Sielbeck Forest State Natural Area, IL

[Jess Riddle]

NTS,

Illinois does not come within 400 miles of the ocean, and eroded hills, mountains in miniature, cover most of the southern end of the state. However, the low ground in southern Illinois supports forests striking similar to southern bottomland hardwoods found in places like Congaree National Park, and supports such iconic southern species as bald cypress. Much of the flat area has been drained and converted to agriculture, but the Sielbeck family preserved a 125 acre block of forest for decades. The Nature Conservancy then purchased the tract at auction and transferred it to the state to create the Sielbeck Forest State Natural Area (Davis, 2003).

Only a few miles off the interstate, the site sounded like a convenient old-growth stand to stop at as I traveled cross country for the holidays, but I almost turned around before I got there. Each stream I crossed as I approached was over its banks from the recent storm, and flooded fields greeted me as I turned off the interstate. I found the site mostly shallowly inundated, but some areas adjacent to the uplands were merely squishy with abundant puddles. Consequently, I saw only a little of the site, and did not visit the wetter cypress-tupelo portion.

The forest sits in the middle of a crescent of 125’ high rounded hills that opens to the north and occupies most of the half mile wide valley bottom. The state has abandoned the agricultural lands that surround the forest to provide a buffer. Dense thickets of 20’ tall sweetgums with an occasional sycamore of swamp white oak now occupy the old fields. Sweetgum also forms the overstory with the help of cherrybark oaks and, in slightly wetter areas, pin oak. Green ash, swamp white oak, overcup oak, shagbark hickory, and sycamore grow much more widely scattered in the overstory. Green ash is also common in the well-developed midstory along with Carolina red maple, sugarberry, and a mixture of elms. Saplings of those midstory species combine with spicebush, paw paw, greenbrier, and a few possumhaw to create a surprisingly think understory.

SielbeckMeasurements.JPG (27.77 KiB) Viewed 762 times

Three foot diameter trees are common except in swaths where storms hade broken up the overstory. The trees were probably taller before a severe ice storm hit the region in February 2009. All of the upper branches of the red oaks and sweetgum ended in roughly four inch diameter stubs surrounded by a dense bush of new growth. The white oaks on the other had appeared to suffer little damage from the ice.

11'4" cbh x 111.9' tall pin oak

The dominance of early successional species and their evenness of size make me question whether the site is really old-growth or not. Some of the small streams that converge in the stand are ditched and have an artificial levee on one side. The sweetgums appear to regenerating, but I saw only one small oak.

I think this site could prove very valuable for helping to understand how species sizes vary across their ranges. Cherrybark oak, overcup oak, sweetgum, bald cypress, water tupelo, all, to varying degrees, approach their northern range margins in the area, and I explored only a fraction of the site.

Jess

Davis, M. B. (2003). Old Growth in the East: a survey. Appalachia-Science in the Public Interest. Mt. Vernon, KY.