PARENT SESSION
Wednesday, August 9, 5:00-6:30 pm
Poster Session 18 - Forest ecology and management
Exhibit Hall, Ballroom Level, Cook Convention Center

Compositional changes in central Illinois woodland.

Mullarkey, Alicia^*,1, Smith, Japhia¹, Anderson, Roger¹, ¹ Illinois State University, Normal, IL, United States

ABSTRACT- In the past century, Illinois woodlands on mesic upland sites have undergone a transition from dominance by fire resistant, shade-intolerant oak and hickory species to dominance by shade-tolerant, but fire sensitive mesophytes such as sugar maple. This transition has been attributed to fire cessation associated with European settlement. Changes in species composition and forest structure over the past 28 years were studied in the 13 ha Thaddeus Stubblefield Nature Preserve in central Illinois and were compared with pre-settlement vegetation as described by Government Land Office (GLO) Survey Records. Historic tree data were compiled from GLO records and tree and sapling data were collected from the nature preserve in 1977, 1984, 1994, 2001, and 2005. According to GLO records, white oak (Quercus alba), red oak (Q. rubra), ash (Fraxinus spp.) and elm (Ulmus) spp.) were leading species in the historic vegetation of the prairie grove; Importance Values (IV) were 16, 16, 12, and 10, for the four species, respectively. American elm (Ulmus americana) (IV = 29) was the dominant species in the 1977 sample but was replaced by sugar maple (Acer saccharum) (IV = 46) as the dominant species in the 1984 sample and in subsequent samples. Sugar maple was a minor component of the historic vegetation, but steadily increased in importance in the tree stratum from 1977 (IV =17) to 2001 (IV = 67). Sugar maple declined slightly in IV from 2001 to 2005. Tree diversity (Shannon-Wiener index) steadily decreased from historic times through 2001 but showed a slight increase in the 2005 sample, which is likely due to the decreased importance of sugar maple in the 2005 sample. Currently, sugar maple has the highest relative density (78) in the sapling strata indicating that dominance of sugar maple in this woodland will continue into the future. Absence of Quercus species in the sapling stratum indicates that there is little to no oak regeneration occurring in the nature preserve.

Key words: old-growth deciduous forest, succession, forest ecology