upland hardwoods in Illinois, the commonly used classification is good if the site index is 75 or higher, average if it falls between 55 and 75, and poor if it is 40 to 54. This set of thresholds aligns with Illinois forestry guidelines, reflecting how soil, moisture, and other site conditions translate into height growth and potential timber yield. The option that uses Good: 75+, Average: 55-75, Poor: 40-54 is the one that matches those established categories.