Vegetation of Forest and Savanna Communities on Glacial Sand Deposits in Northeastern Illinois

摘要

Pembroke Township, Kankakee County, Illinois, is part of an extensive glacial sand deposit. In this part of Illinois, some sand savannas retain much of their original natural character and they have high diversity; we detected 574 taxa of plants, including 11 state-listed endangered and threatened species. On five sites, we evaluated vegetation that varied from dry sand savanna to closed sand forest with Quercus velutina (black oak) dominating the overstory and Q. alba (white oak) the only other species of tree commonly encountered. Density of trees averaged 135.7 stems/ha, with an average basal area of 7.94 m2/ha on our five sites. Based on aerial photographs, the extent of woody overstory has more than doubled since 1939.