By looking at the scars in the growth rings of 36 old-growth post oak trees, INHS botanist Greg Spyreas, affiliate John Ebinger and Illinois State Museum botanist William McClain found that there had been more than 100 fires in Southern Illinois between the 1770s and 1996. This repeated burning stabilized prairies and kept the woodlands open until the mid-1800s when fires appear to have been suppressed by the settlers in the area for a 30 year period. Fire suppression altered the plant community by allowing fast-growing, shade-loving species to survive. The study was published in the journal Castanea. Read news coverage of the story by the Science Blog, Science Codex, and Earth Times.