Forest Regeneration on Two Old Fields in Southwestern Illinois

Abstract

Total tallies of trees 2.6 inches DBH or larger and sub- sampling of smaller woody and herbaceous vegetation were done on two old fields in Union Co. which had been abandoned 35 or 40 years prior to 1967. Tulip tree (Liriodendron tu,lipifera) predominated in a closed stand on lower, gentle slopes adjacent to a creek. Sugar maple (Acer saccharum) predominated on flat areas adjacent to another creek. Slopes above the sugar maple stand were partly forested with sweet gum (Liquidambar styraciflua) as the major species and sassafras (Sassafras albidum) locally predominant. Habitat factors related to variations in tree regeneration were soil type, physiography, and proximity to tree cover. The findings extend appreciably reports of old-field successional types in southern Illinois. (Andropogon virginicus L.) or little bluestem (A. scoparius Michx.), has generally been reported for abandoned fields in southern Illinois and adjacent areas (Bazzaz, 1968; Voigt and Mohlenbrock, 1964). Aggressively invading pines of the southeastern states are lacking. Sassafras (Sassafras albidum (Nutt.) Nees) and persimmon (Diospyros virginiana L.) have been reported to be important woody invaders. Very few fields older than 15 years have been studied, and these have chiefly been on uplands. Essentially no fields have been reported in which broomsedge remnants were not important. Bottomland or lower slope fields with good stands of young timber other than sassafras or persimmon are, however, not common. We shall discuss two such stands, and the upper slope old-field vegetation adjoining one of the two stands. NATURAL SETTING OF THE STUDY AREA Southern Illinois lies in the humid mesothernal (Caf-humid sub- tropical, warm summer) province of Trewartha (1954). The south- western portion of the state has a high and rather evenly distributed rainfall averaging over 45 inches per year. Droughty periods in the summer and early fall are not uncommon. Three vegetational regions of Braun (1950), the southern hardwoods of the Mississippi Embay- ment, the western mesophytic, and the oak-hickory, are represented. In southern Illinois these are typically related to bottomlands, ravines, and ridges, respectively. Two study areas are located in Union Co. (89015'W, 37023'N), 5 miles south of Anna-Jonesboro at an approximate elevation of 500 ft in the Illinois Ozarks (Shawnee Hillg), roughly 10 miles from the Mississippi River to the west and 20 miles from the Ohio River to the south near the watershed of these drainages. The underlying rock is 90